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High-throughput quantitative polymerase chain reaction (PCR) of antibiotic resistance genes (ARGs) was used to profile the composition and diversity of ARGs in biosolid-amended soil and in lettuce roots and shoots. Biosolid application significantly increased the ARGs in soil and influenced the soil antibiotics resistome mainly through exogenous introduction. Four dominant ARGs occurred in sterilized and water-washed leaves, namely catB8 , php , vanB and str , which accumulated to >50% of total abundance. Nine subclasses of ARGs were determined in both sterilized and water-washed leaves, and they were shared ARGs among soil, roots and shoots. This suggests that the ARGs in ready-to-eat lettuce were mainly located in endophytes and the internal route may contribute more to the ARGs in routinely consumed raw lettuce. Moreover, a previously unsuspected shift in multridrug ARGs to root and shoot compartments due to biosolid application was discovered. These results reveal that biosolid application drives the evolution and dissemination of ARGs in the soil-plant system. [ABSTRACT FROM AUTHOR]

Illustrates the method in running emergency helplines. Importance of telephone helplines in dealing with health related incidents; Telecommunication equipments needed for helplines; Operation of helplines.

Background and aims: Overyielding in intercropping compared to monoculture has been widely reported. One of the mechanisms may be the alteration of the microbial community in intercropping and especially the amelioration of the negative effects of pathogens that can accumulate in monocultures. Here we test whether inoculation with arbuscular mycorrhizal fungi (AMF) and wheat take-all disease influences overyielding and whether changes in the microbial communities generate feedbacks on plant growth. Methods: In Experiment 1, wheat and faba bean were grown in monoculture or intercropping to form three planting patterns. Plants were inoculated with or without wheat take-all disease ( Gaeumannomyces graminis), and one, six, or no AM fungi, to create 6 soil conditioned treatments. Soils from Experiment 1 were used as inocula in Experiment 2 to test the feedback on plant growth from monocultures and the legacy benefits of intercropping. Results: No significant influence of AMF on plant growth was observed in either experiment. In Experiment 1, AMF had no significant effect in suppressing take-all but take-all tended to decrease AMF colonization. Shoot biomass and competitive ability of wheat was suppressed by take-all in both experiments. Wheat and faba bean showed overyielding in both the take-all and non-take-all treatment in Experiment 1 but only overyielding in the take-all treatment in Experiment 2. Growth of wheat and faba bean were suppressed in conspecific soil, and this negative feedback was observed across all take-all and AMF treatments, and regardless of competition. Biomass of wheat and faba bean was higher in soil from intercropping than in monoculture soil, and this positive legacy benefit of intercropping did not depend on take-all, AMF or plant competition. Conclusions: We find support for alterations of the soil community causing negative plant soil feedback and positive legacy benefits of intercropping. Our results are consistent with microbial dynamics generating overyielding in intercropping by reducing the negative influence of soil pathogen build-up on conspecific host plants and simultaneously compensatively improving growth of neighbor plants. [ABSTRACT FROM AUTHOR]

Foraging strategies in arbuscular mycorrhizal fungi (AMF) for heterogeneously distributed resources in the soil remain to be explored. We used nylon-mesh bags of 30 μm to simulate patches of different phosphorus (P) supply levels (Expt 1) and P forms (organic υ. inorganic, Expts 1 and 2). In Expt 1, host maize (Zea mays) was unfertilised; in each pot, five P-enriched bags were supplied with either Na-phytate or KH2PO4 at P rates of 0 (P0), 50 (P50), 100 (P100), 150 (P150) and 200 (P200) mg P kg-1. In Expt 2, maize plants were supplied with 20 (P20) or 50 (P50) mg P kg-1, and five P-enriched bags were supplied with different P forms (Na-phytate, lecithin, RNA, KH2PO4) and a nil-P control. Three fungal species (Funneliformis mosseae, Rhizophagus irregularis, and Glomus etunicatum) were compared in Expt 1, and the first two species in Expt 2. In Expt 1, the hyphal-length density (HLD) of G. etunicatum was not significantly different among different P levels when supplied with KH2PO4, whereas theHLDof R. irregularis tended to increase at higherPsupply (above P50) in the Na-phytate treatment. TheHLDof F. mosseae increased at P150 when supplied with KH2PO4, and increased at P100 and P150 in the Naphytate treatment relative to P0. APase activity levels were more related to P supply level, in particular with F. mosseae inoculation and uninoculated control, showing that P200 significantly reduced APase relative to P0. In Expt 2, greater hyphal growth of both fungal species tended to occur with KH2PO4. At P20, the HLD of R. irregularis in treatments with KH2PO4 and lecithin, and of F. mosseae with KH2PO4, were higher than in P0. At P50, the HLD of F. mosseae was higher than of R. irregularis; but P form had no significant influence on HLD of F. mosseae, whereas the HLD of R. irregularis in the P-amended treatment (except with Na-phytate) was higher than in P0. APase activity did not differ significantly between the two fungal species. Highest APase activity generally occurred with lecithin, with no significant difference among the other P forms. Our results indicate that the response of AMF to P-enriched patches is complex, and both the form and amount of P supplied should be considered. Variations between AMF in the proliferation of hyphae to heterogeneous nutrient patches might be a mechanism by which these species can maintain diversity in intensive agricultural ecosystems. [ABSTRACT FROM AUTHOR]

BACKGROUND: Maintaining or improving soil chemical quality is critical for sustainable agricultural productivity and environmental safeguards. Organic fertilizer application, a common agricultural practice in banana cultivation, is often associated with greater microbial biomass and activity, which are linked to improvements in soil chemical quality. However, the effect of the duration of organic fertilizer application on soil chemical quality and whether it is microbially driven still needs to be investigated. We collected soil samples from banana plantations consistently applying organic fertilizers for 1 (Y1), 4 (Y4), 7 (Y7) and 10 (Y10) years. Soil chemical quality is expressed as total data set (TDS) and minimum data set (MDS) based on chemical indicators, and soil microorganisms are characterized by phospholipid fatty acid (PLFA). RESULTS: Based on TDS and MDS, the soil chemical quality indices in Y7 and Y10 treatments were significantly higher than that in Y1 and Y4 treatments. Soil total PLFA concentrations and the proportional abundance of fungi and arbuscular mycorrhizal fungi increased with prolonged banana cultivation. Total PLFA concentrations were significantly positive correlation with the soil chemical quality index. Soil gram‐positive bacteria (G+), bacteria, protozoa and ratio of G+ to gram‐negative bacteria (G–) were major drivers of soil chemical quality. CONCLUSION: The organic fertilizer application can significantly improve soil chemical quality, which is regulated by soil bacteria. Regular application of organic fertilizers is important in promoting soil quality and soil biological properties need to be incorporated into the assessment of soil health in banana plantations. © 2022 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Presents a response by the author to a letter to the editor about his article "Feeling the Heat," in the last issue of "Power Engineer."

Presents letter to the editor about temperature change.

Background: Recent advances in the management of acute gallstonepancreatitis include the introduction of laparoscopic cholecystectomy,defining the role of endoscopic retrograde cholangiopancreatography(ERCP) and early cholecystectomy to prevent recurrent pancreatitis.The aim of the present study was to review the current managementof gallstone pancreatitis in Auckland Hospital, compare findingswith a similar study published a decade ago and to determine theextent to which the management is compliant with recently publishedconsensus guidelines. Methods: A retrospective review of consecutive patients admittedwith acute pancreatitis during a 39-month study period was undertaken.Data were recorded regarding demographics, diagnosis, predictedand actual severity of gallstone pancreatitis (index and recurrentattacks), the role of ERCP and computed tomography scanning, thetiming of cholecystectomy (open and laparoscopic), intraoperativecholangiography, duration of hospital stay, complications and mortality. Results : There were 216 patients admitted with acute pancreatitis,106 of whom had proven gallstones. An ERCP was performed in 62(59%) patients with gallstone pancreatitis but not morecommonly in patients with severe pancreatitis, and common bile duct stoneswere identified in 26% of these patients. Of the 70 (66%)patients who had a cholecystectomy, 56 (80%) had it within3 weeks of admission. Although the proportion of patientswith gallstone pancreatitis who had a cholecystectomy is similarto the earlier study, there has been a significant increase in theproportion of patients having a cholecystectomy during the indexadmission (χ2 = 3.83; P = 0.05).This has resulted in a reduction in recurrent pancreatitis (P < 0.001).Although the overall mortality from gallstone pancreatitis has notsignificantly decreased, it has for patients with predicted severegallstone pancreatitis (P = 0.02). Conclusion : There has been reasonable compliance with publishedguidelines and some progress in the management of gallstone pancreatitis,particularly in relation to performing timely laparoscopic cholecystectomywith a reduction in the incidence of recurrent pancreatitis. Concernsremain regarding the overuse of diagnostic ERCP in patients withmild pancreatitis. [ABSTRACT FROM AUTHOR]

Dark septate endophytes (DSE) colonize plant roots extensively and increase host plant growth and nutrition. However, the development of DSE-produced metabolites as plant biostimulants has been largely ignored. DSE growth curves and extracellular metabolite components were analyzed and the growth-promoting effects of DSE extracellular metabolites on alfalfa (Medicago sativa L.) grown for 4, 8 12, 16 and 20 days were evaluated. The growth curve of the DSE strain Alternaria sp. shows days 0-8 in the growth phase, days 8-16 in the stable phase, and days 16-20 in the senescent phase. The extracellular metabolite components of DSE were significantly different at different growth stages. The biomass of alfalfa was increased significantly by DSE extracellular metabolites (P < 0.05). Biomass of alfalfa inoculated with DSE extracellular metabolites more than doubled after growth for 8 days and nutrient availability also increased significantly compared with the uninoculated control. Six DSE extracellular metabolites, calycosin 7-galactoside, 1-[(5-amino-5-carboxypentyl)amino]-1-deoxyfructose, N2-fructopyranosylarginine, 2-(4-methyl-5-thiazolyl)ethyl hexanoate, kenposide B, and medinoside E, were significantly positively correlated with alfalfa biomass (P < 0.01). This study combines the DSE extracellular metabolites with plant and soil traits to provide a theoretical basis for the use of DSE metabolites in the product development of plant biostimulants. • The time factor significantly affects the growth and metabolism of DSE. • The major components of DSE extracellular metabolites are amino acids and peptides. • The addition of DSE metabolites can promote alfalfa growth and nutrient uptake. • DSE metabolites promote plant growth and nutrient uptake through multiple pathways. [ABSTRACT FROM AUTHOR]

Background Phosphorus (P), iron (Fe) and zinc (Zn) are essential elements for plant growth and development, but their availability in soil is often limited. Intercropping contributes to increased P, Fe and Zn uptake and thereby increases yield and improves grain nutritional quality and ultimately human health. A better understanding of how intercropping leads to increased plant P, Fe and Zn availability will help to improve P-fertilizer-use efficiency and agronomic Fe and Zn biofortification. Scope This review synthesizes the literature on how intercropping of legumes with cereals increases acquisition of P, Fe and Zn from soil and recapitulates what is known about root-to-shoot nutrient translocation, plant-internal nutrient remobilization and allocation to grains. Conclusions Direct interspecific facilitation in intercropping involves below-ground processes in which cereals increase Fe and Zn bioavailability while companion legumes benefit. This has been demonstrated and verified using isotopic nutrient tracing and molecular analysis. The same methodological approaches and field studies should be used to explore direct interspecific P facilitation. Both niche complementarity and interspecific facilitation contribute to increased P acquisition in intercropping. Niche complementarity may also contribute to increased Fe and Zn acquisition, an aspect poorly understood. Interspecific mobilization and uptake facilitation of sparingly soluble P, Fe and Zn from soil, however, are not the only determinants of the concentrations of P, Fe and Zn in grains. Grain yield and nutrient translocation from roots to shoots further influence the concentrations of these nutrients in grains. [ABSTRACT FROM AUTHOR]

Phthalate esters (PAEs) are suspected of having adverse effects on human health and have been frequently detected in soils and vegetables. The present study investigated their occurrence and composition in plastic film greenhouse soil–vegetable systems and assessed their potential health risks to farmers exposed to these widespread pollutants. Six priority control phthalates, namely dimethyl phthalate (DMP), diethyl phthalate (DEP), di-n-butyl phthalate (DnBP), butyl benzyl phthalate (BBP), di-(2-ethylhexyl) phthalate (DEHP) and di-n-octyl phthalate (DnOP), were determined in 44 plastic film greenhouse vegetables and corresponding soils. Total PAEs ranged from 0.51 to 7.16 mg kg − 1 in vegetables and 0.40 to 6.20 mg kg − 1 in soils with average concentrations of 2.56 and 2.23 mg kg − 1 , respectively. DnBP, DEHP and DnOP contributed more than 90% of the total PAEs in both vegetables and soils but the proportions of DnBP and DnOP in vegetables were significantly ( p < 0.05) higher than in soils. The average concentrations of PAEs in pot herb mustard, celery and lettuce were > 3.00 mg kg − 1 but were < 2.50 mg kg − 1 in the corresponding soils. Stem and leaf vegetables accumulated more PAEs. There were no clear relationships between vegetable and soil PAEs. Risk assessment indicates that DnBP, DEHP and DnOP exhibited elevated non-cancer risk with values of 0.039, 0.338 and 0.038, respectively. The carcinogenic risk of DEHP was about 3.94 × 10 − 5 to farmers working in plastic film greenhouses. Health risks were mainly by exposure through vegetable consumption and soil ingestion. [ABSTRACT FROM AUTHOR]

Biodegradation is difficult at high temperatures due to the limited capacity of microorganisms to survive and function outside their optimum temperature range. Here, a thermophilic petroleum-degrading consortium was enriched from compost at a temperature of 55 °C. 16S rDNA and metagenomic techniques were used to analyze the composition of the consortium and the mechanisms of degradation. The consortium degraded 17000 mg total petroleum hydrocarbons (TPHs) L−1 with a degradation efficiency of 81.5% in 14 days. The consortium utilized a range of substrates such as n-hexadecane, n-docosane, naphthalene and pyrene and grew well over a wide range of pH (4–10) and salinity (0–90 g L−1). The hydrocarbon-degrading extremophilic consortium contained, inter alia , (relative abundance >1%) Caldibacillus , Geobacillus , Mycolicibacterium , Bacillus , Chelatococcus , and Aeribacillus spp. Metagenomic analysis was conducted to discover the degradation and environmental tolerance functional genes of the consortium. Two alkane hydroxylase genes, alk B and lad A, were found. A microcosm study shows that the consortium promoted the bioremediation of soil TPHs. The results indicate that the consortium may be a good candidate for the high-temperature bioremediation of petroleum-contaminated soils. [Display omitted] • The strain composition of the consortium was stable during degradation. • Bacterial taxa with smaller relative abundances had higher contribution coefficients. • The bacterial consortium promoted the bioremediation of petroleum-contaminated soils. [ABSTRACT FROM AUTHOR]

Contamination of groundwater with chlorinated aliphatic hydrocarbons (CAHs) has become increasingly widespread. Enhanced reductive dechlorination (ERD) by emulsified vegetable oil (EVO) is an environmentally friendly, low-carbon and sustainable technology that effectively eliminates the threat from CAHs. To improve the permeability and bioavailability of EVO in the low-permeability substratum, nano-emulsified vegetable oil (nanoEVO) can be synthesized using a modified phase inversion composition method (MPIC) by increasing the emulsification temperature that reduces the shear force required for the formation of nanodroplets and the interfacial tension between the mixed phase and water. The emulsification temperature of 60 °C, the water content of 40–70%, the droplet diameter (DD) of nanoEVO prepared by MPIC is ∼200 nm, and had good monodispersion (≤0.2). The high molecular weight and low solubility of vegetable oil, and similar size of droplet make nanoEVO remains homogeneous after storage for > one year. NanoEVO can effectively biostimulate indigenous bacteria in CAHs-contaminated groundwater to dechlorinate 1,1,2-trichloroethane (1,1,2-TCA) to ethene via vinyl chloride (VC). The maximum dihaloelimination rate of 1,1,2-TCA was ∼66.06 μM·Cl−·day−1 and the maximum hydrogenolysis rate of VC was ∼35.67 μM·Cl−·day−1. NanoEVO effectively increased the relative abundance of Dehalococcoides from <0.10 to 9.61%. The abundances of Dhc 16S rRNA gene and dehalogenase gene vcr A increased by 102 and 103, respectively. Biostimulation shaped the structure of microbial communities and promoted hydrolytic acidification and anaerobic fermentation. Moreover, the syntrophic VFA-oxidizing bacteria participated in secondary fermentation and were closely correlated with H 2 consumption metabolism. By providing carbon sources and maintaining an anaerobic environment with stable pH and ORP, nanoEVO biostimulated the hydrolytic acidification led by fermentative bacteria, secondary fermentation with syntrophic VFA-oxidizing bacteria and reductive dechlorination carried out by dechlorinator, thus greatly increasing the CAH-dechlorinating ability of indigenous microbial communities. [Display omitted] • The MPIC method can prepared highly stable nanoEVO. • Biostimulation increased the abundance of Dehalococcoides by 102 times and increased the VC dechlorination rate. • Syntrophic VFA-oxidizing bacteria were important in biostimulated dechlorination community. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal fungi (AMF) play an important role in crop productivity, but their response to different fertilization regimes is variable. Understanding the mechanisms governing mycorrhizal responses under various fertilization regimes is key to maximizing the mycorrhizal contribution to ecosystem functioning. Indigenous AMF communities and soil were collected from long-term field experiments with various fertilization regimes. A greenhouse bioassay was carried out to identify the key regulators of the mycorrhizal response to inorganic and organic fertilization. Different fertilization regimes generated continuous gradients for most soil properties and a full spectrum of mycorrhizal phenotypes. Mycorrhizal growth response (MGR) in particular showed complex shifts from positive to neutral to negative, while mycorrhizal phosphorus (P) response was consistently positive and mycorrhizal nitrogen (N) response was consistently negative in fertilized treatments. Soil available P and available N to P (N:P) ratio appeared to be key soil predictors of the mycorrhizal response. Also, the nutrient status of non-mycorrhizal (NM) plants, namely shoot N concentration, shoot P concentration and shoot N:P ratio, were plant predictors of mycorrhizal response. A positive MGR occurred when NM plants were P-limited, and neutral and negative MGR occurred when NM plants were N-limited or co-limited by N and P. Further, the thresholds of soil available P (c. 13 mg kg-1), NM shoot N concentration (c. 14 g kg-1), NM shoot P concentration (c. 0.7 g kg-1) and NM shoot N:P ratio (c. 18), respectively, were estimated to predict mycorrhizal response. We conclude that the relative availability of N and P in soil and NM plants are good predictors of mycorrhizal response in different fertilization regimes. The existing nutrient thresholds combining soil and plant allowed more accurate prediction of mycorrhizal response and this has important implications for optimizing the mycorrhizal association in some important crops by managing soil nutrients. • A wide spectrum of mycorrhizal phenotypes was observed in multiple fertilization regimes. • Soil P availability and N:P ratio were key soil predictors of mycorrhizal response. • N and P status of non-mycorrhizal plants were key plant predictors of mycorrhizal response. • Nutrient thresholds in soil and plants in predicting mycorrhizal response were identified. [ABSTRACT FROM AUTHOR]

The Porphyromonas gingivalis type IX secretion system (T9SS) promotes periodontal disease by secreting gingipains and other virulence factors. By in situ cryoelectron tomography, we report that the P. gingivalis T9SS consists of 18 PorM dimers arranged as a large, caged ring in the periplasm. Near the outer membrane, PorM dimers interact with a PorKN ring complex of ∼52 nm in diameter. PorMKN translocation complexes of a given T9SS adopt distinct conformations energized by the proton motive force, suggestive of different activation states. At the inner membrane, PorM associates with a cytoplasmic complex that exhibits 12-fold symmetry and requires both PorM and PorL for assembly. Activated motors deliver substrates across the outer membrane via one of eight Sov translocons arranged in a ring. The T9SSs are unique among known secretion systems in bacteria and eukaryotes in their assembly as supramolecular machines composed of apparently independently functioning translocation motors and export pores. [ABSTRACT FROM AUTHOR]

F plasmids circulate widely among the Enterobacteriaceae through encoded type IV secretion systems (T4SSFs). Assembly of T4SSFs and associated F pili requires 10 VirB/VirD4‐like Tra subunits and eight or more F‐specific subunits. Recently, we presented evidence using in situ cryoelectron tomography (cryoET) that T4SSFs undergo structural transitions when activated for pilus production, and that assembled pili are deposited onto alternative basal platforms at the cell surface. Here, we deleted eight conserved F‐specific genes from the MOBF12C plasmid pED208 and quantitated effects on plasmid transfer, pilus production by fluorescence microscopy, and elaboration of T4SSF structures by in situ cryoET. Mutant phenotypes supported the assignment of F‐specific subunits into three functional Classes: (i) TraF, TraH, and TraW are required for all T4SSF‐associated activities, (ii) TraU, TraN, and TrbC are nonessential but contribute significantly to distinct T4SSF functions, and (iii) TrbB is essential for F pilus production but not for plasmid transfer. Equivalent mutations in a phylogenetically distantly related MOB12A F plasmid conferred similar phenotypes and generally supported these Class assignments. We present a new structure‐driven model in which F‐specific subunits contribute to distinct steps of T4SSF assembly or activation to regulate DNA transfer and F pilus dynamics and deposition onto alternative platforms. [ABSTRACT FROM AUTHOR]

• Drought stress affected soybean growth and physiology. • Leaf temperature reflected the effect of AMF on plant water status under drought stress. • AMF regulated leaf temperature to affect other physiological activities. The influence of arbuscular mycorrhizal fungi (AMF) on plant water status and growth under drought stress were investigated using soybean subjected to drought stress (40% of soil water-holding capacity (WHC)) and control conditions (60% WHC) either inoculated with AMF or uninoculated controls. Leaf temperature (T leaf) and stomatal conductance (gs) were determined at 10:00, 12:00 and 18:00 on the harvest day. The effects of AMF on the water physiological status and growth of soybeans under drought stress were examined using thermal infrared imaging technology (TIIT). AMF inoculation under drought stress increased plant above- and below-ground biomass, nutritional status, and nitrogen, phosphorus and potassium uptake rates, and reduced plant root/shoot ratio. Monitoring T leaf reflected the effect of AMF on plant water physiological status under drought stress. AMF inoculation resulted in a decline in T leaf of 0.1–0.4 °C as water uptake proceeded compared with an increase of 0.2–1.4 °C in uninoculated controls. Thus, the effects of AMF on soybean drought resistance changed from positive to negative. AMF reduced plant T leaf , promoted the accumulation of photosynthetic products, reduced malondialdehyde accumulation, and increased stomatal regulation and T leaf. These preliminary results provide a basis for further studies on the effects of AMF on the water and growth status of plants under drought stress in arid areas. [ABSTRACT FROM AUTHOR]

Bacteria use type IV secretion (T4S) systems to deliver DNA and protein substrates to a diverse range of prokaryotic and eukaryotic target cells. T4S systems have great impact on human health, as they are a major source of antibiotic resistance spread among bacteria and are central to infection processes of many pathogens. Therefore, deciphering the structure and underlying translocation mechanism of T4S systems is crucial to facilitate development of new drugs. The last five years have witnessed considerable progress in unraveling the structure of T4S system subassemblies, notably that of the T4S system core complex, a large 1 MegaDalton (MDa) structure embedded in the double membrane of Gram-negative bacteria and made of 3 of the 12 T4S system components. However, the recent determination of the structure of ∼3 MDa assembly of 8 of these components has revolutionized our views of T4S system architecture and opened up new avenues of research, which are discussed in this review. [ABSTRACT FROM AUTHOR]

Thermal infrared imaging technology was used to understand the effects of arbuscular mycorrhizal fungi (AMF) and dark septate endophytic (DSE) fungi, both separately and together, on plant growth and physiological status, and to screen and develop efficient microbial agents in a pot experiment design. Eight treatments comprised the control (CK), AMF inoculation alone, DSE fungal treatments (DSE20%, DSE40% and DSE80%; 2, 4, 8 × 105 CFU mL−1) and combined inoculation treatments (DSE20% + AMF, DSE40% + AMF, and DSE80% + AMF). Canopy temperature (Tcanopy) and stomatal conductance (gs) were monitored at different growth stages, and plant biomass-related indicators were obtained at harvest. These indicators were used to assess plant growth and the physiological status resulting from the different inoculation treatments. During plant growth, the plant Tcanopy decreased following inoculation. Differences in Tcanopy between control and inoculated plants were detected by thermal infrared imaging technology and were −3.8 to + 9.3 °C (control–inoculation treatment). Growth index and Tcanopy monitoring indicate that the growth-promoting effect of combined inoculation was higher than that of either fungal type alone, with DSE80% + AMF producing the highest growth promotion. During the growth process of inoculated maize, the effect of inoculated AMF on the physiological condition of maize growth can be better monitored by thermal infrared at 10 a.m., 12 p.m., 2 p.m. and 4 p.m. on the 31st–57th days of the growth period. The method and results of this experiment are conducive to the rapid and efficient monitoring of the effects of microorganisms on plant growth and physiological status and can be applied to the screening, application, and promotion of microbial agents. [ABSTRACT FROM AUTHOR]

Peptidoglycan (PG) hydrolases associated with bacterial type IV secretion systems (T4SSs) are thought to generate localized lesions in the PG layer to facilitate assembly of the translocation channel. The pheromone-responsive plasmid pCF10 of Enterococcus faecalis encodes a putative cell wall hydrolase, PrgK, and here we report that a prgK deletion abolished functionality of the pCF10-encoded T4SS as monitored by pCF10 conjugative transfer. Expression in trans of wild-type prgK fully complemented this mutation. PrgK has three potential hydrolase motifs resembling staphylococcal LytM, soluble lytic transglycosylase (SLT), and cysteine-, histidine-dependent amidohydrolase/peptidase (CHAP) domains. Complementation analyses with mutant alleles established that PrgK bearing two hydrolase domains in any combination supported near-wild-type plasmid transfer, and PrgK bearing a single hydrolase domain supported at least a low level of transfer in filter matings. When exported to the Escherichia coli periplasm, each domain disrupted cell growth, and combinations of domains additionally induced cell rounding and blebbing and conferred enhanced sensitivity to osmotic shock. Each domain bound PG in vitro, but only the SLT domain exhibited detectable hydrolase activity, as shown by zymographic analyses and release of fluorescent PG fragments. Genes encoding three T4SS-associated, putative hydrolases, Lactococcus lactis CsiA, Tn925 Orf14, and pIP501 TraG, partially complemented the ΔprgK mutation. Our findings establish that PrgK is an essential component of the pCF10-encoded Prg/Pcf T4SS and that its hydrolase domains coordinate their activities for full PrgK function. PrgK is indispensable for plasmid transfer in liquid matings, suggestive of a role in formation or stabilization of mating junctions. [ABSTRACT FROM AUTHOR]

Water-dispersible colloids (WDCs) are vital for trace element migration, but there is limited information about the abundance, size distribution and elemental composition of WDC-bound thallium (Tl) and arsenic (As) in mining-contaminated soils and sediments solutions. Here, we investigated the potential mobilization of WDC-bound Tl and As in soils and sediments in a typical Tl/As-contaminated area. Ultrafiltration results revealed on average > 60% of Tl and As in soil solution (< 220 nm) coexisted in colloidal form whereas Tl and As in sediment solution primarily existed in the truly dissolved state (< 10 kDa) due to increased acidity. Using AF4-UV-ICP-MS and STEM-EDS, we identified Fe-bearing WDCs in association with aluminosilicate minerals and organic matter were main carriers of Tl and As. SAED further verified jarosite nanoparticles were important components of soil WDC, directly participating in the migration of Tl and As. Notably, high pollution levels and solution pH promoted the release of Tl/As-containing WDCs. This study provides quantitative and visual insights into the distribution of Tl and As in WDC, highlighting the important roles of Fe-bearing WDC, soil solution pH and pollution level in the potential mobilization of Tl and As in contaminated soils and sediments. [Display omitted] • > 60% of Tl and As in soil solution occurred in water-dispersible colloids (WDCs). • Tl/As-bearing WDCs comprised Fe oxides, aluminosilicates and OM. • Jarosite was an important component of WDCs involved in Tl/As migration. • High pollution levels and solution pH promoted the release of Tl/As-bearing WDCs. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal (AM) fungi contribute to the revegetation of degraded ecosystems such as coal mining areas and may indirectly affect the development of biological soil crusts (biocrusts). However, bacterial diversity and microbial nutrient cycling in the soil underlying biocrusts are seldom considered when assessing ecological restoration effects. Bacterial community composition was quantified and compared using 16S rRNA gene sequencing, metabolic limitation of microbes via extracellular enzymatic stoichiometry and their association with carbon use efficiency (CUE) in soil underlying moss biocrusts in vegetated areas inoculated with an AM fungus or uninoculated and in uninoculated unvegetated areas. The AM fungal inoculum significantly influenced bacterial community composition and diversity, extracellular enzyme activities and CUE in soil underlying moss biocrusts mainly by affecting soil nutrients. Correlation analysis revealed that Actinobacteria, Armatimonadetes, Bacteroidetes, Chlorobi, Cyanobacteria, Saccharibacteria, and Verrucomicrobia were positively correlated with soil nutrients carbon (C), nitrogen (N) and phosphorus (P). A vector analysis of extracellular enzyme activity indicates that soil microbial communities underlying moss biocrusts were limited by P but microbial communities in areas inoculated with the AM fungus had the lowest relative P limitation. The alleviation of microbial P limitation increased the microbial CUE and bacterial phylum community and alpha diversity, leading to an increase in subsoil C content underlying moss biocrusts. This indicates that microbial communities in soil underlying moss biocrusts under in restoration areas containing the AM fungus were more stable under environmental stress, and the inclusion of AM fungal inoculation may be recommended as the preferred option for ecosystem restoration in arid and semi-arid coal mining areas. • Soil microbial communities under moss biocrusts were P-limited. • AM fungal inoculum increased microbial CUE and bacterial biodiversity under biocrusts. • Microbial P limitation was minimum in areas inoculated with the AM fungus. • More diverse soil bacterial communities had higher microbial CUE values. [ABSTRACT FROM AUTHOR]

Summary: Hotspots of N2O emissions are generated from legume residues during decomposition. Arbuscular mycorrhizal fungi (AMF) from co‐cultivated intercropped plants may proliferate into the microsites and interact with soil microbes to reduce N2O emissions. Yet, the mechanisms by which or how mycorrhizal hyphae affect nitrifiers and denitrifiers in the legume residues remain ambiguous. Here, a split‐microcosm experiment was conducted to assess hyphae of Rhizophagus aggregatus from neighbouring maize on overall N2O emissions from stubbles of nodulated or non‐nodulated soybean. Soil microbes from fields intercropped with maize/soybean amended with fertilizer nitrogen (SS‐N1) or unamended (SS‐N0) were added to the soybean chamber only. AMF hyphae consistently reduced N2O emissions by 20.8%–61.5%. Generally, AMF hyphae promoted the abundance of N2O‐consuming (nosZ‐type) denitrifiers and altered their community composition. The effects were partly associated with increasing MBC and DOC. By contrast, AMF reduced the abundance of nirK‐type denitrifiers in the nodulated SS‐N0 treatment only and that of AOB in the non‐nodulated SS‐N1 treatment. Taken together, our results show that AMF reduced N2O emissions from soybean stubbles, mainly through the promotion of N2O‐consuming denitrifiers. This holds promise for mitigating N2O emissions by manipulating the efficacious AMF and their associated microbes in cereal/legume intercropping systems. [ABSTRACT FROM AUTHOR]

Designing an environmentally benign bio-adsorbent for the removal of heavy metal ions from aqueous medium was a sustainable strategy to ensure water safety. Herein, three-dimensional macroscopic aminosilyated nanocellulose aerogels (APTM S -modified TO-NFC) for the removal of heavy metal ions in water were successfully synthesized from bamboo-derived TEMPO-oxidized nanofibrillated cellulose (TO-NFC) and aminopropyltrimethoxysilane (APTMs) via a facile freeze-drying process. Owing to a relatively high BET surface area (129.32 m2 g−1), high porosity (99.14%) as well as high substitution degree of amino groups (0.41), the resulting APTM S -modified TO-NFC aerogel exhibited good adsorption capacity of 99.0, 124.5, and 242.1 mg g−1 for Cu2+, Cd2+ and Hg2+, respectively. Furthermore, the crosslinked and three-dimensionally porous architecture imparted it with relatively high compression strength, good excellent stability in water, and ease of recyclability from water after the usage. The pH value of the solution had a great influence on adsorption efficiency of the aerogel adsorbent, and optimal adsorption efficiency could be achieved at pH 3–7. Thermodynamic parameters suggested the spontaneous and endothermic nature of adsorption process. This work provides a facile method for preparing sustainable bio-adsorbent for effective heavy metal ions removal from aqueous medium. A novel and sustainable APTMs-modified NFC aerogel bio-adsorbent for effective removal of Cu2+, Cd2+ and Hg2+ ions was prepared via a facile freeze-drying of TEMPO oxidized NFC suspension in the presence of APTMs. [Display omitted] [ABSTRACT FROM AUTHOR]

Aims: The rhizosphere microbiome plays an important role in plant growth and behavior during phytoremediation. This work aims to explore how hyperaccumulating plant performance (shoot biomass and Cd uptake) and rhizosphere bacterial community are driven by plant development under a Cd concentration gradient and their relationship during plant growth. Methods: A pot experiment was conducted using the Cd hyperaccumulator Sedum plumbizincicola grown in soil spiked with 0, 5 and 20 mg Cd kg−1 for 13 weeks. Plant performance (shoot biomass and Cd uptake) was determined and the rhizosphere bacterial community was examined by weekly Illumina sequencing. Biomarker genera were identified by the Random Forest model and the functions were predicted by PICRUSt2. Results: The rhizospheres bacterial community tended to stabilize from the 6th or 7th week regardless of the soil Cd concentration, coinciding with the vigorous growth stage of the hyperaccumulator. Biomarker genera Paenibacillus and Streptacidiphilus enriched in the stable stage showed significant positive correlations with Cd uptake. In addition, some predicted gene abundances of enzymes related to plant growth promotion by the rhizosphere bacterial community were influenced to various degrees by plant development and soil Cd concentration. Conclusion: There exists a stable bacterial community in the rhizosphere of S. plumbizincicola during phytoremediation and biomarker taxa enriched at this stage were positively correlated with Cd uptake. Selecting microorganisms that match the developmental stages might further enhance phytoremediation. This provides some theoretical basis for modulating rhizosphere microbes at the appropriate time during phytoextraction to optimize the phytoremediation technique. [ABSTRACT FROM AUTHOR]

Abstract: The bacterial type IV secretion systems (T4SSs) comprise a biologically diverse group of translocation systems functioning to deliver DNA or protein substrates from donor to target cells generally by a mechanism dependent on establishment of direct cell-to-cell contact. Members of one T4SS subfamily, the conjugation systems, mediate the widespread and rapid dissemination of antibiotic resistance and virulence traits among bacterial pathogens. Members of a second subfamily, the effector translocators, are used by often medically-important pathogens to deliver effector proteins to eukaryotic target cells during the course of infection. Here we summarize our current understanding of the structural and functional diversity of T4SSs and of the evolutionary processes shaping this diversity. We compare mechanistic and architectural features of T4SSs from Gram-negative and -positive species. Finally, we introduce the concept of the ‘minimized’ T4SSs; these are systems composed of a conserved set of 5–6 subunits that are distributed among many Gram-positive and some Gram-negative species. [Copyright &y& Elsevier]

Gram-negative bacteria express a wide variety of organelles on their cell surface. These surface structures may be the end products of secretion systems, such as the hair-like fibers assembled by the chaperone/usher ( CU) and type IV pilus pathways, which generally function in adhesion to surfaces and bacterial-bacterial and bacterial-host interactions. Alternatively, the surface organelles may be integral components of the secretion machinery itself, such as the needle complex and pilus extensions formed by the type III and type IV secretion systems, which function in the delivery of bacterial effectors inside host cells. Bacterial surface structures perform functions critical for pathogenesis and have evolved to withstand forces exerted by the external environment and cope with defenses mounted by the host immune system. Given their essential roles in pathogenesis and exposed nature, bacterial surface structures also make attractive targets for therapeutic intervention. This review will describe the structure and function of surface organelles assembled by four different Gram-negative bacterial secretion systems: the CU pathway, the type IV pilus pathway, and the type III and type IV secretion systems. [ABSTRACT FROM AUTHOR]

Abstract: Phytoremediation of phthalic esters (PAE) polluted agricultural soils near electrical-waste dismantling areas in east China is a topic of much public concern. In this study, monocropping and intercropping of alfalfa (Medicago sativa L.), Elsholtzia splendens and Sedum plumbizincicola were compared for their potential in phytoremediation of contaminated soil. Regardless of whether alfalfa was cultivated in monoculture (A) or in combination with E. splendens (AE) or with S. plumbizincicola (AS), and also with all three (AES) in intercropping, concentrations of six PAEs in soil were significantly reduced (p < 0.01) by 87.2, 91.2, 87.2 and 89.4% compared to the control. Intercropping enhanced the decline in soil PAEs and increased soil microbial biomass and microbial functional diversity, and alfalfa shoots and roots took up more of the target pollutants than the other two plant species. DEHP was the most abundant of the target PAEs in soil, roots and shoots. The biological concentration factors (BCFs) of alfalfa in monoculture were relatively high, but the transfer factor (TF) and phytoextraction efficiency, which ranged from 1.16 to 1.69 %, were higher in intercropping systems. Thus, rhizospheric remediation by intercropping of the three-species contributed to PAE removal from the soil and may represent a promising in situ bioremediation strategy for PAE contaminated soils. [Copyright &y& Elsevier]

Abstract: The effects of repeated synthetic fertilizer or cattle slurry applications at annual rates of 50, 100 or 200m3 ha−1 yr−1 over a 38 year period were investigated with respect to herbage yield, N uptake and gross soil N dynamics at a permanent grassland site. While synthetic fertilizer had a sustained and constant effect on herbage yield and N uptake, increasing cattle slurry application rates increased the herbage yield and N uptake linearly over the entire observation period. Cattle slurry applications, two and four times the recommended rate (50m3 ha−1 yr−1, 170kgNha−1), increased N uptake by 46 and 78%, respectively after 38 years. To explain the long-term effect, a 15N tracing study was carried out to identify the potential change in N dynamics under the various treatments. The analysis model evaluated process-specific rates, such as mineralization, from two organic-N pools, as well as nitrification from NH4 + and organic-N oxidation. Total mineralization was similar in all treatments. However, while in an unfertilized control treatment more than 90% of NH4 + production was related to mineralization of recalcitrant organic-N, a shift occurred toward a predominance of mineralization from labile organic-N in the cattle slurry treatments and this proportion increased with the increase in slurry application rate. Furthermore, the oxidation of recalcitrant organic-N shifted from a predominant NH4 + production in the control treatment, toward a predominant NO3 − production (heterotrophic nitrification) in the cattle slurry treatments. The concomitant increase in heterotrophic nitrification and NH4 + oxidation with increasing cattle slurry application rate was mainly responsible for the increase in net NO3 − production rate. Thus the increase in N uptake and herbage yield on the cattle slurry treatments could be related to NO3 − rather than NH4 + production. The 15N tracing study was successful in revealing process-specific changes in the N cycle in relationship to long-term repeated amendments. [Copyright &y& Elsevier]

Deca-bromodiphenyl ether (BDE-209) is the major component of the commercial deca-BDE flame retardant. There is increasing concern over BDE-209 due to its increasing occurrence in the environment and in humans. In this study the behavior of BDE-209 in the soil-plant system was investigated. Accumulation of BDE-209 was observed in the roots and shoots of all the six plant species examined, namely ryegrass, alfalfa, pumpkin, summer squash, maize, and radish. Root uptake of BDE-209 was positively correlated with root lipid content (P < 0.001, R² = 0.81). The translocation factor (TF, Cshoot/Croot) of BDE-209 was inversely related to its concentration in roots. Nineteen lower brominated (di- to nona-) PBDEs were detected in the soil and plant samples and five hydroxylated congeners were detected in the plant samples, indicating debromination and hydroxylation of BDE-209 in the soil—plant system. Evidence of a relatively higher proportion of penta- through di-BDE congeners in plant tissues than in the soil indicates that there is further debromination of PBDEs within plants or low brominated PBDEs are more readily taken up by plants. A significant negative correlation between the residual BDE-209 concentration in soil and the soil microbial biomass measured as the total phospholipid fatty acids (PLFAs) (P < 0.05, R² = 0.74) suggests that microbial metabolism and degradation contribute to BDE-209 dissipation in soil. These results provide important information about the behavior of BDE-209 in the soil-plant system. [ABSTRACT FROM AUTHOR]

Effects of long-term applications (50, 100 and 200 m3 ha−1y−1) of pig and cow slurries on yield, botanical composition and nutrient content of herbage of an original perennial ryegrass sward were assessed in a three-cut silage system and compared with unamended and fertilized controls in the 36th year of the experiment. Cow slurry at 50 m3 ha−1 produced similar annual herbage DM yield to 200 kg ha−1 fertilizer N in 2006, whereas about 100 m3 ha−1 pig slurry were required to produce a similar amount of DM. The highest slurry application rate significantly influenced sward botanical composition without depressing DM yield. The principal invading species were creeping bent and meadow grasses (similar to findings at a previous assessment in 1981) except in the unamended control (which were common bent and Yorkshire fog). Perennial ryegrass remained a main species in plots receiving fertilizer (31 % annual DM yield) and low slurry rates (38 %) but declined to 3 % annual DM yield at the highest slurry rate where the ability of ryegrass to utilize slurry N and P may have been affected by chemically or physically induced deficiencies of other nutrients (e.g. Ca) or direct physical effects such as smothering. [ABSTRACT FROM AUTHOR]

A pot experiment was carried out to investigate the tolerance of cucumber plants (Cucumis sativus L.) to root-knot nematode after inoculation with Glomus intraradices. Plants were inoculated with G. intraradices for four weeks and then transplanted in soil treated with Meloidogyne incognita for a further five weeks. The low phosphorus (P) loamy soil was amended with 50 and 100 mg P kg-1 soil. Mycorrhizal colonization increased shoot dry weight, shoot length, leaf numbers, root fresh weight and shoot P concentration, whereas nematode penetration and reproduction were significantly decreased. Similarly, P fertilization usually increased shoot growth and significantly decreased the number of galls and the number of egg masses and eggs per g root. Our results indicate that inoculation with G. intraradices and P fertilizer confer tolerance of cucumber plants to M. incognita by enhancing plant growth and by suppressing reproduction and/or galling of nematodes during the early stages of plant growth. [ABSTRACT FROM AUTHOR]

Nutrient and water management is crucially important in shallow-rooted vegetable production systems characterized by high input and high environmental risk. A 2-year field experiment on greenhouse cucumber double-cropping systems examined the effects of root zone nitrogen management and planting of sweet corn as a catch crop in the summer fallow period on cucumber yield and soil Nmin dynamics compared to conventional practices. Cucumber fruit yields were not significantly affected by root zone N management and catch crop planting despite a decrease in N fertilizer application of 53% compared to conventional N management. Soil Nmin content to a depth of 0.9 m decreased markedly and root zone (0–0.3 m) soil Nmin content was maintained at about 200 kg N ha−1. Root zone N management efficiently and directly reduced apparent N losses by 44% and 45% in 2005 and 2006, respectively. Sweet corn, the summer catch crop, depleted Nmin residue in the soil profile of 1.8 m at harvest of winter–spring season cucumber by 304–333 kg N ha−1, which contributed 19–22% reduction in N loss. Compared to conventional N management, N loss was reduced by 56% under root zone N management and catch crop planting. [ABSTRACT FROM AUTHOR]

A split root device was designed to assess the possible role of AMF in translocation and detoxification of As by maize plants. Half of each maize root system grew in As-amended or unamended soil and the remainder was inoculated with either Glomus mosseae or Acaulospora morrowiae. External mycelium was collected from a third compartment. Neither shoot nor root As concentrations were affected by inoculation with either fungus. Soil As amendment produced higher As concentrations in roots in the second compartment and in the external mycelium. The As concentrations in the matrix solution of the second root compartment were lower in mycorrhizal treatments with no differences in soluble As in the hyphal compartments. Mycorrhiza exerted little effect on As translocation within plants but may have influenced root As efflux. Deposition of As in external mycelium indicates a possible role of mycorrhizal fungi in the detoxification of As in the host plants. [ABSTRACT FROM AUTHOR]

A pot experiment investigated the response of two maize inbred lines with contrasting root morphology and phosphorus (P) efficiency to inoculation with Glomus mosseae or Glomus etunicatum compared with non-mycorrhizal controls. Soil phosphorus was supplied at rates of 10, 50, and 100 mg P kg -1 soil. Root length, specific root length, and specific phosphorus uptake of maize line 178 (P-efficient) were significantly higher than of line Hc (P-inefficient). Percentage of root length colonized showed the opposite trend regardless of soil P supply level. The two maize lines did not differ significantly in growth response to mycorrhizal colonization. Root colonization rate decreased with increasing soil phosphorus supply. The beneficial effect of the two AM fungi on plant growth and P uptake was greatest at low soil P level and the responses were negative at high P supply. Mycorrhizal responsiveness also decreased with increasing P supply and differed between the two mycorrhizal fungal isolates. [ABSTRACT FROM AUTHOR]

Iron plaque is ubiquitously formed on the root surfaces of rice. However, little is known about the role of iron plaque in Cd movement from soil to the plant aboveground parts. A pot experiment was conducted to investigate the influence of iron plaque in Cd uptake and accumulation by rice seedlings in soil. Rice seedlings were pre-cultivated in solution culture for 16 days. Two seedlings were transplanted in a nylon bag containing no substrate but surrounded by soil amended with Fe and Cd combined at rates of 0, 1, or 2 g Fe kg−1 and 0, 2.0, or 10 mg Cd kg−1 soil. Fe was added to induce different amounts of iron plaque, and Cd to simulate Cd-polluted soils. Plants were grown for a further 43 days and then harvested. The length of the longest leaf and SPAD values of the newly mature leaves were measured during plant growth. Fe and Cd concentrations were determined in dithionite–citrate–bicarbonate (DCB) soil extracts and in plant roots and shoots. Shoot and root dry weights were significantly affected by Fe supply level but not by added Cd. Root dry weight declined with increasing Fe supply but shoot dry weight decreased at 2 g Fe kg−1 and increased at 1 g Fe kg−1 (except at 2 mg Cd kg−1). The length of the longest leaf and SPAD values of the newly mature leaves were significantly affected by plant growth stage and added Fe and Cd. Fe tended to diminish the negative effect of Cd on these two parameters. Cd concentrations in DCB extracts increased with increasing Cd and Fe supply. In contrast, external Fe supply markedly reduced shoot and root Cd concentrations and there was generally no significant difference between the two Fe supply levels. Shoot and root Cd concentrations increased with increasing Cd addition. Root Cd concentrations were negatively correlated with root Fe concentrations. The proportion of Cd in DCB extracts was significantly lower than in roots or shoots. The results indicate that enhanced Fe uptake by plants can diminish the negative effects of Cd to some extent and that iron plaque on root surfaces is of little significance in affecting uptake and accumulation of Cd by rice plants. [Copyright &y& Elsevier]

Abstract: The effects of arbuscular mycorrhizal (AM) fungus (Glomus mosseae) and phosphorus (P) addition (100 mg/kg soil) on arsenic (As) uptake by maize plants (Zea mays L.) from an As-contaminated soil were examined in a glasshouse experiment. Non-mycorrhizal and zero-P addition controls were included. Plant biomass and concentrations and uptake of As, P, and other nutrients, AM colonization, root lengths, and hyphal length densities were determined. The results indicated that addition of P significantly inhibited root colonization and development of extraradical mycelium. Root length and dry weight both increased markedly with mycorrhizal colonization under the zero-P treatments, but shoot and root biomass of AM plants was depressed by P application. AM fungal inoculation decreased shoot As concentrations when no P was added, and shoot and root As concentrations of AM plants increased 2.6 and 1.4 times with P addition, respectively. Shoot and root uptake of P, Mn, Cu, and Zn increased, but shoot Fe uptake decreased by 44.6%, with inoculation, when P was added. P addition reduced shoot P, Fe, Mn, Cu, and Zn uptake of AM plants, but increased root Fe and Mn uptake of the nonmycorrhizal ones. AM colonization therefore appeared to enhance plant tolerance to As in low P soil, and have some potential for the phytostabilization of As-contaminated soil, however, P application may introduce additional environmental risk by increasing soil As mobility. [Copyright &y& Elsevier]

The influence of sulfur (S) supply and mycorrhizal colonization on the growth and pungency of spring onion (Allium fistulosum L.) seedlings grown for four months in Perlite and nutrient solution containing three levels of sulfate [0.1, 1.75, and 4 mM sulfate (SO42-)] were investigated. Plants were inoculated with Glomus etunicatum, Glomus intraradices, or Glomus mosseae, and uninoculated controls were included. Shoot and root dry weights of mycorrhizal and control plants supplied with 4 mM SO42+ were higher than with 0.1 or 1.75 mM SO42-. Enzyme produced pyruvic acid (EPY) and plant sulfur concentrations increased with increasing SO42- supply. The EPY and plant S concentrations were usually higher in mycorrhizal plants than controls irrespective of S supply, and shoot total S concentrations and EPY were strongly correlated. Arbuscular mycorrhizal colonization appeared to make a substantial contribution to the sulfur status of spring onion, and may thus have had a strong influence on its flavor characteristics. [ABSTRACT FROM AUTHOR]

A pot experiment was conducted out to investigate the yield and pungency of spring onion ( Allium fistulosum L.) as affected by inoculation with arbuscular mycorrhizal (AM) fungi and addition of nitrogen (N) and sulfur (S) fertilizers. Plants were inoculated with either Glomus mosseae or Glomus intraradices or grown as uninoculated controls. Two levels of N and S were applied to the soil in factorial combinations of 50 and 250 mg N kg -1 soil and 0 and 60 mg S kg -1 soil. Plants were grown in a greenhouse for 25 weeks and then harvested. Mycorrhizal colonization resulted in increased shoot dry weight, shoot-to-root ratio, shoot length, sheath diameter, and phosphorus (P) concentrations. Shoot dry-matter yield was significantly affected by added N, but not by S. Shoot dry weight increased with increasing N supply (except for non-mycorrhizal controls without additional S fertilizer). Shoot total S concentration (TSC), enzyme-produced pyruvate (EPY), and organic sulfur concentration (OSC) in plants inoculated with Glomus mosseae were significantly lower than those of non-mycorrhizal controls, while these parameters in plants inoculated with Glomus intraradices were comparable to or higher than in the controls. Neither N nor S supply affected shoot EPY or OSC, whereas shoot TSC (except in plants inoculated with Glomus mosseae ) and SO 4 2- concentrations were usually significantly increased by S supply. In soil of high S and low P availability, mycorrhizal colonization had a profound influence on both the yield and the pungency of spring onion. [ABSTRACT FROM AUTHOR]

A pot experiment was conducted to study the growth and pungency of Allium cepa L. grown in Perlite as affected by colonization by the arbuscular mycorrhizal (AM) fungi Glomus versiforme and Glomus intraradices BEG141 and by ammonium:nitrate (NH 4 + :NO 3 - ) ratios of 3:1, 1:1, and 1:3 in 4 m M solutions. Plants were harvested when bulb formation commenced. In general, mycorrhizal colonization resulted in increased shoot dry weight, shoot length, sheath diameter, root nitrogen (N) and phosphorus (P) content (except with G. intraradices and a NH 4 + :NO 3 - ratio of 1:3), shoot N and P concentrations (except with G. versiforme and a NH 4 + :NO 3 = ratio of 3:1) and content. Plants inoculated with G. versiforme had higher growth parameters and N and P content than those with G. intraradices , whereas N and P concentrations showed the opposite trends. Growth parameters and N and P content of non-mycorrhizal plants were highest at a NH 4 + :NO 3 = ratio of 1:3, while those of plants inoculated with G. versiforme or G. intraradices were highest at a ratio of NH 4 + :NO 3 - 3:1 or 1:1. Neither mycorrhizal colonization nor proportion of inorganic N species significantly affected bulb enzyme-produced pyruvate or total or organic sulfur (S) concentrations in plant shoots. Colonization by AM fungi made a substantial contribution to onion growth and may not have been directly related to bulb pungency at early stages of plant growth. However, the influence of AM fungi on plant N and P metabolism may have implications for onion flavor at later stages of plant growth. [ABSTRACT FROM AUTHOR]

Three ectomycorrhizal fungal isolates, Cenococcum geophilum SIV, a putative isolate of Pisolithus microcarpus and a Pisolithus sp., were cultured in vitro without potassium (K) and with three levels of K supply (as K2SO4). Some growth stimulation by K was observed among the fungi. Potassium in the liquid medium led to increased concentrations of nitrogen (N) and K in the fungi compared to K-free controls, and to higher phosphorus (P) concentrations in Pisolithus sp., but lower P in C. geophilum SIV. In a second experiment, the K influx rates of the fungi from external solutions followed Michaelis-Menten kinetics, indicating that K influx was an active process. Mycorrhizal fungi showed quite small Cmin values for K influx, ranging from 2.12 to 5.39 µmol L-1, in relation to K concentrations in the external solution. Such low Cmin values might allow the external hyphae to extract K efficiently from K-deficient soils. Furthermore, the fungi had low Km values for K uptake (<14.85 µmol L-1), indicating high affinities and efficiencies of K carriers. Both Pisolithus sp. and P. microcarpus exhibited similar Cmin and Km values but were different from C. geophilum SIV. Furthermore, Imax values varied significantly among the fungi, ranging from 9.60 to 21.63 µmol g-1 DM h-1, perhaps due to variation in the intracellular K concentrations in the ectomycorrhizal fungi. [ABSTRACT FROM AUTHOR]

Bacteria use type IV secretion systems (T4SS) to translocate DNA (T-DNA) and protein substrates across the cell envelope. By transfer DNA immunoprecipitation (TrIP), we recently showed that T-DNA translocates through theAgrobacterium tumefaciensVirB/D4 T4SS by forming close contacts sequentially with the VirD4 receptor, VirB11 ATPase, the inner membrane subunits VirB6 and VirB8 and, finally, VirB2 pilin and VirB9. Here, by TrIP, we show that nucleoside triphosphate binding site (Walker A motif) mutations do not disrupt VirD4 substrate binding or transfer to VirB11, suggesting that these early reactions proceed independently of ATP binding or hydrolysis. In contrast, VirD4, VirB11 and VirB4 Walker A mutations each arrest substrate transfer to VirB6 and VirB8, suggesting that these subunits energize this transfer reaction by an ATP-dependent mechanism. By co-immunoprecipitation, we supply evidence for VirD4 interactions with VirB4 and VirB11 independently of other T4SS subunits or intact Walker A motifs, and with the bitopic inner membrane subunit VirB10. We reconstituted substrate transfer from VirD4 to VirB11 and to VirB6 and VirB8 by co-synthesis of previously identified‘core’ components of the VirB/D4 T4SS. Our findings define genetic requirements for DNA substrate binding and the early transfer reactions of a bacterial type IV translocation pathway. [ABSTRACT FROM AUTHOR]

A pot experiment was conducted to study the influence of elemental sulphur (S0) on cadmium (Cd), zinc (Zn), and sulphur (S) uptake by oilseed rape (Brassica napus L.) grown in a calcareous soil contaminated with either Cd or Zn or with both Zn and Cd together. Elemental sulphur was applied at two rates (0 and 200 mmol), Cd at two rates (0 and 20 mg), and Zn at three rates (0, 20, and 200 mg) kg−1 soil. Cadmium (as CdCl2) and Zn (as ZnCl2) were added in solution to soil prior to planting. After 10 days, S0 and fertilizer were thoroughly mixed and added to the soil. Plants were harvested after growing for 40 days in a greenhouse. Soil pH and shoot dry weight decreased significantly in response to S0 application. Addition of Zn and Cd did not influence plant growth without S0 supply. Shoot concentrations of Zn and Cd increased significantly with Zn and Cd addition as well as S0 supply. Cadmium addition did not lead to any change in shoot Zn concentration. Shoot Cd concentration decreased in the 200 mg kg−1 Zn addition treatment compared with the control but remained unchanged in all Zn treatments when S0 was applied. Shoot S concentration increased with application of S0, Zn, and Cd. Shoot Zn and Cd uptake by oilseed rape increased significantly with the Zn and Cd addition. However, shoot Zn removal did not increase significantly, and Cd removal decreased when S was applied. In conclusion, S0 acidified the soil and increased shoot concentrations of Zn and Cd, but its depressive effect on shoot biomass was so pronounced that it would not enhance phytoextraction of Cd or Zn from this soil by oilseed rape. [ABSTRACT FROM AUTHOR]

Background: Effects on maize were assessed of dual inoculation with arbuscular mycorrhizal fungi (AMF) and dark septate endophytes (DSE) isolated from other plant species. Methods: Suspensions of DSE isolated from Stipa krylovii were prepared at different densities (2, 4, and 8 × 105 CFU mL− 1) and inoculated separately (AMF or DSE) or together (AMF + DSE), to explore their effects on maize growth. Results: Inoculation with AMF or medium and high densities of DSE and combined inoculation (AMF + DSE) increased plant above-ground growth and altered root morphology. Differences in plant growth were attributable to differences in DSE density, with negative DSE inoculation responsiveness at low density. AMF promoted plant above-ground growth more than DSE and the high density of DSE promoted root development more than AMF. Combined inoculation might lead to synergistic growth effects on maize at low density of DSE and competitive effects at medium and high DSE densities. Conclusions: AMF and DSE co-colonized maize roots and they had positive effects on the host plants depending on DSE density. These findings indicate the optimum maize growth-promoting combination of AMF and DSE density and provide a foundation for further exploration of potentially synergistic mechanisms between AMF and DSE in physiological and ecological effects on host plants. [ABSTRACT FROM AUTHOR]