Question

48. Answer the following using your own words, do not copy from another source.

A. Define the term enterotoxin and give an example of an organism (Genus and species name) that causes food poisoning and produces an enterotoxin.

B. Define the term cytotoxin and give an example of an organism (Genus and species name) that causes food poisoning and produces a cytotoxin.

50. Choose ONE of the following questions to answer. You can write your answer on a separate sheet of paper and submit as a PDF.

A. You have a population of E. coli and would like to isolate an auxotroph in the population that is deficient in the ability to produce the amino acids histidine and leucine. Design a way to isolate the mutant E. coli cells from a populations of wild type cells.

B. Explain quorum sensing in bacteria. Explain how Vibrio cholera uses quorum sensing to regulate gene expression and cause disease in the human host.

Answer 1

ENTEROTOXINS

It is toxin produce by bacteria which acts on a distant site such as the intestine.

bacteria which produces enterotoxins and causes food poisoning are-

a) Staphylococcus aureus.

It produces S. enterotoxins A, B, C, D, E.

CYTOTOXIN

It is a bacterial protein toxin which it acted on a specific cell and is lethal.

clostridium botulinum produces cytotoxins.

QUORUM SENSING-

It is a process by which bacterial communicate with the other bacteria by the production of an auto-inducer (extracellular signaling molecule) so they can form their own niche. It involves four steps i.e. production, release, recognition, change in gene regulation.

Vibrio cholera uses quorum sensing to regulate gene expression-

AHL (auto-inducer molecule) binds to the AI synthetase in the cytoplasm of bacteria

Due to its high level it activates the luminescent system of the luminous bacteria in the media. It leads to induction of expression of the gene is known as quorum sensing.