Truncation as a novel form of variation of the p50 gene in Mycoplasma hominis

Institute for Medical Microbiology and Virology, Moorenstrasse 5, hein rich-Heine-University,40225 Duesseldorf, Germany 2 Author for correspondence: Birgit Henrich. Tel: +49 211 811 5206. Fax: +49 211 811 5323.e-mail: Birgit.Henrich@uni-duesseldorf.de ABSTRACT SUMMARY: A characteristic feature of the mycoplasmas is the presence of variable surface proteins which may play an important role in the adaptation of the cell-wall-less organisms to their host environments. In addition, this antigen variation may be an important pathogenic property of the organism. The ubiquity of the gene encoding P50, an adhesin of Mycop/asrna hominis FBG, and its transcription were analysed in different isolates ofM. horninis. The p50 gene was present in all isolates tested. Based on Southern blot analysis and sequencing of the gene, the isolates could be classified into one of threedistinct groups. Within two groups specific truncations of the p50 gene occurred. The reduction of the gene size was confirmed in Northern blot analysis of representative isolates from each group, with a decrease in transcript length from 1.6 kb in group G-1 down to 076 kb in group 6-3. In addition to truncation, a coincidental duplication of some gene segments was detected. This work has provided evidence for the genetic basis of a further variation in the M. horninis P50 adhesin. Keywords: Mycoplasma hominis, adhesin, antigen variation, gene diversity, mutagenesis