Bacterial Transformation

In transformation, DNA from the environment is absorbed into the bacterial cell. In transduction, a piece of DNA is transported into the cell by a virus. As a result of incorporating new genetic material, an organism can become resistant to antibiotics. Bacterial transformation is the process by which bacterial cells take up naked DNA molecules. If the foreign DNA has an origin of replication recognized by the host cell DNA polymerases, the bacteria will replicate the foreign DNA along with their own DNA. When transformation is coupled with antibiotic selection techniques, bacteria can be induced to uptake certain DNA molecules, and those bacteria can be selected for that incorporation. Bacteria which are able to uptake DNA are called competent and are made so by treatment with calcium chloride in the early log phase of growth. The bacterial cell membrane is permeable to chloride ions, but is non-permeable to calcium ions. As the chloride ions enter the cell, water molecules accompany the charged particle. This influx of water causes the cells to swell and is necessary for the uptake of DNA. The exact mechanism of this uptake is unknown. It is known, however, that the calcium chloride treatment be followed by heat. When E. coli are subjected to 42degC heat, a set of genes are expressed which aid the bacteria in surviving at such temperatures. This set of genes are called the heat shock genes. The heat shock step is necessary for the uptake of DNA. At temperatures above 42degC, the bacteria's ability to uptake DNA becomes reduced, and at extreme temperatures the bacteria will die.

http://faculty.plattsburgh.edu/donald.slish/Transformation.html

http://www.genome.ou.edu/protocol_book/protocol_adxF.html

Photos from Google images

Beneficial Bacteria

Lactobacilli bacteria is one of the most important types of friendly bacteria found in the digestive tract, making mainly the small intestine home. Lactobacillus acidophilus is a specially stabilized type of friendly bacteria that flourishes in the small intestine. One benefit of L. acidophilus is that it inhibits bacteria and microorganisms that produce disease in the urinary tract, especially Candida albicans. Another benefit is its ability to aid in developing natural defenses against foreign intestinal bacteria and viral infections, boosting the immune system. L. acidophilus has also shown promise in the battle against Helicobacter pyloriiv, the pathogen considered to be one of the top two causes for peptic ulcers.

Bifidobacteria bacteria is friendly bacteria, colonizing mainly the large intestine, or colon. Bifidobacteria are considered extremely important to the health of the gastrointestinal tract. Bifidobacterium bifidum is especially good at enhancing the body's immune response and inhibiting harmful enzymes. It encourages resistance to intestinal infections. It has resulted in synthesis of B-complex vitamins and absorption of calcium and also helps improve symptoms of diarrhea and constipation.

Bifidobacterium longum has a high affinity for intestinal colonization, improving the intestinal environment, which leads to better regularity. Bifidobacterium longum is a bacteria that normally inhabits a healthy bowel in most mammals, including humans. It can be found in fermented foods or taken in supplement form. These beneficial bacteria thrive on plant fiber and they may assist digestion, have a protective anti-cancer effect, reduce inflammation and lower cholesterol.

http://www.betterway2health.com/florafood.htm
http://www.buzzle.com/articles/beneficial-bacteria.html
http://www.probiotic.org/Bifidobacterium-Longum.htm

Virtual Diffusion

Villi % of Cell Surface Area: 50
Radius: 1x
Cell Shape: 10:1
# of Dimples: 40
Dimple % of Cell Surface Area: 1
Highest Rate of Diffusion: 4.64(r)

The smaller the surface area, the faster the diffusion rate is, but with a bigger surface area the rate of diffusion is much slower due to a bigger cell. As molecular size(radius) increases, diffusion rate decreases, vice versa. Villi increases the surface area on the intestine which helps in the increase absorption(rate of diffusion). Finally, a cell will have the highest rate of diffusion if it is in a cylindrical shape with many villi and dimples.

http://www.mhhe.com/biosci/genbio/biolink/j_explorations/ch02expl.htm
http://www.biologymad.com/cells/diffusion.htm