Question

Calculation of Microbial Populations

Jack inoculated a broth culture with 12 bacterial cells. After 12 days the culture contained 49,152 bacteria. How many generations had occurred and what was the generation time in hours for this particular bacterium.

A new intestinal isolate of E. coli is known to have a generation time of 12 minutes. If a culture contained 3, 221,225,472 bacterial cells after 6 hrs how many bacteria must have been inoculated into the culture at time 0.

A broth culture is initially inoculated with a single bacterial cell. For the first hour the bacteria has a generation time of 30 minutes, for the second hour the generation time has been reduced to 15 minutes, and for the third hour the generation time has been reduced to 10 minutes. At the end of the third hour how many bacteria are present in the broth culture?

Answer 1

Jack inoculated 12 bacterial cells in the culture and after 12 days, culture contained 49,152 bacteria.

1st Answer -

a. 12 generations

b. generation time is 24 hours

12 24 48 96 192 384 768 1536 3072 6144 12288 24576 49152

12 Bacteria in the beginning. After every 24 hours they were doubling continuously as it is their generation time so after 12 generations they have reached 49,152 bacterial cells.

2nd Answer - E-coli's generation time is 12 mins and after 6 hours the bacterial culture contains 3,221,225,472 E-coli cells.

The number of E-coli cells inoculated into the culture at time zero is 3 E-coli cells.

3, 6, 12, 24, 48, 96, 192, 384, 768, 1536, 3072, 6144, 12288, 24576, 49152, 98304, 196608, 393216, 786432, 1572864, 3145728, 6291456, 12582912, 25165824, 50331648, 100663296, 201326592, 402653184, 805306368, 1610612736, 3221225472.

3rd answer - 1 bacterial cell is inoculated

1st hour 30 mins generation time so 1 - 2 - 4.

2nd hour - 15 mins generation time.

4 - 8 - 16 - 32 - 64

3rd Hour - 10 mins Generation time

64 - 128 - 256 - 512 - 1024 - 2048 - 4096

4096 bacteria are present at the end of 3rd hour.