Bacterial Diversity of Marine Biofilm Communities in Terra Nova Bay (Antarctica) by Culture-Dependent and -Independent Approaches

Applying both culture-independent and -dependent approaches, bacterial diversity of marine biofilm communities colonising polyvinyl chloride panels submerged in Terra Nova Bay (Ross Sea, Antarctica) was investigated. Panels were deployed in two sites subjected to a different degree of anthropogenic impact (Road Bay [RB] impacted site and Punta Stocchino [PTS] control site). Biofilm samples were collected after 3 or 12 months to evaluate both short- and long-term microbial colonisation. Taxonomic composition of the microbial community was studied by 16S rRNA gene amplicon sequencing. Proteobacteria was the predominant phylum, followed by Bacteroidetes, Actinobacteria, Verrucomicrobia and Firmicutes. Impacted RB biofilms were found to contain a relevant fraction of potentially pathogenic bacterial genera, accounting for 27.49% of the whole community. A total of 86 psychrotolerant bacterial strains were isolated from the biofilm samples using culture-dependent techniques designed to enrich in Actinobacteria. These strains were assigned to three different phyla: Actinobacteria (54.65%), Firmicutes (32.56%) and Proteobacteria (12.79%). 2.73% of genera identified by metabarcoding were recovered also through cultivation, while 11 additional genera were uniquely yielded by cultivation. Functional screening of the isolates revealed their hydrolytic and oxidative enzyme activity patterns, giving new insights into the metabolic and biotechnological potential of microbial biofilm communities in Terra Nova Bay seawater.