The team observed viruses as they evolved over hundreds of generations to infect bacteria. They found that when the bacteria could evolve defences, the viruses evolved at a quicker rate and generated greater diversity, compared to situations where the bacteria were unable to adapt to the viral infection.
The study shows, for the first time, that the American evolutionary biologist Leigh Van Valen was correct in his 'Red Queen Hypothesis'. The theory, first put forward in the 1970s, was named after a passage in Lewis Carroll's Through the Looking Glass in which the Red Queen tells Alice, 'It takes all the running you can do to keep in the same place'. This suggested that species were in a constant race for survival and have to continue to evolve new ways of defending themselves throughout time.
Dr Steve Paterson, from the University's School of Biosciences, explains: "Historically, it was assumed that most evolution was driven by a need to adapt to the environment or habitat. The Red Queen Hypothesis challenged this by pointing out that actually most natural selection will arise from co-evolutionary interactions with other species, not from interactions with the environment.
"This suggested that evolutionary change was created by 'tit-for-tat' adaptations by species in constant combat. This theory is widely accepted in the science community, but this is the first time we have been able to show evidence of it in an experiment with living things."
Dr Michael Brockhurst said: "We used fast-evolving viruses so that we could observe hundreds of generations of evolution. We found that for every viral strategy of attack, the bacteria would adapt to defend itself, which triggered an endless cycle of co-evolutionary change. We compared this with evolution against a fixed target, by disabling the bacteria's ability to adapt to the virus.
"These experiments showed us that co-evolutionary interactions between species result in more genetically diverse populations, compared to instances where the host was not able to adapt to the parasite. The virus was also able to evolve twice as quickly when the bacteria were allowed to evolve alongside it."
Erich Feldmeier on 03 Feb 12"Leah Pyter: Well basically what we know is that patients with cancer have a higher likelihood of also developing depression at some point in their disease progression, so whether that occurred before and is predisposing them to cancer, or it's due to the tumours themselves, or other aspects of having the disease, we don't know. We were only studying right now whether the cancer itself can cause depression. Chris Smith: How could a tumour trigger depression, because a tumour can occur anywhere in the body, therefore at the remote sites in the brain, so how could it trigger changes in brain activity? Leah Pyter: Sure, well what we hypothesized was that the tumours themselves can produce cytokines which has been shown before. Chris Smith: These are inflammatory chemicals that drive the immune system? Leah Pyter: Right, exactly! And there is also a pile of research on how cytokines can access the brain specifically regions of the brain that are associated with depression and anxiety and emotional behaviours, and they can access the brain both tumourally through the blood, or neurally through the vegas nerves. "
Cached
