Pair Of Bacteriomes Research Articles

Diversity of bacterial endosymbionts and bacteria–host co‐evolution in Gondwanan relict moss bugs (Hemiptera: Coleorrhyncha: Peloridiidae)

Many hemipterans are associated with symbiotic bacteria, which are usually found intracellularly in specific bacteriomes. In this study, we provide the first molecular identification of the bacteriome-associated, obligate endosymbiont in a Gondwanan relict insect taxon, the moss bugs (Hemiptera: Coleorrhyncha: Peloridiidae), which represents one of the oldest lineages within the Hemiptera. Endosymbiotic associations of fifteen species of the family were analysed, covering representatives from South America, Australia/Tasmania and New Zealand. Phylogenetic analysis based on four kilobases of 16S-23S rRNA gene fragments showed that the obligate endosymbiont of Peloridiidae constitute a so far unknown group of Gammaproteobacteria which is named here 'Candidatus Evansia muelleri'. They are related to the sternorrhynchous endosymbionts Candidatus Portiera and Candidatus Carsonella. Comparison of the primary-endosymbiont and host (COI + 28S rRNA) trees showed overall congruence indicating co-speciation the hosts and their symbionts. The distribution of the endosymbiont within the insect body and its transmission was studied using FISH. The endosymbionts were detected endocellularly in a pair of bacteriomes as well as in the 'symbiont ball' of the posterior pole of each developing oocyte. Furthermore, ultrastructural analysis of the Malpighian tubules revealed that most host nuclei are infected by an endosymbiotic, intranuclear bacterium that was determined as an Alphaproteobacterium of the genus Rickettsia.

Ultrastructure of Bacteriomes and Their Sensitivity to Ambient Temperatures in Prostephanus truncatus (Horn)

In light microscopical sections of Prostephanus truncatus (Horn) (Col.: Bostrychidae) it was shown that both larvae and adults have a pair of bacteriomes dorsally located in the fat body parallel to the midgut. Bacteriome development was shown mainly to occur during larval stages. Bacteriome size was not found to be associated with body size in adults, but in larvae reared at 30°C bacteriome size increased progressively with body length. The shape of the bacteriomes varied from round to conic-oval, but a common feature was that they were larger and rounded in older larvae and females as compared to males, where they usually appeared more shrunken and slightly deformed. Electron microscopy of thin sections showed that the bacteriomes were composed of multinucleate syncytia surrounded by a layer of boundary cells. The syncytia harboured many small coccoid bacteroids. Typical eukaryotic organelles were found in the cytoplasm of the bacteriomes. These and other structural features were outlined. The effect of rearing temperatures at 30, 35 and 37°C on bacteriome development in larvae and adults was examined. The symbiotes could not be eliminated but a significant reduction of bacteriome size was found in females reared at 35°C and 37°C as compared to specimens grown at 30°C. A possible association of bacteriome size and reproduction was evaluated by transferring P. truncatus specimens reared at 35°C and 37°C to 30°C for two months and counting the number of offspring; their reproduction was compared with controls kept at 30°C throughout the experiment. Specimens from 35°C and 37°C had significantly lower reproduction rates than controls. The potential implications of heat sensitivity of bacteriomes of P.truncatus is discussed in an integrated pest management context.