Genomic and phenotypic comparisons reveal distinct variants of Wolbachia strain wAlbB

Abstract

The intracellular bacterium Wolbachia inhibits virus replication and is being harnessed around the world to fight mosquito-borne diseases through releases of mosquitoes carrying the symbiont. Wolbachia strains vary in their ability to invade mosquito populations and suppress viruses in part due to differences in their density within the insect and associated fitness costs. Using whole-genome sequencing, we demonstrate the existence of two variants in wAlbB, a Wolbachia strain being released in natural populations of Aedes aegypti mosquitoes. The two variants display striking differences in genome architecture and gene content. Differences in the presence/absence of 49 genes between variants include genes located in prophage regions and others potentially involved in controlling the symbiont’s density. Importantly, we show that these genetic differences correlate with variation in wAlbB density and its tolerance to heat stress, suggesting that different wAlbB variants may be better suited for field deployment depending on local environmental conditions. Finally, we found that the wAlbB genome remained stable following its introduction in a Malaysian mosquito population. Our results highlight the need for further genomic and phenotypic characterization of Wolbachia strains in order to inform ongoing Wolbachia-based programmes and improve the selection of optimal strains in future field interventions.

DevelopingWolbachia-based disease interventions for an extreme environment

“…The w AlbB infection was originally transferred from Ae. albopictus via microinjection 83 and is a w AlbB-I variant of the strain 84 . The w MelM infection is a clade I variant of w Mel that was transferred from temperate D. melanogaster via microinjection 64 .…”

pWCP is a widely distributed and highly conserved Wolbachia plasmid in Culex mosquitoes worldwide

“…Most pWCP-born genes were initially found exclusively in Wolbachia from Culex quinquefasciatus (wPip, (Klasson et al, 2008) and/or to the phylogenetic supergroup B-Wolbachia. Very recently, several homologous genes were identified in other Wolbachia supergroups from Aedes albopictus mosquitoes and other insect species, as part of other novel plasmids (Martinez et al, 2022). Similar to pWCP, plasmids of Wolbachia endosymbiont wAlbA 1 and 2 (namely pWALBA1 and pWALBA2) include a parAlike partitioning gene and a RelBE toxin-antitoxin system, supporting the likely functional importance of these elements in a plasmid context.…”

Developing Wolbachia-based disease interventions for an extreme environment

“…The wAlbB infection was originally transferred from Ae. albopictus via microinjection [83] and is a wAlbB-Hou variant of the strain [84]. The wMelM infection is a clade I variant of wMel that was transferred from temperate D. melanogaster via microinjection [64].…”