COLWELLIA-DEMINGIAE SP. NOV., COLWELLIA-HORNERAE SP. NOV., COLWELLIA-ROSSENSIS SP. NOV. AND COLWELLIA-PSYCHROTROPICA SP. NOV - PSYCHROPHILIC ANTARCTIC SPECIES WITH THE ABILITY TO SYNTHESIZE DOCOSAHEXAENOIC ACID (22 6-OMEGA-3)/

As part of a general survey of the biodiversity and inherent ecophysio logy of bacteria associated with coastal Antarctic sea-ice diatom asse mblages, eight strains were identified by 165 rRNA sequence analysis a s belonging to the genus Colwellia. The isolates were non-pigmented, c urved rod-like cells which exhibited psychrophilic and facultative ana erobic growth and possessed an Department of absolute requirement for sea water. One isolate was able to form gas vesicles. All strains synt hesized the omega 3 polyunsaturated fatty acid (PUFA) docosahexaenoic acid (22:6 omega 3, DHA) (0.7-8.0 % of total fatty acids). Previously, DHA has only been detected in strains isolated from deep-sea benthic and faunal habitats and is associated with enhanced survival in perman ently cold habitats. The G+C content of the DNA from the Antarctic Col wellia strains ranged from 35 to 42 mol% and DNA-DNA hybridization ana lyses indicated that the isolates formed five genospecies, including t he species Colwellia psychrerythraea (ACAM 550(T)). 16S rRNA sequence analysis indicated that the strains formed a cluster in the gamma-subc lass of the Proteobacteria with Colwellia psychrerythraea. Sequence si milarities ranged from 95.2 to 100% between the various Antarctic Colw ellia isolates. Phenotypic characterization confirmed distinct differe nces between the different genospecies. These studies indicate that th e DHA-producing Antarctic isolates consist of five different Colwellia species: Colwellia psychrerythraea and four novel species with the pr oposed names Colwellia demingiae sp. nov. (ACAM 459(T)), Colwellia psy chrotropica sp. nov. (ACAM 179(T)), Colwellia rossensis sp. nov. (ACAM 608(T)) and Colwellia hornerae sp. nov. (ACAM 607(T)).