Corynebacterium pseudotuberculosis may be under anagenesis and biovar Equi forms biovar Ovis: a phylogenic inference from sequence and structural analysis

Abstract

BackgroundCorynebacterium pseudotuberculosis can be classified into two biovars or biovars based on their nitrate-reducing ability. Strains isolated from sheep and goats show negative nitrate reduction and are termed biovar Ovis, while strains from horse and cattle exhibit positive nitrate reduction and are called biovar Equi. However, molecular evidence has not been established so far to understand this difference, specifically if these C. pseudotuberculosis strains are under an evolutionary process.ResultsThe ERIC 1 + 2 Minimum-spanning tree from 367 strains of C. pseudotuberculosis showed that the great majority of biovar Ovis strains clustered together, but separately from biovar Equi strains that also clustered amongst themselves. Using evolutionarily conserved genes (rpoB, gapA, fusA, and rsmE) and their corresponding amino acid sequences, we analyzed the phylogenetic relationship among eighteen strains of C. pseudotuberculosis belonging to both biovars Ovis and Equi. Additionally, conserved point mutation based on structural variation analysis was also carried out to elucidate the genotype-phenotype correlations and speciation. We observed that the biovars are different at the molecular phylogenetic level and a probable anagenesis is occurring slowly within the species C. pseudotuberculosis.ConclusionsTaken together the results suggest that biovar Equi is forming the biovar Ovis. However, additional analyses using other genes and other bacterial strains are required to further support our anagenesis hypothesis in C. pseudotuberculosis.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-016-0717-4) contains supplementary material, which is available to authorized users.

Rapidly evolving changes and gene loss associated with host switching in Corynebacterium pseudotuberculosis

“…The phylogenetic trees separate biovar Ovis from Equi with at least 90% of confidence value, clearly showing it as a monophyletic group ( S2 and S3 Figs). This confirms what has been seen in previous studies [ 32 , 33 , 87 ]. In addition, the Equi from buffalo and horse formed a clade with two different clusters representing each host.…”

“…In a previous study, C . pseudotuberculosis was suggested to be under anagenesis and that Ovis would replace Equi [ 87 ]. However, Equi has horse and buffalo as exclusive hosts [ 19 , 31 ] and infections of horses are increasing in frequency in North America [ 28 ].…”

Quadruplex PCR assay for identification of Corynebacterium pseudotuberculosis differentiating biovar Ovis and Equi

“…These results are especially significant considering that C. pseudotuberculosis infects a wide range of hosts and produce different clinical manifestations. Furthermore, it was recently suggested that C. pseudotuberculosis biovars have differences at the molecular phylogenetic level, indicating an anagenesis process within the species [ 37 , 49 ]. The evolutionary analysis of conserved genes ( rpoB, gapA, fusA, and rsmE ) suggesting a gradual anagenesis of C. pseudotuberculosis in that study [ 49 ] substantially increases the importance of a molecular technique capable of efficiently separating the biovars Ovis and Equi.…”

“…Furthermore, it was recently suggested that C. pseudotuberculosis biovars have differences at the molecular phylogenetic level, indicating an anagenesis process within the species [ 37 , 49 ]. The evolutionary analysis of conserved genes ( rpoB, gapA, fusA, and rsmE ) suggesting a gradual anagenesis of C. pseudotuberculosis in that study [ 49 ] substantially increases the importance of a molecular technique capable of efficiently separating the biovars Ovis and Equi. In fact, a pan-genome analysis of fifteen C. pseudotuberculosis strains showed a significant number of genes not shared by both biovars, including remarkable differences in the 16 detected pathogenicity islands [ 50 ].…”

Insight of Genus Corynebacterium: Ascertaining the Role of Pathogenic and Non-pathogenic Species

“…Particularly, Phylogenetic approaches can be applied as methods for the identification of new species formation. It was a goal of a recent work showing events of biological speciation (Oliveira et al, 2016 ), among strains of the C. pseudotuberculosis species, in which it was proposed these strains could be under anagenesis process checking information such as: presence of biovar equi or ovis, evolutionary divergences, number of transition, and transversion substitutions and protein structure analysis.…”