ven118lecc10_bacterialdiseaseslecture

ven118lecc10_bacterialdiseaseslecture - VEN 118 Bacterial...

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Unformatted text preview: VEN 118 Bacterial Diseases Bacteria Bacteria are microscopic, rod-shaped or spherical, prokaryotic organisms. Bacteria are usually identified by physiological, biochemical and serological tests. They enter plants through wounds, vectored by other organisms or natural openings as described for fungi. Spore a bacterial cell modified to survive an adverse environment. Distinguishing characteristics at the Division Level Morphology structure of cell wall (some have, some donts), two types: a) gram + and b) gram (with cell walls). Shape: rod, cocci, helixes, spherical Physiology Nutrition source (heterotrophic, saprophytic, obligate aerobes (need O 2 ) or anaerobes (O 2 toxic) Serology applied end of immunology (exploiting mammalian immune system, have an antibody response, inject an animal and it wont get sick but it will still have an immune response, identifies specific organisms with a protein such as when a rabbit is injected with PD. Collect the animals blood and then identify the organism with the serum of the rabbit). Mode of pathogenesis: Their significance as a pathogen stems from the fact that they can produce tremendous numbers of cells in a short time. Under favorable conditions bacteria may divide every 20 minutes 1 bacterium could produce 1,000,000 bacteria in 10 hrs. Vascular bacteria clog xylem, may produce toxins, actually transfer piece of DNA into plant chromosome and takes over part of cellular function (encoding for the formation of PGRs (plant growth regulators), causes multiplication of plant cells; can actually get out all of bacteria but still have piece of DNA in the plants cells). Kingdom Prokaryotae Bacteria : have cell membrane and cell wall Part I : gram-negative aerobic rods and cocci Family : Pseudomonadaceae Genus : Xylella rod shaped, non-motile, aflagellate, non-pigmented, nutritionally fastidious Family : Rhizobiaceae Genus : Agrobacterium rod-shaped, sparse lateral flagella, colonies white, rarely yellow Grapevine bacterial diseases: causal organisms Pierces disease - Xylella fastidiosa Crown gall - Agrobacterium vitis (formerly A. tumifaciens ) Crown gall #1 disease of perennial nurseries world- wide Soil borne, once in soil difficult to eliminate Must enter through a wound (grafting) or vectored It isnt limited to the crown of the vine, can be found on the roots and can find aerial galls (in NY due to freeze damage) Bacterium will become systemic Transformation of plant cells by Tumor Inducing (Ti) plasmid Crown Gall Symptoms: Appears first as small overgrowth on stem (roots?) Early on, tumors are more or less spherical, white or flesh-colored and quite soft (at first they cannot be distinguished from callus The surface of larger tumors become more or less convoluted Later on, outer tissues become dark brown or black due to the death and decay of peripheral cells Generally there is no distinct line of demarcation between the tumor and the plant proper Photo by Austin C. Goheen Photo by Austin C....
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ven118lecc10_bacterialdiseaseslecture - VEN 118 Bacterial...

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