The taxonomic characteristics of two bacterial strains, RB-8(T) and RB-9, isolated
from hydrocarbon-degrading enrichment cultures obtained from Antarctic coastal marine
environments (Rod Bay, Ross Sea), were determined. These bacteria were psychrophilic,
aerobic and Gram-negative with polar flagella. Growth was not observed in the absence
of NaCl, occurred only at concentrations of Na+ above 20 mM and was optimal at an
NaCl concentration of 3-5% (w/v). The major cellular fatty acids were monounsaturated
straight-chain fatty acids. The strains were able to synthesize the polyunsaturated
fatty acid eicosapentaenoic acid (20: 5omega3) at low temperatures. The DNA G + C
contents were 41-42 mol%. The strains formed a distinct phyletic line within the gamma-Proteobacteria,
with less than 89.6% sequence identity to their closest relatives within the Bacteria
with validly published names. Both isolates exhibited a restricted substrate profile,
with a preference for aliphatic hydrocarbons, that is typical of marine hydrocarbonoclastic
micro-organisms such as Alcanivorax, Marinobacter and Oleiphilus. On the basis of
ecophysiological properties, G + C content, 16S rRNA gene sequences and fatty acid
composition, a novel genus and species within the gamma-Proteobacteria are proposed,
Oleispira antarctica gen. nov., sp. nov.; strain RB-8(T) (= DSM 14852(T) = LMG 21398(T))
is the type strain.