Five strains of Gram-negative, oxidase-negative, facultatively anaerobic, fermentative, motile, rodshaped bacterium with the general characteristics of the family Enterobacteriaceae were isolated from the gut of multiple specimens of the pea aphid. All the strains caused aphid mortality when ingested by insects via a synthetic diet. The results of biochemical tests showed that these strains are most related to Erwinia herbicola and Pantoea agglomerans. According to DNA-DNA hybridization, the five strains showed more than 96% relatedness to each other, indicating that these organisms are members of a single species. These strains were most closely related to Erwinia herbicola (22% DNA relatedness). Phenotypic differentiation of these strains from Erwinia herbicola, which was also detected from aphid gut, was based on negative reactions in tests of yellow pigment production, gelatin liquefaction, acid production from inulin, starch and dulcitol, and positive acid production from melibiose, inositol, cellobiose and glycerol. On the basis of these data, the name Erwinia aphidicola is proposed for the new organism. The type strain is strain X 001 (=IAM 14479).
The Microbiology Research Foundation