PHYSICAL AND GENETIC-MAPPING OF THE GENOMES OF 5 MYCOPLASMA-HOMINIS STRAINS BY PULSED-FIELD GEL-ELECTROPHORESIS

We present the complete maps of five Mycoplasma hominis genomes, inclu ding a detailed restriction map and the locations of a number of genet ic loci. The restriction fragments were resolved by field inversion ge l electrophoresis or by the contour-clamped homogeneous-electric-field system of pulsed-field gel electrophoresis. All the ApaI, SmaI, BamHI , XhoI, and SalI restriction sites (total of 21 to 33 sites in each st rain) were placed on the physical map, yielding an average resolution of 26 kb. The maps were constructed using three different approaches: (i) size determination of DNA fragments partially or completely cleave d with one or two restriction enzymes, (ii) hybridization analysis wit h purified restriction fragments and specific probes, and (iii) use of linking clones. A genetic map was constructed by hybridization with g ene-specific probes for rpoA, rpoC, rrn, tuf, gyrB, hup, ftsY, the unc operon, the genes for two M. hominis-specific antigenic membrane prot eins, and one gene encoding a protein with some homology to Escherichi a coli alanyl-tRNA synthetase. The positions of mapped loci were parti ally conserved in the five strains except in one strain in which a 300 -kb fragment was inverted. The numbers and order of mapped restriction sites were only partly conserved, and this conservation was restricte d to certain regions. The gene order was compared with the gene order established for other bacteria and was found to be identical to that o f the phylogenetically related Clostridium perfringens. The genome siz e of the M. hominis strains varied from 704 to 825 kb.