Controlling the Implementation of Transgenic Microbes: Are We Ready for What Synthetic Biology Has to Offer?

Abstract

Synthetic biology has promised and delivered on an impressive array of applications based on genetically modified microorganisms. While novel biotechnology undoubtedly offers benefits, like all new technology, precautions should be considered during implementation to reduce the risk of both known and unknown adverse effects. To achieve containment of transgenic microorganisms, confidence to a near-scientific certainty that they cannot transfer their transgenic genes to other organisms, and that they cannot survive to propagate in unintended environments, is a priority. Here, we present an in-depth summary of biological containment systems for micro-organisms published to date, including the production of a genetic firewall through genome recoding and physical containment of microbes using auxotrophies, regulation of essential genes, and expression of toxic genes. The level of containment required to consider a transgenic organism suitable for deployment is discussed, as well as standards of practice for developing new containment systems.

Directed-evolution of translation system for efficient unnatural amino acids incorporation and generalizable synthetic auxotroph construction

“…In this context, several strategies have been reported to construct UAA-dependent synthetic auxotrophs with low escape frequencies 19 , 20 , 39 – 43 . Despite exciting progress, simple and general strategies to efficiently construct UAA-dependent common bacterial strains with very low escape frequency remain to be an outstanding challenge 42 , 44 , 45 . And the utility of UAA-dependent synthetic auxotrophs in living animals is almost unknown.…”

Cas9-Assisted Biological Containment of a Genetically Engineered Human Commensal Bacterium and Genetic Elements

“…It has been demonstrated that auxotrophy, created by eliminating essential genes, is effective for biological containment 11,12 . Nevertheless, it is possible that the containment system could be breached if HGT from natural microorganisms led to the acquisition of the essential genes 18 .…”

“…Many forms of biological containment have been devised for uncontrolled environments that do not require human monitoring or input 11,12 . There are four main strategies for accomplishing biological containment: auxotrophy, kill switch, xenobiology, and physical containment.…”

Ecosystem consequences of introducing plant growth promoting rhizobacteria to managed systems and potential legacy effects

“…Thus, escape from crops to adjacent ecosystems has a high potential, although persistence may be negligible. Mitigating effects caused by the escape of biostimulant microbes is an area of active research (Jack et al, 2020;Kim & Lee, 2020;Stirling & Silver, 2020;Ke et al, 2021), but the likelihood and frequency that PGPR escape occurs is uncertain.…”