A new study shows that centenarians have a diverse composition of viruses, including bacteriophages – viruses that infect bacteria – in their gut. A researcher says that these viruses are probably important in regulating the composition of gut bacteria, which strongly affects health.
Centenarians have very special gut microbes, which may explain why they live so long.
Researchers previously identified that centenarians have an especially diverse composition of gut bacteria, and a new study shows that they also have a diverse composition of viruses.
The study also describes how the composition of bacteria and viruses in the gut develops throughout life and probably strongly affects health from cradle to grave.
A diverse composition of bacteria and viruses may even explain why some individuals are so healthy that they are still alive even though they were already in their twenties when the Second World War ended.
“The gut of these extremely healthy centenarians clearly has higher levels of certain bacteria and viruses. We want to understand this interaction between viruses, bacteria and health, because it might enable people’s microbial composition to be changed and thereby improve their health and extend their lives,” explains a researcher involved in the study, Simon Rasmussen, Associate Professor and Group Leader, Novo Nordisk Center for Protein Research, University of Copenhagen.
The research has been published in Nature Microbiology.
Algorithms keep track of genes
Simon Rasmussen’s research group focuses on data integration and deep learning to unravel health data and the genetics of gut microbes.
The gut has billions of bacteria and viruses, which together comprise a vast volume of genetic material.
When researchers sequence the total genetic material in the gut, they find tiny fragments of DNA, and Simon Rasmussen develops algorithms that make sense of these fragments and assemble them into relevant bacterial and viral genomes.
The researchers can thus use billions of pieces of sequenced DNA from an individual’s gut microbes to identify which bacteria and viruses a person has in the gut.
“Scientists started taking an interest in gut bacteria, so we know mostly about them and very little about the viruses in the gut. But viruses are also important because the ones that are bacteriophages affect the composition of bacteria, which then affects health,” says Simon Rasmussen.
Previous research has shown that a less diverse composition of gut bacteria with only a few bacteria or specific bacteria either being missing or present can negatively affect health.
Having less diverse gut bacteria is associated with an increased risk of having overweight, type 2 diabetes, cardiovascular disease, autism and nervous system disorders.
Examined stool samples from 195 individuals in Japan and Sardinia
The researchers used their algorithm to identify differences in gut viruses between young adults, individuals older than 60 years and centenarians.
The participants were 195 people from Japan and Sardinia who provided a stool sample from which the researchers extracted bacteria and viruses.
The results show that the diversity of gut viruses declines with age.
Newborns have extremely great diversity, younger adults have less and people older than 60 years even less.
However, the centenarians in this study had surprisingly rich and diverse gut viruses – also greater than people older than 60 years and young adults.
Further, the researchers identified some viruses that were only present in the gut of the oldest participants. Some of these were previously unknown to researchers, who therefore do not know how they affect health.
“These viruses are very infrequent in the gut, which is why we had not identified them until now. However, some of them appear to be associated with the Clostridia class of bacteria,” explains Simon Rasmussen.
Viruses are important for the body’s defences
The examination of the many genes also revealed that the microbes of centenarians have a high potential for producing sulfide, which can act as an anti-inflammatory and kill bacteria.
Simon Rasmussen and colleagues speculate that the body’s health-promoting bacteria use these viral genes to prevent gut infections by undesirable bacteria.
Rather than needing to have the genes for metabolising sulfide to defend against bacteria, the bacteria instead seem to take the genes from viruses.
“We had not imagined that viruses could promote health in this way by comandeering genes for an antibacterial effect that counteracts inflammation. Thus, some viruses, which are especially present in the gut of centenarians, help the health-promoting bacteria to survive, which then probably helps the person to be healthy and survive,” says Simon Rasmussen.
However, he also cautions that the researchers have only identified an association and not proven causality.
Thus, they cannot say whether people live more than 100 years because they have distinct and diverse gut viruses and bacteria or whether their gut viruses and bacteria result from living a healthy life, which has led to them becoming centenarians.
Examined 60,000 stool samples
Since so many factors are still unclear, more research is required that can elucidate the entire interaction between viruses, bacteria and health and how this affects the potential to become a centenarian.
Experiments are currently taking place in which researchers transplant the gut microbes of very healthy people into participants with less diverse gut microbes to determine whether this can promote health.
Simon Rasmussen is carrying out an even larger study examining stool samples from 60,000 individuals to get a better overview of the differences in gut microbes between healthy and sick people and those who live to be centenarians.
“We hope to determine what makes a gut environment healthy and how we can manipulate gut microbes to promote health,” concludes Simon Rasmussen.
