Four Gram-stain positive, rod-shaped bacterial isolates, strains JZ R-183T, JZ RK-117, DI-46 and JZ R-35T, were recovered from bulk tank raw cow's milk from three different dairy farms in Germany. Analysis of their 16S rRNA gene sequences indicated that these isolates belonged to the family Micrococcaceae, closely related to the genera Arthrobacter, Neomicrococcus,Glutamicibacter and Citricoccus. The 16S rRNA gene sequence similarity between the isolates and the next related type strains was below 97.3 %. Phylogenetic analysis of 16S rRNA, recA and gyrB genes revealed that these isolates formed two different groups in an independent cluster within the family Micrococcaceae. Chemotaxonomic analyses determined anteiso-C15 : 0 as predominant fatty acid, but also large amounts of iso-C15 : 0, iso-C16 : 0 and iso-C17 : 0 were detected. The menaquinones MK-9(H2) and MK-7(H2) were present in all of the isolates and the polar lipid pattern contained the phospholipids diphosphatidylglycerol, phosphatidylglycerol and phosphatidylinositol and a glycolipid. The peptidoglycan type of the isolates was A4α, with alanine, lysine and glutamate as dominating cell wall amino acids. The fatty acid and menaquinone profile differentiated the strains from the genera Arthrobacter, Neomicrococcus,Citricoccus and Glutamicibacter. The results of phylogenetic, phenotypic and chemotaxonomic analyses indicated that the isolates belonged to two novel species of a novel genus, for which the names Galactobacter caseinivorans gen. nov., sp. nov. and Galactobacter valiniphilus sp. nov. are proposed. The type strains are JZ R-183T (=DSM 107700T=LMG 30902T) and JZ R-35T (=DSM 107699T=LMG 30901T).
Keywords: Micrococcaceae; bulk tank milk; raw milk.