Relationships among Bacterial Cell Size, Productivity, and Genetic Diversity in Aquatic Environments using Cell...

Area of Science:

• Microbial Ecology
• Aquatic Microbiology
• Cellular Biology

Background:

• Understanding microbial contributions to aquatic ecosystem productivity is crucial.
• Cell size is a key factor influencing microbial activity and ecological roles.
• Natural aquatic communities harbor diverse bacterial populations with varying characteristics.

Purpose of the Study:

• To investigate the relationship between bacterial cell size (biovolume) and cellular activity.
• To determine how cell size affects bacterial abundance and genetic diversity in aquatic environments.
• To identify the dominant bacterial genotypes within different size classes and their productivity.

Main Methods:

• Utilized flow cytometry for sorting microorganisms based on side-angle-scattered (SSC) light, correlating with cell biovolume.
• Incubated bacterial cells with tritiated leucine to measure cellular activity.
• Employed denaturing gradient gel electrophoresis (DGGE) to analyze genetic diversity across different cell size fractions.

Main Results:

• A bell-shaped relationship was observed between bacterial cell biovolume and activity across multiple samples.
• Bacterial abundance showed an inverse relationship with cell biovolume.
• Genetic diversity was predominantly found in smaller cells, with fewer dominant genotypes in larger, more active cells.

Conclusions:

• Medium-sized bacterial cells, despite high growth rates, are likely subject to significant grazing pressure.
• Bacterial genetic diversity is unevenly distributed across cell size classes in aquatic communities.
• Dominant and highly productive cells may be associated with a limited number of specific genotypes.