PAP Bacteria and Virus Notes Ch 19

Bacteria are grouped into two kingdoms: -Eubacteria and Arcahebacteria -Eubacteria and Archaebacteria have different membrane lipids and archaebacteria lack the peptidoglycan found in eubacteria cell walls. -Archaebacterial genes are more like those of eukaryotes than those of eubacteria.

Bacteria are Prokaryotes and have: -Cell Wall -Cell Membrane -NO nucleus -Ribosomes -NO organelles -Flagella (for mobile species)

Bacteria come in three shapes: Bacillus- rod shaped bacteria. Cocci- spherical shaped bacteria. Spirilla- spiral/corkscrew shaped bacteria

Metabolic Diversity Some bacteria are heterotrophs. They are referred to as chemoheterotrophs. As bacteria take in organic molecules for both energy and a supply of carbon. Some bacteria are autotrophs. They are photoautotrophs if they use light energy to convert CO2 and water to carbon compounds. These are often found near surfaces of lakes, streams, and oceans.

Chemoautotrophs can perform chemosynthesis that perform the same task as photoautotrophs except they do not need to use light. They rely on chemical reactions instead. Many are found at hydrothermal vents.

Releasing Energy Obligate aerobes- require a constant supply of oxygen Obligate anaerobes- must live in the absence of oxygen Facultative anaerobes- Can function with or without oxygen.

Growth _Binary_ Fission is when a bacteria divides in half producing identical cells. This is asexual and much simpler than mitosis. _Conjugation__- Some bacteria can exchange genetic information this way when a hollow bridge forms between two bacteria cells and genes move from once cell to the other.

SPORE Formation- In unfavorable conditions, bacteria can form spores that can remain dormant for months while conditions improve. Then the bacteria can germinate and grow again.

Bacteria in the World Decomposers - Bacteria can help the ecosystem by breaking down dead tissue. Very important also in sewage treatments! Nitrogen Fixers- Bacteria can live in the nodules of plant roots and fix nitrogen (nitrogen fixation) which is critical in the nitrogen cycle. -Bacteria are also found in our intestines! They make vitamins that the body cannot produce by itself and we supply the bacteria with a warm and safe home. This is a mutual symbiotic relationship!

Bacteria can also cause disease in animals and plants. -Bacteria can do this by damaging cells ant tissues directly. -Or bacteria can release toxins that travel throughout the body and interfere with the normal activity of the host.

Virus Characteristics -Viruses are not considered alive as they do not have a metabolism or reproduce on their own. -Viruses are composed of DNA or RNA surrounded by a protein coat called a capsid. -If viruses are composed of RNA as their genetic material, they are called retroviruses

Viral Reproduction: -In the lytic cycle, a virus enters a cell and makes copies of itself that causes the cell to burst. ANIMATION!

-In the lysogenic cycle, a virus integrates its DNA into the DNA host cell, and the viral genetic information replicates along with the host cell’s DNA. They do not lyse the host cell right away. ANIMATION! dules/mysterious_invader s/lytic.htm dules/mysterious_invader s/lytic.htm

Viral Disease Like bacteria, viruses also can cause disease by disrupting the body’s normal equilibrium. -Unlike bacterial diseases, antibiotics do NOT work on viruses. -A vaccine can be used to prevent a viral disease.

-Some viruslike particles have been discovered that also can cause disease. -One example is a prion which is a protein infectious particle and contains no DNA or RNA (only protein!). This was found to be the culprit in mad cow disease.