Sequence of a symbiont

Tsetse flies, the vectors of African trypanosomes, feed exclusively on blood and require intracellular microorganisms to provide additional nutrients. In an Advanced Online Publication in Nature Genetics, Akman et al. report the genome sequence of Wigglesworthia glossinidia brevipalpis, the obligate symbiont of the tsetse fly (Nature Genetics, 3 September 2002, DOI:10.1038/ng986). The Wigglesworthia genome consists of a single chromosome of almost 700 kb and a small plasmid, pWig1, of 5,200 bp. The coding content is around 89%, with 621 predicted coding sequences. Notably, the genome lacks a gene encoding the DNA replication initiation protein DnaA, whose function may be provided by the host. Akman et al. assigned potential functions to a large number of the coding sequences, including those implicated in the biosynthesis of cellular structures, and fatty acid metabolism and the synthesis of vitamin metabolites (required for host nutrition). The Wigglesworthia genome provides an opportunity to study the genetics of symbiotic relationships.