Viruses and Bacteria

Discovery of Viruses 1935 – Wendell Stanley discovered that a chemical was poisoning tobacco plants. The chemical was made of RNA and a protein — the first discovered virus. Virus = Poison in Latin

Viral Structure Viruses are not made of cells Are NOT alive. Basic Structure: Protein Coat Nucleic Acid Core (either DNA or RNA)

Virus Size Very, very small About 100 times smaller than a bacteria Can only be seen with electron microscopes

Virus Categories DNA viruses Stable, do not mutate rapidly Smallpox, Hepatitis B RNA viruses Mutate rapidly, unstable HIV, Rhinovirus (common cold)

2. Viral DNA takes over protein synthesis. 4. The cell breaks open and releases viruses. 1. The virus attaches to a cell and injects DNA. 3. New viruses are made. Lytic Cycle

Lysogenic Cycle Instead of copying itself and killing the cell, the virus inserts its DNA into the host cell DNA Cell grows and divides as normal, copying viral DNA along with its own Change in environment (stress, sickness, etc.) causes the virus to activate and enter the Lytic Cycle Chicken Pox  Shingles

Prions and Viroids Prions -- protein particles that cause problems with a cell’s natural protein formation. Mad cow disease! Viroid – single strands of RNA that can affect plants

Viral Diseases Common cold, the flu, rubella, mumps and measles, smallpox, hepatitis, polio, AIDS, and rabies Prevention Vaccinations and avoidance Treatments: Some anti-virals NOT antibiotics! (only work on bacterial infections)

Archaea and Bacteria: Classification and Structure

Archaea and Bacteria are Prokaryotes. Pro – before Karyon – nucleus The simplest forms of life Earth’s first cells were prokaryotes

Bacteria Earth’s most abundant life. They can survive in many environments. They can get energy from many different sources.

Archaea Live in extreme environments: Oxygen-free environments Concentrated salt- water Hot, acidic water

Differences between Archaea and Bacteria 1. Different structure of cell wall. 2. Archaea is more closely related to eukaryotes than to bacteria! 3. Archaea evolved first — oldest organisms on the Earth

Similarities between Archaea and Bacteria 1. Unicellular 2. Prokaryotic 3. Asexual Reproduction – binary fission

Bacterial Shape Rod: bacillus Spheres: coccus Spirals: spirillum

Pili—used to attach bacteria to other cells

Getting Energy 1. Photosynthetic—get energy from Sun 2. Chemosynthetic—get energy from chemicals 3. Heterotrophic—get energy from other things; mainly decomposers

Good Bacteria E. coli — helps digest our food Fermentation – allows us to make cheese, vinegar and beer Industrial uses – acetone; cleaning up oil spills; manufacturing insulin

Bacterial Diseases Bubonic plague, cholera, cavities, dysentary, typhoid fever, MRSA, acne Treatment: Antibiotics – kill bacteria, but not viruses. Some bacteria have evolved resistance to antibiotics. Germ Theory – disease is caused by microscopic organisms

Disproving Spontaneous Generation Redi (1600s) Pasteur (1800s)

Miller-Urey Recreated model of Earth’s early atmospheric conditions Gases + lightening = organic compounds (amino acids) sparks heat source amino acids water “atmosphere” “ocean”

Germ Theory Timeline 1688 – Redi showed that life only comes from life (flies & meat jar experiment) 1840s – Discovery that if midwives washed hands in between deliveries, infant mortality dropped from 10% to 1%

Germ Theory Timeline (cont.) 1860 – Pasteur confirmed Redi’s experiments and disproved Spontaneous Generation (pasteurization process) 1867 – Dr. Lister experimented with chemicals to kill germs. Invented sterilization techniques.

1890 – Robert Koch Koch’s postulates – tests to isolate causes of diseases which are still used today Disease causing organism must be 1. Found in all cases of disease 2. Removed and grown in laboratory 3. Injected into a healthy organism 4. Removed from organism and compared to original sample

Both cultures are the same. Koch’s Postulates