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Phosphorus (P) accumulation in croplands resulting from ever-increasing input of P fertilizer strongly influences soil microbial growth and activities, which is expected to alter the soil priming effect (PE) induced by plant residue. However, the effect of P availability on the magnitude and direction of PE remains largely unexplored and the underlying microbial mechanisms are still unclear. Therefore, a 40-day incubation experiment was established by adding C4-maize straw to C3-soils with or without long-term P fertilizer inputs to investigate PE and accompanied dynamics of microbiota. The results revealed that in both soils, straw application caused positive real PEs via a "microbial co-metabolism" mechanism, accompanied by a microbial succession from the dominance of r- and K-strategists to K-strategists (mainly fungi). In addition, long-term amendment with P increased PE by 83.2% compared with no P fertilization control, which was mainly mediated by K-strategists, especially the fungal families Chaetomiaceae and Myrmecridiaceae. The increased PE was accompanied by enhanced microbial biomass carbon, extracellular enzyme activities, and bacterial gene abundance, confirming the "stoichiometric decomposition" theory. Meanwhile, deviating from the conventional paradigm, higher phosphatase activity and lower enzymatic stoichiometry of carbon (C)-to-P ratios in high-P soil compared with that in low-P soil suggested stronger "P mining" with high-P availability. [ABSTRACT FROM AUTHOR]

In this study, soil samples from the typical rice-wheat cropping system in Jiangsu Province, China, subjected to different fertilizer application treatments-no carbon (CK), urea (UR), straw (SR), pig manure (PM), starch (ST), and glucose (GL)-were used to determine potential anaerobic ammonium oxidation (anammox) rate and its association with bacterial abundance, diversity, and activity by using DNA stable isotope probing combined with N isotope tracing and molecular techniques. The effects of different organic carbon sources on anammox were significant, in the following order: GL > ST, SR > UR > PM; anammox activity differed significantly across treatments; however, the C active anammox bacteria were only closely related to Ca. Brocadia. The anammox hydrazine synthase β subunit functional gene sequences were highly associated with the Candidatus genus Brocadia in PM and CK treatments. The different organic carbon sources had different inhibitory effects with anammox rate, which dropped from 3.19 to 1.04 nmol dinitrogen gas g dry soil h among treatments. About 4.2-22.3% of dinitrogen gas emissions were attributed to anammox and indicated that a specific population of anammox bacteria was present and varied with the addition of exogenous organic compounds in paddy soils, although a small part of dinitrogen gas was emitted from the soil via anammox. [ABSTRACT FROM AUTHOR]

Interactions between roots and microbes affect plant's resistance to abiotic stress. However, the structural and functional variation of root-associated microbiomes and their effects on metal accumulation in hyperaccumulators remain poorly understood. Here, we characterize the root-associated microbiota of a hyperaccumulating (HP) and a non-hyperaccumulating (NHP) genotype of Sedum alfredii by 16S ribosomal RNA gene profiling. We show that distinct microbiomes are observed in four spatially separable compartments: the bulk soil, rhizosphere, rhizoplane, and endosphere. Both the rhizosphere and rhizoplane were preferentially colonized by Proteobacteria, and the endosphere by Actinobacteria. The rhizosphere and endophytic microbiomes were dominated by the family of Sphingomonadaceae and Streptomycetaceae, respectively, which benefited for their survival and adaptation. The bacterial α-diversity decreases along the spatial gradient from the rhizosphere to the endosphere. Soil type and compartment were strongest determinants of root-associated community variation, and host genotype explained a small, but significant amount of variation. The enrichment of Bacteroidetes and depletion of Firmicutes and Planctomycetes in the HP endosphere compared with that of the NHP genotype may affect metal hyperaccumulation. Program PICRUSt predicted moderate functional differences in bacterial consortia across rhizocompartments and soil types. The functional categories involved in membrane transporters (specifically ATP-binding cassette transporters) and energy metabolism were overrepresented in endosphere of HP in comparison with NHP genotypes. Taken together, our study reveals substantial variation in structure and function of microbiomes colonizing different compartments, with the endophytic microbiota potentially playing an important role in heavy metal hyperaccumulation. [ABSTRACT FROM AUTHOR]

The association between microbial communities and plant growth in long-term fertilization system has not been fully studied. In the present study, impacts of long-term fertilization have been determined on the size and activity of soil microbial communities and wheat performance in a red soil (Ultisol) collected from Qiyang Experimental Station, China. For this, different microbial communities originating from long-term fertilized pig manure (M), mineral fertilizer (NPK), pig manure plus mineral fertilizer (MNPK), and no fertilizer (CK) were used as inocula for the Ultisol tested. Changes in total bacterial and fungal community composition and structures using Ion Torrent sequencing were determined. The results show that the biomass of wheat was significantly higher in both sterilized soil inoculated with NPK (SNPK) and sterilized soil inoculated with MNPK (SMNPK) treatments than in other treatments ( P < 0.05). The activities of β-1,4- N-acetylglucosaminidase (NAG) and cellobiohydrolase (CBH) were significantly correlated with wheat biomass. Among the microbial communities, the largest Ascomycota phylum in soils was negatively correlated with β-1,4-glucosidase (βG) ( P < 0.05). The phylum Basidiomycota was negatively correlated with plant biomass (PB) and tillers per plant (TI) ( P < 0.05). Nonmetric multidimensional scaling analysis shows that fungal community was strongly correlated with long-term fertilization strategy, while the bacterial community was strongly correlated with β-1,4- N-acetylglucosaminidase activity. According to the Mantel test, the growth of wheat was affected by fungal community. Taken together, microbial composition and diversity in soils could be a good player in predicting soil fertility and consequently plant growth. [ABSTRACT FROM AUTHOR]

Preferable inorganic fertilization over the last decades has led to fertility degradation of black soil in Northeast China. However, how fertilization regimes impact denitrification and its related bacterial community in this soil type is still unclear. Here, taking advantage of a suit of molecular ecological tools in combination of assaying the potential denitrification (DP), we explored the variation of activity, community structure, and abundance of nirS and nirK denitrifiers under four different fertilization regimes, namely no fertilization control (N0M0), organic pig manure (N0M1), inorganic fertilization (N1M0), and combination of inorganic fertilizer and pig manure (N1M1). The results indicated that organic fertilization increased DP, but inorganic fertilization had no impacts. The increase of DP was mirrored by the shift of nirS denitrifiers' community structure but not by that of nirK denitrifiers'. Furthermore, the change of DP coincided with the variation of abundances of both denitrifiers. Shifts of community structure and abundance of nirS and nirK denitrifiers were correlated with the change of soil pH, total nitrogen (TN), organic matter (OM), C:P, total phosphorus (TP), and available phosphorus (Olsen P). Our results suggest that the change of DP under these four fertilization regimes was closely related to the shift of denitrifying bacteria communities resulting from the variation of properties in the black soil tested. [ABSTRACT FROM AUTHOR]