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Array-based genomic comparative hybridization analysis of field strains of Mycoplasma hyopneumoniae
Melissa L Madsen1, Michael J Oneal, Stuart W Gardner
1Department of Veterinary Microbiology and Preventive Medicine, Iowa State University, Ames, IA 50011, USA.
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 P97 cilium adhesin in 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 breeds and housing conditions. This variation may impact the overall virulence of a single strain. Using microarray technology, this study examined the potential variation of 14 field strains compared to strain 232, on which the array was based. Genomic DNA was obtained, amplified with TempliPhi, and labeled indirectly with Alexa dyes. After genomic hybridization, the arrays were scanned and data were analyzed using a linear statistical model. The results indicated that genetic variation could be detected in all 14 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 the M. hyopneumoniae genome where there is spatial clustering of variability between the field strains and strain 232.
Insights
Genetic variation exists throughout the Mycoplasma hyopneumoniae genome in field strains. This variability, particularly in hypothetical and lipoprotein genes, may influence the virulence of this swine respiratory disease agent.
Area of Science:
- Veterinary Microbiology
- Genomics
- Animal Pathology
Background:
- Mycoplasma hyopneumoniae causes swine enzootic pneumonia, a key component of the porcine respiratory disease complex.
- Pathogenesis mechanisms are not fully understood, but P97 adhesion protein is crucial for binding to ciliated epithelium.
- Previous research noted P97 gene variation, but genome-wide genetic diversity in field strains remained unknown.
Purpose of the Study:
- To investigate the extent of genome-wide genetic variation among 14 Mycoplasma hyopneumoniae field strains.
- To compare field strains against a reference strain (232) using microarray technology.
- To identify potential impacts of genetic variation on strain virulence.
Main Methods:
- Microarray analysis was employed to examine 14 field strains against a reference strain.
- Genomic DNA was extracted, amplified, labeled, and hybridized to the microarray.
- Data analysis utilized a linear statistical model and permutation testing.
Main Results:
- Significant genetic variation was detected across different loci in all 14 field strains.
- Fifty-nine percent of variable loci corresponded to hypothetical genes.
- Twenty-two percent of lipoprotein genes exhibited variation in at least one field strain.
- A specific genomic region showed spatial clustering of variability.
Conclusions:
- Mycoplasma hyopneumoniae field strains display considerable genome-wide genetic variation.
- Hypothetical and lipoprotein genes are frequently involved in this variation.
- Identified variability patterns may contribute to differences in virulence among field strains.
