title: New insights on the biology of swine respiratory tract mycoplasmas from a comparative genome analysis.
abstract: BACKGROUND
  Mycoplasma 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.
  
  
  RESULTS
  The 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.
  
  
  CONCLUSIONS
  The 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.
authors.affiliation: Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, Brazil.
authors.forename: Franciele Maboni
authors.initials: FM
authors.lastname: Siqueira
authors.forename: Claudia Elizabeth
authors.initials: CE
authors.lastname: Thompson
authors.forename: Veridiana Gomes
authors.initials: VG
authors.lastname: Virginio
authors.forename: Taylor
authors.initials: T
authors.lastname: Gonchoroski
authors.forename: Luciano
authors.initials: L
authors.lastname: Reolon
authors.forename: Luiz Gonzaga
authors.initials: LG
authors.lastname: Almeida
authors.forename: Marbella Maria
authors.initials: MM
authors.lastname: da Fonsêca
authors.forename: Rangel
authors.initials: R
authors.lastname: de Souza
authors.forename: Francisco
authors.initials: F
authors.lastname: Prosdocimi
authors.forename: Irene Silveira
authors.initials: IS
authors.lastname: Schrank
authors.forename: Henrique Bunselmeyer
authors.initials: HB
authors.lastname: Ferreira
authors.forename: Ana Tereza Ribeiro
authors.initials: AT
authors.lastname: de Vasconcelos
authors.forename: Arnaldo
authors.initials: A
authors.lastname: Zaha
mesh_terms: D000818:Animals; D002874:Chromosome Mapping; D016678:Genome; D009174:Mycoplasma / Q000145:classification* / Q000235:genetics* / Q000472:pathogenicity; D010802:Phylogeny; D045729:Pneumonia of Swine, Mycoplasmal / Q000235:genetics / Q000382:microbiology* / Q000473:pathology; D012137:Respiratory System / Q000382:microbiology* / Q000473:pathology; D013552:Swine