title: Nutritional upgrading for omnivorous carpenter ants by the endosymbiont Blochmannia.
abstract: BACKGROUND
  Carpenter ants (genus Camponotus) are considered to be omnivores. Nonetheless, the genome sequence of Blochmannia floridanus, the obligate intracellular endosymbiont of Camponotus floridanus, suggests a function in nutritional upgrading of host resources by the bacterium. Thus, the strongly reduced genome of the endosymbiont retains genes for all subunits of a functional urease, as well as those for biosynthetic pathways for all but one (arginine) of the amino acids essential to the host.
  
  
  RESULTS
  Nutritional upgrading by Blochmannia was tested in 90-day feeding experiments with brood-raising in worker-groups on chemically defined diets with and without essential amino acids and treated or not with antibiotics. Control groups were fed with cockroaches, honey water and Bhatkar agar. Worker-groups were provided with brood collected from the queenright mother-colonies (45 eggs and 45 first instar larvae each). Brood production did not differ significantly between groups of symbiotic workers on diets with and without essential amino acids. However, aposymbiotic worker groups raised significantly less brood on a diet lacking essential amino acids. Reduced brood production by aposymbiotic workers was compensated when those groups were provided with essential amino acids in their diet. Decrease of endosymbionts due to treatment with antibiotic was monitored by qRT-PCR and FISH after the 90-day experimental period. Urease function was confirmed by feeding experiments using 15N-labelled urea. GC-MS analysis of 15N-enrichment of free amino acids in workers revealed significant labelling of the non-essential amino acids alanine, glycine, aspartic acid, and glutamic acid, as well as of the essential amino acids methionine and phenylalanine.
  
  
  CONCLUSIONS
  Our results show that endosymbiotic Blochmannia nutritionally upgrade the diet of C. floridanus hosts to provide essential amino acids, and that it may also play a role in nitrogen recycling via its functional urease. Blochmannia may confer a significant fitness advantage via nutritional upgrading by enhancing competitive ability of Camponotus with other ant species lacking such an endosymbiont. Domestication of the endosymbiont may have facilitated the evolutionary success of the genus Camponotus.
authors.affiliation: Department of Behavioural Physiology and Sociobiology (Zoology II), Biocenter, University of Wuerzburg, Am Hubland, 97074 Wuerzburg, Germany. feldhaar@biozentrum.uni-wuerzburg.de
authors.forename: Heike
authors.initials: H
authors.lastname: Feldhaar
authors.forename: Josef
authors.initials: J
authors.lastname: Straka
authors.forename: Markus
authors.initials: M
authors.lastname: Krischke
authors.forename: Kristina
authors.initials: K
authors.lastname: Berthold
authors.forename: Sascha
authors.initials: S
authors.lastname: Stoll
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Mueller
authors.forename: Roy
authors.initials: R
authors.lastname: Gross
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001000:Ants / Q000382:microbiology / Q000502:physiology*; D016172:DNA Fingerprinting; D004269:DNA, Bacterial / Q000235:genetics; D004755:Enterobacteriaceae / Q000502:physiology*; D006458:Hemolymph / Q000737:chemistry; D017404:In Situ Hybridization, Fluorescence; D016133:Polymerase Chain Reaction; D013559:Symbiosis
chemical_list: D000596:Amino Acids; D004269:DNA, Bacterial