SHEWANELLA-GELIDIMARINA SP. NOV. AND SHEWANELLA-FRIGIDIMARINA SP. NOV., NOVEL ANTARCTIC SPECIES WITH THE ABILITY TO PRODUCE EICOSAPENTAENOIC ACID (20 5-OMEGA-3) AND GROW ANAEROBICALLY BY DISSIMILATORY FE(III) REDUCTION/

A polyphasic taxonomic study was performed to characterize dissimilato ry iron-reducing strains mostly isolated from Antarctic sea ice. The s trains were isolated from samples of congelated (land-fast) sea ice, g rease ice, and ice algal biomass collected from the coastal areas of t he Vestfold Hills in eastern Antarctica (68 degrees S 78 degrees E). T he strains were facultatively anaerobic, motile, and rod shaped, were capable of anaerobic growth either by fermentation of carbohydrates or by anaerobic respiration, and utilized a variety of electron acceptor s, including nitrate, ferric compounds, and trimethylamine N-oxide. A phylogenetic analysis performed with 16S rRNA sequences showed that th e isolates formed two groups representing novel lineages in the genus Shewanella. The first novel group included seawater-requiring, psychro philic, chitinolytic strains which had DNA G+C contents of 48 mol%, Th e members of the second strain group were psychrotrophic and did not r equire seawater but could tolerate up to 9% NaCl, The strains of this group were also unable to degrade polysaccharides but could utilize a number of monosaccharides and disaccharides asd had G+C contents of 40 to 43 mol%, The whole-cell-derived fatty acid profiles of the sea ice isolates were found to be similar to the profiles obtained far other Shewanella species, The omega-3 polyunsaturated fatty acid eicosapenta enoic acid (EPA) (20:5 omega 3) was detected in all of the sea ice iso lates at levels ranging from 2 to 16% of the total fatty acids, EPA wa s also found at high levels in Shewanella hanedai (19 to 22%) and Shew anella benthica (16 to 18%) but was absent in Shewanella alga and Shew anella putrefaciens. On the basis of polyphasic taxonomic data, the An tarctic iron-reducing strains are placed In two new species, Shewanell a frigidimarina sp, nov, (type strain, ACAM 591) and Shewanella gelidi marina sp, nor, (type strain, ACAM 456).