Loktanella salsilacus gen. nov., sp nov., Loktanella fryxellensis sp nov and Loktanella vestfoldensis sp nov., new members of the Rhodobacter group, isolated from microbial mats in Antarctic lakes

A taxonomic study was performed on 26 strains isolated from microbial mats in Antarctic lakes of the Vestfold Hills and the McMurdo Dry Valleys. Phylogenetic analysis based on 16S rRNA gene sequences placed these strains within the Rhodobacter group of the a-subclass of the Proteobacteria. Sequence similarity values for the strains with their nearest phylogenetic neighbours (Jannaschia, Octadecabacter and Ketogulonicigenium) ranged between 94-0 and 95-8%. DNA-DNA hybridizations and comparison of repetitive extragenic palindromic DNA-PCR (rep-PCR) fingerprinting patterns revealed that these strains are members of three distinct species. The isolates are Gram-negative, chemoheterotrophic, non-motile rods and their DNA G + C contents range from 59.4 to 66-4 mol%. Whole-cell fatty acid profiles are similar and the primary fatty acid in all the strains is 18 : 1 omega7c (74-1-87-7% of total). Genotypic results together with phenotypic characteristics allowed the differentiation of these species from related recognized species of the alpha-Proteobacteria and the strains are assigned to a new genus, Loktanella gen. nov., with three novel species: Loktanella salsilacus sp. nov. (type species), consisting of ten strains with LMG 21507(T) (=CIP 108322(T)) as type strain; Loktanella fryxellensis sp. nov., consisting of 12 strains with LMG 22007(T) (= CIP 108323(T)) as type strain; and Loktanella vestfoldensis sp. nov., consisting of four strains with LMG 22003(T) (= CIP 10832 1(T)) as type strain.