Haloferax elongans sp nov and Haloterax mucosum sp nov., isolated from microbial mats from Hamelin Pool, Shark Bay, Australia

Extremely halophilic archaea. were cultivated from smooth and pustular microbial mats collected from Hamelin Pool, Shark Bay, Western Australia. On the basis of morphology, two phenotypes were present and 16S rRNA gene sequence analysis indicated that all strains were most closely related to members of the genus Haloferax (98.1 -99.4 % similarity). One representative T strain from each phenotype was selected for further taxonomic characterization. Strain SA5(T) isolated from the smooth mat, formed small (similar to 1 mm diameter), red, translucent colonies on agar medium and strain PA12(T), isolated from the pustular mat, formed large (3-5 mm diameter), pink, mucoid, domed colonies. Both strains grew in media with 1.7-5.1 M NaCl, required at least 0.2 M Mg2+ for growth and had pH optima of 7.4. The 16S rRNA gene similarity between strains SA5(T) and PA12(T) was 97.1 %. Physiological properties, G + C content and polar lipid composition supported placement of both strains in the genus Haloferax. Phenotypic analysis indicated that the two strains were distinct from each other and from all other members of the genus. This was confirmed by the low DNA-DNA relatedness between strains SA5(T) and PA12(T) (1 8-30%) and between both strains and all other recognized Haloterax species. Two novel species of the genus Haloferax are proposed to accommodate these novel isolates, Haloferax elongans sp. nov. (type strain SA5(T)=jCM 14791(T) = ATCC BAA- 1513(T)= UNSW 104100(T)) and Haloterax mucosum sp. nov. (type strain PA12(T)=jCM 14792(T)=ATCC BAA-1512(T)= UNSW 104200(T)).