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  1. People that contributed to Phytobacteriology
    • -Woronin 1866: bacteria in Lupin nodules
    • -Significant Contributions:Burrill 1878 in IL (Fire blight of pear and apple)apple): transmitted the disease from diseased to healthy
    • -Wakker 1883Arthur 1885 at Cornell (first PhD in Science from Cornell)bacteria in hyacinth yellows
    • -Arthur 1885 at Cornell: Koch’s postulates for fire blight
    • -E. F. Smith 1893-1900Significant Contributions:Bacteria in Relation to Plant Diseases Bacterial Diseases of Plants (3 vols) Studied crown gall disease: ‘cancer’ of the plants
    • -1977: Mary Dell Chilton’sgroup: crown gall bacterium physically transfers part of its plasmid
    • -C. Elliott 1930Manual of Bacterial Plant Pathogens
  2. Characteristics of bacteria
    • -Prokaryotic
    • -Microscopic 0.6-3.5 μm x 0.5-10 μm
    • -Unicellular = single-cells
    • -Cell walls in most
    •  -no sub-cellular organelles; genetic material (DNA) is not bound by a membrane (no nucleus)
    • -Ubiquitous (everywhere!)
    • Can be motile
    • absorbs nutrients via extracellular enzymes
  3. Characteristics of bacteria cell walls
    • Cell walls present (in most!)
    • •peptidoglycan, teichoic acid, protein, polysaccharide, lipoprotein, and lipopolysaccharide•Slime layer or capsule
    • -Gram-stain reaction
    •   gram-negative = g- (pink)  gram-positive = g+ (Purple)
  4. Examples of g+ and g– genera of plant pathogenic bacteria
    • g+: Clavibacter, Curtobacterium
    • g-: Agrobacterium, Erwinia, Pseudomonas, Xanthomonas, Xylella
    • -A majority of the plant pathogenic bacteria are gram negative!
  5. Name the different shapes of bacteria
    • Cocci or spherical
    • Bacilliform, rod-shaped,or coryneform
    • Spiral or helical
    • Filamentous
  6. How do bacteria reproduce?
    • reproduce by binary fission (asexual only)
    • growth is logarithmic
    •    known as doubling time
  7. Genetic characteristics of bacteria
    • 1 circular chromosome/cell
    • Plasmid:
    • Circular, extra chromosomal
    • element; autonomous
    • in replication; (one to many copies)
    • replicates along with the chromosome
    • Some confer antibiotic resistance to the
    • bacterium
  8. Types of bacterial DNA exchange
    • Transformation (physical uptake of a piece
    • of DNA or ‘whole’ plasmid DNA)
    • Conjugation (mating between two
    • bacterial cells)
    • Transduction (phage-mediated
    • DNA transfer)
  9. Additional Characteristics of
    Phytopathogenic Bacteria
    • Mode of parasitism:
    • mostly facultative saprophytes
    • Survival:
    • epiphytically (grows harmlessly on another plant) ooze, seed, vectors
    • Dissemination:
    • water debris, humans, vectors
  10. What causes Crown gall
    Agrobacterium tumefaciens
  11. What does the Ti plasmid do?
    • Ti plasmid Determines the virulence and host range
    • 200 kbp in size
    • T-DNA is transferred to plant cell;
    • Transcribed by plant cell machinery: produces auxin, cytokines, opines: results in abnormal cell division, cell enlargement, uncontrolled growth (Opines are good nutritional source for the pathogen)
  12. Pathogenic Specialization of phytobacterium
    • Host species = pathovar; pv.
    • e.g. Pseudomonas syringae
    • pv. phaseolicola - bean
    • pv. pisi - pea
    • pv. tomato - tomato
    • 42 pathovars at last count!
    • Cultivar = race
    • e.g. Pseudomonas syringae
    • pv. phaseolicola race 1
  13. How to Identify Bacteria
    • Visible characteristics:
    • Size & shape rod-shaped, except actinomycetes
    • Colony characteristics shape, growth rate & color
    • e.g. Xanthomonas, “coryneforms”
    • Gram-stain reaction
    • Bacterial Pigmentation ex. Clavibacter sp. have yellow halo with orange center
    • Physiological characteristics
    • Nutritional tests food sources
    • tolerance/toxicity
    • Oxygen requirements
    • most are obligate aerobes except some Pectobacterium
    • Gram Stain
    • Molecular techniques (DNA fingerprinting/RFLP/PCR)
    • Selective media
    • Biochemical analyses: fatty acid profiles
    • Pathogenicity tests (on various species and
    • varieties of host plants)
    • Fatty acid profiles
    • Pathogenicity tests
    • Selective media
  14. What is the most common way to ID bacteria?
    Selective media
  15. What causes Watermelon fruit blotch?
    • Acidovorax avenae subsp.
    • citrulli
  16. List Symptoms Caused by Bacteria
    • leaf spots
    • blights
    • soft rots of fruits, roots, and storge organs wilts
    • overgrowths
    • scabs
    • cankers
    • A given type of symptom may be caused by more than one type of bacterial pathogen
    • A given baterial pathogen can cause different types of symtpoms
Card Set:
2015-10-23 15:15:59
Plant path
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