Interesting Quiz-Errors with Serial Dilutions for viable counts - Errors which will over-estimate, under-estimate or have no effect (Dec/14/2008 )

We are carrying out experiments with serial diluting and have considered the following errors with this process. The following error will either over-estimate(O), under-estimate(U) or will have no effect(N) on the number of bacteria present.

Can you guess what each of these will lead to: (( i.e. decide whether it will over-estimate(O), under-estimate(U) or will have no effect(N)))

1. Cell Clumping
2. High carryover of cells from 10^-2 to 10^-4 high dilution
3. Volume of diluting fluid in tubes lower than intended
4. Volume transferred higher than intended
5. Low level contamination of 10^-2 tube
6. Loss of viability during dilution
7. Plate medium does not support good growth of organism

We are carrying out experiments with serial diluting and have considered the following errors with this process. The following error will either over-estimate(O), under-estimate(U) or will have no effect(N) on the number of bacteria present.

Can you guess what each of these will lead to: (( i.e. decide whether it will over-estimate(O), under-estimate(U) or will have no effect(N)))

1. Cell Clumping - overestime
2. High carryover of cells from 10^-2 to 10^-4 high dilution over
3. Volume of diluting fluid in tubes lower than intended over
4. Volume transferred higher than intended over
5. Low level contamination of 10^-2 tube over
6. Loss of viability during dilution under
7. Plate medium does not support good growth of organism under

Also, if you can, please feel free to list other sources of error with serial dilution for viable count.

Thanks.