Characterization of the symbiosis between intracellular bacteria and ants
Project management at the University of Würzburg:
More than a 100 years ago F. Blochmann described the presence of intracellular bacteria in midgut and ovarial cells of ants of the genus Camponotus. Recently we started to investigate this symbiotic relationship on the molecular level. Cloning and analysis of the 16S rRNA genes of the symbiotic bacteria of fourteen Camponotus species collected in Europe and Southern- and Northern America allowed their classification within the gamma-subclass of the Proteobacteria. The ant symbionts are more closely related to each other than to any other known organism and have recently been proposed to be members of a novel genus: Candidatus Blochmannia (gen. nov.). The closest relatives are endosymbiotic bacteria of the tsetse fly (Wigglesworthia spp.) and of aphids (Buchnera aphidicola) which together form a huge cluster of symbiotic organisms and have a common ancestor with the Enterobacteriaceae. In parallel to the phylogenetic analysis of the bacteria we performed a related analysis with the host animals characterizing their mitochondrial cytochome oxidase subunit I gene sequences. Interestingly, the phylogenetic trees of the ants and their symbionts are congruent indicating a long lasting cospeciation of these organisms. In fact, the bacteria appear to be transmitted maternally, as in situ hybridization with symbiont specific oligonucleotides unequivocally showed the bacteria in the midgut and in the ovaries to be identical. The characterization of the symbiont migration during embryogenesis by in situ hybridization revealed an early association of the bacteria with endodermal tissues. The genomic sequence of Blochmannia is currently being determined. This sequence confirms the close relationship of Blochmannia with the Enterobacteriaceae. Similar to other bacteriocyte symbionts, Blochmannia has a strongly rationalized genome of about 700 kb. The aim of this study is to investigate the molecular basis of this symbiosis, adaptation mechanisms of the partners to each other and to understand the biological significance of this interspecies interaction. The project is performed in close collaboration with the group of Prof. Andres Moya (Institut Cavanilles de Biodiversitat i Biologia Evolutiva, Universitat de Valencia), were the genomic sequencing was performed.
Projekt period: from 01.2001 to 12.2003