Taxonomic profile of bacterial communities detected with 16S-rRNA in mature phototrophic and heterotrophic marine biofilms used for aquaculture

Bacterial diversity of phototrophic (PAb) and heterotrophic (Hb) biofilms was studied over time (0, 15 and 30 days of culture) using high throughput sequencing and considering the V3 and V4 hypervariable regions of the 16S rRNA gene. Bacterial composition in terms of relative abundance and diversity showed slight changes during the trial. Proteobacteria was the most abundant phylum in both biofilms during the experimental period. Chlamidiae-Verrucomicrobia, Bacteriodetes, and Planctomycetes were also abundant phyla in the PAb, whereas Planctomycetes, Bacteriodetes, Actinobacteria, and Chlamydiae were the abundant phyla in the Hb. Of the reads assigned up to species level, a total of 27 heterotrophic and autotrophic species were detected in both biofilms, most of them associated with the metabolism of nitrogenous and sulfurous metabolites and organic matter, and the rest with the structural functions in the biofilm. This is the first time some of these species have been reportedly detected in these biofilms or in the marine environment. Results suggest complex interaction networks in microbial conglomerates formed in biofilms, in which bacterial populations seem to play important metabolic and physiological roles.