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Lecture 10

MBIO 1010 Lecture 10: Lecture 10

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MBIO 1010
Christopher Rathgeber

Microbiology 1010 – Lecture Notes Flagella and Swimming Motility (Continued…) Differences in swimming motions (Figure 2.54) o Peritrichously flagellated cells move slowly in a straight line o Polarly flagellated cells move more rapidly and typically spin around Tumble – change in direction. Unidirectional flagella - Doesn’t have ability with CCW direction so it has to stop. 55 Microbiology 1010 – Lecture Notes Gliding Motility Flagella-independent motility (Figure 2.56) Slower and smoother than swimming Requires surface contact Mechanisms o Excretion of polysaccharide slime o Type IV pili o Gliding-specific proteins Chemotaxis and Other Taxes Taxis: directed movement in response to chemical or physical gradients o Chemotaxis: response to chemicals o Phototaxis: response to light o Aerotaxis: response to oxygen o Osmotaxis: response to ionic strength o Hydrotaxis: response to water If it’s extremely isotonic in the environment (he hopes) and he can move depending on if the environment starts to go hypo or hypertonic. Chemotaxis Chemotaxis o Best studied in E. coli o Bacteria respond to temporal, not spatial, difference in chemical concentration o “Run and tumble” behavior (Figure 2.57) o Attractants and repellants sensed by chemoreceptors 56 Microbiology 1010 – Lecture Notes Chemotaxis (Continued…) Directed movement toward an attractant or away from a repellent (^^this happens from a concentration gradient) o Biased random walk ex. E. coli shows biased random walk toward glucose when there is a concentration gradient The cell still exhibits a series of runs If it senses that the [glucose] is increasing: The tumble is delayed The run lasts longer Chemotaxis (Continued…) Measuring chemotaxis (Figure 2.58) Measured by inserting a capillary tube containing an attractant or a repellent in a medium of motile bacteria o Can also be seen under a microscope 57 Microbiology 1010 – Lecture Notes Cell Size Eukaryotes have: Lower surface area to volume ratio  Need more sophisticated transport mechanisms Grow slower
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