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Identifying and Classifying Bacteria What is a prokaryote? Cells that lack a true nucleus. Cells that lack membranebound organelles. Most surrounded by a cell wall. Many secrete a protective slime capsule. How big is a prokaryotic cell? 1- 5 micrometers (1 millionth of a meter) Classification Archae vs Bacteria Archae Surrounded by a cell wall lacking peptidoglycan. Live in extreme conditions Examples of Archae Methanogens: convert H2 and CO2 into methane gas for energy Halophiles: love salt Thermoacidophiles: love heat and acid Bacteria: Surrounded by a cell wall made of peptidoglycan. Example: E. coli Identifying Prokaryotes 1. Shape: • Coccus – spherical • Bacillus – rod-shaped • Spirillum – spiral • Vibrio – comma shape Coccus Bacillus Vibrio Spirillum Cocci and Bacilli may group together Prefixes for arrangements: Diplo – two Ex. Diplococcus Strepto – chain Streptococcus Streptobacillus Staphylo - clustered Staphylococcus 2. Motility: ability to move Flagella: whip-like structure used to propel bacteria Slime: glide along slime secretion Spiral motion: cork-screw motion (spirillum) 3. Metabolism: Oxygen or NOT Obligate Aerobes: Need oxygen Obligate Anaerobes: cannot live in oxygen Facultative anaerobes: can live with or without oxygen 3.Metabolism: Obtaining Energy Autotroph vs. Heterotroph • Photoautotroph- uses light energy for photosynthesis • Chemoautotroph- uses energy from inorganic chemicals for chemosynthesis • • Photoheterotrophs- uses photosynthesis and eats organic compounds Heterotroph – consumes organic compounds Bacterial Reproduction Asexual: Binary fission 1. 2. 3. Circular DNA replicates Cell membrane and cell wall divide Identical daughter cells separate How fast does this happen? http://www.youtube.com /watch?v=gEwzDydciWc &feature=related approximately 20 minutes every Disease Pathology is the study of disease. Pathogens: organisms that cause disease. Gram-staining Test Gram-positive: bacteria contain lots of peptidoglycan in cell walls. Stains purple. Gram- negative: bacteria contain little peptidoglycan in cell walls. Stains red. Exotoxins Poisonous proteins that are released by some grampositive bacteria. For example Clostridium tetani secretes an exotoxin that causes tetanus. Tetanus muscles. causes stiffness in Clostridium botulinum produces a very powerful exotoxin that causes the fatal disease, botulism. 1 g of botulism toxin can kill 1 million people. Endotoxins Lipids and carbohydrates in the cell membranes of some Gram-negative bacteria, that are poisonous. They are released when the bacteria die. For example: species of Salmonella, are endotoxin producing bacteria. Salmonella typhi, causes typhoid fever. Most Antibiotics Antibiotics interfere with the bacteria’s cellular activities. For example: Penicillin: blocks the building of the cell wall. “Accidently” discovered by Alexander Fleming in 1920s Tetracyline: blocks protein synthesis. Where do antibiotics come from? Antibiotics are naturally made by some fungi and bacteria. Some are made synthetically in labs. Antibiotic-Resistance Bacteria can quickly adapt to their environment because of their rapid rate of reproduction. 1. 2. 3. Antibiotic-Resistance If one bacterium mutates and becomes resistant, then in the presence of antibiotics, bacteria not resistant die Those with the resistance take over the population.