Safety

Saccharomyces cerevisiae, or baker’s yeast, is a low risk chassis commonly used in synthetic biology. The common yeast is widely seen in brewing and baking, and poses low risk to the environment and public under most circumstances. Risk of infection from working with yeast is minimal, as most people have already developed immunity from contact with yeast over their lifetimes. Even when infections do occur, they are not very dangerous and are very treatable. Despite the already low risks, proper safety procedures are taken; all experiments are being conducted in BSL 1 laboratories, and sterile techniques are followed in addition to the use of gloves and lab coats and other personal protection. Furthermore, our strain of yeast lacks functional pathways for seven essential amino acids including histidine and leucine, making our yeast unable to survive in the wild without enriched media. The genes that we are implementing in our yeast are unlikely to provide a selective advantage for the microorganisms, as the vitamins are not utilized by the yeast. Overall, our project poses minimal risks to the student researchers, the public, and the environment.

Our new BioBrick parts are designed to allow the production of vitamins, which are essential to the human diet, and to facilitate manipulation of DNA in yeast. As such, the use of our new BioBrick parts will not result in the production of toxins or other harmful agents, and we do not believe that our BioBrick parts raise any safety issues. Our yeast, however, do produce ethanol naturally, which the public often intentionally ingest.

Our project complies with Section III-F-6 of the NIH Guidelines for Research Involving Recombinant DNA Molecules by use of the Saccharomyces chassis as detailed in Appendix C-III of the NIH Guidelines. As stated by Section III-F-6, our project is exempt from the NIH Guidelines and does not require registration with the Institutional Biosafety Committee. As mentioned above, our experiments are conducted under BSL-1 containment, which is also recommended by the NIH Guidelines.

The local biosafety groups and review boards include the Johns Hopkins Biosafety Office and the Johns Hopkins Medicine Institutional Review Boards. Our project is registered with the Biosafety Office for experiments with recombinant DNA that are exempt from the NIH Guidelines, and does not need further IRB approval. While our wet lab work does not need IRB approval, we anticipate that our human practices project, which consists of a survey regarding the public’s knowledge in genetically modified food, will require IRB approval before the project can be initiated. We are currently completing the necessary applications.

Unchecked proliferation checking mechanism is a possible mechanism that we could implement into our yeast strain to prevent unrestricted proliferation of the starter cultures for bread, beer, and other yeast products. We could create a genetic switch controlled by the quorum sensing mechanism in yeast, such that an apoptosis gene is transcribed, killing the cells, unless there is a certain critical population of yeast cells present in the immediate vicinity. This would effectively prevent individual spores from escaping and spreading through the environment and make the yeast cells very easy to contain. It would also not require any external substrate, like most antibiotic markers do, and would not negatively affect the competency of the cell, which is important to us as we are trying to optimize yield of a small molecule.

In the yeast Saccharomyces cerevisiae, the quorum sensing molecules are the aromatic alcohols tryptophol and phenylethanol. Quorum sensing regulates the transition between the solitary yeast form and the filamentous form. The addition of these quorum sensing molecules to yeast cultures causes large changes in gene expression, but how these changes are orchestrated and whether or not this system is conserved in related fungal species is still unknown. What is known is that the transcription factors CAT8 and MIG1 are key transcriptional regulators that control the differential expression of the genes affected by aromatic alcohol communication. Thus, it may be possible to take advantage of this known system and link it to an apoptosis or cytotoxic gene to create a novel bio safety genetic circuit.