gene406(d) - C Yes collagenases are carried by phages This...

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Part 1) Seq A - The toxin associated with this amino acid sequence is in the enterotoxin b family, and is called toxin b. Vibrio cholerae expresses it. The gene is carried on a vibrio phage CTX. SeqB - The toxin associated with this amino acid sequence is in the ribosome-inactivating protein family, and is called shiga toxin. Escherichia coli expresses it. The gene is carried on an enterobacteria phage. SeqC - The toxin associated with this amino acid sequence is a neurotoxin. Clostridium botulinum expresses it. The gene is carried on a clostridium phage. Part 2) I chose Clostridium perfringens . A - Bacillus cereus , Bacillus thuringiensis , Clostridium histolyticum , Bacillus anthracis , and Bacillus weihenstephanensis all have a similar collagenase. B - Yes, collagenases are considered virulence factors. These enzymes target the connective tissue in muscle cells and organs and destroy the peptide bonds in collagen. They are considered exotoxins, which cause major damage to the host.
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Unformatted text preview: C - Yes, collagenases are carried by phages. This is due to the fact that non-infected bacteria are not pathogenic. Only the bacteria that harbor a prophage are pathogenic. This verifies the fact that the genes encoding these enzymes are carried on the phage. Another way of confirming this fact is to examine the phage genome and the bacterial genome. A bacterium with collagenase activity will have a prophage. This segment of DNA should be conserved when examining the phage genome. Part 3) The new nonvirulent strain is safe because if the gene encoding the toxin is deleted completely, Bacterium X is no longer pathogenic. Even if the lysogenized cell is stressed and induces the phage to enter a lytic phase, any phage progeny are nonvirulent. The gene encoding the toxin is missing, thus it cannot be replicated. However, it is possible that a second virulent phage can infect the nonvirulent strain, making the strain pathogenic once again....
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This note was uploaded on 05/10/2010 for the course BIOL 406 taught by Professor Staff during the Spring '08 term at Texas A&M.

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