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Lecture 3

week 3 microbio.docx

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Department
Biology
Course
BIOL 2900
Professor
Malini Persaud
Semester
Fall

Description
Structure/function of Bacteria - all cellular life has this characteristics in common:  Cell membrane (curves outside the cell. Regulates the flow of nutrients and wastes that enter and leave the cell.)  DNA as its genetic material.  RNA molecules  Proteins (includes various types of enzymes)  Basic chemicals  Reproduction  Energy - Prokaryotic cell organization and structure A. Flagellum: long structures that extend beyond surface of cell - flagella maybe arranged differently depending on species. Function: I. responsible for movement (rotation propels bacterium through environment II. used in chemotaxis (movement towards or away from substances). Bacteria can sense high and low concentration of various substances and know how to either go towards the high or swim away from the low concentration, this is called chemotaxis. III. B. Axial filaments: similar function to flagella. - run lengthwise along cell (look like snakes, family of spirochetes). Some of them can cause lime disease - snake-like movement C. Fimbria and Pili - Fimbria: sticky projections, used by bacteria to adhere to one another, to hosts and to substances in environment - Maybe 100s per cell and are shorter than flagella. - Fimbria maybe evenly distributed over entire surface used for attachment. For ex. E.Coli has other organism’s DNA. 875? - Pili - long hollow tubules - longer than fimbria but shorter than flagella. Bacteria typically only have one or two per cell - join two bacterial cells and mediate the transfer of DNA from one cell to another (conjugation) D. Capsule or slime layer - capsule: is a thick layer of gel, firmly attached to cell surface - slime layer: is thinner than capsule, loosely attached to cell surface For ex. Sugar and other stuff will cover bacteria from the outside. - sticky substances surrounding the outside of cell - almost always observed on the surface of cells growing in nature (as opposed to the
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