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(6pts) A student working with Myxococcus xanthus wants to run an experiment on a

ID: 282888 • Letter: #

Question

(6pts) A student working with Myxococcus xanthus wants to run an experiment on a population that is as dense as possible without actually being in stationary phase. In CTTYE (Casitone/Tris/Yeast Extract) broth, commonly used to grow M. xanthus, cells begin entering stationary phase at a cell density of approximately 5 x 10' cells/mL. She inoculates a 10mL culture with 1500 cells and sets it up in a shaking incubator at 30°C, knowing that after about two hours of lag time M. xanthus should double every 3 hours (this is a particularly quickly growing strain of M. xanthus). How long can she leave to go play Monster Hunter before she has to be back in lab for her experiment? (show work for partial credit) 3.

Explanation / Answer

just before entering stationary phase dentsity = 5x107 cells/ml

inoculation of 10ml culture

initial no. of cells = 1500 = 150 cells/ml

lag phase time = 2hrs

Doubling time = 3hrs

final cell density required =5 x 107 cells/ml

We know that

k = log Bn – log B0 /log2

where, Bn = final cell no. and Bo =initial cell no.

So

n = log 5x107– log 150/0.301

= 7log 5 – 2 log1.5/0.301

= 7*0.69- 2* 0.17

= 4.49/0.301

14.9 = approx 15

we know

G= t/n

3 = t/15

t = 45 hrs

Soshe needs 45+2 = 47 hrs to get the final density