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Contents 1 Results 1.1 CheZ Knockout detection in E. coli 2443 and Salmonella SL7207 1.1.1 Colony PCR test 1.1.2 Swimming Test 1.2 Regulation of CheZ expression 1.2.1 Swimming test 1.2.1.1 No Chloramphenicol 1.2.1.2 Chloramphenicol added 1.2.2 Western Blotting

Results

CheZ Knockout detection in E. coli 2443 and Salmonella SL7207

Colony PCR test

The expected DNA size of this test was about 400bp, which showed the success recombination procedure.

Swimming Test

After 8 hours’ bacteria swimming, the patterns three strains formed below showed that the ineffectiveness of the swimming ability of the bacteria, which was an indication of the successful knockout of cheZ gene in E.coli YBE01 and S.typhimurium YBS01.

Regulation of CheZ expression

Swimming test

Test plac-his-cheZ-cm under 0.0005, 0.001, 0.002, 0.004, 0.008, 0.012mmol/L IPTG in MG3 stain.

No Chloramphenicol

Chloramphenicol added

The results above are ambiguous, and we tried to verify if we were successful in achieving differential levels of CheZ in MG3 by doing western blotting.

Western Blotting

From the results above, it can be seen that the CheZ concentration in MG3 was proportional to the concentration of IPTG added to the cultures when the induced time was about 24 hours. The samples with induced time less than 24 hours showed no obvious bands in the Western Blotting.

According to the result of Western Blotting, we could explain the similar swimming abilities of bacteria with different IPTG concentrations. As the speeds of swimming were tested within 9 hours, which were too short for the induced reactions to undergo, the speeds were more or less the same. Another problem was that even negative control strain (no IPTG added) swam, which was probably caused by leaky expression.