Microbial community dynamics in replicate membrane bioreactors--natural reproducible fluctuations

Area of Science:

• Environmental microbiology
• Microbial ecology
• Biotechnology

Background:

• Engineered microbial systems rely on predictable community dynamics.
• Understanding microbial evolution in replicate bioreactors is crucial for process stability.

Purpose of the Study:

• To investigate the evolutionary trajectories of microbial communities in parallel membrane bioreactors (MBRs).
• To determine if acclimated microbial inocula evolve similarly when distributed evenly into replicate systems.
• To compare the evolution of overall microbial communities with specific nitrifying communities.

Main Methods:

• Operated 4 replicate MBRs with an acclimated seed inoculum.
• Utilized 16S rRNA gene cloning and sequencing, and terminal restriction fragment length polymorphism (T-RFLP) for microbial community analysis.
• Monitored the amoA functional gene using T-RFLP.
• Applied diversity indices, moving window similarity, non-metric multi-dimensional scaling (NMS), and multi-response permutation procedures (MRPP) for data analysis.

Main Results:

• 16S rRNA-based microbial communities initially diverged across MBRs, then converged by Day 4 and evolved similarly thereafter (average p-value=0.49).
• Nitrifying communities, monitored via amoA gene T-RFLP, showed no discernible temporal shifts and formed a single cluster (average p-value=0.83).
• The study confirmed similar evolutionary paths for microbial communities under unchanged operational parameters.

Conclusions:

• Acclimated microbial communities exhibit predictable and similar evolutionary trajectories in stable engineered systems.
• Nitrifying communities within these systems are less dynamic over the observed period.
• Operational stability is key to achieving consistent microbial community evolution in MBRs.