Laboratory horror stories: Poison in the agars
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Abstract
The fission yeast Schizosaccharomyces pombe is a single-celled eukaryote that can be cultured as a haploid or as a diploid. Scientists employ mating, meiosis, and the plating of ascospores and cells to generate strains with novel genotypes and to discover biological processes. Our two laboratories encountered independently sudden-onset, major impediments to such research. Spore suspensions and vegetative cells no longer plated effectively on minimal media. By systematically analyzing multiple different media components from multiple different suppliers, we identified the source of the problem. Specific lots of agar, from different suppliers, were toxic. Interestingly, the inhibitory effect was attenuated on rich media. Consequently, quality control checks that use only rich media can provide false assurances on the quality of the agar. Lastly, we describe likely sources of the toxicity and we provide specific guidance for quality control measures that should be applied by all vendors as preconditions for their sale of agar.
Graphical Abstract
Take-away
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Sporadically, batches of agar from different suppliers strongly inhibit the plating efficiency of S. pombe spores and vegetative cells on minimal media.
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Quality control checks that are not quantitative or that use only rich media can provide false assurances on the quality of the agar.
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Vendors should conduct rigorous, thorough, organism-specific tests for potential toxicity of each lot of agar as a pre-condition for its sale.
Article activity feed
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Lastly, we encourage members of research communities to be vigilant and proactive. If one encounters newly arising difficulty in plating a given organism, one should suspect—and test for—toxicity within the agar. This could be done expeditiously and inexpensively by comparing growth within liquid media to that on solid media. Confirmed or suspected problems with agar should be brought as soon as possible to the attention of the vendor and members of the relevant research community (e.g., via the PombeList email server). These actions will help colleagues to avoid wasting their precious time and resources and will help the vendors to identify and correct potential defects in their products.
Will do! Appreciate this clear call-to-action.
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not attributable to a specific vendor
While this may be true, were you ever able to discuss this with any of the vendors to provide potential insights into the lots in question?
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agar lot-specific toxicity
Are you aware of any other lab organisms that are sensitive to this?
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Wow, this was so much work!
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I really, really appreciated this report on many levels. First and foremost, I found it to be super useful and practical. Second, I enjoyed the straight forward, honest reporting on the true scientific process (and all the frustrations it brings!). And finally, love the title. Thank you!
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