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| Figure 3-1. Bacterial colonies on a nutrient medium. Note that the bacteria have been diluted through streaking. The small, round colonies are made up of hundreds of cells and probably grew from a single bacterium. |
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Figure 3-2.
A bacilliform bacterium, typical of plant pathogens. Note that it has polar flagella. Pseudomonas sp.
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| Figure 3-3.
Phytoplasmas (arrows) in a phloem cell of an infected plant. Note that the phytoplasmas are pleomorphic (variably shaped). |
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Figure 3-4.
Spiroplasmas in phloem cells of an infected corn plant. Note the helical shape. |
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| Figure 3-5. Bacterial cell. Note the EPS (extracellular polysaccharide) and polar flagellum. |
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Figure 3-6. Thomas J. Burrill in a laboratory with students, 1882. |
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| Figure 3-7. Ooze, a diagnostic sign of a bacterial infection. In bacterial wilt of cucurbits, the sticky strands of bacterial ooze become evident as two portions of a cut stem are pulled apart. Bacterial wilt of cucurbits caused by Erwinia tracheiphila. |
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Figure 3-8. A, To diagnose Stewart’s wilt, a section of symptomatic corn leaf tissue is placed in a drop of water on a microscope slide. B, Bacterial streaming, viewed with a compound microscope. Erwinia stewartii (syn. Pantoea stewartii). |
| Figure 3-9. Angular leaf spots typical of those caused by Pseudomonas spp. and Xanthomonas spp. |
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Figure 3-10. Soft rot in a potato tuber. Erwinia carotovora. |
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| Figure 3-11.
Crown gall on euonymous caused by Agrobacterium tumefaciens. |
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Figure 3-12.
Bacterial wilt of tomatoes caused by Ralstonia solanacearum. |
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| Figure 3-13.
Brooming in lime infected by a phytoplasma. |
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Figure 3-14.
The glassy-winged sharpshooter, a leafhopper vector of Xylella fastidiosa. These insects subsist on xylem fluid and often feed upside down. |
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| Figure 3-15.
Various modes of penetration and invasion of a leaf by fungi (left) and bacteria (right). Water is required for bacteria to enter cells. |
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Figure 3-16.
Dilution plating to obtain pure colonies of a bacterium. The tissue is torn apart to release the bacteria. The sample is then diluted to reduce background contaminants. A sample of each dilution is spread on a plate of nutrient medium. |
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| Figure 3-17.
Commercial chipping machine used to chip citrus trees infected by or exposed to citrus canker in urban Miami, Florida. Citrus canker is caused by Xanthomonas axonopodis pv. citri and X. axonopodis pv. aurantifolii. |
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Figure 3-18.
Typical air-blast sprayer for application of copper sprays or antibiotics. |
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| Figure 3-19.
Pepper plants susceptible (left) and resistant (right) to specific strains of the leaf spot bacterium, Xanthomonas axonopodis pv. vesicatoria. |
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