Abstract
Members of the haloarchaeal genera Halosarcina and Halogeometricum (family Halobacteriaceae) are closely related to each other and show 96.6-98 % 16S rRNA gene sequence similarity. This is higher than the accepted threshold value (95 %) to separate two genera, and a taxonomic study using a polyphasic approach of all four members of the two genera was conducted to clarify their relationships. Polar lipid profiles indicated that Halogeometricum rufum RO1-4(T), Halosarcina pallida BZ256(T) and Halosarcina limi RO1-6(T) are related more to each other than to Halogeometricum borinquense CGMCC 1.6168(T). Phylogenetic analyses using the sequences of three different genes (16S rRNA gene, rpoB' and EF-2) strongly supported the monophyly of these four species, showing that they formed a distinct clade, separate from the related genera Halopelagius, Halobellus, Haloquadratum, Haloferax and Halogranum. The results indicate that the four species should be assigned to the same genus, and it is proposed that Halosarcina pallida and Halosarcina limi be transferred to the genus Halogeometricum as Halogeometricum pallidum comb. nov. (type strain, BZ256(T) = KCTC 4017(T) = JCM 14848(T)) and Halogeometricum limi comb. nov. (type strain, RO1-6(T) = CGMCC 1.8711(T) = JCM 16054(T)).