We are trying to grow liquid cultures of Mycobacterium smegmatis as a host for bacteriophages, but we have been having issues with contamination. Our latest attempt went like this:
- Tuesday 1 pm: Added 20 ml 7H9 broth, 2 ml Albumine-Dextrose solution, 0.02g CaCl2, one colony from master M. smegmatis culture was added to 100 ml Erlenmeyer flask. Incubated in a shaker at 35° C.
- Wednesday 6pm: Added 20 ul of carbenicillin (should have been added from the top, but the carbenicillin arrived a day late)
- Thursday 1pm: liquid culture is turbid white and clumpy as expected.
- Friday 2pm: Culture is still turbid white and clumpy. Inoculated a streak on left half of L-agar plate.
- Saturday 3pm: Streak plate shows streaks of yellow-white colonies (as expected), but also a blue diffuse contaminant which smells very bad. This is similar to what we've seen in our previous attempt at growing this culture
Now, the question is: What could this blue contaminant be? The original culture protocol used Cycloheximide to control for fungal growth, but ours has not arrived yet.
A related question is. Where could it have come from?