A researcher has isolated a new species of bacterium, Grande caffeinum, from a c

Question

A researcher has isolated a new species of bacterium, Grande caffeinum, from a compost heap heavily enriched with coffee grinds. She discovered that it could grow using caffeine as its only carbon source but it grows slowly. She decided to compare its growth rate in defined minimal media (MM) that contains glucose as the sole carbon source with its growth rate in MM containing caffeine. She inoculated G. caffeinum into both caffeine MM and glucose MM at 9 AM and measured the turbidity at regular intervals throughout the day. She graphed the turbidity (optical density units, O.D.) over time and determined that both cultures were in exponential phase from 10 AM – 10 PM.

Which carbon source does G. caffeinum prefer? Use the data in the table (above) to calculate the growth rates in both media. Show your work

Explanation / Answer

Growth rate= ln Nt- ln N0/ t2-t1= 0.301 (log Nt-logNo)/t2-t1        where 0.301= log 2

Lag phase is between 9 am and 11 am.

For Caffeine,

0.D of 1= 1* 109cells/ml

OD of 0.0994= 0.994*109 cells/ml= 0.994*109 cells/ml

OD of 0.091= 0.091* 109=0.091*109 cells/ml

Growth rate= 0.301 (log0.994*109 – log 0.091*109 )/21-11 = 0.301(8.994-7.95)/(21-11)          (in hours)

Growth rate= 0.314/10= 0.0314

For Glucose,

OD of 0.021= 0.021*109 cells/ml= 0.021*109 cells/ml

OD of 0.412= 0.412* 109=0.412*109 cells/ml

Growth rate= 0.301( log 0.412*109-log 0.021*109)/ 21-11= 0.301(8.615-7.322)/21-11           (in hours)

Growth rate= 0.389/10= 0.0389

Hence, the growth in glucose is preferred as carbon source as it has a higher growth rate.

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.