I managed to grow countable yeast colonies(chillphysicsenjoyer.substack.com)
chillphysicsenjoyer.substack.com
I managed to grow countable yeast colonies
https://chillphysicsenjoyer.substack.com/p/i-managed-to-grow-countable-yeast
12 comments
Countable is a relative term in microbiology. I like that the author stuck to the phrase "countable colonies", since colony forming units are not really "countable as cells".
Allan Konopka does a good deep dive into "The Great Plate Count Anomaly" here: https://thinkmicrobe.substack.com/p/the-great-plate-count-an...
Allan Konopka does a good deep dive into "The Great Plate Count Anomaly" here: https://thinkmicrobe.substack.com/p/the-great-plate-count-an...
Ah, brings me back to the countless nights I spent counting plate after plate of HEK293 cells using a Haemocytometer [0], a light microscope, and a mechanical counter [1].
At least with HEK293 cells you could mostly tell if they were dead through the microscope (dead cells are darker).
[0] https://en.wikipedia.org/wiki/Hemocytometer
[1] https://en.wikipedia.org/wiki/Tally_counter
At least with HEK293 cells you could mostly tell if they were dead through the microscope (dead cells are darker).
[0] https://en.wikipedia.org/wiki/Hemocytometer
[1] https://en.wikipedia.org/wiki/Tally_counter
Sometimes I miss the benchwork, but moving into bioinformatics/data science full-time has been much better for my physical and mental health.
I've made the same transition and feel the same way. I miss the bench, but I don't miss the late hours, vending machine dinners, and Christmas day cell culture maintenance.
Reminds me of phage work.
For growing up phage you start by mixing different dilutions of phage with the host and a thin top agar, then plate it. On those plates with a countable number of plaques you work backwards to your plaque forming units (PFU) per mL. Once you know this you can produce "lacy plates." You add enough PFUs so that you expect the plaques to just touch. This produces a plate that has the appearance of lace. The web of surviving bacteria provide evidence that it actually grew, while delivering a high yield. Finally you scrape off the top agar, suspend it and run it through a filter. Good times.
For growing up phage you start by mixing different dilutions of phage with the host and a thin top agar, then plate it. On those plates with a countable number of plaques you work backwards to your plaque forming units (PFU) per mL. Once you know this you can produce "lacy plates." You add enough PFUs so that you expect the plaques to just touch. This produces a plate that has the appearance of lace. The web of surviving bacteria provide evidence that it actually grew, while delivering a high yield. Finally you scrape off the top agar, suspend it and run it through a filter. Good times.
1:100 is very countable using automated techniques.
Nice. Could I use a petri dish to figure out what sort of organism spoiled my homebrew?
yeah, colony on this plate is likely aspergillus spp.
Why would it be mold if the OP was culturing bakers yeast?
look at the 1:10 plate. there's colonies that isn't yeast there. luckily, it got diluted out, or, maybe that plating was a bit more careless than the others.
i didnt mean to imply that all of the colonies aren't yeast.
i didnt mean to imply that all of the colonies aren't yeast.
The culture was contaminated with fungal spores.
I do this at an industrial scale. It gets really annoying as you scale up to hundreds / thousands of different strains, all of which need pickable colonies.
A serial dilution 3 or 4 times seems to always do the trick. Typically on a robotic workstation you have to aspirate 6.5uL, then slowly dispense 5.5uL above the Petri dish (sbs format) and then stab into the agarose. Makes lovely perfectly-sized and separated wells, so 96 cell lines fit on only 3 or 4 plates.
With better plate reading you can get that down to 1 or 2 plates but it’s less reliable