Assigning new supergroups V and W to the Wolbachia diversity

Abstract

Wolbachia are endosymbiotic and alphaproteobacteria that belong to the order Rickettsiales. They are known to infect half of the insect population and cause host manipulation, and have been categorized into 19 monophyletic lineages called supergroups. Recently, two strains, wCfeJ and wCfeT were isolated from cat fleas (Ctenocephalides felis), but their supergroup relationships were not assigned. In this article, we have attempted to classify these two novel strains and establish their evolutionary lineage (i.e., supergroup designation). For this we performed 16S rRNA similarity analysis and reconstructed 16S rRNA phylogeny of 52 Wolbachia strains (including two novel strains) belong to 19 supergroups. We also performed average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) studies to measure genomic similarity between the two novel genomes. The results revealed that 16S rRNA similarity between the two novel strains is 97.94%, which is below the threshold value of 98.6% and phylogeny shows that they are placed at the two different positions (i.e., showing distinct evolutionary lineages). Further, genomic similarity analysis revealed that the novel genomes have ANI and dDDH values 79% and 22.4% respectively, which were below the threshold value of ANI (95%) and dDDH (70%). These results suggested that the novel strains neither shared a species boundary between them nor with any other previously identified supergroups, which designate them as two new supergroups, namely supergroup V (strain wCfeJ) and supergroup W (strain wCfeT).

A survey of Wolbachia infection in brachyceran flies from Iran

“…Wolbachia is a widespread intracellular bacterial symbiont that has been isolated from various insect species, ticks, and nematodes [20][21][22]. The Wolbachia genus has only one species, which has recently, based on gene sequence information, been classified into 21 major clades of Wolbachia known as 'supergroups' (A-F, H-Q, and S-W), with each group being classified into dozens of different subgroups, often based on analysis of the bacterial surface protein (wsp) [23][24][25][26][27][28][29]. Supergroups A and B are known to exclusively infect arthropods.…”

“…It is known that different primer sets vary in their capability to detect Wolbachia in their hosts [35]. Different molecular markers such as 16s rRNA, ftsZ and wsp have been widely used to detect and to study the phylogenetics of Wolbachia [28,36], however, several investigations have shown the false negative for ftsZ [21,37,38] or false positive results for 16s rRNA and wsp markers in discriminating between supergroups A and B which can lead to unreliable results in bacterial detection when these primer sets are used alone [39]. Besides, detection of recombination both between and within Wolbachia genes [40] suggests that a single-locus approach to strain characterization may be misleading [41].…”