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Virus & Bacteria Unit Part 1: Viruses Big Idea: VIRUSES ARE NOT LIVING BECAUSE THEY DON’T FULFILL ALL THE CHARACTERISTICS OF LIVING THINGS. Definition Viruses are tiny particles unlike any other organism. A virus consists of genetic material such as RNA or DNA wrapped in a protein coat. Characteristics of Life Homeostasis Nutrition Transport Respiration Synthesis Growth Excretion Regulation Reproduction Is a virus living? Is it living? No, because a virus can not reproduce on its own. It needs a host cells. How does a virus’ size relate to the size of the cell? Viruses are much smaller than a cell and that is why they can easily get into a cell How are viruses characterized? Characterized as: Plant Animal Bacterial virus What are the two parts that comprise a virus? Nucleic Acid Core (either RNA or DNA) Protein Coat called a capsid Shapes of Viruses 1. Rod shaped (tobacco mosaic virus) Shapes of Virus 2. Polyhedral (Mumps) Shapes of Virus 3. Helical (Herpes) How does a DNA virus replicate? DNA virus produces RNA (transcription) RNA directs production of viral proteins OR Viral DNA combines with host cell’s DNA How does RNA virus replicate or reproduce itself? Once inside the host, an RNA virus directs the host cell to produce proteins OR Viral RNA may make DNA Retrovirus Virus that has RNA as its genetic material Example is HIV Bacteriophage Virus that attacks a bacterial cell Two types of infection: A. B. Lytic Cycle Lysogenic Cycle Lytic Cycle Bacteriophage attaches to host cell and injects its DNA Foreign DNA produces more proteins in the host cell Causes cell to lyse (or break open) and the virus/phage is released into the host’s body Lytic Cycle Lysogenic Cycle Bacteriophage injects DNA into the host cell Bacteriophage’s DNA integrates itself into a chromosome Bacteria reproduces Lysogenic Cycle Bacteria Unit Big Idea: BACTERIA ARE PROKARYOTIC CELLS THAT HAVE DIFFERENT SHAPES, STRUCTURES, & FUNCTIONS IN THEIR ENVIRONMENT. 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 Archaebacteria vs Eubacteria Archaebacteria 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 Eubacteria: Surrounded by a cell wall made of peptidoglycan. Example: rhizobiumnitrogen–fixing bacteria Identifying Prokaryotes 1. Shape: • Coccus – spherical • Bacillus – rod-shaped • Spirillum – spiral • Vibrio – comma shape Bacillus Coccus 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 review What role do chemosynthetic bacteria have in the ecosystem? http://www.youtube.com/watch?v=4lmwbB zClAc&NR=1 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 Genetic recombination Sharing or exchanging of genetic material 3 types: 1. Conjugation 2. Transformation 3. Transduction 1. Conjugation A temporary bridge forms between two cells. A plasmid, a separate section of DNA, is transferred from one cell to the other. Often the plasmid contains useful genes, like antibiotic resistance. 2. Transformation Bacteria takes in DNA from the environment. Dead bacteria may break apart and release DNA. Other bacteria can pick up this DNA and become genetically different. 3. Transduction Viruses can pick up small amounts of DNA from a host bacteria. When it infects another bacteria, the new DNA is transferred into that cell. Disease Pathology is the study of disease. Pathogens: organisms that cause disease. Exotoxins Poisonous proteins that are released by some grampositive bacteria. For example Clostridium tetani secretes an exotoxin that causes tetanus. Tetanus causes stiffness in muscles. 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: Most species of Salmonella, are endotoxin producing bacteria. Salmonella typhi, causes typhoid fever. 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. But most used in treatment still come from bacteria. 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. Which diseases are preventable by better sanitation practice? Cholera Salmonella Tetanus Staph What are other ways that antibiotic resistance is passed? Genetic recombination