AUTHOR=Elbir Haitham , Abi-Rached Laurent , Pontarotti Pierre , Yoosuf Niyaz , Drancourt Michel 

TITLE=African Relapsing Fever Borreliae Genomospecies Revealed by Comparative Genomics

JOURNAL=Frontiers in Public Health

VOLUME=2

YEAR=2014

URL=https://www.frontiersin.org/journals/public-health/articles/10.3389/fpubh.2014.00043

DOI=10.3389/fpubh.2014.00043

ISSN=2296-2565

ABSTRACT=<p><bold>Background:</bold> Relapsing fever borreliae are vector-borne bacteria responsible for febrile infection in humans in North America, Africa, Asia, and in the Iberian Peninsula in Europe. Relapsing fever borreliae are phylogenetically closely related, yet they differ in pathogenicity and vectors. Their long-term taxonomy, based on geography and vector grouping, needs to be re-apprised in a genomic context. We therefore embarked into genomic analyses of relapsing fever borreliae, focusing on species found in Africa.</p><p><bold>Results:</bold> Genome-wide phylogenetic analyses group Old World <italic>Borrelia crocidurae, Borrelia hispanica, B. duttonii, and B. recurrentis</italic> in one clade, and New World <italic>Borrelia turicatae</italic> and <italic>Borrelia hermsii</italic> in a second clade. Accordingly, average nucleotide identity is 99% among <italic>B. duttonii, B. recurrentis</italic>, and <italic>B. crocidurae</italic> and 96% between latter borreliae and <italic>B. hispanica</italic> while the similarity is 86% between Old World and New World borreliae. Comparative genomics indicates that the Old World relapsing fever <italic>B. duttonii, B. recurrentis, B. crocidurae</italic>, and <italic>B. hispanica</italic> have a 2,514-gene pan genome and a 933-gene core genome that includes 788 chromosomal and 145 plasmidic genes. Analyzing the role that natural selection has played in the evolution of Old World borreliae species revealed that 55 loci were under positive diversifying selection, including loci coding for membrane, flagellar, and chemotaxis proteins, three categories associated with adaption to specific niches.</p><p><bold>Conclusion:</bold> Genomic analyses led to a reappraisal of the taxonomy of relapsing fever borreliae in Africa. These analyses suggest that <italic>B. crocidurae, B. duttonii</italic>, and <italic>B. recurrentis</italic> are ecotypes of a unique genomospecies, while <italic>B. hispanica</italic> is a distinct species.</p>