0
$\begingroup$

It seems that the requirements to perform colony counting and cell counting in petri dishes are quite different. This is especially true, because colony counting can be done with the naked eye, even though it can get very tiring.

Since I am interested to find out what tasks most biological labs have to go through, I was wondering whether these two tasks might be requested by the same types of labs.

$\endgroup$
  • $\begingroup$ I don't think people actually count cells on Petri dishes. In my experience, cell counting is done for liquid cultures not for Petri dishes. In this case, you can use counting chambers (microscope slides with a grid) $\endgroup$ – Flo Nov 23 '16 at 11:23
0
$\begingroup$

There is a multitude of reasons to use one or the other.

Colony counting is often used on petri dishes for antibiotic resistance screening for practical reasons. One of the downside of this versus cell counting is the need to incubate the bacteria for 12h+ after you have done your experiment before having the result.

In some cases, you will need to know the concentration of cells you have immediately to perform specific dilutions or calibrations etc, you then use cell counting.

Cell counting is normally done with a liquid culture of the bacteria. it can be used to determine the concentration of the whole culture or count during or shortly after an experiment. Some bacteria will have a hard time growing on solid media or some molecules that you might want to test for resistance are not soluble, so you can't plate them to colony count.

So it basically all depends on your needs for the specific experiment and what you are working with (bacteria, medium, molecules etc.).

$\endgroup$
0
$\begingroup$

Any lab that would like to make the distinction between live and dead cells in a cheap way would use both techniques. You count colonies on petri dishes to get the number of living cells, and count in counting chambers under the microscope to get the total number of cells.

There are easier ways to do this though, for example using this: https://www.thermofisher.com/de/de/home/brands/molecular-probes/key-molecular-probes-products/live-dead-viability-brand-page.html in a flow cytometer. That's not that cheap though.

$\endgroup$
  • $\begingroup$ For mammalian cells (I don't know about bacteria/fungi), you can simply use Trypan blue exclusion or acridine orange/propidium iodide staining to determine the number of cells with intact vs. compromised membranes, which generally correlates to live and dead cells, respectively. Viability dyes are great if you're already doing flow, but I wouldn't use them just for determining live/dead status and nothing else. $\endgroup$ – MattDMo Nov 23 '16 at 17:50

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.