title: Tetraponera ants have gut symbionts related to nitrogen-fixing root-nodule bacteria.
abstract: Some Tetraponera ants (Formicidae, Pseudomyrmecinae) subsist almost entirely on amino acid deficient honeydew secretions of pseudococcids and harbour a dense aggregation of bacterial symbionts in a unique pouch-shaped organ at the junction of the midgut and the intestine. The organ is surrounded by a network of intruding tracheae and Malpighian tubules, suggesting that these bacteria are involved in the oxidative recycling of nitrogen-rich metabolic waste. We have examined the ultrastructure of these bacteria and have amplified, cloned and sequenced ribosomal RNA-encoding genes, showing that the ant pouch contains a series of close relatives of Flavobacteria and Rhizobium, Methylobacterium, Burkholderia and Pseudomonas nitrogen-fixing root-nodule bacteria. We argue that pouch bacteria have been repeatedly 'domesticated' by the ants as nitrogen-recycling endosymbionts. This ant-associated community of mutualists is, to our knowledge, the first finding of symbionts related to root-nodule bacteria in animals.
authors.affiliation: Zoological Institute, University of Leuven, Naamsestraat 59, B-3000 Leuven, Belgium.
authors.forename: Steven
authors.initials: S
authors.lastname: van Borm
authors.forename: Alfred
authors.initials: A
authors.lastname: Buschinger
authors.forename: Jacobus J
authors.initials: JJ
authors.lastname: Boomsma
authors.forename: Johan
authors.initials: J
authors.lastname: Billen
mesh_terms: D000818:Animals; D001000:Ants / Q000033:anatomy & histology / Q000382:microbiology* / Q000648:ultrastructure; D001419:Bacteria / Q000235:genetics* / Q000302:isolation & purification* / Q000648:ultrastructure; D005260:Female; D007422:Intestines / Q000033:anatomy & histology / Q000382:microbiology / Q000648:ultrastructure; D008297:Male; D009586:Nitrogen Fixation; D010802:Phylogeny; D012329:RNA, Bacterial / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D013559:Symbiosis
chemical_list: D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S