Short Communication Diversity and Distribution of nirK-Harboring Denitrifying Bacteria in the Water Column in the Yellow River Estuary

We investigated the diversity and community composition of denitrifying bacteria in surface water from the Yellow River estuary. Our results indicated that the diversity of the denitrifying community in freshwater based on the nirK gene was higher than that in seawater. Furthermore, phylogenetic analysis suggested that the bacteria community could be distributed into eight clusters (Clusters I to VIII). Redundancy analysis (RDA) revealed that community compositions were related to multiple environment factors, such as salinity and nitrate concentration. The results of the present study have provided a novel insight into the denitrifying community in water columns in estuaries. Key words: denitrification, nirK gene, Yellow River estuary, water column Nutrient removal has played an important role in pre venting the eutrophication of receiving waters (22). Denitrification, as an effective way to remove nitrogen, is an alternative anaerobic respiration process that removes nitro gen via the microbial stepwise reduction of NO3 − to gaseous products (NO, N2O, N2) (5). Nitrite reductase is the rate limiting enzyme in denitrification, and catalyzes the step from nitrite reduction to nitric oxide. Thus, it has commonly bee