Presentation Information
[3EMT-04]Microbial density drives community assembly via predation and necromass recycling
○Yuya Sato1, Kyosuke Yamamoto1, Hiroshi Habe1 (1. AIST (Japan))
Keywords:
Microbial community assembly,interspecies interactions,predation,cross-feeding,activated sludge
Background: Understanding how microbial communities assemble is crucial because community structure is closely linked to ecosystem function. While environmental conditions and microbial interactions are known to shape community assembly, the role of microbial density itself remains poorly understood. We hypothesized that higher microbial density increases the frequency of microbial interactions, thereby accelerating community dynamics, while maintaining similar directional trajectories when the initial community composition is identical.
Methods: Activated sludge was used as a model microbial community. Six density conditions (25, 50, 75, 100, 150 and 200%, N = 5) were prepared by dilution or concentration while maintaining identical initial community composition. Samples were incubated aerobically at 25°C for one month without external nutrient input. Microbial community dynamics were analyzed using 16S rRNA gene amplicon sequencing, along with shotgun metagenomic and metatranscriptomic analyses.
Results and Discussion: Community composition changes followed similar trajectories across all density conditions, but the rate of change increased with microbial density, supporting our hypothesis. In the absence of external nutrients, these dynamics are likely driven by interspecies interactions such as microbial predation and cell degradation. Members of the Chitinophagaceae, which include predatory or degradative bacteria, became dominant under high-density conditions, suggesting activation of density-dependent biomass turnover. In contrast, Rhodanobacter, which lacks the capability to degrade other microorganisms, also became dominant, particularly at higher densities and earlier time points. This suggests that nutrients released from degraded microbial biomass were utilized via cross-feeding. These interpretations are supported by metagenomic and metatranscriptomic evidence. Together, our results demonstrate that microbial density is a key driver of community assembly by regulating density-dependent predation and necromass recycling.
Methods: Activated sludge was used as a model microbial community. Six density conditions (25, 50, 75, 100, 150 and 200%, N = 5) were prepared by dilution or concentration while maintaining identical initial community composition. Samples were incubated aerobically at 25°C for one month without external nutrient input. Microbial community dynamics were analyzed using 16S rRNA gene amplicon sequencing, along with shotgun metagenomic and metatranscriptomic analyses.
Results and Discussion: Community composition changes followed similar trajectories across all density conditions, but the rate of change increased with microbial density, supporting our hypothesis. In the absence of external nutrients, these dynamics are likely driven by interspecies interactions such as microbial predation and cell degradation. Members of the Chitinophagaceae, which include predatory or degradative bacteria, became dominant under high-density conditions, suggesting activation of density-dependent biomass turnover. In contrast, Rhodanobacter, which lacks the capability to degrade other microorganisms, also became dominant, particularly at higher densities and earlier time points. This suggests that nutrients released from degraded microbial biomass were utilized via cross-feeding. These interpretations are supported by metagenomic and metatranscriptomic evidence. Together, our results demonstrate that microbial density is a key driver of community assembly by regulating density-dependent predation and necromass recycling.
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