BACKGROUND: Mycobacterium tuberculosis causes tuberculosis, one of the world’s deadliest diseases. It is an acid-fast bacillus that is 2-4 um in length and 0.2-0.5 um in width.
How many weeks, days,& hours would it take to see a M.tuberculosis colony on solid media? Its generation time is listed in the reading (above). Assume that bacterial colonies are not visible to the naked eye unless they contain ≥ 2 millioncells. This species forms aggregates of 5 cells on average. Show your work.
When a bacteria grows, it divide in the manner of binary fission. (i.e. one bacterial cell give rise to the 2 bacterial cells).
the growing pattern is like, from 1 bacteria after one generation it is 2 bacteria, then from 2 bacteria after one more generation it is 4 bacteria.
So, the number of bacterila cells after 'n' generation = 2n (if you start with only single bacteria).
Now, if you start with 'm' number of bacteria the the number of bacterila cells after 'n' generation = m 2n .
For, growing the bacteria you have to do spread plate analysis. Now after the spread plating one aggregate of 5 cells (for M.tuberculosis ) will give rise to one colony which contain ≥ 2 millioncells.
So, we suppose after 'n' generation, the total bacterial count will be, 2 million.
So, according to the formula,
m 2n = final cell number,
or, 5 2n = 2000000
or, 2n = 400000
Now to solve this we have to take log (base 10) in both side,
So, n log 2 = log (400000)
or, n log 2 = 5.6
or, n = 5.6/ log 2
or, n = 18.6.
Now the generation time of M.tuberculosis is 24 hours or 1 day. So, it will take 18.6 days to generate visible colonies.
BACKGROUND: Mycobacterium tuberculosis causes tuberculosis, one of the world’s deadliest diseases...
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