Temporal dynamics of bacterial communities and predicted nitrogen metabolism genes in a full-scale wastewater treatment plant

Abstract

The dynamics of bacterial communities in a full-scale wastewater treatment plant (WWTP) were investigated using Illumina MiSeq sequencing and PICRUSt (phylogenetic investigation of communities by reconstruction of unobserved states) over a one-year period. Results showed that the temporal dynamics of structure, diversity and abundance of bacterial community were not obvious. The persistent species had low diversity but high relative abundance. Dechloromonas, Thauera, Nitrosomonas and Nitrospira were the four dominant persistent genera. The intermittent and transient genera showed different dynamics with persistent genera. Variation partitioning analysis suggested that water quality indexes (13.40%) had the greatest contribution to bacterial community variation, followed by temperature (9.20%). Quantitative polymerase chain reaction analysis revealed the stable abundances of nitrifying and denitrifying bacteria, and the occurrence of complete ammonia oxidizers (Comammox) in the full-scale WWTP. Functional prediction showed that the bacterial functional compositions were also relatively stable, and metabolism was the most dominant functional category. Many genes involved in the nitrogen metabolism pathway were predicted to be present with high gene counts, e.g., nirB, nirD, nasA, norB, nirK, nosZ and nifH. Most of these genes were predicted to be mainly contributed by Rhizobiales, Burkholderiales, Rhodocyclales and Actinomycetales. Overall, the composition and function of bacterial community in a long-term monitoring were relatively stable, which is important for maintaining the high wastewater treatment capability in full-scale WWTPs.