No, not all bacteria cause infections. In fact, some are even beneficial!
- The Microbiome
Enter the microbiome, or microbiota. We all carry a very large colony of microbes (bacteria, fungi, viruses) on our skin, in our gut, and other places. There is a link between us and our microbiome, and between us, our microbiome and the environmental microbes (yes, there are microbes everywhere!). This is a delicate balance, and disrupting this can have a profound effect on our health.
For example, the "old friend hypothesis" suggests that changes in our environment has lead to a change in our microbiome, with losses of beneficial microbes, and subsequently this has lead to an increase in diseases like allergies and inflammatory bowel disease, which are linked to a dysfunction of the immune system, as well as type 2 diabetes, cancer and even depression.
Another benefit of the microbiome is what is called "colonisation resistance". This is where the microbiome essentially prevents potentially pathogenic microbes from colonising the site, due to the fact that its already there. For example, the bacterium Clostridium difficile (C. diff) can be prevented from causing problems in the gut by the microbiome, however once the microbiome is disrupted by the use of antibiotics, C. diff can take over and cause a nasty infection. This is one example of "antibiotic associated diarrhoea".
Clearly, our microbiome is important in keeping us well. If you're interested in finding out more about the gut microbiome and ways to support it, have a look at cleverguts.com. And while we are on this subject, are pro-biotics - foods which contain some beneficial bacteria - are good for us? Well, research suggests that they may not be as beneficial as the marketing suggests!
- Metabolic engineering
What else can bacteria do that is beneficial? Well, metabolism in bacteria can be manipulated so that they will produce certain desirable compounds, like biofuels and medicines. One recent example is turning type A blood into type O blood.
On the surface of red blood cell, there can be markers (antigens) present. The presence and absence of a group of antigens lead to the ABO blood types; people with type A blood have the A antigen present on their red blood cells, and people with type B blood have the B antigen on their red blood cells. If your red blood cells produce have both A and B antigens, you are type AB and if you have neither then you are type O.
This is important for blood transfusions, because you can develop immune reactions in the form of antibodies. For example, a type A person will develop antibodies against the B antigen (anti-B antibodies), and so a type B person will develop antibodies against the A antigen (anti-A antibodies). A person with type AB will not form neither antibody, as they have both A and B antigens on their red blood cells, while a type O person will have both anti-A and anti-B antibodies.
This means that if a type A person is given type B blood, the anti-B antibodies present in the recipient (type A) will react with the type B blood, which could potentially be fatal. The same would happen if a type B recipient received type A blood, or if a type O recipient receives either type A, type B or type AB blood.
Now, type O blood, as mentioned before, does not have A or B antigen. Therefore, anti-A or anti-B antibodies will have nothing to react against in type O blood. Hence, type O blood can safely be given to anyone and thus is very much needed. Recently, researchers discovered that a bacterial enzyme could actually remove the A antigen from donated blood, thus changing it from type A to type O. This is early days, but could be promising in terms of making sure there is enough type O blood for emergencies.
So there we have it. You see, there is more to bacteria than just infections!
Hope you found this post interesting,
Maho
Sources
https://www.sciencedirect.com/science/article/pii/S1369527418300535
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3533696/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4790290/
https://www.sciencedirect.com/topics/medicine-and-dentistry/metabolic-engineering