Shewanella donghaensis sp nov., a psychrophilic, piezosensitive bacterium producing high levels of polyunsaturated fatty acid, isolated from deep-sea sediments

Abstract

A Gram-negative, motile, rod-shaped, psychrophilic bacterium, ILT17(T), was isolated from deep-sea sediments (3300 m depth) of the East Sea (Sea of Japan). Optimal growth of LT17(T) requires the presence of 2.5 % (w/v) NaCl, a pH of 7.0-7.5 and a temperature of 17 degrees C. The isolate grows optimally under a hydrostatic pressure of 10 MPa and growth is possible between 0.1 and < 30 MPa. The novel strain is positive in tests for catalase, oxidase, lipase, beta-glucosidase and gelatinase activities and reduces nitrate to nitrate. The predominant cellular fatty acids are iso-C13:0, iso-C15:0, C16:0, C16: 1 omega 7 and C20:5 omega 3. The DNA G+C content of strain LT17(T) is 38.8 mol%. Phylogenetic analysis of 16S rRNA gene sequences places this bacterium in the class Gammaproteobacteria, within the genus Shewanella. The closest relatives of strain LT17(T) are Shewanella japonica (97.8 % gene sequence similarity), Shewanella pacifica (97.5 %), Shewanella olleyana (96.8 %), Shewanella frigidimarina (96.5 %) and Shewanella gelidimarina (95.4 %). The DNA-DNA hybridization levels between the novel isolate and its closest known phylogenetic relatives, S. japonica and S. pacifica, are lower than 14 %. On the basis of this polyphasic evidence, strain ILT17(T) represents a novel species of the genus Shewanella, for which the name Shewanella donghaensis sp. nov. is proposed. The type strain is LT17(T) (= KCTC 10635BP(T)=JCMI 12524(T)).