Most Probable Number (multiple-tube test) Overview
For this lab:
We prepared 3 tubes per dilution. The larger the number of tubes per dilution, the greater the precision of the test. Also, this increases the overall sample size, which improves the detection limit of the method.
Ideally, your highest dilution (10-3)* will have no gas production (no gas bubble in the Durham tube) in any or most of the tubes (there may be 1 or so that has some gas). Your lowest dilution (10-1)* will have gas in some or all of the tubes.
Please use Table 4.2 on page 66 of the lab manual to determine the estimated number (MPN/g).
**Remember** you took 1 ml of 100 and added that to 9 ml of LST, so that is now a 1:10 dilution, or the 10-1 sample. In the chart, this is 0.1 g. Each of your subsequent dilutions are 10-2 (0.01 g) and 10-3 (0.001 g)