There are ten times more of them in and on our bodies than human cells, so it is perhaps surprising that the 10,000 species of bacteria in the body have not previously been harnessed to any great extent to improve health. But as genetic science advances, research is pointing towards bacteria as a useful diagnostic tool in the detection of cancer, diabetes, Crohn’s disease and periodontitis.
Researchers have genetically modified Escherichia coli bacteria to emit light in the presence of tumours or glucose. In the first experiment, E coli that grew on particular types of tumour while ignoring healthy tissue were harvested from a readily available probiotic. The bacteria were modified to produce an easily detectable enzyme and given to mice with liver tumours. The mouse urine changed colour or gave off light depending on which additional substances were added to the signalling system.
In a second experiment, also recently published in Science Translational Medicine, E coli were genetically engineered to change colour in the presence of sugar. They then changed colour when added to urine that contained glucose.
Separate research has shown that the metabolism of bacteria living in the mouth changes significantly when the person has certain conditions. Researchers at the University of Texas used a supercomputer to map the metabolic pathways of 60 different species of bacteria. They analysed more than 160,000 genes to create a ‘subway map’ using different coloured lines to denote pathways that were unchanged between disease and health, and those that were upregulated during either health or disease.
Periodontitis, one of the most prevalent diseases in the world, was chosen to study because broadly the same bacteria are present in the mouth in both healthy and disease states. But oral bacteria also change behaviour in diseases such as diabetes and Crohn’s disease. This research could be used to develop diagnostic biomarkers for certain conditions. If the bacteria could be modified back to their ‘healthy’ state this technology could even be used as a treatment.
But genetic modification outside of the lab remains controversial, and use of GM organisms has been limited by fears of the impact of GM material on the environment. Scientists have attempted to solve the potential problem of GM bacteria escaping into the wild in a variety of ways, including the creation of bacteria that depend on nutrients they can’t make themselves.
But these bacteria might survive in the wild by receiving those nutrients from natural organisms. One potential solution would be to create genetically engineered bacteria that are dependent on nutrients not found in nature.