Ecological processes shaping highly connected bacterial communities along strong environmental gradients

Area of Science:

• Microbial Ecology
• Environmental Microbiology
• Metagenomics

Background:

• River-sea continuums exhibit strong environmental gradients and high microbial dispersal.
• Understanding microbial community assembly mechanisms is crucial for ecological dynamics.

Purpose of the Study:

• To compare homogenizing dispersal and heterogeneous selection in shaping bacterial communities.
• To investigate seasonal differences (wet/dry) in assembly mechanisms.
• To differentiate between total and active bacterial community responses.

Main Methods:

• High-throughput sequencing of 16S rRNA genes (total bacteria) and 16S rRNA transcripts (active bacteria).
• Sampling across a salinity gradient (freshwater to marine) in the Pearl River-South China Sea Continuum.
• Analysis of bacterial community assembly mechanisms during wet and dry seasons.

Main Results:

• Heterogeneous selection was a stronger force than homogenizing dispersal for both total and active bacterial communities.
• Homogeneous selection dominated overall, except in active communities during summer.
• Active bacterial communities showed greater responsiveness to environmental gradients compared to total communities.

Conclusions:

• Bacterial community assembly in connected, heterogeneous environments is complex.
• Environmental gradients significantly influence active microbial communities.
• Seasonal dynamics play a role in the relative importance of selection and dispersal.