Am I correct in my assessment that this is a fungus or yeast?
In the past it has proven to be unresponsive to 2.5 ug/mL amphotericin-B.
As usual Bob1 is giving good advice. The contamination is definetely a fungus. In my experience the fungus will be from the CO2 Incubator. This in turn will be contaminated by the tissue culture users of that incubator. I have proven this over the years by settle plates:
This is done by placing agar plates in the:-
Class II cabinet
By the waterbath
Under ventilation baffles
These are put in place for 4 hours and then incubated in a bacterial incubator for 24, 48 and 72 hours.
The results are always the same:-
Class II Caninet - Negative
CO2 - massively positive fungal growth after just 24 hours.
By the waterbath- Negative after 72hrs incubation.
Under ventilation baffles- Negative after 72 hrs.
This tells the users that the room environment is "clean". The cabinet hepa filters are not compromised.
Practical measures to reduce fungal contamination:
Replace the distilled water in thye CO incubator WEEKLY.
Replace the water in the waterbath WEEKLY.
Wipe all TC flasks and dishes with 70% IMS in and out of the Incubator.
Wipe up all media spilss in the CO2 incubator.
PURCHASE a CO2 Incubator with a DECONTAMINATION Cycle.
Hope this is useful.
(now 35 years doing tissue and cell culture)