Symbiont genome

In the Early Edition of the Proceedings of the National Academy of Sciences van Ham et al. report the sequencing of the genome of the intracellular symbiont Buchnera aphidicola from the aphid Baizongia pistacea (BBp) (Proc Natl Acad Sci USA 2002, 10.1073/pnas.02359811). As neither bacteria nor the host can be easily cultured in the laboratory, insects were collected from the field (from galls of a natural population on Pistacia trees), and bacterial DNA was then isolated for whole-genome shotgun sequencing. The BBp genome consists of a 616 kb chromosome and a 2,399 bp plasmid, containing 544 putative genes and nine pseudogenes. In addition, van Ham et al. found extensive intra-population variation and over 1,000 dimorphic SNPs. Comparison with two other sequenced Buchnera genomes revealed almost perfect chromosomal synteny; 78% of genes are present in all three genomes.