Bee study reveals environmental vulnerability and food production threat

A study carried out by scientists at the University of Lausanne, published in Nature Microbiology, has revealed that bees produce nutrients, which aid in the colonisation of their gut bacteria, highlighting a symbiotic host-microbiota relationship and offering insights into bees’ environmental weaknesses.

Why are gut bacteria important?

Gut bacteria play an important role for their host. They provide energy by degrading indigestible food, they train and regulate the immune system, they protect against invasion by pathogenic bacteria and they synthesise neuroactive molecules that regulate the behaviour and cognition of their host.

How was the study conducted?

Scientists began by looking for evidence that the gut bacteria of bees share nutrients with one another when bees are fed nothing other than sugar water. Initial results showed that one specific bacterium in the gut, Snodgrassella alvi, which cannot metabolise sugar to grow, still colonised the bee gut when no other bacteria were present. This raised the question of how Snodgrassella alvi were obtaining their nutrients.

By measuring metabolites in the gut, the scientists discovered that the bee synthesises multiple acids, including citric, malic and 3-hydroxy-3-methylglutaric, which are exported into the gut and found to be less abundant when S. alvi was present. These results led them to pose an unexpected hypothesis, ‘does the bee directly enable S. alvi to colonise its gut by furnishing the necessary nutrients?’.

In order to prove this hypothesis, the University of Lausanne scientists approached the laboratory of Professor Anders Meibom (affiliated with UNIL and EPFL). Professor Meibom and his team measured the flux of metabolites in complex environments at nanometer scale resolution, using Nanoscale Secondary Ion Mass Spectrometry (NanoSIMS). Together the two teams devised an experiment in which microbiota-free bees received a special diet of glucose, where the natural 12C atoms of carbon in the glucose were replaced with the naturally rare 13C ‘labelled’ isotopes. The bees were then colonised with S. alvi. The final stage involved the fixed guts embarking on a journey, first passing by the electron microscopy facility of UNIL, led by Senior Lecturer Christel Genoud, then onto the laboratory of Professor Meibom and his NanoSIMS.