Genetic diversity helps to limit infectious disease

April 13, 2016

New research by University of Exeter academics shows that genetic diversity helps to reduce the spread of diseases by limiting parasite evolution.

The idea that host diversity can limit disease outbreaks is not new. For example, crop monocultures in agriculture - which lack genetic diversity - can suffer severe disease outbreaks that sweep through the entire population. But why is this?

The study led by the University of Exeter provides an answer. To study the effects of host diversity on disease spread, the researchers used a virus that can infect and kill bacteria. The bacteria defend themselves using a sophisticated immune system, known as CRISPR-Cas, which captures random DNA fragments from the virus. This "genetic memory" protects the bacteria against future infections.

CRISPR-Cas generates lots of diversity because every bacterium captures a different piece of virus DNA. Hence, after virus exposure every bacterium with CRISPR-Cas immunity is unique and diversity in the population is therefore high. This turned out to be ideal to test if and why host diversity limits the spread of disease.

In their experiments, the researchers isolated individual bacteria, and grew them either in monoculture, or mixed them together in diverse populations. 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."

Next, the researchers investigated why viruses could persist so much easier on monocultures compared to diverse bacterial host populations. They found that this was because of rapid evolution of the virus, which evolved to overcome CRISPR-Cas immunity of bacterial host monocultures. However, on mixed bacterial populations - which have much more genetic diversity in the CRISPR-Cas system - the virus was unable to evolve and therefore went extinct. The ability of viruses to evolve high infectivity was thus shown to directly depend on the level of host genetic diversity. Hence, mixing monocultures together can increase the immunity level of the population as a whole, a feature known as herd immunity.

The conceptual insights from this fundamental research on bacteria and their viruses are likely to be general and the conclusions could therefore have future application in for example agriculture and conservation biology.

The paper, The diversity-generating benefits of a prokaryotic adaptive immune system, is published in the journal Nature.
The research was conducted with academics from the CNRS-Université de Montpellier; the Department of Integrative Biology at the University of California, Berkeley; the Department of Microbiology and Immunology at the University of California, San Francisco; and the Institute of Integrative Biology at the University of Liverpool.

University of Exeter

Related Bacteria Articles from Brightsurf:

Siblings can also differ from one another in bacteria
A research team from the University of Tübingen and the German Center for Infection Research (DZIF) is investigating how pathogens influence the immune response of their host with genetic variation.

How bacteria fertilize soya
Soya and clover have their very own fertiliser factories in their roots, where bacteria manufacture ammonium, which is crucial for plant growth.

Bacteria might help other bacteria to tolerate antibiotics better
A new paper by the Dynamical Systems Biology lab at UPF shows that the response by bacteria to antibiotics may depend on other species of bacteria they live with, in such a way that some bacteria may make others more tolerant to antibiotics.

Two-faced bacteria
The gut microbiome, which is a collection of numerous beneficial bacteria species, is key to our overall well-being and good health.

Microcensus in bacteria
Bacillus subtilis can determine proportions of different groups within a mixed population.

Right beneath the skin we all have the same bacteria
In the dermis skin layer, the same bacteria are found across age and gender.

Bacteria must be 'stressed out' to divide
Bacterial cell division is controlled by both enzymatic activity and mechanical forces, which work together to control its timing and location, a new study from EPFL finds.

How bees live with bacteria
More than 90 percent of all bee species are not organized in colonies, but fight their way through life alone.

The bacteria building your baby
Australian researchers have laid to rest a longstanding controversy: is the womb sterile?

Hopping bacteria
Scientists have long known that key models of bacterial movement in real-world conditions are flawed.

Read More: Bacteria News and Bacteria Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to