These endosymbionts are dispersed throughout different arthropod classes, including a wide range of insect species . Although their biological role needs to be largely elucidated, these ‘arthropod Rickettsia’ can act as reproductive parasites. In the ladybirds
Adalia bipunctata and Adalia decempunctata as well as in the buprestid beetle Brachys tessellatus the endosymbiont has been RepSox demonstrated to cause male embryonic lethality [19–21]. Further, parthenogenesis find more induction is described in the parasitoid wasps Pnigalio soemius and Neochrysocharis formosa [22, 23]. Perotti et al.  also found evidence of an obligate Rickettsia in the booklouse Liposcelis bostrychophila with a key role for egg production. Endosymbiotic bacteria have been described in harmful as well as beneficial arthropods. The presence and role of endosymbionts are well studied in certain groups of beneficial arthropods, including hymenopteran parasitoids and coccinellid predators . However, relatively few studies Selleckchem 4EGI-1 have focused on the endosymbiotic bacteria of predatory Heteroptera (true bugs), despite their economic importance as biological control agents of agricultural pests . In the
present study, the microbial community of Macrolophus spp. is examined. Macrolophus is a genus of polyphagous mirid predators commonly used in European greenhouses for the biological control of whiteflies, spider mites, thrips, aphids, and leaf miners [27, 28]. The two major species that have been used in commercial biological control are M. caliginosus and M. pygmaeus. It has been established that M. pygmaeus carries Wolbachia, which induces strong CI in its host and may thus have a substantial impact on the practical use of the predator in programmes of biological pest control . However, other endosymbiotic bacteria have not been demonstrated to
infect Macrolophus spp. The microbial population of M. pygmaeus and M. caliginosus was examined by 16S rRNA gene sequencing and denaturing gradient gel electrophoresis (PCR-DGGE). The latter technique has been used to characterize complex bacterial compositions of environmental acetylcholine samples [30, 31], but also proved useful to explore bacterial communities in arthropods [32–34]. Furthermore, a fluorescence in situ hybridization (FISH) analysis was performed to visualize the co-localization of different endosymbionts. Improving our understanding of the composition and functions of the endosymbiotic community of these predatory insects may contribute to optimizing their use as natural enemies of agricultural pests. Methods Insect populations Adults of different Macrolophus populations were collected from sites in Greece, Spain and Italy (Table 1) and preserved in 70% ethanol. A laboratory strain of M. pygmaeus originating from Koppert B.V.