Bacterial community structure within an activated sludge reactor added with phenolic compounds

Area of Science:

• Environmental microbiology
• Bioreactor technology
• Microbial ecology

Background:

• Biodegradation of phenolic compounds in bioreactors is crucial for environmental remediation.
• Understanding bacterial population dynamics during this process is less explored.
• Activated sludge is a common inoculum for bioreactors.

Purpose of the Study:

• To investigate the dynamic changes in bacterial populations during the biodegradation of phenolic compounds in a bubble column bioreactor.
• To correlate shifts in microbial communities with the addition of specific phenolic compounds.

Main Methods:

• A glass bubble column bioreactor was inoculated with activated sludge.
• The reactor was spiked with 2-chlorophenol, phenol, and m-cresol over 56 days.
• Bacterial community composition was monitored using 16S rRNA gene sequencing from metagenomic DNA.

Main Results:

• Initial inoculum dominated by Proteobacteria (68.1%).
• Significant shifts observed: Bacteroidetes and Firmicutes decreased, while Actinobacteria and TM7 increased.
• Phenol addition led to a surge in Proteobacteria (94.2%, mainly Brevundimonas), followed by a later increase in Bacteroidetes (47.3%, mainly Leadbetterella).
• Alphaproteobacteria initially unaffected but decreased as Bacteroidetes increased.

Conclusions:

• Biodegradation of phenolic compounds induces rapid and significant shifts in bacterial community structure within bioreactors.
• Specific phenolic compounds like phenol can selectively enrich certain bacterial groups, altering the microbial ecosystem over time.
• The study highlights the dynamic interplay between pollutant introduction and microbial population shifts in engineered environments.