Bio 14 Lab Report

In the BIO 14 Lab, we to designed a competition experiment that would tell us something about the relative fitness of the E939 and E938 strains of E. Coli and that looked into answering whether it was better to have a low or high mutation rate and under what conditions. In our experiment, we looked into what concentration can the E938 strain coexist with the E939 strain in an equal number of colonies. We plated various concentration of the strains (Figure 1) and predicted that the disparity between the growth of each strain will be greater as the concentration of the high mutator increases. Our results did not support this hypothesis, instead it showed that the E938 dominated competition at all concentrations that could be analyzed (Plates D, E & G). It could have been that we needed to dilute E938 even further than 103 cell/mL to see equal competition, but with the given results only the conclusion that can be made is that the high mutator will outcompete

For the error in plate C, there could be multiple possible sources of error, however the two that are most likely could be preparation of the competition tubes and in plating. It is not as likely that the error arose in the competition tubes as for plating as the other plates that were made under the same conditions did show growth. However, error could have occurred in having the sample of E. Coli in that tube contaminated by an outside pathogen that outcompeted killed all of the strains, but when but on Rif + Agar plate the pathogen did not have rifampicin resistance, thus resulting in no growth. Another error could have occurred in plating specifically plate C. This could have occurred in that when sterilizing the glass spreader with the burning of ethanol there could have been the failure to wait a sufficient amount of time for the spreader to cool. Thus the both strains would die upon contact with the very hot