Jack W. Rutter & Chania Clare: How can we Engineer Bacteria to Treat Human Diseases?

How do Bacteria Keep People Healthy?

Bacteria are living things made up of just one cell, but they come in all kinds of shapes and sizes. Bacteria are so tiny that they cannot be seen without a microscope, but they can be very different from each other, allowing them to live in lots of different places and perform many jobs. Bacteria are everywhere, from deep in the ocean to active volcanoes, in the air, and on every plant and animal on the planet—even people! Even though you cannot see them with your eyes, bacteria are responsible for supporting life on Earth. They can break down nutrients in the soil to help plants grow, and they help you digest the food in your gut [1].

Bacteria often get a bad reputation, as some species A group of similar organisms that can exchange DNA.

(specific types of bacteria) can make people sick—which is why it is important to always wash your hands! But there are many other species that actually help you to stay healthy. Many bacteria and other microbes live in and on your body, and they can protect you from harmful bacteria (called pathogens Harmful microorganisms, like bacteria, that can cause disease) and help your immune system. In your intestines, you have many types of bacteria all working together and performing important jobs. Intestinal bacteria help you digest the food you eat, produce essential vitamins, and fight against harmful bacteria or microbes you accidentally ingest (Figure 1). In fact, the human gut hosts approximately 100 trillion microbes, which play a vital role in human health [2]. This bacterial community is important not just for your physical health [3]—some studies have even shown that the bacteria in and on your body can affect your mental health, too [4]. Now that you know how bacteria work in your body to keep you healthy, let us look at how scientists are trying to change the job of bacteria to help fight diseases!

How do we use Bacteria to Treat Disease?

Scientists can take two main approaches if they want to use bacteria to treat diseases. The first is to use bacteria that exist in the environment naturally, either on their own or working together in groups. The second is to engineer bacteria in a laboratory to carry out a specific task. Many foods contain natural bacteria that help to keep people healthy—for example, the bacteria in natural yogurt break down food in the gut, which helps the body to access the nutrients it needs to grow. These natural bacteria can also be taken as a tablet, called a probiotic Beneficial bacteria or other microorganisms that help keep your body healthy, especially your digestive system. to make sure people get enough of the helpful bacteria. Probiotics are currently being tested in humans, to help researchers discover new ways of helping patients [5].

Every cell in the body has a job, whether it is making the hair on your head or forming the muscle in your heart, so every cell contains a set of instructions called DNA Genetic material that contains instructions for how living things look and function. that tell the cell what to do. Researchers can edit the DNA of bacteria to give them new instructions, so they can perform specific tasks for people, and this is called genetic engineering A way scientists change an organism’s DNA to give it new traits or abilities. 

For example, if your body does not produce enough of a protein it needs, we can take the gene A section of DNA that controls a specific trait, which is inherited from your parents. (a section of DNA that performs a specific function) that produces that human protein and add it to the DNA of bacteria. Once the bacteria have the new instructions, they will produce the lacking protein, and we can use those bacteria to make a medicine that you can take when your body needs it. In this way, we can work with bacteria so that they can make the medicine people need [6]. This allows scientists to correct errors in people’s bodies and prevent patients from getting sick.

To design engineered bacteria to combat disease, there are many questions that we need to consider. Firstly, depending on the disease we want to treat, we can use different species of bacteria. For example, if we want to treat a disease in the gut, we could use bacteria that already live inside the intestines.

Some commonly used species are Escherichia coli Nissle 1917 [7], which was discovered in the gut of a First World War soldier, and Lactobacillus bacteria, which are often found in the yogurt at your local supermarket. Once the right bacteria for the job are chosen, we need to engineer their DNA to produce the medicine or drug we want, and then check that everything is working as expected (Figure 2).

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