Genetic Systems in Phytopathogenic Bacteria

Abstract

Studies of bacterial genetics have made a major contribution to the knowl­ edge of the nature, function, and regulation of the genetic determinants of phenotype. Although the genetics of has been intensively investi­ gated, the scope of these studies remained so narrow that Millard Susman, with tongue in cheek, stated that bacteria means Escherichia coli K12 (93). This viewpoint is apparent when surveying the literature for informa­ tion on the role of the bacterial genome in biological interactions between organisms, especially in phytopathogenicity. It is evident that this area has received little attention. Phytopathologists are interested in defining mechanisms of pathogenicity among diverse bacterial pathogens (leaf-spotters, wilt-inducers, toxin-pro­ ducers, blighters, gall-inducers, and soft-rotters). One obvious advantage in using genetics to study pathogenicity would be employing a different point of view in approaching these studies. Hitherto, classical studies of phytopa­ thogenesis have considered how the environment affects the expression of pathogenicity, how the host defends against the pathogen, or how the chemical products produced in host-pathogen interactions might contribute to pathogenesis. The critical question of what is in the genome of the pathogen that makes it capable of causing pathogenesis has been largely left unstudied.