title: Detection of Low-Level Cardinium and Wolbachia Infections in Culicoides.
abstract: Bacterial endosymbionts have been identified as potentially useful biological control agents for a range of invertebrate vectors of disease. Previous studies of Culicoides (Diptera: Ceratopogonidae) species using conventional PCR assays have provided evidence of Wolbachia (1/33) and Cardinium (8/33) infections. Here, we screened 20 species of Culicoides for Wolbachia and Cardinium, utilizing a combination of conventional PCR and more sensitive quantitative PCR (qPCR) assays. Low levels of Cardinium DNA were detected in females of all but one of the Culicoides species screened, and low levels of Wolbachia were detected in females of 9 of the 20 Culicoides species. Sequence analysis based on partial 16S rRNA gene and gyrB sequences identified "Candidatus Cardinium hertigii" from group C, which has previously been identified in Culicoides from Japan, Israel, and the United Kingdom. Wolbachia strains detected in this study showed 98 to 99% sequence identity to Wolbachia previously detected from Culicoides based on the 16S rRNA gene, whereas a strain with a novel wsp sequence was identified in Culicoides narrabeenensis. Cardinium isolates grouped to geographical regions independent of the host Culicoides species, suggesting possible geographical barriers to Cardinium movement. Screening also identified Asaia bacteria in Culicoides. These findings point to a diversity of low-level endosymbiont infections in Culicoides, providing candidates for further characterization and highlighting the widespread occurrence of these endosymbionts in this insect group.
authors.affiliation: Bio21 Institute and School of BioSciences, The University of Melbourne, Parkville, Victoria, Australia CSIRO Health & Biosecurity, Australian Animal Health Laboratory, Geelong, Victoria, Australia.
authors.forename: Peter T
authors.initials: PT
authors.lastname: Mee
authors.affiliation: Bio21 Institute and School of BioSciences, The University of Melbourne, Parkville, Victoria, Australia.
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Weeks
authors.affiliation: CSIRO Health & Biosecurity, Australian Animal Health Laboratory, Geelong, Victoria, Australia.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Walker
authors.affiliation: Bio21 Institute and School of BioSciences, The University of Melbourne, Parkville, Victoria, Australia.
authors.forename: Ary A
authors.initials: AA
authors.lastname: Hoffmann
authors.affiliation: CSIRO Health & Biosecurity, Australian Animal Health Laboratory, Geelong, Victoria, Australia Jean-Bernard.Duchemin@csiro.au.
authors.forename: Jean-Bernard
authors.identifier: http://orcid.org/0000-0001-5044-4855
authors.initials: JB
authors.lastname: Duchemin
mesh_terms: D000818:Animals; D001315:Australia; D041963:Bacteroidetes / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D002519:Ceratopogonidae / Q000382:microbiology*; D016000:Cluster Analysis; D027081:DNA Gyrase / Q000235:genetics; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D008969:Molecular Sequence Data; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D020577:Wolbachia / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*
chemical_list: D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S; D027081:DNA Gyrase