New insights on the biology of swine respiratory tract mycoplasmas from a comparative genome analysis

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.

Global Multilocus Sequence Typing Analysis of Mycoplasma bovis Isolates Reveals Two Main Population Clusters

“…However, other authors have demonstrated, using complete genome analysis, a possible role for sexual reproduction in the evolution of M. agalactiae (33). Moreover, recent studies have shown how recombination is directly involved in the evolution of members of the Mycoplasma mycoides cluster (34), as well as the porcine mycoplasmas M. hyopneumoniae and Mycoplasma flocculare (35). Given the extreme relatedness to M. agalactiae and the evidence of the effects of recombination in the evolution of other mycoplasmas, it is possible that M. bovis has followed a similar evolutionary pathway and therefore the lack of recombination observed after LIAN analysis can be explained by the choice of the housekeeping genes analyzed.…”

Comparative proteomics of twoMycoplasma hyopneumoniaestrains andMycoplasma flocculareidentified potential porcine enzootic pneumonia determinants

“…Genomic comparative analyzes demonstrated that the sets of adhesin-encoding genes from M. hyopneumoniae 7448 and J, and M. flocculare are quite similar, containing few qualitative differences between the adhesin repertoires of M. hyopneumoniae and M. flocculare [9]. The only differences are the absence of M. flocculare orthologs for one P97 paralog (P97 copy-1, MHP7448_0198), and one P102 paralog (P102 copy-1, MHP7448_0199), and some rearrangements in M. hyopneumoniae genomic regions containing adhesin genes in comparison to M. flocculare .…”

“…Comparisons between the genomes of M. hyopneumoniae pathogenic and non-pathogenic strains (7448 and J, respectively) revealed no extensive genomic differences [7]. Moreover, previous comparative phylogenetic and phylogenomic studies provided evidences of the close relationship of M. hyopneumoniae and M. flocculare [7–9], which share most of the known virulence-related genes [10]. The differences between M. hyopneumoniae and M. flocculare include the absence, in M. flocculare , of the glpO gene, related to M. hyopneumoniae hydrogen peroxide generation and cytotoxicity [11,12], and differential domains between orthologs from the P97 family of adhesins and from other surface proteins [13].…”

“…The differences between M. hyopneumoniae and M. flocculare include the absence, in M. flocculare , of the glpO gene, related to M. hyopneumoniae hydrogen peroxide generation and cytotoxicity [11,12], and differential domains between orthologs from the P97 family of adhesins and from other surface proteins [13]. However, 90% of M. flocculare predicted surface proteins are shared with M. hyopneumoniae [9], and the observed genomic differences between M. hyopneumoniae strains, and between M. hyopneumoniae and M. flocculare so far do not fully explain their differential phenotypes of virulence/pathogenicity.…”

Mycoplasma hyorhinis infection in early cases of mycoplasmal pneumonia in swine and evaluation of diagnostic assays

“…In vitro, M. hyorhinis growth is faster than M. hyopneumoniae. Siqueira et al (2013) showed the presence of metabolic genes in the M. hyorhinis genome that are absent in M. hyopneumoniae, suggesting a possible factor associated with the in vitro growth of this species.…”