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External Structures

External Structures - through water 4mm to 6 mm per minute...

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External Structures : a. Glycocalyx or Capsule (computer slides) 1. Slime formation prevents dehydration. 2. allows for colony stability under adverse circumstances. Can be a big problem with biofilm development in catheters or industrial pipes. Dangerous source of infection in hospitals which is not readily removed by disinfection. 3. Non pathogenic organisms also have a capsule. Alcaligenes viscolactis is one of them. 4. Capsule can interfere with immune defenses of the host. It can interfere with phagocytosis. It swells during an infection, in many cases (Quellung reaction base of serological testing). 5. Streptococcus mutans sticks to teeth due to a capsule. Plaque becomes tartar if not removed. 6. Alcaligenes Viscolactis in milk. b. Flagella--protein = flagellin. Anchored through the cell wall to a series of rings which rotate. Flagella is rigid and works more like an outboard motor than a whip. Must rotate thousands of times a minute in order to push cells with all that surface
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Unformatted text preview: through water. 4mm to 6 mm per minute in E.coli. Flagella can rotate at 2500 rpm. All spirilla have flagella (axial filaments or endoflagella) about 1/2 of the bacilli and a few cocci. DEFINITIONS: 4. Polar, lophotrichous, amphitrichous, peritrichous. 5. Runs and tumbles. Taxis, chemo, photo, thermo, magneto. When a stimulus is present tumbles are inhibited and the flagella turns counterclockwise constantly toward the stimulus. This is positive taxis. When a substance initiates tumbles the cell's flagella go clockwise and the cell tumbles, resuming its run in another direction. c. cell walls (exceptions--Mycobacterium, mycoplasma, archaebacteria, L-forms, spheroplasts, protoplasts. 1. Surrounding, encasing molecule is peptidoglycan. Visual. NAM-NAG-NAM-NAG-NAM-NAG-NAM-NAG This is the Glycan portion of peptidoglycan. Held together by beta linkages. Each Glycan strand held together by chain of amino acids to another strand. "Chain Link Fence" analogous....
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