Comparison of microbial communities in replicated woodchip bioreactors

Denitrification in woodchip bioreactors is a microbial process, but the effects of variations in bioreactors operation on microbial community structure are not well understood. Here, our goals were to understand hydraulic retention time (HRT) as a factor that influences woodchip bioreactor microbial community variation and structure in replicated field bioreactors and to evaluate relationships between microbial community membership and marker genes for denitrification. We used a combination of quantitative polymerase chain reaction of nirS, nirK, nosZI, and nosZII and 16S rRNA amplicon sequencing to characterize the microbial communities of nine pilot-scale woodchip bioreactors located at Iowa State University. Our results showed dynamic microbial communities but with persistent taxa between two sampling years and three HRTs. Similarities between functional gene copy numbers across sampling year and HRT indicate that the potential for denitrification is conserved despite differences in the microbial communities. These results are evidence that there are specific and persistent taxa within replicated bioreactors. Woodchip bioreactor microbial community membership is recommended to be the focus of future studies to better understand the relationship between microbial community functions and bioreactor management.

Automated summary

This study used quantitative PCR and sequencing techniques to analyze microbial communities in woodchip bioreactors. The results showed dynamic microbial communities with persistent taxa between different sampling years and hydraulic retention times. The similarities in functional gene copy numbers suggest that the potential for denitrification is conserved across different microbial communities. The study recommends focusing on woodchip bioreactor microbial community membership in future research.