Bacterial diversity of the cultivable fraction of a marine electroactive biofilm

Stainless steel electrodes were cathodically polarized at -200 mV versus an Ag/AgCl reference electrode in natural seawater in order to produce current. The current increased and stabilized at 0.5 A/m2 in less than 10 days. The cultivable fraction of the microbial biofilm population formed on the surface of the current harvesting cathodes was examined by culture dependent techniques. Three hundred fifty six isolates were obtained. They were primarily characterized by whole cell fatty acid methyl ester analysis followed by 16S rRNA gene sequencing. The results showed that the isolates represented different phylogenetic groups including members of the Alpha- and Gammaproteobacteria, the phylum Firmicutes, the family Flavobacteriacae and the phylum Actinobacteria. Denaturing gradient gel electrophoresis demonstrated that the microbial population of the biofilm formed on the cathode and of the surrounding seawater comprised the same dominant members. This study demonstrated that the cultivable microbial fraction of a marine electroactive biofilm is phylogenetically highly diverse.