Question

A bacterium divides every 35 minutes. If the culture containing ${10^5}$ cells per ml is grown for 175 minutes, what will be the concentration after that period?
A. $175 \times {10^5}$ cells per ml
B. $35 \times {10^5}$ cells per ml
C. $5 \times {10^5}$ cells per ml
D. $32 \times {10^5}$ cells per ml

Answer 1

Hint: Cell division in bacteria is the process by which 2 daughter cells having a copy of chromosome are formed from the parent bacterial cell. Modes of cell division in bacteria: 1. Binary Fission 2. Mitosis 3. Meiosis. The binary fission is a mode of asexual reproduction. While the mitosis and meiosis occur in the sexual mode of reproduction. They help the chromosomes and genetic material to equally divide.

Complete answer:
Culture medium is a liquid or semi-solid medium used to support the growth of microorganisms. They need aseptic conditions to grow because any contamination will not give us pure cultures. Culture media can be basal media, selective media, enriched media etc. Depending on the requirement we can use them.
The media for the bacterium growth are added with Agar in the Petri dishes to solidify. Keeping them overnight can give us enough colonies. A particular colony can be picked and examined.
It is given that a bacterium will divide in every = 35 minutes
At 0 minutes that is initially, the culture has = ${10^5}$ cells/ml
After 35 minutes, the culture will contain ${2^1} \times {10^5}$ cells/ml
Similarly, after 175 minutes which means after 5 generation (as $35 \times 5 = 175$)
The number of cells will be ${2^5} \times {10^5}$cells/ml = $32 \times {10^5}$ cells/ml

Thus, the correct answer is option D – $32 \times {10^5}$ cells per ml.

Note: The bacterial culture is easy to culture because it has very short multiplying time. We can culture them fast in aseptic conditions. They can form colonies. The bacterial culture best grows at 37 degrees Celsius. Their culture needs a medium to grow to have all the nutrients like LB medium or nutrient broth.