by crescit_eundo on 10/14/25, 8:36 PM with 8 comments
by koeng on 10/23/25, 10:52 PM
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
by rbartelme on 10/23/25, 10:09 PM
Allan Konopka does a good deep dive into "The Great Plate Count Anomaly" here: https://thinkmicrobe.substack.com/p/the-great-plate-count-an...
by bhickey on 10/24/25, 3:34 AM
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.
by throwawaymaths on 10/23/25, 11:50 PM
by flipfluck on 10/23/25, 11:21 PM