In a number of weevil species it has been shown that endosymbionts are frequently found within specialized host cells (so-called bacteriocytes) sometimes forming a distinctive organ,

the bacteriome, which is often associated with the larval midgut [29, 30, 41–43]. As Buchner [44] has described a bacteriome in Otiorhynchus spp., we assume that the four Otiorhynchus species analysed in the present study also harbour their endosymbiotic bacteria intracellularly in a bacteriome. However, this assumption has to be confirmed via microscopic examinations of the respective organs. For a couple of insects and their associated microorganisms it has been shown, that endosymbiotic bacteria are known AZD8186 order to be involved in protecting their host MLN8237 purchase insect against natural antagonists such as predators and pathogens or are even implicated in insecticide resistance OICR-9429 ic50 mechanisms (for a review see Zindel et al [45]). Moreover, particularly obligatory endosymbionts are essential for central functions of their host insect [3]. Accordingly, endosymbiotic bacteria are an interesting target for direct or indirect manipulation, thus offering new possibilities for designing insect control strategies [45–47]. Identification of respective endosymbiotic organisms of the target insect is an important step in exploring

these associations for potential use in insect pest control. Thanks to the agar-based artificial diet for rearing of O. sulcatus [48], physiological, nutritional and reproductive studies will be carried out to analyse the respective effects of symbionts on the host development and reproduction. Conclusions In this study, endosymbiotic bacterial diversity in weevil larvae was assessed via multitag 454 pyrosequencing of a bacterial 16S rRNA fragment. Pyrosequencing is therefore a promising, fast and economic alternative to other culture-independent methods in metagenomics like

DGGE (Denaturing Gradient Gel Electrophoresis) or SSCP (Single Strand Conformation Polymorphism), which have been Urease used in bacterial community studies of the red turpentine beetle [49] or for diversity assessment of gut microbiota in bees [50], respectively. However, as 454 pyrosequencing generates only quite short sequences, results of such studies can just be regarded as a first step towards identifying respective endosymbiotic species in insects. Accordingly, a subsequent analysis of sequences of specific gene regions of selected endosymbiont genera detected via 454 pyrosequencing revealed the presence of endosymbionts of the genera Rickettsia and “Candidatus Nardonella” in Otiorhynchus spp.. Further studies are now required to clarify the biological function of these endosymbiotic bacteria in Otiorhynchus spp. and their potential as novel targets for weevil pest control.