Gram Positive, Irregular Rods and Filamentous Bacteria
a) Irregular Rods: Corynebacterium (Plant Pathogenic)
1. Characters of Curtobacterium
Cells small short rods, coccoid cells found in old cultures, weakly gram negative, frequently old cell lose Gram Positivity generally motile by lateral flagella; cell multiplication by bending type of cell division; pleomorphism only slight; major cell wall amino acid is ornithine; G + C content of the DNA ranges form 66 to 71 moles per unit.
Curtobacterium flaccumfaciens pv. Flaccumfaciens (Hedges) Collins and Jones (Corynebacterium flaccumfaciens Dowson) causes vascular wilt of beans.
2. Characters of Clavibacter:
The cells are Gram positive; non avoid fast plemorphic rods, often arranged at an angle to give V-formation as a result of snapping or bending type of cells division, no coccoid cells are seen; non endospore forming; non motile; strict aerobes; nutritionally exacting; nitrate not reduced; cell wall peptidoglycan contains diaminobutyric acid; G+C content of the DNA is 70 +-5 moles per cent.
Clavibactor michinganese subspecies michiganese (Smith) Davis et al. (Corynebacterium michiganese or C. michiganese pv. michiganese or C. michiganese sub species michiganese causes canker of tomato and chilli.
b) Filamentous Bacteria:
Slender, coenocytic filaments, 0.5 to 2.0 microns in diameter; aerial mycelium at maturity forms chains of three to many spores; cell walls contain diaminopimelic acid; Gram Positive; aerobic; heterotrophs; generally reduce nitrates, on isolation colonies are small, 1 to 10 mm in diameter, descrete and lichenoid , leathery or butyrous, initially relatively smooth but later develop a weft of aerial mycelium that may appear granular, powdery, velvety or floccosed.
S. scabis causes common scab of potato.