Question

A bacterial strain called XYZ living in the lake MBG223 near Bilkent University requires to synthesize tryptophan continuously.  The reason is, the essential proteins (essential means, the proteins required for survival of the bacteria) contain high content of tryptophan.  Therefore, this bacterial strain XYZ has a tryptophan operon.  Unfortunately, the tryptophan level of nutrition available in lake MBG223 is very limited during summer and winter time and the other nutrition levels are high. During the summer time, as the lake MBG223 partially evaporates, the salinity of the water increases, the temperature of the lake arises and the pH of the environment turns from natural to acidic.  Changes in salinity, pH and temperature is known to disrupt hydrogen bonding in nucleotide base-pairings and also the structure of the proteins.  Here, assuming that the structure/function of the proteins are not effected please answer the followings.

a) İnside the XYZ bacteria, what would you observe with regards to synthesis of tryptophan bearing proteins during summer vs. winter time?  How would this effect bacterial growth rate during the summer time vs winter time? (18pts)

b) In another neighboring lake called MBG222, they found a different bacterial strain called WOWWW to have mutant tRNAs on the anti-codon region of the tRNA.  This tRNA carries Phenylalanine to wherever it encounters the sequence UGG (tryptophan) on the mRNA. What happens to the regulation of the trypthophan operon in bacteria that has 1) high tryptophan and low phenylalanine vs. bacteria that has low tryptophan and high phenylalanine? (12 pts)

Answer 1