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 co ntain two tandemly repeated ORFs. The deduced amino acid sequence of t he two ORFs showed significant homologies with ATP-binding cassette (A BC) transporter proteins, particularly those of the eukaryotic multidr ug resistance (MDR) protein family (up to 21% identity and 47% similar ity). 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 bl ot hybridization of several M. hyopneumoniae strains showed that all f ield 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.