Hi, Beautiful picture! It's too bad that the situation is nasty. You've got an apparently young culture (the hyphae are small) however there's a large quantity of free-floating individual cells, which strongly suggests that the fungus may be dimorphic (or that the agitative motion of your culture breaks up mycelia over a certain size). The magnification is not optimal, but there seem to be branching conidia on some of the hyphae.
Using antifungal drugs when you have persistent fungal contamination is a palliative measure. Furthermore, you will be breeding drug-resistant fungi in your lab, so eventually the contamination will resurface with a vengeance. Likely sources of contamination: 1) air conditioning/heating vents. By far the likeliest source of spores. Fungi *love* the air ducts, especially if the humidity is constantly high. There may be persistent colonies deep inside the ducts, that constantly shed spores into the airstream 2) people. The second most likely source is the culture handlers and/or visitors to the lab. 3) environment. Are you in the basement? How about wall damp? Is the lab very humid? Are there old wooden panels, etc. in the vicinity? What to do about it: 1. Figure out your specific contamination routes. Leave an open Petri dish with some nutrient agar under a few of your vents for a couple of minutes, then see what grows. You can use a Kan+Amp medium to exclude most bacteria, or just develop the dish at lower temperature (most fungi grow just as fast at 15C as they do at 22, whereas most bacteria slow down considerably). Swab your surfaces and streak the cultures to see if there's persistent contamination all over the place. Peek under the hanging stuff on the walls and the stuff that covers the floor, see what may be growing there. 2. If you have air duct contamination you have to get professional cleaners to clean & disinfect them. Barring that, filters on the duct ends may be of some help, but they mess up the airflow. You may have to do all of your open-container work in a flow hood if your air is full of spores from the AC. 3. if you have surface contamination and things coming out of the walls, try to disinfect and cover the sources. Drying the lab out (i.e. by means of an industrial strength dehumidifier) is always a good idea. Cover all the accessible cracks with sticky plastic. 4. people-borne contagion is easy to alleviate. Examine your staff's sterile technique. Use large stick to correct mistakes :) Disposable paper overalls, overshoes and frequent glove changes may be in order. Artem -----Original Message----- From: CCP4 bulletin board [mailto:[EMAIL PROTECTED] On Behalf Of Filipp Frank Sent: Friday, April 04, 2008 3:49 PM To: CCP4BB@JISCMAIL.AC.UK Subject: [ccp4bb] Off-topic: fungus contamination of SF9 cells Dear all, sorry for this off topic question. I am using baculovirus/insect cell expression and I have had persisting problems with contamination that seems to be some kind of fungus. I have a picture attached showing the filamentous structure of it. This contamination has persisted for a few months now and always seems to occur when we go to large 2.8 L flasks (however, there was also one instant where this was not the case). We have autoclaved all flasks for 90 minutes each and still we get contamination. Does anybody have experience with this kind of contamination? And what would you suggest for us to do? We will (again) disinfect our incubator and the hood. Also we are thinking about using an antimycotic/antifungal drug to get rid of this problem. Thanks a lot for any suggestion! Filipp
