Besides their ancient association withBuchneraand facultative
associations with Regiella and other symbionts within the
Enterobacteriaceae [51], aphids sometimes harbor Spiroplasma
species, Rickettsia species, and Wolbachiaspecies as heritable
endosymbionts.
Screening of the genome project data for bacterial sequences
revealed a large number of genes of apparent bacterial origin, even
after vector contaminants had been screened out. However, a
majority of these were on small contigs (mostly under 5 kb) that
did not contain evident aphid sequence; PCR experiments on a