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Chapter 18 VIRUSES & BACTERIA Microbiology Viruses & Bacteria History of Microbiology • • • • 1668 Redi disproves spontaneous generation 1675 Leeuwenhoek describes bacteria Jenner 1798 • Makes small pox vaccine (1st vaccine) used cowpox virus. • 1818-1865 • Semmelweis Made connection between disease and cleanliness. PASTURE • 1860 • Discovered cause of fermentation (yeast) • Disproved spontaneous generation. Pasture • Organisms can be carried by air. • Cure for silk worm disease. • Helped develop resistance for fowl cholera. Pasture • Immunization for Anthrax. • Rabies Vaccine. Koch 1876 • Germ theory of disease. • Koch’s postulates. • Discovered microbes grow best on a solid in colonies. Koch 1876 • Developed AGAR. • Assistant: Petri invented the Petri dish. Koch’s postulates: • 1. Microbe is present in all cases of the disease. • 2. Isolate the microbe and grow in pure culture. Koch’s postulates • 3. Pure culture put back into test animal to cause the disease. • 4. Take it out of the 2nd host, isolate and identify. Lister 1878 • Developed antiseptic surgery. • Used phenol on everything. Beijerinck 1880 • Discovered nitrogen fixing bacteria. • N2 to NO2 Iwanowski 1892 • Transferred tobacco mosaic virus into healthy tobacco plant, plant became sick. Gram 1884 • Developed ways to stain bacteria. • Gram + • Gram • All bacteria fit into these two categories. Loeffler & Frosch 1898 • Studied Hoof and Mouth Disease. • Determined that a virus was smaller than a bacteria. Ehrlich 1910 • After 605 failures discovered Drug # 606. • Used as 1st real drug. • Used to cure Syphilis. • Organic Arsenic. d’ Herelle 1917 • Discovered Bacteriophage. • Agent (virus) that eats bacteria. Fleming 1928 • Discovers penicillin from mold. • One of the greatest medical discoveries of all time. • Kills bacteria. Interesting note: • By 1997 some bacteria have evolved to the point they are completely immune to ALL antibiotics. Stanley 1935 • 1st American to distinguish himself as a microbiologist. • Purified viruses, showed what they were. • TMV. Thomas D. Brock 1966 • Discovers the first Organism living in water that is near boiling! • Names it Thermus aquaticus • Key to PCR technique. Dr. Carl Woese 1977 • Proposed that a new Domain be created for extreme bacteria. • Name of Domain: Archaea What is a Virus??? Viruses • A virus is about 1/2 to 1/100th the size of the smallest bacterium. • Most scientists consider them non living. Viruses • Come in many shapes and sizes: – Polyhedral – Enveloped polyhedral – Helical – Enveloped Helical – Complex Why non living? • Viruses DO NOT exhibit all 7 characteristics of life. • Cells ………no • Organization……Yes • Energy Use…….only in host • Response…….Yes Alive or Not??? • Growth……….Yes in host • Reproduce…….Yes in host • Adaptation……..Yes What do viruses do? • • • • • • • • Cause disease Influenza Aids Measles shingles warts colds HIV What do viruses do? • Used in Genetic Engineering. 2 Main Kinds • Virulent: Immediately cause disease. • Temperate: Does not cause disease immediately. 4 Classes of Viruses • RNA • DNA • Viroids • Prions RNA Viruses • Nucleic acid is RNA • Mutate more often than DNA viruses. • Enter the cell and produce proteins right away using hosts ribosomes. EXAMPLES • Polio RNA retroviruses • Use enzyme reverse transcriptase to make DNA from RNA. • New DNA makes new RNA then proteins. EXAMPLE • HIV/AIDS DNA viruses • Once in a cell the DNA makes new RNA and then proteins. • Splices it’s DNA into a celss DNA then produces new proteins. EXAMPLES • Pink-eye Viroids • Short single strand of RNA, free floating. • Not long enough to make a full protein. • Usually interferes with normal cell function. Prions • Glycoprotein particle containing about 250 AA. • Associated w/ diseases that have a long incubation period. • KURU degenerative nerve disease in humans. The Bacteriophage Anatomy of a Bacteriophage The Lytic Cycle • T2-T4-T6-T8…. • Lytic phages explode host cell to get free. Lytic Cycle • • • • • • Five phases: Absorption Entry Reproduction Assembly Release Absorption • Virus attacks host. • Tail fibers contain chemicals that are attracted to the surface of the cell. Entry • Virus releases an enzyme that weakens the cell wall. • Tail contracts • base plate perces the cell wall • DNA or RNA is injected into the cell Replication • Viral DNA takes complete control of cell activity. • They direct the cell to make viral DNA, proteins, and Parts. Assembly • Proteins coded for by viral DNA act as enzymes that put the new virus parts together. • This continues until cell is completely stuffed with new viruses. Release • Viruses release an enzyme that digests the host cell wall (lysis) allowing the new viruses free to start the process over again. Lysogenic Cycle T1-T3-T5-T7 etc. Lysogenic Cycle • Temperate viruses go though this process. • DNA injected into cell. • DNA is incorporated into the host cells DNA (prophage). • Host cell lives normally. • Host cell divides, usually many times. • Each new cell has viral DNA in it now. • Usually the prophage within each host cell lays dorment until triggered by something. • Replication • Assembly • Release