Arsenophonus apicola sp. nov., isolated from the honeybee Apis mellifera

Abstract

The genus <i>Arsenophonus</i> has been traditionally considered to comprise heritable bacterial symbionts of arthropods. Recent work has reported a microbe related to the type species <i>Arsenophonus nasoniae</i> as infecting the honey bee, <i>Apis mellifera</i>. The association was unusual for members of the genus in that the microbe-host interaction arose through environmental and social exposure rather than vertical transmission. In this study, we describe the <i>in vitro</i> culture of ArsBeeUS^T, a strain of this microbe isolated from <i>A. mellifera</i> in the USA. The 16S rRNA sequence of the isolated strain indicates it falls within the genus <i>Arsenophonus</i>. Biolog analysis indicates the bacterium has a restricted range of nutrients that support growth. <i>In vivo</i> experiments demonstrate the strain proliferates rapidly on injection into <i>A. mellifera</i> hosts. We further report the closed genome sequence for the strain. The genome is 3.3 Mb and the G+C content is 37.6 mol%, which is smaller than <i>A. nasoniae</i> but larger than the genomes reported for non-culturable <i>Arsenophonus</i> symbionts. The genome is complex, with six extrachromosomal elements and 11 predicted intact phage elements, but notably less complex than <i>A. nasoniae</i>. Strain ArsBeeUS^T is clearly distinct from the type species <i>A. nasoniae</i> on the basis of genome sequence, with 92 % average nucleotide identity. Based on our results, we propose <i>Arsenophonus apicola</i> sp. nov., with the type strain ArsBeeUS^T (CECT 30499^T=DSM113403^T=LMG 32504^T).