Multiple parts short answer - Essay Example

Interdisciplinary nature of Biology Lethal dose in explained in terms of the way the patient mortality rate relate with the number of cells ingested;
If LD50 is taken, vibrio cholerae changes from 108 cells to 104 cells in concentration. There is a fall of the concentration of vibrio cholerae by 104 in number. Since the infection is reduced by 50%, which is the ratio of the cells ingested, the mortality rate should also fall by the same rate.
2. Effect of low pH on the growth of vibrio cholerae
Low Ph results in acidic environment around the bacteria. They are able to survive the conditions through thickening their outer covering (Linde, p 45). The lethal dose administered kills the bacteria by raising the ph, which makes them suck in too much liquid and die. Low ph would, therefore, increase the growth of vibrio cholerae.
3. The way in which the lethal dose of 50% may change over time.
With continue administration of lethal 50 dose, the bacteria in the body obtain a way to survive in its presence as they get used to it. They, therefore, produce molecules that are known as virulence factors, which enable them to colonize the host. The process occurs when the pathogenic bacteria, vibrio cholerae in this case spreads the virulence factors through the genetic elements that are mobile. The genes are transferred horizontally making the harmless genes obtain the harmful chromosomes from the vibrio cholerae. Through the process, the lethal dose 50% becomes ineffective and has to be changed.
Part 2: Relationship between micro organisms and humans
1. Escherichia coli strain A and Escherichia coli strain B are structurally different in their amino acid composition. E. coli A has one polypeptide chain that contains 177 amino acids while the latter has 153 residues (Lowry et al, p 36). The higher weight of E. coli A makes it destructive to its host.
2. Of E. coli A and B, the latter benefits from colonization of the host because they co-exist.
3. The symbiotic relationship between the host and the bacterial pathogen is through the way the host provides the bacteria a habitat and food. The bacterial pathogen facilitates normal physiology in the host.
Works cited
Linde, E.1999. History of clinical microbiology. Clin. Microbiol. 100:123­234. [Online.] 
Lowry, O. H., N. J. Rosebrough, A. L. Farr, and R. J. Randall.1951. Protein measurement 
with the Folin phenol reagent. J. Biol. Chem.193:265­275.  Read More