Array-Based Genomic Comparative Hybridization Analysis of Field Strains of Mycoplasma hyopneumoniae

Departments of Veterinary Microbiology and Preventive Medicine and Statistics, Iowa State University, Ames, IA

^* To whom correspondence should be addressed. Email: fcminion{at}iastate.edu.

	Abstract

Mycoplasma hyopneumoniae is the causative agent of porcine enzootic pneumonia and a major factor in the porcine respiratory disease complex. A clear understanding of the mechanisms of pathogenesis does not exist although it is clear that M. hyopneumoniae adheres to porcine ciliated epithelium by action of a protein called P97. Previous studies have shown variation in the gene encoding the P97cilium adhesin within different strains of M. hyopneumoniae, but the extent of genetic variation among field strains across the genome is not known. Since M. hyopneumoniae is a worldwide problem, it is reasonable to expect that a wide range of genetic variability may exist given all of the different breed and housing conditions. This variation may impact the overall virulence of a single strain. Using microarray technology, this study examined potential variation of fourteen field strains in comparison to strain 232 on which the array was based. Genomic DNA was obtained, amplified with TempliPhi^TM, and labeled indirectly with Alexa dyes. Post genomic hybridization, the arrays were scanned and data analyzed using a linear statistical model. Results indicate that genetic variation could be detected in all fourteen field strains but across different loci, suggesting that variation occurs throughout the genome. Fifty-nine percent of the variable loci were hypothetical genes. Twenty-two percent of the lipoprotein genes showed variation in at least one field strain. A permutation test identified a location in M. hyopneumoniae genome where spatial clustering of variability between the field strains and strain 232 exists.