Thirty-five isolates obtained from a marine electroactive biofilm grown on a stainless steel cathode (Genoa, Italy) were investigated by a polyphasic taxonomic approach. Whole-cell fatty acid methyl ester analysis indicated that the isolates belonged to the class Gammaproteobacteria and were closely related or belonging to the genus Alteromonas. Genomic fingerprinting using the BOX-PCR primer delineated five clusters of isolates with similar BOX-PCR fingerprints. This study demonstrated that isolates from four of the BOX-PCR clusters belonged to Alteromonas macleodii and that the 14 isolates representing BOX-PCR cluster 1 constituted a novel species, which shared 98.4 % 16S rRNA gene sequence similarity with its nearest phylogenetic neighbour, Alteromonas hispanica. Both phenotypic and genotypic analyses enabled this novel species, for which the name Alteromonas genovensis sp. nov. is proposed, to be differentiated from established species of the genus Alteromonas. The DNA G+C content of Alteromonas genovensis sp. nov. is 44.5 mol% and the type strain is LMG 24078(T) (=CCUG 55340(T)).