What is a probiotic?

Probiotic bacteria has been very important throughout human history. They have been extensively used for fermentation and food preservation and represents an ancient and very primitive form of biotechnology. They are also essential for our digestive health, they synthesize important nutrients and keep pathogenic bacteria in check. Studies have shown that probiotic bacteria play important roles in immunology and digestive functions.[1] They have also been shown to have an alleviating effect on infectious diseases, diarrhea and some other illnesses. Today there are a lot of probiotic products on the market that are sold and eaten for their health benefits.

Yoghurt is usually made by fermenting milk with the addition of two kinds of lactic acid bacteria, one which is Lactobacillus bulgaricus.

Why work with lactobacillus?

Lactic acid bacteria constitute the largest group of probiotic bacteria out of which many are a part of the Lactobacillus genus. Their long and extensive use as probiotics means they have been proven safe to eat and make them suitable as a new probiotic chassi.

Lactobacillus also have several other interesting properties, it's a gram-positive lactic acid bacterium. The name comes from that all lactobacillus transform lactose and some other sugar to lactic acid.[2] The lactic acid lowers the pH levels. This ability together with their ability to express and export bacteriocins is what gives them their ability to outcompete other bacteria and gives them their food preserving properties. We used specifically three species of lactobacillus in our project: Lactobacillus Bulgaricus, Lactobacillus Plantarum and Lactobacillus Reuteri.

In the picture the rod shaped form of Lactobacillus bulgaricus is clearly shown. It’s used in the production of yoghurt.

A new probiotic chassi for iGEM

Historicaly most iGEM teams have worked with only a few model organisms, the vast majority of which is E. coli. While there are probiotic species of E. coli, like Nissle, which we also use in the project, we felt that it was important to help and extend the range of chassis available to allow people to take advantage of their different properties. For this reason we have decided to make the Lactobacillus genus more approachable for future iGEM teams and provide some fundamental parts for biobrick based synthetic biology. To learn more about our work with the Lactobacillus chassi check out chassi page .


[1] Genetically Engineered Lactobacilli for Technological and Functional Food Applications - María J. Yebra, Vicente Monedero, Gaspar Pérez-Martínez and Jesús Rodríguez-Díaz Departamento de Biotecnología de los Alimentos IATA- CSIC Spain

[2] Health and Nutritional Properties of Probiotics in Food including Powder Milk with Live LacticAcid Bacteria - Food and Agriculture Organization of the United Nations