TRUNCATION AS A NOVEL FORM OF VARIATION OF THE P50 GENE IN MYCOPLASMA-HOMINIS

A characteristic feature of the mycoplasmas is the presence of variabl e surface proteins which may play an important role in the adaptation of the cell-wallless organisms to their host environments. In addition , this antigen variation may be an important pathogenic property of th e organism. The ubiquity of the gene encoding P50, an adhesin of Mycop lasma hominis FBG, and its transcription were analysed in different is olates of M. hominis, the p50 gene was present in all isolates tested. Based on Southern blot analysis and sequencing of the gene, the isola tes could be classified into one of three distinct groups. Within two groups specific truncations of the p50 gene occurred. The reduction of the gene size was confirmed in Northern blot analysis of representati ve isolates from each group, with a decrease in transcript length from 1.6 kb in group G-1 down to 0.76 kb in group G-3. In addition to trun cation, a coincidental duplication of some gene segments was detected. This work has provided evidence for the genetic basis of a further va riation in the M. hominis P50 adhesin.