A Young Microbiome Transplant Extends Life in Fish

Consuming microbes from the gut of younger fish improves health and extends life in killifish 

Largely neglected in the 20th century, the importance of our microbiome is only recently being understood. Some scientists consider our microbial brethren inhabiting our gut and skin an additional organ - performing an important function in the maintenance of good health. Indeed, multiple studies have correlated a diverse gut microbiome consisting of a range of beneficial species to be protective against a range of conditions. Our microbes not only assist us in digesting food and providing crucial anti-inflammatory compounds, but also prevent the colonisation of nasty bacterial varieties and ensure a healthy gut lining; preventing an influx of inflammatory microbes into our bloodstream. We know that as we age, most people will experience a loss of microbial diversity alongside an enrichment of specific species. There are even particular species of bacteria associated with centenarians such as Christensenellaceae

Can a microbiome transplant improve health? 

Turquoise killifish live only a few months in pools in Mozambique and Zimbabwe, and due to their short lifespan can be an excellent model of study.  They also resemble human microbiome aging, and both young and old fish can be distinguished in part through their microbiome signature. Now, researchers at the Max Planck Institute for Biology of Ageing have tested the impact of ingestion of the microbes inhabiating the gut of young killifish. 

The turquoise killifish. Credit: Frank Vinken for Max Planck Society

The turquoise killifish. Credit: Frank Vinken for Max Planck Society

The team first treated middle aged fish with antibiotics to sterilise their gut microbiome, before placing them in a tank filled with the gut contents (waste) of young fish or middle aged fish, for 12 hours. Strikingly they found that median lifespans were 41% longer in the fish that consumed young microbiome samples than those who consumed middle aged varieties. There was also a 37% increase in contrast to untreated animals. Antibiotic treatment by itself actually increased lifespan, but to a much smaller degree. At 16 weeks old fish who had received a youthful transplant were more active. Curiously, young fish who received a transplant from older fish were not affected negatively - suggesting that they could overcome any potentially detrimental effects. 

“The challenge with all of these experiments is going to be to dissect the mechanism. I expect it will be very complex”

Right now it's not known how these bacterial infusions are able to improve health, but one theory is that a depleted immune system in elderly fish may allow harmful bacterial species to grow more than others. Rebalancing the numbers out could also have a therapeutic effect on the immune system, signalling behavioural changes for example. We'll have to await further study to elucidate the mechanisms and see whether this research could apply to humans too. 

Read more at Nature