Analysis of putative ABC transporter genes in Mycoplasma hyopneumoniae

A previously described DNA probe specific for Mycoplasma hyopneumoniae (I-141) was fully sequenced and found to consist of 1618 bp and to contain two tandemly repeated ORFs. The deduced amino acid sequence of the two ORFs showed significant homologies with ATP-binding cassette (ABC) transporter proteins, particularly those of the eukaryotic multidrug resistance (MDR) protein family (up to 21% identity and 47% similarity). A somewhat lower homology was evident with the secretion protein HlyB of the RTX-haemolysin from Escherichia coli. The location of the two ORFs on the M. hyopneumoniae chromosome was downstream of the rrl gene encoding the 23S rRNA, but transcribed in the opposite direction. PCR amplification and subsequent chromosomal analysis by Southern blot hybridization of several M. hyopneumoniae strains showed that all field strains contained the two putative ABC transporter genes. However, some culture collection strains derived from strain J had lost these genes as the result of a 2221 bp deletion.