Bartonella kosoyi sp. nov. and Bartonella krasnovii sp. nov., two novel species closely related to the zoonotic Bartonella elizabethae, isolated from black rats and wild desert rodent-fleas

Abstract

The genus <i>Bartonella</i> (Family: <i>Bartonellaceae</i>; Order: <i>Rhizobiales;</i> Class: Alphaproteobacteria) comprises facultative intracellular Gram-negative, haemotropic, slow-growing, vector-borne bacteria. Wild rodents and their fleas harbor a great diversity of species and strains of the genus <i>Bartonella</i>, including several zoonotic ones. This genetic diversity coupled with a fastidious nature of the organism results in a taxonomic challenge that has led to a massive collection of uncharacterized strains. Here, we report the genomic and phenotypic characterization of two strains, members of the genus <i>Bartonella</i> (namely Tel Aviv and OE 1-1), isolated from <i>Rattus rattus</i> rats and <i>Synosternus cleopatrae</i> fleas, respectively. Scanning electron microscopy revealed rod-shaped bacteria with polar pili, lengths ranging from 1.0 to 2.0 µm and widths ranging from 0.3 to 0.6 µm. OE 1-1 and Tel Aviv strains contained one single chromosome of 2.16 and 2.23 Mbp and one plasmid of 29.0 and 41.5 Kbp, with average DNA G+C contents of 38.16 and 38.47 mol%, respectively. These strains presented an average nucleotide identity (ANI) of 89.9 %. <i>Bartonella elizabethae</i> was found to be the closest phylogenetic relative of both strains (ANI=90.9-93.6 %). The major fatty acids identified in both strains were C_18:1ω7<i>c</i>, C_{18 : 0} and C_{16 : 0}. They differ from <i>B. elizabethae</i> in their C_{17 : 0} and C_{15 : 0} compositions. Both strains are strictly capnophilic and their biochemical profiles resembled those of species of the genus <i>Bartonella</i> with validly published names, whereas differences in arylamidase activities partially assisted in their speciation. Genomic and phenotypic differences demonstrate that OE 1-1 and Tel Aviv strains represent novel individual species, closely related to <i>B. elizabethae</i>, for which we propose the names <i>Bartonella kosoyi</i> sp. nov. and <i>Bartonella krasnovii</i> sp. nov.