A microbe that stays forever young and could help unlock the secrets of ageing has been discovered by scientists.

The yeast microbe, called S. pombe, is said to be immune to ageing, as it rejuvenates every time it reproduces.

Researchers say the discovery of S. pombe "provides fundamental insights into the mechanism of ageing".

A team from the University of Bristol and the Max-Planck Institute of Molecular Cell Biology and Genetics in Germany found the common species of yeast microbe has evolved to stay young.

Studies have found there are mechanisms in place to ensure one half receives older, often defective cell material, while the other half is equipped with new fully-functional material.

But ageing is not inevitable for S. pombe, with research published in Current Biology showing the yeast reproduces by splitting into two halves that both inherit their "fair share" of old cell material.

Iva Tolic, lead investigator of the project, said: "However, as both cells only get half of the damaged material, they are both younger than before."

This means S. pombe - unlike others species - is rejuvenated each time it reproduces and can escape ageing as long as it keeps dividing fast enough.

But further tests found the unusual feature only occurred when S. pombe was in favourable conditions.

Researchers exposed the yeast to heat, ultraviolet radiation and damaging chemicals, which caused the speed of growth to slow.

The researchers say S. pombe could potentially serve as a model of certain non-ageing types of cells in humans.