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HTML I managed to grow countable yeast colonies
bhickey wrote 12 hours 25 min ago:
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.
throwawaymaths wrote 16 hours 9 min ago:
1:100 is very countable using automated techniques.
flipfluck wrote 16 hours 38 min ago:
Nice. Could I use a petri dish to figure out what sort of organism
spoiled my homebrew?
throwawaymaths wrote 16 hours 30 min ago:
yeah, colony on this plate is likely aspergillus spp.
schwartzworld wrote 4 min ago:
Why would it be mold if the OP was culturing bakers yeast?
koeng wrote 17 hours 7 min ago:
Very chill :)
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
itâs less reliable
rbartelme wrote 17 hours 50 min ago:
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:
HTML [1]: https://thinkmicrobe.substack.com/p/the-great-plate-count-anom...
jszymborski wrote 16 hours 57 min ago:
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] [1]
HTML [1]: https://en.wikipedia.org/wiki/Hemocytometer
HTML [2]: https://en.wikipedia.org/wiki/Tally_counter
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