| Abstract | Two strains belonging to the genus Shewanella, HAW-EB2T and HAW-EB5T, were isolated previously from marine sediment sampled from the Atlantic Ocean, near Halifax harbour in Canada, for their potential to degrade explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). In the present study, strains HAW-EB2T and HAW-EB5T were found to display high 16S rRNA gene sequence similarity (90-99.5 %) to species of Shewanella, but their gyrB sequences were significantly different from each other and from species of Shewanella (79-87.6 %). Furthermore, DNA-DNA hybridization showed that the genomic DNA of the two strains was only 22 % related and showed less than 41 % relatedness to closely related species of Shewanella. In comparison to other species of Shewanella, strains HAW-EB2T and HAW-EB5T were also unique in some phenotypic properties such as activities of beta-galactosidase and tyrosine arylamidase and the ability to metabolize certain organic acids and sugars. Both strains HAW-EB2T and HAW-EB5T utilize malate, valerate, peptone and yeast extract as sole carbon and energy sources. The major membrane fatty acids of the two strains were C14 : 0, iso-C15 : 0, C16 : 0, C16 : 1{omega}7, C18 : 1{omega}7 and C20 : 5{omega}3 and their major quinones were Q-7, Q-8 and MK-7. On the basis of these results, strain HAW-EB2T (=NCIMB 14238T =CCUG 54553T) is proposed as the type strain of Shewanella canadensis sp. nov. and strain HAW-EB5T (=NCIMB 14239T =CCUG 54554T) is proposed as the type strain of Shewanella atlantica sp. nov. |
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