Responses of Soil Rare and Abundant Sub-Communities and Physicochemical Properties after Application of Different Chinese Herb Residue Soil Amendments.

Microbial diversity in the soil is responsive to changes in soil composition. However, the impact of soil amendments on the diversity and structure of rare and abundant sub-communities in agricultural systems is poorly understood. We investigated the effects of different Chinese herb residue (CHR) soil amendments and cropping systems on bacterial rare and abundant sub-communities. Our results showed that the bacterial diversity and structure of these sub-communities in soil had a specific distribution under the application of different soil amendments. The CHR soil amendments with high nitrogen and organic matter additives significantly increased the relative abundance and stability of rare taxa, which increased the structural and functional redundancy of soil bacterial communities. Rare and abundant sub-communities also showed different preferences in terms of bacterial community composition, as the former was enriched with Bacteroidetes while the latter had more Alphaproteobacteria and Betaproteobacteria. All applications of soil amendments significantly improved soil quality of newly created farmlands in whole maize cropping system. Rare sub-communitiy genera Niastella and Ohtaekwangia were enriched during the maize cropping process, and Nitrososphaera was enriched under the application of simple amendment group soil. Thus, Chinese medicine residue soil amendments with appropriate additives could affect soil rare and abundant sub-communities and enhance physicochemical properties. These findings suggest that applying soil composite amendments based on CHR in the field could improve soil microbial diversity, microbial redundancy, and soil fertility for sustainable agriculture on the Loess Plateau.

Stochasticity versus determinism: Microbial community assembly patterns under specific conditions in petrochemical activated sludge.

The pattern of microbial community assembly in petrochemical sludge is not well-explained. In this study, three kinds of petrochemical activated sludge (AS) from the same seed sludge were investigated to determine their microbial assembly pattern for long-term adaptation. Beta Nearest Taxon Index analysis revealed that the assembly strategies of the abundant and rare operational taxonomic unit (OTU) sub-communities are different for archaeal and bacterial communities. Abundant OTUs preferred deterministic processes, whereas rare OTUs randomly formed due to weak selection. Canonical correspondence analysis/variation partition analysis and Mantel testing results revealed that ammonium, petroleum, and chromium (Cr (VI)) mainly structured the abundant sub-communities. On the other hand, environmental variables, including ammonium, petroleum, and heavy metals, shaped the rare sub-communities. The PICRUSt2 tool was used to predict the functions. Results indicated a greater abundance of microbes harboring the hydrocarbon degradation pathway and heavy-metal-resistant enzymes. Cross-treatment experiments using one type of AS to treat the other two kinds of wastewater were conducted. The results of the cross-treatment experiments and qPCR both suggest the functional adaptation of the microbial community. We revealed selection strategies for the adaptation of bacteria and archaea in AS during environmental changes, providing a theoretical basis for petrochemical wastewater treatment.

Contrasting Patterns of the Bacterial Communities in Melting Ponds and Periglacial Rivers of the Zhuxi glacier in the Tibet Plateau.

Since the early 21st century, global climate change has been inducing rapid glacier retreat at an unprecedented rate. In this context, the melt ponds impart increasing unique footprints on the periglacial rivers due to their hydrodynamic connection. Given that bacterial communities control numerous ecosystem processes in the glacial ecosystem, exploring the fate of bacterial communities from melt ponds to periglacial rivers yields key knowledge of the biodiversity and biogeochemistry of glacial ecosystems. Here, we analyzed the bacterial community structure, diversity, and co-occurrence network to reveal the community organization in the Zhuxi glacier in the Tibet Plateau. The results showed that the bacterial communities in melt ponds were significantly lower in alpha-diversity but were significantly higher in beta-diversity than those in periglacial rivers. The rare sub-communities significantly contributed to the stability of the bacterial communities in both habitats. The co-occurrence network inferred that the mutually beneficial relationships predominated in the two networks. Nevertheless, the lower ratio of positive to negative edges in melt ponds than periglacial rivers implicated fiercer competition in the former habitat. Based on the significantly higher value of degree, betweenness, and modules, as well as shorter average path length in melt ponds, we speculated that their bacterial communities are less resilient than those of periglacial rivers.

Abundant and rare microbial sub-communities in anammox granules present contrasting assemblage patterns and metabolic functions in response to inorganic carbon stresses.

Nitrogen-transforming microorganisms play pivotal roles for the microbial nitrogen-cycling network in the anammox granular system. However, little is known about the effects of inorganic carbon (IC) stresses on the assemblage patterns and functional profiles of abundant and rare taxa. Herein, the community assemblage and functional traits of abundant and rare sub-communities were investigated. Results revealed that insufficient IC had adverse influences on the process performance, while anammox activity could be recovered by IC addition. Co-occurrence network analysis indicated that abundant and rare sub-communities present divergent co-occurrence patterns. Additionally, environmental filtering had different influences on the ecological adaptability of bacterial sub-communities. Furthermore, qPCR results illustrated that NH4+-N and NO2--N consumption were regulated by abundant sub-community, while their accumulation was mediated by rare sub-community. Collectively, these findings suggest that abundant and rare sub-communities present contrasting assemblage patterns and metabolic pathways, and functional profiles dominated selection of bacterial sub-communities under IC stresses.

Divergent assemblage patterns of abundant and rare microbial sub-communities in response to inorganic carbon stresses in a simultaneous anammox and denitrification (SAD) system.

Inorganic carbon has profound influence on anammox system and distinct microbial communities play pivotal roles in nitrogen removal, yet little is known about the ecological patterns of abundant and rare sub-communities in response to inorganic carbon stresses in simultaneous anammox and denitrification systems. Here the aspects of community ecology of abundant and rare taxa under abiotic constraints were explored. Results showed that different IC/NH4+-N ratios have significant influences on NH4+-N and TN removal. Co-occurrence networks revealed that abundant and rare taxa present contrasting assemblage patterns and ecological strategies. Spearman's correlation indicated that environmental filtering had discrepancy influences on these two bacterial sub-communities. Moreover, rare taxa were the key regulators for NH4+-N accumulation and NO2--N consumption. qPCR results indicated that nitrogen removal was mediated by multiple nitrogen transformation pathways. These findings collectively suggest that abundant and rare sub-communities have discrepant ecological patterns and provide insights into their structure-functional relationships.