Two slightly orange-pigmented, oxidase-positive bacterial strains (M1-83T and M2-116), isolated from horse blood collected during slaughter in Giessen, Germany, were studied in a polyphasic taxonomic approach. Cells of the isolates were coccoid and stained Gram-negative. The two strains shared identical 16S rRNA gene sequences but their genomic fingerprint patterns differed, indicating the genetic distinctiveness of the two strains. A comparison of the 16S rRNA gene sequence of strain M1-83T with sequences of the type strains of the most closely related Paracoccus species showed highest sequence similarities to Paracoccus acridae (98.2 %) and Paracoccus aerius (98.1 %). 16S rRNA gene sequence similarities to all other Paracoccus species were below 97.6 %. The fatty acid profile of the two strains consisted mainly of the major fatty acids C18 : 1 ω7c and C18:0, which is typical for the genus Paracoccus. The polyamine patterns of strain M1-83T contained major amounts of putrescine and spermidine. The major quinone was ubiquinone Q-10. The diamino acid of the peptidoglycan was meso-diaminopimelic acid. The polar lipid profile was characterized by the major lipids diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine, an unidentified aminolipid and an unidentified glycolipid. DNA-DNA hybridization experiments between M1-83T and the type strains of P. acridae and P. aerius resulted in similarity values of 17 % (reciprocal, 60 %) and 23 % (reciprocal 30 %), respectively. DNA-DNA hybridization results together with the differentiating biochemical and chemotaxonomic properties showed that strain M1-83T represents a novel Paracoccusspecies, for which the name Paracoccus haematequi sp. nov. (type strain M1-83T=LMG 30633T=CIP 111624T=CCM 8857T), is proposed.
Keywords: Paracoccus haematequi; taxonomy.