INTRACELLULAR ENDOSYMBIOTIC - BACTERIA OF CAMPONOTUS SPECIES (CARPENTER ANTS) - SYSTEMATICS, EVOLUTION AND ULTRASTRUCTURAL CHARACTERIZATION

Intracellular endosymbiotic bacteria inherent to ants of the genus Cam ponotus were characterized, The bacteria were localized in bacteriocyt es, which are specialized cells of both workers and queen ants; these cells are intercalated between epithelia[ cells of the midgut, The bac teriocytes show a different morphology from the normal epithelial cell s and carry a large number of the rod-shaped Gram-negative bacteria fr ee in the cytoplasm, The bacteria were never observed in the neighbour ing epithelial cells, but they were found intracellularly in oocytes, strongly indicating a maternal transmission of the bacteria. The 16S D NA encoding rrs loci of the endosymbionts of four species of the genus Camponotus derived either from Germany (C. herculeanus and C. lignipe rdus), North America (C. floridanus) or South America (C. rufipes) wer e cloned after polymerase chain reaction (PCR) amplification using oli gonucleotides complementary to all so far known eubacterial rrs sequen ces, The DNA sequences of the rrs loci of the four endosymbionts were determined, and, using various genus- and species-specific oligonucleo tides derived from variable regions in the rrs sequences, the identity of the bacteria present in the bacteriocytes and the ovarian cells wa s confirmed by PCR and in situ hybridization techniques, Comparison of the 16S DNA sequences with the available database showed the endosymb iotic bacteria to be members of the gamma-subclass of Proteobacteria, They formed a distinct taxonomic group, a sister taxon of the taxons d efined by the tsetse fly and aphid endosymbionts, Within the gamma-sub class, the cluster of the ant, tsetse fly and aphid endosymbionts are placed adjacent to the family of Enterobacteriaceae, The evolutionary tree of the ant endosymbionts reflects the systematic classification a nd geographical distribution of their host insects, indicating an earl y co-evolution of the symbiotic partners and a vertical transmission o f the bacteria.