A few, previously (in the 1990s) morphologically identified Chlamydomonas strains turned to be Scenedesmus and Chlorella strains after my phylogenetic analysis. Morphology was not the scope of my submitted paper. It is only about identifying them phylogenetically, because this was never applied to the strain collection before.

In my manuscript I stated that the strains in question must have been misidentified morphologically. According to the reviewer, it is hard to imagine that one would misidentify a coccoid as a flagellate. Then the reviewer referred to the fact that Chlorella/Scenedesmus species may contaminated the original isolate of Chlamydomonad, and later predominated in the culture. As it is almost impossible to prove, the reviewer asks to discuss the topic in the resubmitted manuscript.

Additionally, the reviewer says that the original Chlamydomonads may survive in the culture as a minority, and that the authors should check if the strains in question include Chlamydomonad.

This is where I am asking for your advice.

I would like to know that what would be the most cost/time-saving and still scientific way to check the Chlamydomonas presence?

If I only have light microscopy, how long and to what extent should I screen the strains to conclude reasonably that they are no longer Chlamydomonas?

I mean, is that enough if I state that I did not find Chlamydomonas minority after microscopy or are there any other more serious ways in the scientific sense to state that?

What type of answers would you accept if you were my reviewer? : )

Could you also provide references to papers related to the ‘strain contamination topic’?

Thank you

Szabina