General Information: Temp: Mesophile; Habitat: Host. Pectobacterium carotovorum causes soft-rot diseases of various plant hosts through degradation of the plant cell walls. Formerly Erwinia, these organisms are plant-specific pathogens that invade the vascular systems of plants. Pectobacterium colonize the intercellular spaces of plant cells and deliver potent effector molecules (Avr - avirulence) through a type III secretion system (Hrp - hypersensitive response and pathogenicity). Avr proteins control host-bacterium interactions, including host range. Expression of the plant cell-wall-degrading enzymes is controlled through a quorum-sensing mechanism that quantifies the number of Pectobacterium bacteria through measurement of the concentration of small molecules (acyl homoserine lactones) produced by Pectobacterium.