Conjugation and Transposition in Escherichia Coli Essay

2736 Words Sep 23rd, 2008 11 Pages
The purpose of this experiment was to study the transfer of genetic information on plasmid F’lac by using Escherichia coli. Plasmid transfer was measured by using two different methods. The first one was by using selection and contraselection with three antibiotics: streptomycin(which was replaced by naladixic acid for the second part of the experiment),ampicillin and kanamycin and the second one by using a colour indicator ( X-gal). As significant results, the percentage of transfer for F’lac was higher than the percentage for transposition. Also, the experiment demonstrated that E.coli can quickly acquire resistance to several different antibiotics through the transfer of the F’lac plasmid. It was concluded that significant
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The trend of increasing number of colonies on plates with a decreasing number of antibiotics is reflected by the counts of both the individual group and the class means.
Table 2 shows the percentage of plasmid transfers which took place between donor and the recipient cells, as well as the frequency of transposition. There is no great difference between the group and class results, both follow the same trend which is that there is a higher percentage on transfer F’lac and a very small on transposition, which correlated with the small percentage of transfer F’lac::Tn5.
Table 3 shows the bacterial counts in the second part of the experiment. Plates #5,6 and 7 show similar numbers. Both the class and group results have the same trend in which plate #5 has the largest bacterial counts and plate #6 the smaller. However, there is a great difference between plate # 1, where the group has 32 bacterial colonies and the class mean has 1114.4.
Like Table 2, Table 4 summarizes the frequency of conjugation which took place between the donor and recipient cells. The % transfer of Kanamycin resistance which marks for the Tn5 transposon and the % transfer of Ampicillin which marks for Tn1 have similar frequency, being 107% and 111% respectively. The group results follow the same logic but the group results differ widely from the class, since they are very large numbers.

Table 1. Mean and group bacterial colonies counted for E.coli in the

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