Basic Bacteriology – Calculating the Growth Rate of Bacteria
Basic Bacteriology – Calculating the Growth Rate of Bacteria
Example Problem:
Example Problem:
E. coli bacteria divide every 20 minutes. If you have 30 bacteria cells at the
beginning of your experiment, how many E. coli cells do you have after 2
hours?
E. coli bacteria divide every 20 minutes. If you have 30 bacteria cells at the
beginning of your experiment, how many E. coli cells do you have after 2
hours?
Formula: 2number of generations x initial number of bacteria = total bacteria
present
Formula: 2number of generations x initial number of bacteria = total bacteria
present
Solution: In 2 hours, E. coli will divide 6 times. So, n=6, or 26 which means
2x2x2x2x2x2 = 64
Solution: In 2 hours, E. coli will divide 6 times. So, n=6, or 26 which means
2x2x2x2x2x2 = 64
64 x 30 = 1,920 E. coli cells
64 x 30 = 1,920 E. coli cells
Use the same formula for the next 3 problems:
Use the same formula for the next 3 problems:
1. A child at a buffet restaurant sticks his finger in the macaroni & cheese.
When he does this, about 500 Staphylococcus aureus are transferred to the
macaroni. S. aureus divides every 10 minutes. About 3 hours later you come
to the restaurant. How many S. aureus bacteria are now living in the
macaroni & cheese?
1. A child at a buffet restaurant sticks his finger in the macaroni & cheese.
When he does this, about 500 Staphylococcus aureus are transferred to the
macaroni. S. aureus divides every 10 minutes. About 3 hours later you come
to the restaurant. How many S. aureus bacteria are now living in the
macaroni & cheese?
2. During a basketball game, Lucas accidentally gets spit in his eye. About 5
Neisseria meningitidis bacteria are transferred to the tissues in his eye. N.
meningitidis divides every 30 minutes. After 12 hours, how many N.
meningitidis bacteria are in his eye?
2. During a basketball game, Lucas accidentally gets spit in his eye. About 5
Neisseria meningitidis bacteria are transferred to the tissues in his eye. N.
meningitidis divides every 30 minutes. After 12 hours, how many N.
meningitidis bacteria are in his eye?
3. While swimming in a public lake, Nancy ingests about 10 Enterococcus
faecalis bacteria. E. faecalis divides every 15 minutes inside her mouth and
stomach. About 5,000 cells will make her sick. In 3 hours, how many
bacteria are now living in her upper digestive tract? Is she sick?
3. While swimming in a public lake, Nancy ingests about 10 Enterococcus
faecalis bacteria. E. faecalis divides every 15 minutes inside her mouth and
stomach. About 5,000 cells will make her sick. In 3 hours, how many
bacteria are now living in her upper digestive tract? Is she sick?