Five Mycoplasma strains have been isolated from the oropharynx of southern sea otters (Enhydra lutris nereis) from the Central California Coast, USA. These strains were phenotypically and genetically characterized and compared to other established Mycoplasma species. All five strains hydrolysed arginine but not urea, but did not produce acid from glucose, and all were isolated and propagated under anaerobic and aerobic atmospheric conditions at +35-37 ˚C using either SP4 or PPLO medium supplemented with arginine. Colonies on solid medium showed a typical fried-egg appearance and transmission electron microscopy revealed a typical mycoplasma cellular morphology. Molecular characterization included assessment of the following genetic loci: 16S rRNA, 16S-23S rRNA ITS, rpoB, rpoC, polC, topIIA, tufB, arcA and smc. Complete 16S rRNA gene sequence analysis indicated that these strains were most closely related to M.ycoplasma phocicerebrale, and to M.ycoplasma arginini, M.ycoplasma gateae and M.ycoplasma canadense with nucleotide similarities of 99 and 98 %, respectively. Nucleotide analysis of other genetic loci revealed 73-91 % nucleotide similarity to the corresponding genes of the above closely related species. All five strains clustered into a distinct group on the 16S rRNA and rpoB phylogenetic trees. Serological testing via growth inhibition and metabolic inhibition tests employing antiserum to type strains of M. phocicerebrale, M. arginini, M. gateae and M. canadense failed to recognize these novel strains. Our results suggest that the strains isolated from southern sea otters represent a novel species of the genus Mycoplasma, for which the name Mycoplasma enhydrae sp. nov. is proposed; the type strain is 6243-11T (=DSM 106704T=ATCC TSD-140T).
Keywords: mycoplasmas; southern sea otters; wildlife.