Metabolic workings in cockroaches revealed
A team of partly EU-funded researchers from Spain have gained new insights into the physiology of cockroaches. Their findings, now published in the open-access journal Public Library of Science (PLoS) Genetics, could ultimately help develop new strategies for controlling this pest. In addition to grants offered by the Spanish government, part of the funding for this research came out of the CRAB ('Combating resistance to antibiotics') project, supported under the 'Life science, genomics and biotechnology for health' Thematic area of the Sixth Framework Programme (FP6). The Seventh Framework Programme (FP7) project TARPOL ('Targeting environmental pollution with engineered microbial systems a la carte') provided further support. The scientists describe the genome sequence of the Blattabacterium strain Bge of the German cockroach (Blatella germanica). This endosymbiont (an organism dwelling within the body of its symbiotic partner) that lives in specialised cells of the cockroaches' abdominal fat is responsible for eliminating excess nitrogen in the insects' bodies by emitting ammonia. The Blattabacterium's metabolism 'employs an apparently inefficient mechanism: bacterial enzymes simultaneously synthesise, by an energetically expensive pathway, and destroy the same molecule, urea,' explains one of the leaders of the research team, University of Valencia's Dr Amparo Latorre. Urea is key to the disposal of excess nitrogen in many organisms' metabolisms, mostly excreted through urine. Urea is synthesised in the body of many organisms either from the oxidation of amino acids or from ammonia. In the German cockroach, the endosymbiont takes care of this cycle. Similar processes are well-known in the world of insects. 'Bacterial endosymbionts of insects play a central role in upgrading the diet of their hosts,' the study reads. 'In certain cases, such as aphids and tsetse flies, endosymbionts complement the metabolic capacity of hosts living on nutrient deficient diets, while the bacteria harboured by omnivorous carpenter ants are involved in nitrogen recycling.' The latter is also true of the Blattabacterium in cockroaches. The researchers find, however, that cockroaches and carpenter ants must have developed this remarkably similar metabolic mechanism by completely independent evolutionary pathways, since the two different endosymbiontic bacteria belong to very distant bacterial lineages. 'This constitutes a nice example of evolutionary convergence of two endosymbionts belonging to very different bacterial phyla [groupings] that have evolved a similar repertoire of functions according to the host,' the paper says. Dr Latorre concludes that 'a better knowledge of the evolutionary mechanisms behind the symbiotic associations between insects and bacteria is necessary not only to understand the basic physiology and behaviour of the host, but also to design new strategies in pest control'.
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