Generally, these bacteria are confined to intracellular locations, although, for instance, Wigglesworthia, the primary endosymbiont of tsetse flies, can also be found extracellularly in the milk gland lumen from where the bacteria can infect the developing brood [7]. In contrast to primary endosymbionts, invasion of different tissues is observed frequently for secondary endosymbionts which are not essential for the animals [8]. Early observations indicated that Blochmannia may also have a cell invasive capacity, when the bacteria evade from bacteriocytes

in the midgut tissue in order to infiltrate the oocytes thus guaranteeing the vertical transmission of the bacteria [9]. Bacteriocyte endosymbionts are frequently observed in animals with a specialized diet lacking nutrients essential for the animals such as aphids or tsetse flies feeding exclusively VS-4718 concentration on plant sap or blood, respectively [10]. There is ample evidence that these mutualists contribute to host nutrition by supplementing the host’s diet with, for example, RepSox concentration essential amino acids in the Buchnera-aphid endosymbiosis or vitamins in the Wigglesworthia-tsetse fly interaction. In contrast, ants of the genus Camponotus and related

genera such as Polyrhachis harboring endosymbiotic Blochmannia are generally considered to be omnivorous [11]. However, ants are often limited by nitrogen availability, especially in habitats that are generally poor in nitrogen compounds such as tropical rain forest KU-57788 cell line canopies [12]. Blochmannia encodes a functional urease and glutamine synthetase

and may therefore be involved in nitrogen recycling. Recently, it was shown that Blochmannia upgrades the diet of individual ants by the synthesis of essential amino acids. This is probably also relevant on the colony level by improving the quality of food provided to larvae by care-taking young workers which feed the larvae by trophallaxis [13, 14]. Ants are holometabolous animals and these metabolic capabilities of the endosymbiont may be of particular relevance during metamorphosis when the animals are excluded from external food resources. In line with this assumption, massive replication of the bacteria Gemcitabine chemical structure and an upregulation of amino acid biosynthesis genes and urease were observed in particular during pupal stages [14–16]. Very little is known about the cell biology, developmental origin and evolution of bacteriocytes. A general characteristic of such cells appears to be a high degree of polyploidy, possibly reflecting the high metabolic output of these cells [17–20]. The ontogeny of bacteriocytes to date was investigated only in early developmental stages of hemimetabolous aphids, which can reproduce parthenogenetically. The endosymbiotic bacteria are transmitted directly from mother to developing embryos in the blastoderm stage. A two-step recruitment of bacteriocytes was observed in the aphid Acyrthosiphon pisum using bacteriocyte specific markers.