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Chapter 19 Bacteria and Viruses 19-1 BACTERIA 19-2 VIRUSES 19-3 DISEASES CAUSED BY BACTERIA AND VIRUSES 19-1 Bacteria Bacteria are prokaryotes- unicellular organisms that lack a nucleus. Classification was the Kingdom Monera Now, in two separate Kingdoms: Eubacteria Archaebacteria Bacteria What’s the Difference? Eubacteria- new bacteria Example: Escherichia coli (E. coli) Found water, land, on and in us. Archaebacteria- ancient bacteria Examples: Methanogens Found in harsh environments: thick mud, digestive tracts of animals, hot springs Identifying Prokaryotes Shape Cocci – spherical Bacilli – rod shaped Spirilla - spiral How do they obtain energy? Most are heterotrophs and many are autotrophs Types of heterotrophs: “other” Chemoheterotrophs (chemical) Photoheterotrophs (light) Types of autotrophs: “self” Photoautotrophs (surface of lakes, oceans) Chemoautotrophs (deep ocean) Growth and Reproduction Can divide every 20 minutes! Two ways to reproduce: Binary fission – dividing in half Conjugation – form bridge and exchange DNA When conditions become unfavorable: Spore formation – help it survive in extreme conditions, such as heat, dryness, lack of nutrients. Binary fission conjugation Spore formation Importance of bacteria Decomposers – Help ecosystem recycle nutrients by breaking down dead tissue Help in sewage treatment Human Uses Used in industry – clean up oil spills Remove wastes and poisons from water Make drugs Used in food 19-2 Viruses Viruses are composed of a core of DNA or RNA surrounded by a protein coat (capsid) Virus means poison Virus Structures Tobacco Mosaic Virus T4 Bacteriophage Head DNA Influenza Virus RNA Capsid RNA Capsid proteins Tail sheath Tail fiber Surface proteins Membrane envelope How does a Virus work? Proteins of virus bind to receptors on the surface of a cell. Cell gets “tricked” into letting the viral DNA in. Cell then transcribes and translates viral genes. Bacteriaphage- infects bacteria Viral Replication Two different processes can occur: Lytic Cycle: viral DNA enters host, copies are made, and cell lyses (bursts). Lysogenic Cycle: viral DNA enters host, viral genes are replicated indefinitely. Prophage- viral DNA incorporated in cell’s DNA The Lytic Cycle... The Lysogenic Cycle... Both Cycles... Retroviruses Retrovirus- contains RNA as its genetic information Genetic info is copied backwards from RNA to DNA. “Retro” means “backwards” Ex. AIDS is caused by a retrovirus (HIV) Comparison… 19-3 Diseases caused by Bacteria and Viruses Disease causing agents are pathogens Bacteria produce disease in one of two ways: Break down cells for food Release toxins (poisons) Examples for food or toxin release TB – tuberculosis – destroys lung tissue Strep throat releases toxins into blood stream FLU EBOLA SMALL POX COLD VIRUS Common Diseases Caused by Bacteria Section 19-3 Diseases caused by Bacteria Disease Pathogen Prevention Tooth decay Streptococcus mutans Regular dental hygiene Lyme disease Borrelia burgdorferi Protection from tick bites Tetanus Clostridium tetani Current tetanus vaccination Tuberculosis Mycobacterium tuberculosis Vaccination Salmonella food poisoning Salmonella enteritidis Proper food-handling practices Pneumonia Streptococcus pneumoniae Maintaining good health Cholera Vibrio cholerae Clean water supplies Controlling Bacteria Sterilization – using high temperatures Disinfectants – chemical solutions Food storage and processing – storing in fridge or cooking food Preventing Bacterial Disease Vaccine – weakened or killed pathogen Examples – meningitis, whooping cough Antibiotics – block the growth and reproduction of bacteria Examples- Penicillin or tetracycline Common Diseases Caused by Viruses Diseases caused by Viruses Section 19-3 Type of Virus Nucleic Acid Disease Oncogenic viruses DNA Cancer Retrovirus RNA Cancer, AIDS Adenoviruses DNA Respiratory infections Herpesviruses DNA Chickenpox Poxviruses DNA Smallpox Viral disease in humans Cannot be treated with antibiotics Vaccines Examples – polio, measles, mumps, chicken pox, hepatitis b