Classification of three airborne bacteria and proposal of Hymenobacter aerophilus sp. nov

Abstract

Three aerobic, gram-negative, rod-shaped, non-spore-forming, red-pigmented, airborne bacteria (I/26-Cor1T, I/32A-Cor1 and I/74-Cor2) collected in the Museo Correr (Venice, Italy) were investigated to determine their taxonomic status by analysing their biochemical, physiological and chemotaxonomic features and the G+C content of genomic DNA and by comparing their genomic fingerprints. Additionally, the almost complete 16S rRNA gene sequence of strain I/26-Cor1T was analysed. The three strains were nearly identical in their morphological, physiological, biochemical and chemotaxonomic properties. The strains contained a menaquinone system with the predominant menaquinone MK-7 and a fatty acid profile with C15:0 anteiso, C15:0 iso and C16:1 predominant. Phosphatidylethanolamine and several unidentified lipids were detected in the polar lipid profiles. The polyamine pattern consisted of sym-homospermidine as the major compound. meso-Diaminopimelic acid was found as the characteristic cell-wall diamino acid. The DNA base composition of the three strains ranged from 60 to 63 mol% G+C. Phylogenetically, strain I/26-Cor1T was most closely related to Hymenobacter actinosclerus (95.8% 16S rRNA gene sequence similarity). Physiological and genomic characteristics indicated that the two strains I/26-Cor1T and I/32A-Cor1 are representatives of the same species. The phylogenetic distance to any validly described taxon as indicated by 16S rRNA gene sequence similarities demonstrates that I/26-Cor1T and I/32A-Cor1 represent a novel species, for which the name Hymenobacter aerophilus sp. nov. is proposed, with the type strain I/26-Cor1T (= DSM 13606T = LMG 19657T). I/32A-Cor1 (= DSM 13607 = LMG 19658) is another strain of the species Hymenobacter aerophilus. Since the taxonomic status of strain I/74-Cor2 within the genus Hymenobacter was not determined unambiguously, it is designated Hymenobacter sp. I/74-Cor2 (= DSM 13611 = LMG 19659).