Ecophysiological diversity of a novel member of the genus Alteromonas, and description of Alteromonas mediterranea sp. nov.

Abstract

Nine non-pigmented, motile, Gram-negative bacteria originally designated as Alteromonas macleodii deep-sea ecotypes, were isolated from seawater samples collected from four separate locations; two deep-sea sites in the Mediterranean Sea and surface water of the Aegean Sea and English Channel. The six strains studied in vitro were found to tolerate up to 20% NaCl. The DNA-DNA relatedness between the deep-sea ecotype strains was found to be between 75 and 89%, whilst relatedness with the validly named Alteromonas species was found to be between 31 and 69%. The average nucleotide identity (ANI) amongst the deep-sea ecotype strains was found to be 98-100%; the in silico genome-to-genome distance (GGD), 85-100%; the average amino acid identity (AAI) of all conserved protein-coding genes, 95-100%; and the strains possessed 30-32 of the Karlin's genomic signature dissimilarity. The ANI between the deep-sea ecotype strains and A. macleodii ATCC 27126(T) and Alteromonas australica H 17(T) was found to be 80.6 and 74.6%, respectively. A significant correlation was observed between the phenotypic data obtained in vitro and data retrieved in silico from whole genome sequences. The results of a phylogenetic study that incorporated a 16S rRNA gene sequence analysis, multilocus phylogenetic analysis (MLPA) and genomic analysis, together with the physiological, biochemical and chemotaxonomic data, clearly indicated that the group of deep-sea ecotype strains represents a distinct species within the genus Alteromonas. Based on these data, a new species, Alteromonas mediterranea, is proposed. The type strain is DE(T) (=CIP 110805(T)=LMG 28347(T)=DSM 17117(T)).