BUCHNERA GEN-NOV AND BUCHNERA-APHIDICOLA SP-NOV, A TAXON CONSISTING OF THE MYCETOCYTE-ASSOCIATED, PRIMARY ENDOSYMBIONTS OF APHIDS

All aphids are thought to have an association with primary endosymbionts, which are located within specialized cells known as mycetocytes. The primary endosymbionts are gram-negative, spherical or slightly oval cells which have not been cultivated outside aphid hosts. Recently, it has been shown that the 16S rRNA sequences of the primary endosymbionts of 11 host species belonging to four aphid families are similar and thus that these organisms are related. Comparisons with the 16S rRNAs of other procaryotes indicated that the primary endosymbionts form a distinct lineage within the gamma-3 subgroup of the Proteobacteria. On the basis of these results we propose that the primary endosymbionts should be placed in Buchnera gen. nov. and Buchnera aphidicola sp. nov. The primary endosymbiont found in the mycetocytes of Schizaphis graminum (green bug) is designated the type strain of this species.