Horizontal Gene Transfer

The role of Horizontal Gene Transfer events in evolution of Prokaryotes and Archea has long been underestimated. However the last decade of Genome Sequencing has made it clear that the phenomena has played a major role, and occurs very frequently.
When genetically modified organisms are released into nature there is hence a certain risk of the genetic modification to leak into these micro-organisms. This risk however is very hard to predict and quantify, making the risks involved in using Genetically Modified organisms very unpredictable. Antibiotic resistance genes are very commonly used as screening mechanisms. When these genes undergo Horizontal Gene Transfer, there is a legitimate risk of these genes accumulating in Pathogenic Organisms. These genes often offer resistance to multiple similar Antibiotics.
There is little literature which records such events, but many reviews state that this line of thought has been insufficiently and non-conclusively explored. Decreasing the usage of Antibiotic Resistance Genes to select and maintain Genetic Modifications will contribute to reducing the development of antibiotic resistant pathogens.

A Safe Screening Technique

We propose a light-based transformant screening technique in our project. This technique uses a vector designed by our team, pSB1Pc, wherein the Antibiotic resistance gene is replaced by Green-light absorbing Proteorhodopsin. The stress used for screening is the substrate limitation in minimal media, and the survival advantage is the ability to use light as an energy source.

Antibiotic Resistance gene has been conventionally in use for screening for transformants in cloning. Dependence on antibiotic, which are chemical toxins, has the following disadvantages.

Horizontal gene transfer of Antibiotic Resistance gene, which can contribute to development of Drug resistant strains

Risk of spread of Antibiotic resistance/tolerance among the bacterial flora

Release of Antibiotics, which are essentially toxins, into the environment

Due to these disadvantages, we discourage antibiotic based screening and propose an alternative light-based screening, which is cleaner and environmentally responsible. The only chemical input for this technique, other than the media itself, is Retinal, or Vitamin A aldehyde, it can be bio-synthesized and also degraded endogenously and is safe and non toxic. Using the LED based lighting system which we designed, modifying existing bioreactors and incubators to adapt to the light-dependent screening in the lab and industrial levels is feasible. This makes the adapting to the new technique easier.
We hope that in the near future, synthetic biology will be toxin-free and environmentally more responsible, using our light based screening technique.

Spreading the Word

To encourage the scientists, engineers and researchers to apply their minds to Synthetic biology, we presented our project at the "Research Expo, Shaastra 2011 (The annual technical festival of IIT Madras)". It was an exhibit for innovative projects from around the country, which had an audience of about 60,000 students, young researchers, engineers, biology enthusiasts and senior scientists.

Team Members Sonia and Avaneesh at the Research Expo during Shaastra 2011 (The annual technical festival of IIT Madras)