Co-occurrence of pederin-producing and Wolbachia endobacteria in Paederus fuscipes Curtis, 1840 (Coleoptera: Staphilinidae) and its evolutionary consequences

Abstract

The dual occurrence of Pseudomonas-like and Wolbachia endobacteria has not been investigated in the Pederus beetles yet. We investigated pederin-producing bacteria (PPB) infection in Paederus fuscipes specimens from the southern margins of the Caspian Sea by designed genus-specific (OprF) and species-specific (16S rRNA) primers. Wolbachia infection was studied through a nested-PCR assay of Wolbachia surface protein (wsp) gene. Of the 125 analyzed beetles, 42 females (82.35%) and 15 males (20.27%) were positive to PPB infection; this is the first study reporting male P. fuscipes infection to PPB. Wolbachia infection was found in 45 female (88.23%) and 50 male (67.57%) analyzed beetles. Surprisingly, a number of 36 females (70.59%) and 13 males (17.57%) were found to be infected with both PPB and Wolbachia endosymbionts. In general, population infection rates to PPB and Wolbachia were determined to be 45.6% and 76%, respectively. The infection rates of female beetles to PPB and PPB-Wolbachia were significantly higher than males. In Paederus species, only female beetles shelter PPB and the discovery of this bacterium in adult males may reflect their cannibalistic behavior on the contaminated stages. Phylogenetic analysis showed that the sequences of OprF gene were unique among Pseudomonas spp.; however, sequences of 16S rRNA gene were related to the PPB of Pederus species. The co-occurrence and random distribution of these endobacteria may imply putative tripartite interactions among PPB, Wolbachia, and Paederus. In order to elucidate these possible tripartite interactions, further studies are required even at gender level.

Keywords: 16S rRNA; OprF; Paederus; wsp; Pseudomonas-like; pederin.

Figure 1

Maximum likelihood tree showing the phylogenetic relationships between the OprF gene sequences obtained in this study (solid/empty circles) and other isolates of Pseudomonas spp. Solid and empty circles: bacterial genome amplified from female and male Paederus fuscipes, respectively; solid diamond: clinical isolate of Pseudomonas spp.; empty diamonds: environmental isolate of Pseudomonas spp. Pseudomonas putida was designated as outgroup. The numbers at the branch points are bootstrap values based on 1,000 replicates

Figure 2

Maximum likelihood tree showing the phylogenetic relationships among pederin‐producing bacteria (PPB) in Paederus spp. based on 16S rRNA gene sequences. Sequences obtained in this study are shown by solid circles. Pseudomonas aeruginosa was set as outgroup. The numbers at the branch points are bootstrap values based on 1,000 replicates