Examples of Viruses and Bacteria
Viruses – Pages 475-483
Don’t grow or develop
Only reproduce within a host (can’t do it alone MUST have a host)
Virus multiply through the lytic cycle where the virus attacks the host, injects it nucleic acid into the host, and then spreads or bursts from the host.
Structure = Made up of
(1) protein coat- capsid (located on the outside)
(2) small amount of nucleic acid - DNA or RNA (located on the inside).
Shape of Viruses
Viruses have three distinct shapes
How are viruses named?
Named after the disease it causes. For example, rabies viruses or polio viruses
Named after the tissues they infect. For example, Adenoviruses cause common cold found in the adenoids tissues between the back of the throat and the nasal cavity.
Today viruses are given a genus name ending in the word virus and a species name.
If a virus affects bacteria it is called a bacteriophage or phage.
Examples of Viruses
HIV - RNA virus called retrovirus. HIV in a human host affects white blood cells. People with HIV eventually will get AIDS because more white blood cells become infected and produce new viruses. Remember white blood cells are used to fight diseases leaving the body unable to protect itself.
Cancer - Some viruses are linked to cancer. Hepatitis B is a virus that can cause liver cancer and disrupts the normal growth and division of cells.
Plant viruses - Plant viruses require wounds or bites to enter the host. ex. Tobacco mosaic virus – disease in tobacco plants which stunts plant growth.
Kingdom Monera (Bacteria) – Pages 485-495
Archaebacteria - Extreme environment
Eubacteria (page 487) - Common, majority
Thrive in harsh environments previously through inhabitable
Archa – means ancient
Thought to be similar to the first organisms on earth
Single celled or clustered together to form filaments
Cell wall lacks peptidoglycan (a protein-carbohydrate molecule found in all other bacteria),
cell membrane and ribosomal RNA
Anaerobic (can not tolerate oxygen)
Producers, Consumers or Decomposers
Classified according to the environment in which they live
1. Methanogens – produce methane gas and live in places such as soil and intestines of herbivores
2. Halophiles – live in extremely salty environments – like the Dead Sea
3. Thermoacidophiles – live in acid sulfur springs of Yellowstone National Park and Undersea Vents
Reproduce asexually by Binary fission (asexual à copy chromosomes, attach and divide).
Binary Fission - How does this work?
First the bacterium copies its chromosomes. The original chromosome and copy become attached to the cells plasma membrane for a while. The cell grows larger and larger, and eventually the two chromosomes separate and move to opposite ends of the cell. Then a partition forms between the chromosomes. The partition separates cell into two smaller cells. Because each new cell has either the original or copy of the chromosome the resulting cells are identical. This process is rapid!
Also reproduce asexually by budding
Single celled or cluster together to form colonies
Cell wall, cell membrane and circular DNA called a plasmid
Heterotrophic, autotrophic, chemotropic
Found everywhere and most are harmless
Some are decomposers
Reproduce asexually through budding or binary fission
Are they Helpful?
Eu- means true - True bacteria
MOST are HELPFUL!!!
Fertilize fields (nitrogen fixation)
Recycle nutrients (decomposers à breakdown dead organism and waster into nutrients.
Produce Food and medicine (food such as cheese, pickles, yogurt, vinegar, sauerkraut, and antibiotics such as streptomycin, erythromycin, bacitracin)
Are they harmful?
YES - Examples