Newly found research by the University of Exeter have found that genetic diversity has helped reduce the risk of spreading diseases by limiting parasite evolution.
Even though this study is not new, the answer to why this happens was newly founded. Researchers used a virus that infected and killed bacteria. By using this virus, they could study the effects host diversity had on disease spread. The bacteria defended themselves by using a defense system that they have called CRISPR-Cas. CRISPR-Cas captures random DNA fragments from the virus, thus creating a ‘genetic memory’ of some sort. Now because each bacteria will copy different DNA fragments from the virus, this causes a diversity of bacteria to be formed.
In order for the researchers to see if and why diversity limits the spread of disease, they isolated individual bacteria and grew them in monoculture or mixed them together with other bacteria of diverse populations before exposing them to the virus. The virus spread on the monocultures because the virus was eventually able to outgrow and overcome the CRISPR-Cas immunity. The mixed populations were able to overcome the virus and the virus eventually went extinct; this is because the bacteria had a much larger diversity and were able to overcome the virus all together by herd immunity.
Dr. Stineke van Houte recalls: "Viruses could spread on monocultures but when the individual bacteria were mixed together, the virus went extinct very rapidly. This revealed a strong monoculture effect in our experimental system."
I think this article was very interesting in proving that different variations of bacteria can overcome a virus when they are mixed together. This shows that diversity is good when it comes to bacteria but it could also become harmful if they are harmful bacteria. The mixture of bacteria were able to survive because they were able to increase the immunity of the population as a whole.