Abstract
Mycoplasma haemocanis is a hemotrophic mycoplasma (hemoplasma), blood pathogen that may cause acute disease in immunosuppressed or splenectomized dogs. The genome of the strain Illinois, isolated from blood of a naturally infected dog, has been entirely sequenced and annotated to gain a better understanding of the biology of M. haemocanis. Its single circular chromosome has 919 992 bp and a low G + C content (35%), representing a typical mycoplasmal genome. A gene-by-gene comparison against its feline counterpart, M. haemofelis, reveals a very similar composition and architecture with most of the genes having conserved synteny extending over their entire chromosomes and differing only by a small set of unique protein coding sequences. As in M. haemofelis, M. haemocanis metabolic pathways are reduced and apparently rely heavily on the nutrients afforded by its host environment. The presence of a major percentage of its genome dedicated to paralogous genes (63.7%) suggests that this bacterium might use antigenic variation as a mechanism to evade the host’s immune system as also observed in M. haemofelis genome. Phylogenomic comparisons based on average nucleotide identity (ANI) and tetranucleotide signature suggest that these two pathogens are different species of mycoplasmas, with M. haemocanis infecting dogs and M. haemofelis infecting cats.
Highlights
Hemotrophic mycoplasmas are uncultivable cell-wall less bacteria, formerly classified as Haemobartonella and Eperythrozoon species, that adhere to the surface of the erythrocytes of their vertebrate hosts
In 1961, Dr Lumb published the manuscript “Canine haemobartonellosis and its feline counterpart”, reporting cross-transmission experiments: it was shown that when blood from cats infected with M. haemocanis was injected into susceptible splenectomized dogs, organisms could be seen on their peripheral blood smears [8]
Mycoplasma haemocanis strain Illinois genome features The complete singular circular chromosome of M. haemocanis strain Illinois has a size of 919 992 base pairs and G + C content of 35%; these genomic features are similar to other hemoplasmas species sequenced to date [23,24,26,27] and within the range reported for other members of the genus Mycoplasma (Table 1)
Summary
Hemotrophic mycoplasmas (hemoplasmas) are uncultivable cell-wall less bacteria, formerly classified as Haemobartonella and Eperythrozoon species, that adhere to the surface of the erythrocytes of their vertebrate hosts. M. haemocanis, proposed species name since 2002 [5], is a pleomorphic bacterium with coccoid and ring forms that can be visualized in the host’s peripheral blood smear either singly or in chains that can resemble a “violin-bow” form [8] It may cause overt, hemolytic anemia in Similarities with the feline hemoplasma M. haemofelis [Haemobartonella felis], together with the fact that hemoplasmas are not species-specific as previously thought [15,16], led some research groups to hypothesize that these two bacteria could be the same species infecting different hosts [17,18]. In 1961, Dr Lumb published the manuscript “Canine haemobartonellosis and its feline counterpart”, reporting cross-transmission experiments: it was shown that when blood from cats infected with M. haemocanis was injected into susceptible splenectomized dogs, organisms could be seen on their peripheral blood smears [8]. While the results of the RNase P genes did not support the hypothesis that M. haemocanis and M. haemofelis were identical, this additional data was still considered insufficient to determine whether these organisms should be classified as different species, subspecies, or strains of the same species [18]
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