Complete Genome Sequence of the Wolbachia wAlbB Endosymbiont of Aedes albopictus

Wolbachia , an alpha-proteobacterium closely related to Rickettsia is a maternally transmitted, intracellular symbiont of arthropods and nematodes. Aedes albopictus mosquitoes are naturally infected with Wolbachia strains w AlbA and w AlbB. Cell line Aa23 established from Ae. albopictus embryos retains only w AlbB and is a key model to study host-endosymbiont interactions. We have assembled the complete circular genome of w AlbB from the Aa23 cell line using long-read PacBio sequencing at 500X median coverage. The assembled circular chromosome is 1.48 megabases in size, an increase of more than 300 kb over the published draft w AlbB genome. The annotation of the genome identified 1,205 protein coding genes, 34 tRNA, 3 rRNA, 1 tmRNA and 3 other ncRNA loci. The long reads enabled sequencing over complex repeat regions which are difficult to resolve with short-read sequencing. Thirteen percent of the genome is comprised of IS elements distributed throughout the genome, some of which cause pseudogenization. Prophage WO genes encoding some essential components of phage particle assembly are missing, while the remainder are scattered around the genome. Orthology analysis identified a core proteome of 536 orthogroups across all completed Wolbachia genomes. The majority of proteins could be annotated using Pfam and eggNOG analyses, including ankyrins and components of the T4SS. KEGG analysis revealed the absence of 5 genes in w AlbB which are present in other Wolbachia . The availability of a complete circular chromosome from w AlbB will enable further biochemical, molecular and genetic analyses on this strain and related Wolbachia .