Camelimonas lactis gen. nov., sp. nov., isolated from the milk of camels

Abstract

Three strains of Gram-negative, rod-shaped, non-spore-forming bacteria (M 2040(T), M 1973 and M 1878-SK2), isolated from milk of camels at a camel-milk production farm in the United Arab Emirates, were investigated for their taxonomic allocation. On the basis of 16S rRNA gene sequence similarities, all three strains were shown to belong to the Alphaproteobacteria and were most closely related to Chelatococcus asaccharovorans and Chelatococcus daeguensis (95.1 and 95.2 % sequence similarity to the respective type strains). meso-Diaminopimelic acid was detected as the characteristic peptidoglycan diamino acid. The predominant compound in the polyamine pattern was spermidine, and sym-homospermidine was not detectable. The quinone system was ubiquinone Q-10. The polar lipid profile included the major compounds phosphatidylcholine and diphosphatidylglycerol and moderate amounts of phosphatidylethanolamine, phosphatidylglycerol, an unidentified glycolipid and two unidentified aminolipids. Minor lipids were also detected. The major fatty acid profile, consisting of C₁₉ :₀ cyclo ω8c and C₁₈:₁ ω7c, with C₁₈ :₀3-OH as the major hydroxylated fatty acid, was similar to those of the genus Chelatococcus. The results of DNA-DNA hybridization experiments and physiological and biochemical tests allowed both genotypic and phenotypic differentiation of the isolates from described Chelatococcus species. Isolates M 2040(T), M 1973 and M 1878-SK2 were closely related on the basis of DNA-DNA reassociation and therefore represent a single novel species. In summary, low 16S rRNA gene sequence similarities of 95 % with Chelatococcus asaccharovorans and marked differences in polar lipid profiles as well as in polyamine patterns support the description of a novel genus and species to accommodate these strains, for which the name Camelimonas lactis gen. nov., sp. nov. is proposed. The type strain of Camelimonas lactis is M 2040(T) (=CCUG 58638(T) =CCM 7696(T)).