Search

This research investigated a synthetic amendment to improve composting and resource recycling of pig manure and biogas residue. We further examined whether adding a synthetic amendment impacts the microbial ecosystem in the composted materials. Three mixing ratios were used to investigate composting performance: no synthetic amendment (T0), 5% synthetic amendment (T1), and 10% synthetic amendment (T2) (T1 and T2 were measured as a wet weight ratio). There were no significant differences in the fundamental characteristics between composting products in T0 and T1. The moisture content of composting material in T0, T1, and T2 significantly decreased from a baseline of approximately 65% to 35.5%, 37.3%, and 55.9%, respectively. Meanwhile, the germination index significantly increased to 111.6%, 155.6%, and 62.3%, respectively. When an optimal proportion of synthetic amendment was added, T1 showed high degree of humification, lignocellulase activities, and effective biodegradation. Firmicutes, Actinobacteria, Proteobacteria, and Bacteroidetes were the dominant bacteria, while Ascomycota and Basidiomycota were the dominant fungi in all treatment groups. Amino sugar and nucleotide sugar metabolism, glycolysis, starch, and sucrose metabolism were among the primary pathways in predicted functions. The synthetic amendment can generate a mature composting product and can be reused or recycled to conserve resources.

Haloxylon salicornicum is a xero-halophyte growing in saline and arid regions of the world. Metabolite profiling was carried out in shoot of both control and salinity treated (400 mM NaCl) samples by GC-QTOF–MS and HPLC-DAD analysis to decipher the salinity tolerance mechanism in this xero-halophyte. The present study investigates the alteration in metabolite profile of H. salicornicum that support the salinity tolerance of the plant. The metabolomic analysis of H. salicornicum shoot identified 56 metabolites, of which 47 metabolites were significantly changed in response to salinity. These metabolites were mainly included in the category of amino acids, organic acids, amines, sugar alcohols, sugars, fatty acids, alkaloids, and phytohormones. In response to salinity, most of the amino acids were down-regulated except alanine, phenylalanine, lysine, and tyramine, which were up-regulated in H. salicornicum. In contrast to amino acids, most sugars and organic acids were up-regulated in response to salinity. Correlation and pathway enrichment analysis identified important biological pathways playing significant roles in conferring salt tolerance of H. salicornicum. These biological pathways include amino sugar and nucleotide sugar metabolism, citrate cycle (TCA cycle), starch and sucrose metabolism, phenylalanine metabolism, cysteine, methionine, glycine, serine, and threonine metabolism, etc. The data presented here suggest that the modulations of various metabolic pathways facilitate H. salicornicum to survive and grow optimally even under high salinity condition. This study offers comprehensive information on metabolic adaptations and overall salt tolerance mechanisms in H. salicornicum. The information gained through this study will provide guidance to plant breeders and molecular biologists to develop salinity tolerant crop varieties.

Mowing can facilitate the incorporation of cover crop shoots into soil and improve the properties of soils in apple orchards. This article evaluated how apple orchard soil responds to the decomposition of the shoot residues of three cover crops[native mixed herbs (NMS), red clover (RCS), and ryegrass (RES)] in terms of microbial metabolism and biomass, and discussed the relationships between microbial responses and shoot chemistry. The chemical composition of shoots was analysed and a buried bag experiment was carried out to simulate shoot decomposition in an apple orchard. The results revealed significant differences in the chemical compositions and shoot C:N ratios (NMS: 10.9, RCS: 19.1, and RES: 12.9) of the three cover crops. The decomposition of the cover crop shoots promoted microbial metabolism and boosted soil bacterial reproduction (increase in the biomass indicator muramic acid: 19.44, 124.15, and 14.83 mg kg−1, respectively. But there are different types of effects on soil fungal reproduction (change in the biomass indicator glucosamine: 712.51, 887.45, and 103.97 mg kg−1), and they are obviously negative, significantly positive, and non-significant respectively. Thus, the native mixed herbs and red clover are preferable swards for better shoot enhancement in apple orchard. Keywords: Cover crop, Soil management, py-GC/MS, Amino sugar, Soil microbial CLPP

In Tunisia, the coastal Chenini oasis is characterized by a lush vegetation cover, whereas more inland continental oases (e.g., the Guettaya oasis) have a very scarce vegetation cover. For sustaining date palm production in these areas, organic fertilizers are applied, either spread on the soil surface (in Chenini) or buried under a sand layer (in Guettaya). We examined at a molecular level how these management techniques affect soil organic matter composition in oasis systems. A dominance of fresh plant input for Guettaya was indicated by solid-state 13C nuclear magnetic resonance spectroscopy signals, which was most pronounced in the uppermost soil close to palms. Evidence for more degraded organic matter was found in deeper soil near the palms, as well as in the soil distant from the palms. Amino sugar contents were low in the uppermost Guettaya soil near the palms. The overall microbial amino sugar residue contents were similar in range as those found in other dryland environments. With increasing distance from trees, the amino sugar contents declined in Guettaya, where the palms grow on bare soil, but this was not the case for Chenini, which has multi-layer vegetation cover under palms. In agreement with the results from previous dryland studies, the soil microbial community in both oasis systems was dominated by fungi in topsoil, and a shift toward bacteria-derived residues in subsurface soil. This might be due to higher variability of temperature and moisture in topsoil and/or lower degradability of fungal remains; however, further research is required to confirm this hypothesis.

The contribution of microbial residues to soil organic carbon (SOC) is a process highly influenced by soil properties. We evaluated the presence of microbial amino sugar residues in soil (0–50 cm) of control and warmed plots in an alpine meadow on the Qinghai-Tibet Plateau. Alpine grasslands in the Qinghai-Tibet Plateau store large amounts of soil C and are highly vulnerable to climate change. Results showed that warming significantly increased total microbial residues across the 0–50 cm soil depth. The proportion of microbial-derived C to SOC significantly increased in warmed plots (52% on average) by soil depth compared to the control (38%). Higher microbial turnover and selective preservation into organo-mineral complexes likely explains the observed result. Given insignificant change in total SOC, our results infer an alteration of the SOC source configuration (microbial-derived vs. plant-derived). The observed greater magnitude of warming effects on fungal residues compared to bacterial illustrate a distinct community response to warming. We conclude that warming has the potential to influence soil C sequestration through increased microbial residue inputs, consequently altering its composition and source configuration. Our work provides valuable insights at the molecular level to identify mechanisms of microbial-mediated C processes that are influenced by climate change in high elevation ecosystems.

Understanding the processes controlling amino sugar accumulation in soil is essential for predicting the contribution of microbial residues to soil organic matter (SOM). The accumulation of amino sugars in soil is affected by multiple factors. Seldom are those factors examined together. We measured amino sugar concentration, extracellular enzyme activity, microbial respiration rate, and soil aggregate composition in an agricultural soil under 33-years of conservation management. The accumulation patterns of different amino sugars under the effects of no-tillage farming and cover cropping were compared and contrasted. The relative importance of physical, biochemical, and microbial controls of amino sugar accumulation was quantified using structural equation modelling. Our results show that although different types of amino sugars exhibited similar accumulation patterns in soil, their stabilization mechanisms might vary as demonstrated by structural equation models. The structural equation models indicate that macroaggregates had the largest total effect (0.59, P

Organic fertilizers increase soil organic matter (SOM) stocks, but the underlying processes depend on the fertilizer type and remain largely unknown. To evaluate the predominant C stabilization mechanisms, upland Ultisols subjected to 27 years of mineral and organic fertilization were analyzed for SOM content, aggregate size classes, and amino sugar composition. The long-term field experiment had seven treatments: no fertilization (Control), mineral NPK fertilizers (NPK), NPK plus lime (NPK + Lime), NPK plus peanut straw (NPK + PeanutStraw), NPK plus rice straw (NPK + RiceStraw), NPK plus radish residue (NPK + RadishResidue), and NPK plus pig manure (NPK + PigManure). The 27-year application of mineral fertilizers (NPK and NPK + Lime), NPK + crop residues, and NPK + PigManure increased SOM content by 11.0–13.2%, 16.3–25.3%, and 44.3%, respectively, compared with the Control. The aliphaticity and recalcitrance indices based on 13C nuclear magnetic resonance spectra of organic fertilizers were higher for pig manure than for crop residues. Both indices were closely correlated with SOM content after 27 years, so higher proportions of recalcitrant C in manure facilitated SOM accumulation. NPK + PigManure increased the mass proportion of large macroaggregates 2.9-fold compared with the Control, and reduced the effective diffusion coefficient of oxygen in the soil. Consequently, NPK + PigManure limited the activity and abundance of aerobes and the accessibility of SOM to microorganisms, in turn facilitating SOM accumulation. The application of mineral fertilizers, NPK + crop residues, and NPK + PigManure increased microbial necromass to 2.85–3.03, 3.21–3.45, and 3.62 g C kg−1, respectively, from 2.63 g C kg−1 in the Control. Compared with crop residues, pig manure did not affect bacterial necromass but increased fungal necromass from 2.19 to 2.39 g C kg−1 to 2.58 g C kg−1, which might associate with increased SOM stability. However, the relative contribution of microbial necromass to SOM was lower under NPK + PigManure than under NPK + crop residues, since more added C was protected in the NPK + PigManure soil. Our results suggest that manure may contribute to SOM accumulation and stabilization in three ways: directly through the input of recalcitrant organic C, indirectly through the stabilization of aggregates and physical protection of C, and to a lesser extent through increasing fungal necromass.

O-polysaccharide (O-antigen) was isolated from the lipopolysaccharide of Vibrio cholerae O100 and studied by component analyses and 1D and 2D NMR spectroscopy. The following structure of the O-polysaccharide was established: →3)-β- d -QuipNAc4N(dHh)-(1 → 3)-α- d -Fucp4N(RHb)-(1 → 3)-α- l -FucpNAc-(1→ where Hb and dHh indicate 3-hydroxybutanoyl and 3,5-dihydroxyhexanoyl, respectively. The O-antigen gene cluster of V. cholerae O100 has been sequenced. The gene functions were tentatively assigned by comparison with sequences in the available databases and found to be in agreement with the OPS structure.

Global warming may have a great impact on soil organic carbon (SOC) turnover in permafrost peatlands. The response of microbial residues, as precursors of SOC, to climate warming remains unknown. A 6-year in situ warming experiment was conducted in the permafrost peatlands of Great Hing'an Mountains. Three commonly used amino sugars (glucosamine, GluN; galactosamine, GalN; muramic acid, MurA), for the quantification of microbial residues, were determined in two depths (0–15 cm, shallow soil; 15–30 cm, deep soil) of the bulk and rhizosphere soil of the shrub and Eriophorum vaginatum L. The amount of GluN, GalN, and MurA in deep shrub rhizosphere soil in the warming treatment decreased by 12.65%, 26.11%, and 14.78%, respectively, as compared to that in the control treatment. Yet, warming did not alter the amount of amino sugars in shallow and deep bulk soil. Warming decreased the concentrations of GluN, MurA, and total amino sugars in the deep rhizosphere soil of Eriophorum vaginatum L. by 22.04%, 26.14%, and 18.71%, respectively. Amino sugars in the deep rhizosphere soil of Eriophorum vaginatum L. had a higher temperature sensitivity than those in the deep bulk soil, while total amino sugars in the shallow rhizosphere soil of Eriophorum vaginatum L. had a lower temperature sensitivity than those in the deep rhizosphere soil.

The industrial and agricultural applications of rare earth elements (REEs) lead to considerable REE emissions into environment. Yet, little is known about the molecular-level effects and interactions of REEs in terrestrial plants. Herein, the individual and joint effects of La and Ce in Triticum aestivum were investigated using mass spectrometry-based metabolomics. Metabolic effect level index (MELI) was utilized as a readable endpoint for quantifying mixture interactions. Exposure to single La/Ce at environmentally relevant levels induced significant dose-dependent metabolic changes. The highly overlap of differential metabolites and perturbed pathways of La and Ce suggested their similar mode of action. Exposure to La-Ce mixtures did not induce additional metabolic pathway perturbation. Specifically, metabolism of amino sugar and nucleotide sugar, starch and sucrose, fructose and mannose, glycerophospholipid and purine were disrupted for both single and binary exposures. These results, together with physiological indicators, point to REE-induced oxidative stress, energy expenditure, DNA damage and membrane disturbance. The MELI calculations showed that La and Ce interacted synergistically at the overall metabolic level, which could be causally linked to synergistic interaction at the individual level (root elongation). This work proved metabolomics could be an important and effective strategy for interpreting toxicity and interactions of REE mixtures.

Heterotrophic soil microbes are increasingly recognized as a key mediator transforming labile organic carbon (OC) into relatively stable soil carbon (C) in the form of microbial necromass (dead cells) and extracellular compounds associated with minerals. However, the accumulation of microbial necromass relative to labile OC consumption and its regulating factors remain poorly understood, although it has vital implications for soil C sequestration and modeling. Here by mimicking microbial C accumulation in constructed model soils using fructose as the sole OC substrate, we present a benchmark comparison of microbial C accrual versus OC mineralization under declining substrate availability and mineralogy. By quantifying various microbial components including biomass (living cells; indicated by phospholipid fatty acids), necromass (indicated by amino sugars) and total microbial C (including biomass, necromass and extracellular compounds; estimated as the difference between added and residual substrate C minus respiration) in a simple soil system, we compare microbial metabolic quotient (qCO2; i.e., microbial respiration rate per unit of biomass), amino sugar accumulation efficiency (AAE; i.e., ratio of amino sugars to respiration) and microbial C accumulation efficiency (mCAE; i.e., ratio of total microbial C to total microbial C and respiration), and assess their regulating factors. We find that while clay (bentonite) promotes microbial respiration, it enhances the rate as well as efficiency of amino sugar accumulation without affecting qCO2 or mCAE. On the contrary, ferrihydrite increases qCO2 and decreases AAE but promotes labile OC preservation via inhibiting microbial growth in the alkaline model soil. Hence, amino sugar accrual is more efficient in clay-rich model soils while labile OC is less consumed in model soils containing iron (hydr)oxide. Furthermore, while mCAE was correlated with qCO2 in all but the model soil with 6% clay, AAE was correlated with qCO2 only in model soils with 12% clay when the mineral treatments were considered separately. Collectively, our findings suggest that mCAE and AAE heavily depend on mechanisms preserving microbial C components but not solely on the metabolic efficiency and is mediated by soil mineral content as well as composition. Parameters considering microbial C preservation such as mCAE or AAE warrant further study for modelling and managing the formation of microbial derived stable soil OC.

Understanding the response of microbial-derived nitrogen (N) in the soil to N availability is essential for optimizing N fertilizer management. In this study, based on amino sugar biomarker assays in a conservation tillage agroecosystem, we evaluated the effects of 3-year fertilizer N reduction (reduced from 240 to 190, 135, 0 kg N ha−1) and crop residue return on microbial necromass N dynamics. The stock of microbial necromass N declined with the decrease of N input, and the decline of bacterial necromass was greater than that of fungal necromass. However, the decrease of 7.3% in microbial necromass N following the cessation of fertilization indicated a dominant role of microbial necromass in soil N retention despite its compensation ability for N demand. Maize residue return alleviated N deficiency in the soil-crop system and favored the maintenance of the soil organic N pool by preferentially improving the net accumulation of fungal necromass.

Soil organic carbon (SOC) has significant implications in regulating soil health. Emerging insights emphasize the important role of microbial anabolism in SOC storage by continuously transforming plant fragments into persistent microbial residues. However, knowledge of the sequestration pathway of root versus shoot carbon (C) is under debate. While recent studies have shown that labile shoot residue is disproportionately important for stable SOC accumulation through microbial assimilation, how plant root vs. shoot residue retention impacts microbial-derived C under different soil fertility conditions remains elusive. Here, we conducted a 500-d in situ experiment using Alfisols with low fertility (LF) and high fertility (HF) amended with maize root or shoot (both stem and leaf) residues. The microbial residues (amino sugar biomarkers) and microbial communities (lipid biomarkers) were analyzed at 60, 90, 150, and 500 d after the amended materials were added. The results showed that shoot residue input facilitated microbial residue accumulation more efficiently than root input before 150 d. However, at the end of the experiment, the treatment containing added root residue accumulated more microbial residues and produced a higher proportion of microbial residue in SOC, compared with shoot treatment. These results provide novel evidence that root residue can also yield SOC efficiently through the organic substrate–microbial anabolism pathway, but it depends on the decomposition period. Moreover, soil fertility plays an important role in regulating the quantity and relative composition of microbial residues. Specifically, crop residue application greatly increased the contribution of microbial residue C to SOC in the LF treatment compared to that in the HF treatment on day 500. Meanwhile, crop residue addition had a more positive effect on fungal residue accumulation in the LF soil, while it facilitated the accumulation of bacterial residue in the HF soil. These findings highlight that crop residue addition (especially root residue) is an effective approach for improving microbial-derived C sequestration in infertile soils.

Understanding the temporal changes of soil organic C (SOC) pools and microbial residues is essential for clarifying SOC dynamics in agroecosystems; however, this information remains largely unclear in greenhouse vegetable production (GVP) systems. Here, based on information of SOC pools (i.e., oxidizable organic C pools) and microbial residue C (MRC, as indicated by amino sugars differentiation), a 10-year (2009–2019) field experiment with fertilization was conducted to evaluate how fertilization alters SOC dynamics in a GVP field in Tianjin, China. The experiment includes four treatments (equal N, P2O5, and K2O inputs): 100% chemical N (N100), 50% substitution of chemical N with manure-N (N50M50), straw-N (N50S50), and manure-N plus straw-N (N50M25S25). Results showed that the values of SOC, lability index, and C management index increased and decreased linearly with time in N50M50- and N100-amended soils, respectively, which were mainly induced by the changes in labile C fractions. Based on logistic regression models, we found that these indices in straw-amended soils (N50M25S25 and N50S50) were rapidly increased between 2009 and 2013, and then approach steady levels between 2015 and 2019. These findings suggested that we should guarantee enough C inputs to maintain the level and quality of SOC, otherwise it will cause C loss in the unique GVP soils. Besides, straw-amended treatments increased MRC contents and enlarged their contributions to SOC sequestration, whereas these indices in N100 treatment decreased linearly with the time of fertilization. In conclusion, long-term chemical application alone was not beneficial for SOC accumulation, whereas organic amendments brought several benefits for SOC sequestration in GVP soils. Our results implied that C sequestration in GVP soils is to a large extent determined by the amounts and time of fertilization.

Mineral nutrient inputs to soil may alter microbial activity and consequently influence the accumulation of microbial residues. In this study, we investigated the effects of application rates and ratios of mineral fertilizers on the microbial residue carbon (MRC) of reddish paddy soils after long-term (15-year) fertilizer applications in southern China. Contents of three soil amino sugars as microbial residue contents were determined and MRC were calculated based on amino sugars. Results showed that three individual amino sugar contents increased as fertilizer application rates increased until maximum values were reached at a rate of 450-59-187 kg ha−1 year−1 (N-P-K). The three amino sugar contents then declined significantly under the highest mineral fertilizer application rate of 675-88-280 kg ha−1 year−1 (N-P-K). In addition, to enhance the microbial residue contents, it was more beneficial to double P (N:P:K = 1:0.26:0.41) in fertilizers applied to the P-deficient reddish paddy soils than to double either N (N:P:K = 2:0.13:0.41) or K (N:P:K = 1:0.13:0.82). The contents of the three individual amino sugars and microbial residues under different fertilizer application rates and ratios were significantly and positively correlated with soil organic carbon (SOC), total N, total P, and pH. Increases in values of the fungal C to bacterial C ratios showed that soil organic matter (SOM) stability increased because of the fertilizer applications over the past 15 years. The contents and ratios of amino sugars can be used as indicators to evaluate the impact of mineral fertilizer applications on SOM dynamics in subtropical paddy soils. The results indicated that fertilizer applications at a rate of 450-59-187 kg ha−1 year−1 (N-P-K) may improve crop yields, SOC contents, and SOC stability in subtropical paddy soils.

In this study, C6-HSL and C8-HSL were separately introduced into anammox biofilm reactors to facilitate the anammox performance at 15 ℃. After operation 138 d, total nitrogen removal efficiencies in reactors with amendment C6-HSL or C8-HSL at 15 ℃ reached 76.2% and 74.6%, respectively. Content of extracellular polymeric substances increased by 19.8%, 67.7% and 121.2% in control group, C6-HSL and C8-HSL addition group, respectively. Genes associated with nitrogen removal (i.e., hzo, hzsB, nirS, and ccsB) showed higher expression level at amendment C6-HSL or C8-HSL group. Metagenomics analysis found that amendment of C6-HSL or C8-HL resulted in an increased abundance of genes related to the tricarboxylic acid cycle, amino sugar and nucleotide sugar metabolism, and also genes associated with amino acid biosynthesis pathways. Overall, amendment C6-HSL or C8-HSL had been confirmed as the effective method to improve the performance of anammox bioreactor at 15 ℃.

Organic Aerosols (OAs) are typically defined as highly complex matrices whose composition changes in time and space. Focusing on time vector, this work uses two-dimensional nuclear magnetic resonance (2D NMR) techniques to examine the structural features of water-soluble (WSOM) and alkaline-soluble organic matter (ASOM) sequentially extracted from fine atmospheric aerosols collected in an urban setting during cold and warm seasons. This study reveals molecular signatures not previously decoded in NMR-related studies of OAs as meaningful source markers. Although the ASOM is less hydrophilic and structurally diverse than its WSOM counterpart, both fractions feature a core with heteroatom-rich branched aliphatics from both primary (natural and anthropogenic) and secondary origin, aromatic secondary organics originated from anthropogenic aromatic precursors, as well as primary saccharides and amino sugar derivatives from biogenic emissions. These common structures represent those 2D NMR spectral signatures that are present in both seasons and can thus be seen as an “annual background” profile of the structural composition of OAs at the urban location. Lignin-derived structures, nitroaromatics, disaccharides, and anhydrosaccharides signatures were also identified in the WSOM samples only from periods identified as smoke impacted, which reflects the influence of biomass-burning sources. The NMR dataset on the H–C molecules backbone was also used to propose a semi-quantitative structural model of urban WSOM, which will aid efforts for more realistic studies relating the chemical properties of OAs with their atmospheric behavior.

There are five known general catalytic mechanisms used by enzymes to catalyze carbohydrate epimerization. The amino sugar epimerase N-acetylmannosamine-6-phosphate 2-epimerase (NanE) has been proposed to use a deprotonation–reprotonation mechanism, with an essential catalytic lysine required for both steps. However, the structural determinants of this mechanism are not clearly established. We characterized NanE from Staphylococcus aureus using a new coupled assay to monitor NanE catalysis in real time and found that it has kinetic constants comparable with other species. The crystal structure of NanE from Staphylococcus aureus, which comprises a triosephosphate isomerase barrel fold with an unusual dimeric architecture, was solved with both natural and modified substrates. Using these substrate-bound structures, we identified the following active-site residues lining the cleft at the C-terminal end of the β-strands: Gln11, Arg40, Lys63, Asp124, Glu180, and Arg208, which were individually substituted and assessed in relation to the mechanism. From this, we re-evaluated the central role of Glu180 in this mechanism alongside the catalytic lysine. We observed that the substrate is bound in a conformation that ideally positions the C5 hydroxyl group to be activated by Glu180 and donate a proton to the C2 carbon. Taken together, we propose that NanE uses a novel substrate-assisted proton displacement mechanism to invert the C2 stereocenter of N-acetylmannosamine-6-phosphate. Our data and mechanistic interpretation may be useful in the development of inhibitors of this enzyme or in enzyme engineering to produce biocatalysts capable of changing the stereochemistry of molecules that are not amenable to synthetic methods.

Soil nitrogen (N) cycling can be affected by no-tillage and crop residue application. However, it remains unclear how crop residue application rates affect soil organic N (SON) fractions, N-hydrolyzing enzymes and their relationships. A field experiment was conducted in northeastern China to investigate the effects of no-tillage (NT) and residue application at either 0 (NTR0%), 33 (NTR33%), 67 (NTR67%) or 100% (NTR100%) on SON fractions, soil N-hydrolyzing enzyme activities, and their relationships at depths of 0−10 and 10−20 cm. The results showed that in the 0−10 cm soil layer, compared with the NTR0% treatment, concentrations of hydrolysable NH4+-N, amino sugar-N and active-SON and N-acetyl-β- d -glucosaminidase (NAG) activity were significantly increased in the NTR33% treatment. Amidase showed a significantly higher activity under the NTR100% treatment. Urease activity was significantly increased in residue application treatments. In the 10−20 cm soil layer, compared to the NTR0% treatment, the NTR33% treatment showed a significantly higher concentration of active-SON. Concentrations of hydrolysable unknown-N and stable-SON were significantly increased in both NTR67% and NTR100% treatments. NTR33% and NTR67% treatments significantly increased protease and amidase activities, respectively, and urease showed a significantly higher activity under the two treatments. The results of redundancy analysis indicated a relationship of SON fractions with soil microbial biomass carbon and pH in the 0−10 cm soil layer, and with protease and NAG activities in the 10−20 cm soil layer. These results suggested that crop residue application at a low rate (33 %) had a greater potential for enhancing active SON supplies, whereas moderate and high rates (67 % and 100 %) of crop residue application were more effective in maintaining a stable SON pool in the Phaeozem area of northeastern China.

Microbial residues may make a more significant contribution to soil organic carbon (SOC) than traditionally believed. However, little is known about the accumulation characteristics of fungal and bacterial residues and their contribution to SOC in salt-affected soils. We investigated changes in fungal and bacterial residues using amino sugar biomarkers along a salinity gradient in coastal salt-affected soils. As salinity increased, the content of fungal residue decreased from 337.6 to 111.6 mg kg−1, while the bacterial counterpart increased from 62.5 to 142.4 mg kg−1. The contribution of microbial residues to SOC was salinity-dependent. There was an increase for microbial residue contribution to SOC and a shift from fungal to bacterial residue dominated contribution to SOC with increasing salinity. Hence, salinization had a significant impact on microbial-mediated SOC accumulation.

Hass avocado postharvest ripening heterogeneity creates several logistics problems at destination markets. Although several approaches mainly based on targeted analysis have been undertaken to broaden our understanding of the potential causes of this postharvest ripening heterogeneity, still the secret is not yet unveiled. In this study biopsies from individual fruit displaying contrasting ripening behavior (slow vs fast) and subjected to different storage conditions (immediately after harvest, 30 d regular air at 5 °C and 30 d at 5 °C and 4 kPa O 2 and 6 kPa CO 2 ) were analyzed for targeted fatty acid analysis and cell wall enzyme activity combined with a more integrative approach based on gel free proteomics LC–MS/MS. The high throughput proteomics was capable of discriminating between slow and fast ripening avocado fruit. Proteins that were mainly less abundant in the slow ripening phenotype were annotated to correct protein folding, translation and de novo synthesis and higher abundant proteins were annotated to amino sugar and nucleotide metabolism, detoxification and stress response and proteolysis. Our study opens new insights into the causes of heterogeneous ripening and may provide new markers for avocado ripening at harvest and after prolonged storage.

Microbial residues are a significant component of soil organic carbon (C), yet their distribution and function remain understudied. We evaluated changes in microbial residues and their contribution to organic C along a soil development sequence on three contrasting parent materials (granite, basalt and andesite) and three conifer biomes (ponderosa pine (Pinus ponderosa Laws.), PP; white fir (Abies concolor Lindl.), WF; and red fir (Abies magnifica A. Murr.), RF) at different elevations in the Sierra Nevada of California. Soil samples were taken from both A and B horizons and microbial residues were determined by amino sugar analysis. The effect of conifer biome on amino sugars was complex and dependent on parent material and horizon. We found parent material significantly influenced soil amino sugars which exhibited a pattern of andesite > basalt > granite in both A and B horizons. Both correlation and redundancy analyses indicated a significant correlation of amino sugars with the amount of short-range-order materials. This suggests soil mineralogy plays an important role in influencing amino sugar accumulation. This is further supported by larger differences among parent materials than between conifer biomes in ratios of fungal-to bacterial-derived amino sugars. The proportion of amino sugars to soil organic C was significantly influenced by parent material in the B horizon following the pattern of basalt > andesite > granite, but not affected by conifer biome. Our results suggest that mineralogy strongly influences the degree to which soil microbial residues persist in temperate forest soils.

Theory and experiments suggest that rhizodeposition can accelerate N-cycling by stimulating microbial decomposition of soil organic matter (SOM). However, there are remarkably few experimental demonstrations on the degree to which variations in root exudation alter rhizosphere N dynamics in the field. We conducted a series of in situ substrate addition experiments and a modeling exercise to investigate how exudate mimics and enzyme solutions (at varying concentrations) influence rhizosphere SOM and N dynamics in a loblolly pine ( Pinus taeda ) plantation (Duke Forest). Exudates were added semi-continuously to unfertilized and fertilized soils in summer and fall; enzymes were added during the following summer. Exudate additions enhanced the microbial biomass specific activities of enzymes that degrade fast-cycling N pools (i.e., amino acids and amino sugars), and increased microbial allocation to N-degrading compounds. More, such effects occurred at low exudate concentrations in unfertilized soil and at higher concentrations in fertilized soil. Direct additions of a subset of enzymes (amino sugar- and cellulose-degrading) to soils increased net N mineralization rates, but additions of enzymes that cleave slow-cycling SOM did not. We conclude that exudates can stimulate microbes to decompose labile SOM and release N without concomitant changes in microbial biomass, yet the investment of plants to trigger this effect may be greater in N-rich soils.

Subsoils of alpine grasslands on the Qinghai-Tibetan Plateau represent a tremendous yet poorly investigated reservoir of soil organic carbon (SOC) on a global “hotspot” of warming. Compared with the temperature sensitivity of SOC decomposition, microbial anabolism of new carbon and priming of native SOC remain poorly constrained under warming-enhanced labile carbon input in these subsoils. Here we employed an innovative approach to investigate the sequestration of freshly added carbon in microbial necromass versus SOC priming in the top- (0–10 cm) and subsoils (30–40 cm) from a field experiment that simulated varied warming scenarios in an alpine grassland on the Qinghai-Tibetan Plateau. The 13C composition of microbial necromass-derived amino sugars was analyzed in tandem with respired CO2 and dissolved SOC components (including dissolved lignin) in an 86-day laboratory incubation with 13C-labeled glucose. A higher fraction of freshly added carbon was respired while a smaller proportion was stabilized as amino sugars in the subsoil relative to the topsoil, leading to a much lower microbial carbon accumulation efficiency at depth. Meanwhile, a higher relative priming effect was observed in the subsoil (47± 14%) compared to the topsoil (14± 4%), suggesting a higher vulnerability to substrate-induced SOC loss at depth, although such changes may be associated with higher glucose addition rate (relative to SOC) in the subsoil. Furthermore, enhanced winter warming significantly reduced degradable SOC (assessed by SOC mineralization and dissolved lignin content) in the subsoil and potentially intensified nitrogen limitation under labile carbon additions, which further decreased microbial carbon accumulation (in the form of amino sugars) in the subsoil without affecting the topsoil. These results collectively indicate a limited microbial carbon sequestration potential and a higher vulnerability to warming-induced substrate changes in the subsoil of this alpine grassland, which warrants better understanding to predict soil carbon responses to climate warming on the Qinghai-Tibetan Plateau.

There has been an increasing interest in studying microbial necromasses and their contribution to soil organic carbon (SOC) accumulation. However, it remains unclear how the interaction among climate, plants, and soil influence the microbial anabolism and how microbial necromass contribute to SOC formation. Here, we assessed the relative contribution of microbial residues to SOC pool across a subtropical elevation gradient (ranged from 630 to 2130 m a.s.l.) representing a subtropical ecosystem on Wuyi Mountain in China, by using amino sugars as tracers. Analysis of topsoil (0–10 cm) amino sugars and the composition of microbial community across this gradient revealed that the soil total amino sugars accounting for 12.2–25.7% of the SOC pool, decreased with increasing elevation. Moreover, the linear reduction in the bacterial-derived carbon (C) and an increase in the ratio of fungal- to bacterial-derived C with increasing elevation suggested the reduction in the contribution of bacterial-derived C to SOC pool across this elevation gradient. The divergent changes in the contribution of the microbial residues to SOC infer a potential change in SOC composition and stability. The microbial-derived SOC formation and its climatic responses are influenced by the interaction of vegetation types and soil properties, with soil amorphous Fe being the determiner of soil amino sugar accrual. Our work highlights the importance of understanding ecosystem type and mineral composition in regulating microbial-mediated SOC formation and accumulation in responses to climate change in subtropical ecosystems.

Understanding long-term microbial immobilization of nitrogen (N) fertilizer is essential for N management in agricultural soils. Evaluating the transformation and accumulation of N fertilizer into microbial residues is critical for developing such an understanding due to the requirement of time-integrated biomarkers and a 15N-labeling technique. By tracing the dynamics of amino sugars derived from annually applied fertilizer over 8 years, we investigated the influence of continuous maize residue mulching on the temporal immobilization of fertilizer N in an agricultural soil and quantified the turnover of microbial residues in situ. We found that the amino sugar transformation rate from fertilizer N was constant over time in both fertilization-only and maize residue mulching managements, but it was significantly higher in the upper cultivation layer (0–10 cm) after maize residue mulching. Mulching with maize residue facilitated initial fertilizer N transformation, while the subsequent 7-year application maintained the increased transformation rate. Consequently, the accumulation of fertilizer-derived amino sugars increased linearly in both managements within the 8 years of our field experiment. The mean residence time (MRT) of soil amino sugar-N was estimated by using extrapolation and first-order kinetics approaches, respectively. The calculated MRT of amino sugar-N using first-order kinetics (78 and 154 years at 0–10 and 10–20 cm, respectively) was slightly shorter than that estimated by the extrapolation (89 and 165 years at 0–10 and 10–20 cm, respectively) in the fertilization-only management. Mulching with maize residue did not change the MRT of amino sugar-N because maize residue addition enhanced the immobilization of maize residue-derived N or the transformation of indigenous soil N in addition to those of fertilizer N, leading to the same proportion of new N assimilated in microbial residues.

Soil carbon (C) dynamics are closely mediated by microorganisms and microbial residues could constitute a significant pool of soil organic C (SOC). However, little is known about the nitrogen (N) deposition effect on the contribution of microbial residues to SOC balance in tropical forest ecosystems. Here, we assessed microbial residues using amino sugar biomarkers in surface soils of a tropical forest ecosystem under 11-year continuous N addition at different rates (0, 50, 100 and 150 kg N ha−1 yr−1). Nitrogen addition didn't affect either fungal or bacterial residues in soil apparently, but high-N addition (150 kg N ha−1 yr−1) significantly decreased the contribution of fungal residues to SOC indicated by both ratios of fungal/bacterial amino sugars and fungal residues/SOC. Consequently, high-N addition whittled down microbial contribution to SOC pools. Those findings may have implications for our predictions of global change impacts on soil C dynamics.

Rhizosphere microbial communities play an essential role in determining plant productivity, particularly in agriculturally marginal environments. Perennial plants like switchgrass (Panicum virgatum) are thought to particularly influence microbial community composition and function within their rhizosphere. We compared microbial communities in switchgrass rhizospheres and their associated bulk soils in two regions of the U.S. upper Midwest (Michigan and Wisconsin) with contrasting soil types, and at two site types with differing switchgrass establishment ages and management intensities. We characterized microbial communities with a range of culture-independent methods, including amplicon sequencing of 16S/18S rRNA and nifH genes, and membrane lipid profiling. In addition, we quantified abundances of soil amino sugars, a time-integrative indicator of microbial necromass. We found that amino sugar contents and microbial lipid profiles differed between rhizosphere and bulk soils, while DNA-based assays did not provide this discriminatory power. Differences between rhizosphere and bulk soils were not significantly affected by region or site type. Rhizosphere soils had higher microbial lipid abundances, particularly those associated with arbuscular mycorrhizal fungi and Gram-negative bacteria, while amino sugar abundances decreased in the rhizosphere. Our findings suggest switchgrass rhizospheres systematically stimulate microbial growth and microbial residue turnover.

Amino sugars are useful indicators for the accumulation of microbial residues. A 14-day incubation experiment with C4 and C3 sucrose additions was carried out to investigate the relationships between amino sugar-specific shifts in δ13C values and those of CO2 production, microbial biomass C, K2SO4 extractable C and soil organic C (SOC). High performance anion exchange chromatography (HPAEC-IRMS) was able to measure amino-sugar specific δ13C values for muramic acid (MurN), galactosamine (GalN), and glucosamine (GlcN) in the range of natural abundance. At day 7, the initial application of C4 sucrose significantly increased the δ13C value of MurN by 1.0‰ in comparison with the non-amended control treatment, whereas that of GalN and GlcN remained unchanged. This significant increase had disappeared by day 14. This means that the HPAEC-IRMS method is not useful for short-term incubation experiments in the natural abundance range, as the pool size, especially of GalN and GlcN, was too large for a significant response in δ13C values. The δ13C values significantly decreased in the order MurN (−23.2‰) > GalN (−25.7‰) > GlcN (−26.5‰) in the control treatment. Similar δ13C values were measured in GlcN, microbial biomass C, and SOC. MurN exhibited δ13C values similar to the K2SO4 extractable fraction. These results may be caused by differences in the access of bacteria and fungi to different SOC fractions or differences in metabolic fractionation in bacteria and fungi. C3 sucrose application without further nutrient supply seven days after C4 sucrose application together with N and P led to strong mineralization of freshly formed microbial residues.

The majority of oligosaccharides used as prebiotics typically consist of a combination of 3 kinds of neutral monosaccharides, d-glucose, d-galactose, and d-fructose. In this context, we aimed to generate new types of prebiotic oligosaccharides containing other monosaccharides, and to date have synthesized various oligosaccharides containing an amino sugar, uronic acid, and their derivatives. In this study, we investigated the effects of 4 kinds of sucrose (Suc) analog disaccharides containing d-glucosamine, N-acetyl-d-glucosamine, d-glucuronic acid, or d-glucuronamide as constituent monosaccharides, on the growth of 8 species of bifidobacteria and 3 species of lactobacilli isolated from the human intestine. The results of these experiments were compared with those obtained from identical experiments using Suc. We confirmed that all bacterial strains could utilize Suc as a nutrient source for growth; in contrast, only specific species of bifidobacteria showed growth with Suc analog disaccharides. When oligosaccharides are utilized as a nutrient source by bacteria, they are often broken down into monosaccharides or their derivatives by cellular enzymes before entering the intracellular glycolytic pathway. Therefore, to clarify the above phenomenon involved in the growth of bifidobacteria using Suc analog disaccharides, we investigated the cellular glycosidases of 3 strains of bifidobacteria shown to be capable or incapable of growth in the presence of these disaccharides. As the result, it was confirmed that the strains capable of growth using Suc analog disaccharides show greater productivity of glycosidases that degrade these disaccharides than strains not capable of growth; however, we have not identified the enzymes here.

The dynamics of microbial necromass of municipal solid waste over long-term landfill remain unknown. This study presents the first investigation on the dynamics of bacterial and fungal necromass of municipal sludge in non-aeration versus alternating aeration landfill bioreactors by using amino sugar biomarkers. Results showed that under non-aeration treatment, the decomposition rate of muramic acid derived from bacteria is higher than that of fungal-derived glucosamine. The relative change in glucosamine and muramic acid in the early period of landfills under the alternating aeration treatment is consistent with that under non-aeration treatment. However, with the increase in alternating aeration cycles, bacterial necromass muramic acid exerts a lower decomposition rate than fungal necromass glucosamine. Throughout the entire landfill period, galactosamine is the amino sugar with the slowest decomposition rate under non-aeration mode but the amino sugar with the fastest decomposition rate under alternating aeration mode. The present work fills the knowledge gap of microbial necromass dynamics of municipal solid waste in landfills.

While it is recognized that the accumulation and turnover of soil organic carbon (SOC) is driven by plant inputs and their subsequent microbial-mediated transformations, the roles of plant residue chemistry and microbial processes in controlling SOC dynamics under different fertilizer application regimes have not been well explored. In the present study, amino sugars and lignin phenols were used as biomarkers to investigate the changes in microbial necromass and plant-derived components in a 30-year cultivated Mollisol (0–20 cm) in response to different fertilizer application treatments, including synthetic fertilizers (NPK, 165 kg N ha−1, 82.5 kg P2O5 ha−1, and 82.5 kg K2O ha−1 per year), pig manure at two application rates of 30 and 60 t ha−1 per year, and combinations of manure and synthetic fertilizers (30 or 60 t ha−1 manure per year plus 165 kg N ha−1, 82.5 kg P2O5 ha−1, and 82.5 kg K2O ha−1 per year). Compared with the unfertilized plot (Control), 30-year application of synthetic fertilizers increased microbial biomass (161%) and amino sugar production (19.7%), but did not alter lignin phenol and SOC concentrations despite the increased plant input. Comparatively, long term manure applications increased the concentration of SOC (30.8–70.9%), as well as that of amino sugars (82.9–107%) and lignin (96.8–212%) in soil. Nevertheless, despite the enhanced microbial biomass from low to high manure application rate, the proportion of amino sugars in the SOC decreased, reflecting a diluted contribution of microbial necromass in SOC pool buildup at high-rate manure application. On the contrary, the proportions of lignin phenols in the SOC in the manure treatments, as well as the ratios of lignin phenols and amino sugars (0.26–0.42), were larger than that in the NPK treatment (0.22) and increased with increasing manure application rate. Therefore, the manipulation of synthetic or organic fertilizer on SOC dynamics is associated with differential accumulation of microbial necromass and plant lignin in agro-ecosystems. The manure amendment enhanced the contribution of plant-derived components more than microbial necromass to long term SOC accumulation.

Plant residue incorporation improves soil microbial nitrate immobilization, which in turn alleviates nitrate accumulation, thereby improving N retention capacity and reducing N losses. However, how and why the respective nitrate immobilization by fungi and bacteria, which are dominant microorganisms in soil, responds to residue addition remains unknown. By adopting a novel amino sugar-based stable isotope probing approach, we show that both fungal and bacterial nitrate immobilization increased after Paspalum notatum residue addition. The increased proportion of the former was higher than that of the latter, and their difference became much larger with the increased residue addition rate. Furthermore, 70% and 32% of the variations in fungal and bacterial nitrate immobilization activities were explained by their respective biomass. The relative importance of fungal and bacterial nitrate immobilization shifted in a consistent manner with the relative abundance of fungi and bacteria, and the magnitude of these shifts was related to the residue addition rate. Our work demonstrates strong links between increased residue inputs, alterations in microbial community composition, and enhanced ecosystem functioning of nitrate immobilization and retention in soil.

There is insufficient evidence for how cover crop-driven changes to the soil microbial community affect soil organic carbon (SOC) accumulation. One mechanism by which enhanced microbial activity can contribute to SOC accrual is through the conversion of plant inputs to microbial biomass and ultimately necromass that may form organo–mineral associations with soil particles. Here we investigated the effects of winter rye as a cover crop and winter rye harvested as a forage double crop on SOC, chemically labile and complex C fractions, microbial necromass biomarkers (amino sugars), and potential extracellular enzyme activities following a seven–year continuous corn silage trial in southern Wisconsin, North Central US. Whereas SOC increased when winter rye was used as a cover crop compared to no cover, there were no changes to SOC when winter rye was harvested as a forage crop. A positive relationship between chemically labile aliphatic soil–C and total SOC indicates that higher SOC stocks may result from persistence of simple compounds rather than chemically complex, aromatic materials. However, the accumulation of microbial necromass, as inferred from amino sugar biomarker concentrations, was largely unaffected by winter rye use, despite a positive relationship between SOC and amino sugar residue concentrations. Greater potential extracellular enzyme activities indicates increased microbial activity with winter rye. Together, these results suggest that despite some microbial stimulation and potential soil health benefits, winter rye did not increase the contribution of microbial necromass to SOC accrual in this seven–year continuous corn silage field trial.

The conversion of organic nitrogen determines the quality of composting and its environmental impact, but its underlying microbial mechanism is unclear. Hence, in static composting reactors with forced ventilation, vegetable waste, straw and pig manure were used as raw materials to simulate the composting for 33 days with or without adding 9% biochar. In composting, amino acid and amino sugar nitrogen were most easily converted to ammonium and hydrolysable unknown nitrogen was synthesized from ammonium. The aprA and chiA-related bacteria converted amino acid nitrogen to ammonium, and ammonium to hydrolysable unknown nitrogen, while amoA and HAO-related bacteria converted amine and amino sugar nitrogen to ammonium. Additionally, soluble microbial byproduct-like materials (62.4%) significantly affect organic nitrogen transformation, and could reduce ammonia emission by increasing ammoxidation rates. Thus, whether or not adsorbent substances are added, microorganisms affect the production of ammonia by controlling the conversion of organic nitrogen.

A bacterium isolated from wastewater sludge, identified as Bacillus subtilis F9, was confirmed to produce bioflocculant with excellent flocculation activity. The effects of culture conditions such as initial pH, temperature, carbon source, nitrogen source, and inoculum size on bioflocculant production were studied here. The results indicated that 2.32g/L of purified bioflocculant could be extracted with the following optimized conditions: 20gL(-1) sucrose as the carbon source, 3.5gL(-1) peptone as the nitrogen source, an initial pH of 7.0, and a temperature of 40°C. The purified bioflocculant consisted of 10.1% protein and 88.3% sugar, including 38.4% neutral sugar, 2.86% uronic acid, and 2.1% amino sugar. The neutral sugar consisted of sucrose, glucose, lactose, galactose, and mannose at a molar ratio of 2.7:4.7:3.2:9.1:0.8. Elemental analysis of the purified bioflocculant revealed that the weight fractions of carbon, hydrogen, oxygen, nitrogen, and sulfur were 30.8%, 5.3%, 54.7%, 6.4%, and 2.9%, respectively. Furthermore, the purified bioflocculant was pH tolerant within the range of 2-8 and thermotolerant from 10°C to 100°C, with optimal activity at pH 7.0 and at a temperature of 40°C. The purified bioflocculant showed industrial potential for the treatment of drinking water. Considering these properties, especially its low molecular weight (5.3×10(4)Da), this bioflocculant with excellent solubility and favorable flocculation activity is particularly suited for flocculating small particles.

Microbial residues are important contributors to soil organic matter (SOM). However, the effect of mineral composition on microbial activity and thereby SOM development is not well understood. Here, we used artificial soils composed of four different mixtures containing illite, montmorillonite, ferrihydrite and charcoal to study the effect of mineral composition on SOM development. In addition, silt- and sand-sized quartz were used to provide texture, sterilised manure was added as OM source and the mixtures were inoculated with a microbial community extracted from a natural soil. The mixtures were incubated in the dark for 3–18 months and amino sugar and muramic acid content of the bulk soil and

Microbial residues represent a significant soil organic matter pool and participate in soil aggregation. The addition of organic manure is known to modify soil aggregation and strongly influence soil microbial residues. How manure application influences the spatial distribution of microbial residues in soil aggregates is largely unknown. This study attempts to determine the effect of manure application at various rates on the content and distribution of microbial residues among aggregates of different sizes. We used a long-term manure application experiment in a Mollisol in northeastern China, where manure has been applied since 2001 at rates of 0, 7.5, 15, and 22.5 Mg ha−1 yr−1 (dry weight). The abundance of microbial residues was indicated by amino sugar analysis. Glucosamine and muramic acid were used as biomarkers for fungal and bacterial residues, respectively. Amino sugars were examined within four aggregate fractions: large macroaggregate (>2000 μm), small macroaggregate (250–2000 μm), large microaggregate (53–250 μm) and small microaggregate ( 250 μm macroaggregates compared with microaggregates. However, effects of manure application rates on amino sugar accumulation in larger aggregates were limited when manure rate was increased from 15 to 22.5 Mg ha−1 yr−1. The response of fungal- and bacterial-derived amino sugars to manure application rates differed among aggregate fractions, i.e., glucosamine associated with macroaggregates increased more than that of microaggregates, whereas the enhancement of muramic acid was prominent in both macroaggregates and large microaggregates. The mass proportions of macroaggregates and MWD showed significant positive correlations with amino sugar contents, indicating that these microbial residues are involved in the formation and stabilization of aggregates. Manure applications greatly increased the contribution of microbial residues to soil organic C (SOC) in small macroaggregates and large microaggregates (P ≤ 0.05). We conclude that higher manure input may promote soil aggregation and higher SOC storage, which is closely related to a greater microbial residues-mediated improvement of soil aggregate stability. Our results also suggest that measurement of amino sugar content is a useful approach to assess fungal and bacterial contributions to soil aggregation.

A number of novel 2-(N-(2-(5,5-dimethyl-1,3-dioxane-2-yl)ethyl)aminoacyl)amino-2-deoxy- d-glucopyranoside were synthesized from a readily available starting material, glucosamine, 2,2-dimethyl-1,3-propanediol and 1,1,3,3-tetramethoxypropane, and evaluated for their anti-inflammatory activity. Our results showed that all of the compounds tested exhibited a significant inhibition of xylene-induced inflammation in mice.

The chemical structures of the unusual hopanoid-containing lipid A samples of the lipopolysaccharides (LPS) from three strains of Bradyrhizobium (slow-growing rhizobia) have been established. They differed considerably from other Gram-negative bacteria in regards to the backbone structure, the number of ester-linked long chain hydroxylated fatty acids, as well as the presence of a tertiary residue that consisted of at least one molecule of carboxyl-bacteriohopanediol or its 2-methyl derivative. The structural details of this type of lipid A were established using one- and two-dimensional NMR spectroscopy, chemical composition analyses, and mass spectrometry techniques (electrospray ionization Fourier-transform ion cyclotron resonance mass spectrometry and MALDI-TOF-MS). In these lipid A samples the glucosamine disaccharide characteristic for enterobacterial lipid A was replaced by a 2,3-diamino-2,3-dideoxy-d-glucopyranosyl-(GlcpN3N) disaccharide, deprived of phosphate residues, and substituted by an α-d-Manp-(1→6)-α-d-Manp disaccharide substituting C-4' of the non-reducing (distal) GlcpN3N, and one residue of galacturonic acid (d-GalpA) α-(1→1)-linked to the reducing (proximal) amino sugar residue. Amide-linked 12:0(3-OH) and 14:0(3-OH) were identified. Some hydroxy groups of these fatty acids were further esterified by long (ω-1)-hydroxylated fatty acids comprising 26-34 carbon atoms. As confirmed by mass spectrometry techniques, these long chain fatty acids could form two or three acyloxyacyl residues. The triterpenoid derivatives were identified as 34-carboxyl-bacteriohopane-32,33-diol and 34-carboxyl-2β-methyl-bacteriohopane-32,33-diol and were covalently linked to the (ω-1)-hydroxy group of very long chain fatty acid in bradyrhizobial lipid A. Bradyrhizobium japonicum possessed lipid A species with two hopanoid residues.

Tillage disturbance influences soil microorganisms and consequently the production and decomposition of microbial residues such as amino sugars. However, our understanding is still limited with respect to the changes in amino sugars which occur in soil after tillage operations. In this study, changes in amino sugars in a clay loam soil (mesic Typic Argiaquoll) in Ontario, Canada were tracked in long-term (29 years) no-tillage (NT), long-term conventional moldboard plow tillage (MP), and long-term bluegrass ( Poa pratensis L.) sod (BG) as well as when long-term (13 years) NT was converted to MP, long-term MP was converted to NT, and long-term BG was converted to MP. Our objective was to determine if the quantity of amino sugars in the soil as well as their composition (i.e. whether they originate from bacterial or fungal residues) would respond to changes in tillage practices. We also wanted to evaluate the effects of converting from grassland to arable cropping (corn and soybean) on the amino sugar composition of soils. Soil samples were collected at depths of 0–5, 5–10, and 10–20 cm after 1 (1997), 6 (2002), 11 (2007), and 16 (2012) years following tillage conversion. Concentrations of amino sugars were much greater under long-term BG than under both long-term NT and MP treatments. In the 0–5 cm depth, long-term NT significantly increased total amino sugars and fungal-derived glucosamine (GluN) by 18 and 25%, respectively, compared with long-term MP whereas long-term NT had 26% lower MurA concentrations than long-term CT. Concentrations of total amino sugars in the 0–5 cm depth were reduced significantly within the first year after conversion of long-term NT and BG to MP, due primarily to decreases in the GluN concentrations. On the other hand, concentrations of amino sugars in soil accumulated gradually after conversion of long-term MP to NT. The results confirmed our hypothesis that loss of soil amino sugars is rapid and substantial when MP is initiated after NT and BG, while their recovery is gradual when NT is initiated after MP.

Amino sugars including bacterial biomarker muramic acid (Mur) were investigated in suspended particulate matter (SPM) to understand their distribution, origin, and biogeochemical cycling and the contribution of bacteria to particulate organic matter (POM) of the Mandovi estuary. SPM was collected from 9 sampling stations in the Mandovi estuary during the pre-monsoon (March) and monsoon (August). Total particulate amino sugar (TPAS) concentrations and yields varied spatially and were 2 to 5 times higher during the monsoon than the pre-monsoon. Negative correlation between salinity and TPAS-C yields [TPAS-C/particulate organic carbon (POC)×100] indicates the influence of terrestrial organic matter on the transport of TPAS-carbon. Glucosamine (GlcN), galactosamine (GalN), and mannosamine (ManN) were abundant during the monsoon. Low GlcN/GalN ratios (

Microbial residue represents a significant amount of soil organic matter, and its component amino sugar can serve as time-integrated indicators that reflect chronic effects of agricultural management. We evaluated the influence of different land-use and fertilization treatments on the amounts and patterns of amino sugars (glucosamine and galactosamine) and muramic acid in a Mollisol (Udolls, USDA Soil Taxonomy System) in northeastern China. The treatments included: BL, bareland, without any vegetation; GL, restored grassland which allows plants to re-vegetate naturally; AL, arable land without any fertilizer; ALF, arable land with chemical fertilizer; and ALMF, arable land with chemical fertilizer and pig manure. The amino sugar concentrations differed significantly between various treatments after 26 years, with the order of ALMF > GL > ALF > AL > BL. This suggests that long-term contrasting management changed microbial residue accumulation in soil, which is strongly related to soil organic carbon content. The larger ratios of glucosamine to muramic acid in the GL plots than the AL and BL plots indicated a shift toward fungal-derived residues after 26 years of natural restoration. Our results suggested that different land-use and fertilization treatments clearly influenced amounts and patterns of microbial residues and their contribution to SOM accumulation, primarily due to differences in organic C inputs.

Microbial residues can be a significant component of soil organic matter, and their component amino sugars are integrative indicators of biologically relevant ecosystem properties. We evaluate the impact of soil attributes, microbial functional group biomass, and cropping system type on soil amino sugar profiles in three model biofuel cropping systems in southern Wisconsin, USA. Total soil carbon and clay content explained differences in soil amino sugar profiles, with glucosamine and galactosamine more strongly related to soil carbon and muramic acid associated with clay content. Amino sugars were not correlated to cropping system or to microbial functional group lipid abundance, suggesting amino sugar differences among locations were due to differences in soil legacy properties such as total carbon, clay content and culture age rather than to current biotic drivers. The disconnect between the current biotic composition and legacies of past microbial activity suggests that microbial residues should be considered as trajectories over time rather than static system properties.

There is a need for methods that can rapidly measure multiple biological properties simultaneously. A near infrared spectroscopy (NIRS) method was used to predict β-glucosidase (EC 3.2.1.21) and β-glucosaminidase (NAGase, EC 3.2.1.52) activities, and soil organic C and amino sugar N concentrations in 184 diverse soils of Ohio. The laboratory-measured values of the variables were calibrated against NIR spectral data with partial least squares regression analysis. Statistical analysis of the spectral data was done using the multivariate analysis software Unscrambler 8.0 (CAMO Inc). The first differential transformation of the spectral data in the NIR region (1100–2498 nm) generally yielded best results for developing multivariate calibration models. The multivariate models developed were validated using the full cross validation method and the test set method with a test set size of approximately 45 samples. The R 2 values, testing variation between concentrations as measured by the NIR method and chemical methods, were 0.91 for organic carbon (OC), 0.92 for amino sugar N, and 0.82 for both soil β-glucosidase and β-glucosaminidase enzyme activities. Our study showed that the NIRS method has the potential to simultaneously, rapidly and accurately predict values of multiple related variables. The equipment needed for the NIRS method is not expensive and can be used where very large numbers of samples need to be rapidly analyzed. Indeed, the prediction equations can be constantly improved as more data points are entered into the correlations between laboratory-measured values and NIRS values.

A high performance anion exchange chromatography (HPAEC) isotopic ratio mass spectrometry (IRMS) method was developed for amino sugar-specific δ 13 C analysis in plant hydrolysates. The HPAEC-IRMS method provided good validation parameters and the amino sugar concentrations were similar to those obtained by reversed phase (RP) high performance liquid chromatography (HPLC) and fluorescence (Fl) detection. The limit of quantification (LOQ) was 150 μmol l −1 . This optimised HPAEC-IRMS method opens up the possibility of a glucosamine (GlcN) specific δ 13 C analysis in plant material. Thus, it was possible to determine the δ 13 C values in newly formed fungal GlcN for the first time. The formation and turnover of saprotrophic fungi was investigated by using the improved HPAEC-IRMS method for GlcN-specific δ 13 C analysis. The cultivation of saprotrophic fungi ( Lentinula edodes and Pleurotus species) in beech wood mixed with maize or wheat straw showed the preferred formation of fungal biomass from maize-derived (80%) rather than from beech wood-derived C. The results indicate a faster formation of fungal biomass from maize than from wheat straw as co-substrate.

The carbohydrate composition of the algal cell wall was investigated for its role in cell flocculation. Cultures of Chlorella variabilis NC64A, which were found to have different levels of neutral sugar, uronic acid and amino sugar in the cell wall when cultured in different nitrogen sources and concentrations, were subjected to flocculation with chitosan at dosages of 0–69.6 mg/l and pH values of 5.5, 7 and 8.5. In addition, flocculations of another three strains of Chlorella , which have different levels of cell wall components, were tested. Flocculation improved for all strains at pH 8.5 suggesting that inter molecular forces such as hydrogen bonding might be more important than charge neutralization in the flocculation of Chlorella . Total carbohydrate content in the cell wall was the most significant factor positively affecting the flocculation efficiency of C. variabilis NC64A cells with different cell wall compositions and the other Chlorella strains. The results presented in this study suggest that chitosan flocculation can be improved by optimizing the cell culture conditions to achieve higher cell wall polysaccharide content or selecting an algal strain with higher cell wall polysaccharide content.

(−)-α-Conhydrine was synthesized from propargyl alcohol in 20% overall yield in nine steps. The key intermediates were obtained via a regioselective epoxide opening, cross-metathesis, tandem hydrogenation and hydrogenolysis, and stereoselective dihydroxylaton. The side product from the epoxide ring opening was used to synthesize the seven-membered amino sugar DMJ analogue.

Carbon (C) and/or nitrogen (N) in plant residues can be assimilated into microbial biomass during the plant residue decomposition before incorporation into SOM in the form of microbial residues. Yet, microbial transformation of plant residue-N into microbial residues and the effects of inorganic N inputs on this process have not been well documented. Here, we undertook a 38-week incubation with a silt loam soil amended with a 15N-labeled maize (Zea mays L.) residue to determine how the transformation of maize residue-N into soil amino sugars was affected by rates of inorganic N addition. The newly metabolized amino sugars derived from maize residue-N were differentiated and quantified by using an isotope-based gas chromatography–mass spectrometry technique. We found that greater amounts of maize residue-N were transformed into amino sugars with lower inorganic N addition at the early stages of the plant residue degradation. However, the trend was reversed during later stages of decay as greater percentage of maize residue-N (8.6–9.4%) were enriched in amino sugars in the Nmed and Nhigh soils, as compared with N0 and Nlow (7.5–8.2%). This indicated that higher availability of inorganic N could delay the transformation process of plant-N into microbial residues during the mineralization of plant residues. The dynamic transformations of the plant residue-N into individual amino sugars were compound-specific, with very fast incorporation into bacterial MurAM-new found during the initial weeks, while the dynamics of maize residue-derived GluN exhibited a delayed response to assimilate plant-N into fungal products. The findings indicated differential contributions of maize residue decomposing microorganisms over time. Moreover, we found no preferential utilization of inorganic N over plant residue-N into amino sugars during the incubation course, but inorganic N inputs altered the rate of plant-N accumulation in microbial-derived organic matters. Our results indicated that higher N availability had a positive impact on the accumulation or stabilization of newly-produced microbial residues in the long term.