Controlling contamination in Chlamydomonas cultures


Figure 1 from Wang et al. 2016.  Effects of bactericide/fungicide cocktails on the removal of microbial contaminants from Chlamydomonas reinhardtii cultures.

Figure 1 from Wang et al. 2016. Effects of bactericide/fungicide cocktails on the removal of microbial contaminants from Chlamydomonas reinhardtii cultures. (A) Control plate. (B) Plate with the One-shot Solution cocktail composed of ampicillin, cefotaxime, and carbendazim. (C) Plate with axoxystrobin and nalidixic acid. (D) Plate with tebuconazole and nalidixic acid. 1: uncontaminated cultures; 2–4: contaminated cultures containing fungi and bacteria.

A new paper in BioTechniques describes an improved antibiotic cocktail for controlling bacterial and fungal contamination of Chlamydomonas cultures. This is a problem that has cost our lab many hours, especially when using media that include acetate.

Liang Wang and colleagues compared the effectiveness of three mixtures of antibiotics and fungicides in clearing contaminants:

Pan et al. found that the combination of carbendazim, ampicillin, and cefotaxime, termed the One-shot Solution, can effectively remove bacterial and fungal contaminants…Here we report two improved antibiotic/antifungal cocktails (nalidixic acid/azoxystrobin and nalidixic acid/tebuconazole) for eliminating contaminating bacteria and fungi from Chlamydomonas reinhardtii cell cultures.

Both of the new mixtures were more effective than the One-shot solution at removing the unidentified contaminants. The contaminants were unidentified because

…contaminants vary greatly under different laboratory conditions.

More likely because identifying them would have required a bunch of extra work for not much benefit. I noticed this in the Methods: the images in Figure 1 were

…captured by a Galaxy S5 camera from Samsung Electronics, Seoul, Korea.

That’s right, the pictures were taken with a cell phone camera. Well, why not. The authors conclude that

…these new combinations of bactericides and fungicides are more economical, convenient, and effective at eliminating mixed contamination by bacteria and fungi of C. reinhardtii cultures [than the One-shot solution]

and recommend alternating among the three cocktails to prevent the evolution of resistant bacteria and fungi.

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