Chapter 18 VIRUSES BACTERIA Microbiology Viruses Bacteria History

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 (1 st 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 2 nd 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 1 st 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 • 1 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 1/100 th 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 • T 2 -T 4 -T 6 -T 8…. • 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 T 1 -T 3 -T 5 -T 7 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