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BACTERIA (Ch. 24) AND VIRUSES (Ch. 25) BACTERIA: Simplest & most primitive life forms (fossils from 3.5 bya) 2 Kingdoms: Archaebacteria Eubacteria Archaebacteria: “ancient bacteria” live in extreme environments Thermoacidophile: thrives in hot, acidic environments Halophile: thrives in salty environments Methanogen: thrives in methane-rich environment Eubacteria “true bacteria” live in “normal” environments Simple Structure: PROKARYOTE no nucleus or membrane-bound organelles Chromosome is in one loop, not in pairs Chromosome # 1 Have ribosomes; needed to make structural proteins and enzymes Cell Wall: Some cell walls have a thick layer of peptidoglycan, a carbohydrate Gram Positive: stains purple; stain is held by peptididoglygan layer Gram Positive Gram Negative: Stains pink; stain resistant since there is a layer over the peptididoglycan layer Gram Negative Cell Parts: Classified by Shapes 1.Bacillus: ovals 2.Coccus: round 3.Spirillus: wavy or bent Configurations: Diplo: in pairs Diplococcus Strepto: in chains Streptococcus Streptobacillus Staphylo: in clusters Reproduction: Binary Fission Rapid life cycle since there is no mitosis Some genetic recombination by three different methods: 1.Conjugation Two bacteria join up at the pili (conjugation bridge) and exchange a small loop of DNA that has detached from the main DNA (plasmid) The plasmid is incorporated into the DNA of the receiving cells conjugation bridge Transformation: •Substitutes new DNA for a similar fragment in its original DNA Transformation: Transduction: •A virus obtains a piece of DNA from host bacterium •Virus transfers DNA to new cell that it infects Transduction: NUTRITION: AUTOTROPHIC by photosynthesis or chemosynthesis Heterotrophic: many are saprophytic-eat dead stuff METABOLISM/ RESPIRATION: Obligate Aerobe Must have Oxygen to survive Obligate Anaerobe: Can only survive in the absence of oxygen Facultative Anaerobe: Can live with or without oxygen Effects on Humans: •Decomposers •Food & Drug industries •Clean up toxic waste naturally •Natural pesticides Nitrogen fixation Extract nitrogen from the environment for plants to use •Cause diseases by releasing toxins into host organism Exotoxins: •Produced by Gram positive cells •Toxins constantly produced and steadily released by cell •Protein-based toxins Endotoxins: •Produced by Gramnegative cells •Toxins released when bacterium dies •Lipid or carbohydrate based toxins How can we control bacteria? Antibiotics! Wash hands! Good sanitation! Pasteurization Immunizations! Safe sex!!! Problem: ANTIBIOTIC RESISTANCE •From overuse (antibiotics only work on gram-positive bacteria; doctors have prescribed for any bacteria and also viruses •Patients don’t take all prescribed medication, as directed •Bacterial mutations occur that also result in resistance Example: Tuberculosis used to respond to penicillin but now it doesn’t