Dissemination - water, insects, animals, humans. Major Genera 1. Agrobacterium rod shaped, motile, gram negative, soil inhabitants - crown gall 2. Amylovora - blight or wilt diseases. Carotovora-soft rots, pectolytic activity.
All species are plant pathogens and are found only in association with plants or plant material.
Streptomyces - Slender branched hyphae without cross walls. At maturity the aerial mycelium forms chains of three to many spores. Gram positive, scab diseases. Specific examples of diseases caused by prokaryotes - 1. Agrobacterium tumefaciens - Crown gall .