Characterization of the variability of a 75-kDa membrane protein in Mycoplasma hominis

The gene p75 encoding a 75-kDa surface-exposed membrane protein P75 was clo ned and sequenced from Mycoplasma hominis type strain PG21(T). To investiga te the intraspecies variability, sequences were obtained from an additional two isolates 7488 and 183, and the three sequences were compared. The nucl eotide and amino acid differences were not confined to specific regions of the gene/protein, but when comparing the three sequences, differences were present as single site substitutions or small insertions or deletions of nu cleotides/amino acids. The intraspecies variability was further investigate d by restriction enzyme analysis with two restriction enzymes (AluI and Mbo II) of PCR products amplified from p75 from 28 M. hominis isolates. On the basis of band patterns produced by the two restriction enzymes, the isolate s could be divided into five and sis groups. These groups neither matched c ategories of the M. hominis vaa gene nor the M. hominis p120 gene classes. indicating that the three genes vary by different mechanisms and possibly i ndicating horizontal gene transfer. (C) 2000 Federation of European Microbi ological Societies. Published by Elsevier Science B.V. All rights reserved.