A fundamental challenge in microbiome research lies in elucidating the functional capacity of microbial communities through community membership and genomic data. As community structuring and emergent functional traits are determined by bacterial community metabolic networks, it is important to gain insights into the principles that govern bacteria-bacteria interactions. Here, we applied an integrative framework linking individual strain-level traits to community structuring in a simplified synthetic bacterial community (SSC8) that promotes the growth of ungrafted watermelon. By combining mono- and coculture assays with genome-scale metabolic modeling and metabolomic profiling of spent media, we characterized directional interactions and resource dependencies among community members. Our findings show that positive interactions dominated the community network, accounting for 55% of all pairwise combinations, indicating a high prevalence of growth-promoting effects among strains. Genome-scale metabolic modeling showed that functional divergence among strains enhanced the potential for metabolic complementarity as phylogenetic distance increased. Integrating metabolic modeling with metabolomics further suggested that Pseudomonas azotifigens Q6 not only benefited from all other community members, but also exhibited mutualistic interactions with the other three strains, with metabolite exchange involving compounds such as L-lysine and L-cysteine. Pseudomonas azotifigens Q6 acted as an important driver of community composition by affecting the abundance of several other consortium members in vitro. These findings highlight the role of metabolic complementarity in driving community structuring by promoting selective persistence of specific strains. Our work provides mechanistic insights into microbial interaction networks in vitro and offers a conceptual foundation for the rational design of functionally robust and plant-beneficial microbiomes.
Yi-Zhu Qiao, Ting-Ting Wang, He Zhang et al.· Ecology· 0 citations
INTRODUCTION
The stability of the vast soil carbon pool, crucial for climate regulation, depends on microbial processes that govern carbon loss as CO2 or its stabilization in soil. Microbial life-history strategies, representing tradeoffs between resource acquisition (A-strategy) and growth yield (Y-strategy), are central to soil organic carbon (SOC) dynamics. However, how abiotic factors modulate these strategies and, in turn SOC fate remains unclear.
OBJECTIVES
Using the black soil region of Northeast China, which harbors substantial yet vulnerable SOC reserves, this study aimed to identify the dominant abiotic driver shaping microbial life-history strategies and to elucidate how this driver influences SOC stabilization pathways.
METHODS
We conducted a field survey combining metagenomic profiling of microbial attributes (diversity, functional potential, and inferred life-history strategy) with measurements of soil properties including extracellular enzyme activities and SOC fractions. This integrative approach traced the pathway from abiotic drivers to microbial traits and ultimately to carbon allocation.
RESULTS
Soil pH emerged as the key environmental gradient, with a threshold at pH 6.43 marking a systemic shift in microbial ecology and carbon processing. Acidic soils (pH 4.60-6.43) favored A-strategists, characterized by large genomes, enriched carbohydrate-active enzymes, and high extracellular enzyme activity, enabling polymer degradation and humification but limiting mineral-associated organic carbon (MAOC) formation. In contrast, neutral soils (pH 6.43-8.87) supported Y-strategists with streamlined genomes and biosynthetic metabolism, promoting microbial necromass accumulation and MAOC stabilization. Distinct functional guilds underpinned the A- and Y-strategies and frequent horizontal gene transfer in acidic soils further reinforced the A-strategy dominance under low pH.
CONCLUSION
Our findings reveal a mechanistic link between microbial life-history strategies and SOC stabilization, demonstrating that pH may shape the balance between A- and Y-strategists and their contrasting carbon pathways. This insight enhances predictive models of SOC dynamics and highlights pH management as a key lever for agroecosystems carbon retention.
Xiyuan Xu, Kunkun Fan, Ning Ling et al.· Journal of Advanced Research· 0 citations
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