nester03b - Important Point: Chapter 3: Microscopy and Cell...

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Unformatted text preview: Important Point: Chapter 3: Microscopy and Cell Structure Typical Bacterial Shapes Typical Bacterial Arrangements streptococci sarcina staphylococci Also Pleomorphic Bacteria, which vary in their shape (e.g., Corynebacterium). Prokaryotic Cell Structures Typical Prokaryotic Cell 1 Others of these proteins allow a bacterium to sense its surrounding environments (e.g., as in chemotaxis). Movement is via: Simple Diffusion (including osmosis) Facilitated Diffusion (with concentration gradient & no energy expended) Active Transport (against concentration gradient & energy expended) Simple Diffusion -- Osmosis Many of these proteins are involved in transport across membranes. solute molecules/ions Protein-Mediated Transport Cytoplasmic Membrane Cytoplasmic Membrane Movement across membrane for many substances is controlled by membrane proteins. Escherichia coli has >200 membrane proteins. Active Transport The Prokaryotic Cell Wall 2 The Prokaryotic Cell Wall In Bacteria, composed of Peptidoglycan. Target for antibiotics. Part of cell envelope. Gram-Positive Cell Envelope Gram-Negative Cell Envelope LPS: Protection from antibiotics such as penicillin plus against certain toxins. Periplasm: Site of preliminary nutrient degradation. Gram-Negative Cell Envelope Prevents osmotic lysis. In some cases recognized by host immune system. Lipopolysaccharide (LPS) Determines cell shape. Gram-Pos vs. Gram-Neg. endotoxin cell wall Carbohydrate has negative charge and provides protection against some antibiotics & some toxins (e.g., detergents). Lipid A = Endotoxin 3 Glycocalyx Mycoplasma lack Cell Walls Protection (e.g., Streptococcus pneumoniae from phagocytosis) Note: Pleomorphic Mycoplasma pneumoniae causes “Walking Pneumonia” Attachment (e.g., Streptococcus mutans causing dental plaques) Capsules are more regular and gelatinous. Slime Layers are less regular and more diffuse. Also Phototaxis, etc. Polar Flagellum e.g., E. coli Chemotaxis Flagellar Arrangements Capsule Staining Bacteria Flagella (plural) also “atrichous” 4 Pili (sing. Pillus) Fimbriae (a kind of pilli) Tips are Adhesins, used to adhere, e.g., to animal tissues Closed Circular Chromosome Ribosomes: Sites of Translation Also Plasmids, which are smaller, circular pieces of DNA. Plasmids usually encode expendable functions, e.g., antibiotic resistance. Endospores Form inside of vegetative cells (hence “endo”). On order of 10,000 per cell! Link to Next Presentation Characteristic of many soil bacteria, e.g., Bacillus spp. & Clostridium spp. Highly resistant to heat, U.V., desiccation, etc. 5 ...
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This note was uploaded on 06/03/2011 for the course MCB 205 taught by Professor Abedon during the Spring '11 term at Ohio State.

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