Abstract
BackgroundMycoplasma hyopneumoniae, Mycoplasma flocculare and Mycoplasma hyorhinis live in swine respiratory tracts. M. flocculare, a commensal bacterium, is genetically closely related to M. hyopneumoniae, the causative agent of enzootic porcine pneumonia. M. hyorhinis is also pathogenic, causing polyserositis and arthritis. In this work, we present the genome sequences of M. flocculare and M. hyopneumoniae strain 7422, and we compare these genomes with the genomes of other M. hyoponeumoniae strain and to the a M. hyorhinis genome. These analyses were performed to identify possible characteristics that may help to explain the different behaviors of these species in swine respiratory tracts.ResultsThe overall genome organization of three species was analyzed, revealing that the ORF clusters (OCs) differ considerably and that inversions and rearrangements are common. Although M. flocculare and M. hyopneumoniae display a high degree of similarity with respect to the gene content, only some genomic regions display considerable synteny. Genes encoding proteins that may be involved in host-cell adhesion in M. hyopneumoniae and M. flocculare display differences in genomic structure and organization. Some genes encoding adhesins of the P97 family are absent in M. flocculare and some contain sequence differences or lack of domains that are considered to be important for adhesion to host cells. The phylogenetic relationship of the three species was confirmed by a phylogenomic approach. The set of genes involved in metabolism, especially in the uptake of precursors for nucleic acids synthesis and nucleotide metabolism, display some differences in copy number and the presence/absence in the three species.ConclusionsThe comparative analyses of three mycoplasma species that inhabit the swine respiratory tract facilitated the identification of some characteristics that may be related to their different behaviors. M. hyopneumoniae and M. flocculare display many differences that may help to explain why one species is pathogenic and the other is considered to be commensal. However, it was not possible to identify specific virulence determinant factors that could explain the differences in the pathogenicity of the analyzed species. The M. hyorhinis genome contains differences in some components involved in metabolism and evasion of the host’s immune system that may contribute to its growth aggressiveness. Several horizontal gene transfer events were identified. The phylogenomic analysis places M. hyopneumoniae, M. flocculare and M. hyorhinis in the hyopneumoniae clade.
Highlights
Mycoplasma hyopneumoniae, Mycoplasma flocculare and Mycoplasma hyorhinis live in swine respiratory tracts
General genome features of M. flocculare and M. hyopneumoniae 7422 The M. flocculare and M. hyopneumoniae 7422 genomes are composed of single, circular chromosomes of 763,948 and 899,887 bp with 28.9% and 28.4% GC contents, respectively
The comparative analyses of three mycoplasma species that inhabit the swine respiratory tract facilitated the identification of some characteristics that may promote the understanding of their different behaviors
Summary
Mycoplasma hyopneumoniae, Mycoplasma flocculare and Mycoplasma hyorhinis live in swine respiratory tracts. We present the genome sequences of M. flocculare and M. hyopneumoniae strain 7422, and we compare these genomes with the genomes of other M. hyoponeumoniae strain and to the a M. hyorhinis genome These analyses were performed to identify possible characteristics that may help to explain the different behaviors of these species in swine respiratory tracts. M. hyopneumoniae is the etiological agent of porcine mycoplasmal pneumonia, while M. hyorhinis, which causes polyserositis and arthritis, is frequently found in swine respiratory tracts [13]. While M. flocculare is restricted to the swine respiratory tract, M. hyopneumoniae and M. hyorhinis can colonize other sites, such as cardiac or joint tissues [14,16] These bacteria can even colonize different hosts; M. hyorhinis has been detected in human carcinoma tissues [17,18]. The genetic maps of M. flocculare ATCC 27716 and M. hyopneumoniae strain J have been compared, revealing that at least three chromosomal inversions have occurred since the divergence of both species [19]
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