Predation increases multiple components of microbial diversity in activated sludge communities.

Area of Science:

• Microbial Ecology
• Environmental Microbiology
• Wastewater Treatment

Background:

• Protozoan predators are crucial in activated sludge, influencing wastewater treatment efficiency.
• The precise mechanisms by which protozoan predation affects bacterial communities and ecosystem functions remain largely unexplored.

Purpose of the Study:

• To experimentally investigate the impact of protozoan predation pressure on bacterial diversity, composition, and functionality in activated sludge.
• To elucidate the relationship between predation intensity, predator diversity, and bacterial community responses.

Main Methods:

• Experimental manipulation of protozoan predation pressure in activated sludge microcosms.
• Analysis of bacterial diversity (richness, evenness, genetic, beta diversity) and community composition.
• Assessment of putative functional impacts, particularly on nitrogen removal.

Main Results:

• Bacterial diversity metrics (richness, evenness, genetic, beta diversity) increased with higher protozoan predation pressure, exhibiting non-linear, hump-shaped relationships.
• Predator diversity had mixed effects: positive on bacterial richness but negative on evenness and phylogenetic distinctiveness.
• Reduced top-down control by protozoa negatively impacted taxa vital for treatment efficiency, especially nitrogen removal.

Conclusions:

• Bacterial diversity and community composition are key mechanisms linking protozoan predation to activated sludge ecosystem functioning.
• Protozoan predation plays a critical role in structuring microbial communities and maintaining wastewater treatment efficacy.
• Understanding these predator-prey dynamics is essential for optimizing wastewater treatment processes.