Roles of nitrite in mediating the composition and metacommunity of multispecies biofilms

Abstract

Nitrite-based methods have been increasingly applied in various settings with the purpose of either biofilm control or bioprocess optimization. Nevertheless, little is known regarding how the bacterial community responds to nitrite exposure. In this study, it was found that exposure to low nitrite concentrations (0–60 mg-N/L) resulted in biomass increases in both mature and aging biofilms. However, exposure to higher nitrite concentrations (100 and 200 mg-N/L) led to decreased amounts of aging biofilms. The presence of nitrite resulted in decreased Live/Dead ratio of bacteria (from 24.97 ± 1.35–5.67 ± 0.57 in mature biofilm and from 18.67 ± 3.37 to 2.30 ± 0.30 in aging biofilm), but enhanced the aggregation of bacterial clusters. Sequencing analysis also indicated a dynamic succession of bacterial community structure. In comparison, the relative abundance of the Bacteroidetes phylum decreased with the addition of nitrite (from 22.83 ± 4.83 % at 0 mg-N/L to 1.21 ± 0.55 % at 200 mg-N/L). Interestingly, biofilm-forming bacteria in the same phylum (i.e., Proteobacteria) were found to respond to nitrite exposure differently, e.g., the relative abundance of the Aeromonas genus decreased (from 30.01 ± 8.76 % at 0 mg-N/L to 27.24 ± 1.21 % at 100 mg-N/L) but the Pseudomonas genera (from 8.73 ± 5.26 % at 0 mg-N/L to 30.04 ± 1.91 % at 100 mg-N/L) bloomed in mature biofilms. These results suggest that the presence of nitrite can not only determine the biofilm amounts but also impact the biofilm community structure.