Diversity, abundance, and distribution of anammox bacteria in shipping channel sediment of Hong Kong by analysis of DNA and RNA.

Anammox bacteria have been detected in various ecosystems, but their occurrence and community composition along the shipping channels have not been reported. In this study, anammox bacteria were recovered by PCR-amplified biomarker hzsB gene from the genomic DNA of the sediment samples. Phylogenetic tree revealed that Candidatus Scalindua and Ca. Brocadia dominated the anammox community of the Hong Kong channels; Ca. Scalindua spp. was present abundantly at the sites farther from the shore, whereas Ca. Jettenia and Ca. Kuenenia were detected as the minor members in the estuarine sediments near the shipping terminals. The highest values of Shannon-Wiener index and Chao1 were identified in the sediments along the Urmston road (UR), suggesting the highest α-diversity and species richness of anammox bacteria. PCoA analysis indicated that anammox bacterial communities along UR and Tai Hong (TH) channel were site-specific because these samples were grouped and clearly separated from the other samples. The maximum diversity of anammox bacteria was detected in UR samples, ranging from 6.28 × 10 to 1.28 × 10 gene copies per gram of dry sediment. A similar pattern of their transcriptional activities was also observed among these channels. Pearson's moment correlation and redundancy analysis indicated that NH-N was a strong factor shaping the community structure, which showed significant positive correlation with the anammox bacterial abundance and anammox transcriptional activities (p < 0.01, r > 0.8). Also, NH-N, (NO + NO)-N, and NH/NO were additional key environmental factors that influenced the anammox community diversity and distribution. This study yields a better understanding of the ecological distribution of anammox bacteria and the dominant genera in selective niche.