Wigglesworthia gen. nov. and Wigglesworthia glossinidia sp. nov., taxa consisting of the mycetocyte-associated, primary endosymbionts of tsetse flies.

The primary endosymbionts (P-endosymbionts) of tsetse flies (Diptera: Glossinidae) are harbored inside specialized cells (mycetocytes) in the anterior region of the gut, and these specialized cells form a white, U-shaped organelle called mycetome. The P-endosymbionts of five tsetse fly species belonging to the Glossinidae have been characterized morphologically, and their 16S ribosomal DNA sequences have been determined for phylogenetic analysis. These organisms were found to belong to a distinct lineage related to the family Enterobacteriaceae in the gamma subdivision of Proteobacteria, which includes the secondary endosymbionts of various insects and Escherichia coli. These bacteria are also related to the P-endosymbionts of aphids, Buchnera aphidicola. Signature sequences in the 16S ribosomal DNA and genomic organizational differences which distinguish the tsetse fly P-endosymbionts from members of the Enterobacteriaceae and from the genus Buchnera are described in this paper. I propose that the P-endosymbionts of tsetse flies should be classified in a new genus, the genus Wigglesworthia, and a new species, Wigglesworthia glossinidia. The P-endosymbiont found in the mycetocytes of Glossina morsitans morsitans is designated the type strain of this species.