Good Things about Genetic Engineering: How to Turn a Pathogen into a Friendly Bacterium

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Genetic Engineering Advances

Ever since the creation of the world’s first genetically engineered organism, scientists have been tinkering at the sub-cellular level to manipulate an organism’s genes. The basic concept of genetic engineering is to manipulate an organism’s DNA in such a way as to confer some desired trait or benefit. The approaches, such as gene therapy, and the genetic modification of crops are met with varying degrees of success and all have attracted controversy; the pros and cons of genetic engineering being vigorously debated.

A further genetic engineering application is to alter the genomes of pathogens, and to use the resulting genetically modified organisms (GMOs) for the benefit of patients.

Good Things about Genetic Engineering - Modifying a Pathogen

Listeria monocytogenes is a potentially lethal food poisoning bacteria, and one of the most virulent food borne pathogens. However, genetic engineering has been used to extinguish its flame and turn it into a friendly bacterium that can be used to deliver medicines to patients. Many individuals prefer pills to injections, but the difficulty with vaccines is that many cannot be given orally because they will be broken down by stomach acids without being absorbed by the body. Genetically modified bacteria could be used to overcome this problem.

Scientists from Monash University genetically engineered a recombinant L. monocytogenes strain to be harmless. It is capable of being packed with proteins or DNA, in other words vaccines or medicines. The genetically modified bacterium is able to infect nondividing epithelial cells and on entering the cells bursts and dies, releasing its contents into the cytoplasm. The researchers were able to demonstrate proof of principle by using the genetically modified bacterium to invade intestinal cells grown in the lab and deposit a protein without harming the cells.

Good Things about Genetic Engineering - Tackling Prostate Cancer

In other research Listeria monocytogenes has been genetically engineered to potentially deliver a vaccine to prostate cancer patients. The system is still in the experimental stages, but researchers from the University of Pennsylvania have reported it as a potential candidate vector to deliver therapeutics. A team of scientists from the same University has also published research to demonstrate the possibility of using listeria-based vaccines against breast cancer. The application of genetically modified bacteria resulted in the regression of some tumours in mice models.

Listeria-based vaccines are a promising area of research and demonstrate how genetic engineering can be used to commandeer a harmful bacterium and turn it to our advantage. Research of course is still in the early stages, and there’s no sign of when such a system may be used on patients, but the potential is there.


Kuo et al. A Stably Engineered, Suicidal Strain of Listeria monocytogenes Delivers Protein and/or DNA to Fully Differentiated Intestinal Epithelial Monolayers. Molecular Pharmaceutics, 2009; 090526130050086 DOI: 10.1021/mp800153u

Reshma Singh. Evaluation of Listeria Monocytogenes Based Vaccines for HER-2/neu in Mouse Transgenic Models of Breast Cancer. Pentagon Reports