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 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. N 2 to NO 2

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.By 1997 some bacteria have evolved to the point they are completely immune to ALL antibiotics.

Stanley st 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