Interspecific barrier effect driven by heavy metals makes soil bacterial functional assembly more stochastic

Area of Science:

• Environmental Microbiology
• Soil Science
• Ecotoxicology

Background:

• Heavy metals in soil negatively impact microbial community stability and aggregation.
• Understanding microbial responses to heavy metals requires analyzing bacterial communication and diversity maintenance.
• Soil contamination by heavy metals poses a significant threat to ecosystem health.

Purpose of the Study:

• To investigate the ecological response of indigenous soil microbial communities to heavy metal contamination.
• To analyze bacterial interspecies communication and community diversity maintenance mechanisms under heavy metal stress.
• To explore the adaptive evolution and ecosystem restoration strategies for heavy metal-polluted soils.

Main Methods:

• Soil samples were collected from a heavy-metal-contaminated site in China.
• High-throughput sequencing was employed to analyze bacterial taxa and functions.
• Ecological indices such as species diversity, functional diversity, and niche breadth were assessed.

Main Results:

• Bacterial taxa and functions exhibited unusual decoupling phenomena under heavy metal stress.
• Species diversity remained stable, but functional diversity significantly decreased with increasing heavy metal concentrations (Hg, Se, Cr).
• Community stability declined as average niche breadth increased, with species assembly consistently being a deterministic process (NST <0.5).
• Bacterial functional assembly shifted from stochastic to deterministic, then back to stochastic (NST >0.5) under high heavy metal concentrations, indicating a change in stress resistance mechanisms.

Conclusions:

• Heavy metals induce functional diversity loss and alter community assembly processes in soil microbial communities.
• The shift in assembly processes suggests a transition from positive mutation to passive functional propagation in bacterial stress resistance.
• Findings provide new insights into microbial adaptive evolution and inform strategies for ecosystem restoration in contaminated soils.