Microbiota may communicate with human gut cells through enzyme signalling
The new study, published in Cell Reports, initially set out to investigate phytate is broken down in our bodies, with the team noting that despite the fact that we already understand that the vital compound is broken down in our gut - we have very little understanding of how this break-down is achieved.
To address this Dr Regis Stentz from the UK Institute of Food Research (IFR) and colleagues screened the genomes of hundreds of different species of gut bacteria - finding that one of the most prominent gut bacteria species - a type of Bacteroides - produces an enzyme that is able to break down phytate and is also able to facilitate 'cross-kingdom communication.'
"Our study provides a breakthrough in understanding how bacteria communicate across different kingdoms to influence our own cells' behaviour, as well as how we digest our food," said Stentz.
Commenting on the breakthrough, Professor Simon Carding who leads IFR's research into gut health said the team has "cracked one of the big mysteries in gut health – how do beneficial bacteria communicate with human cells."
"The enzyme we've uncovered has dual roles, in providing dietary nutrients as well as in modifying host cell behaviour," he explained. "This opens up a number of very exciting areas of research."
After identifying the enzyme using genomic sequencing, the team mapped its 3D structure in order to better characterise it and its functions. In the process of this 2D structuring and characterisation, process revealing that the enzyme is was highly effective at processing phytate into the nutrients the body needs.
In addition the team found suggestions that the enzyme - which is released in small 'cages' called outer membrane vesicles (OMVs) by the Bacteroides bacteria - have a direct impact on calcium signalling of our own gut wall cells and as such are a valuable mechanism for communication between our gut bacteria and human cells. The team noted that the purpose of these OMVs may be to allow phytate in for nutrient processing but prevent the enzyme itself from being destroyed by our own protein-degrading enzymes.
The finding that the enzyme filled OMV is able to induce calcium signalling in our gut epithelial cells (cut wall cells) suggests that bacteria are using OMV-packaged enzymes to communicate directly with our cells and influence their behaviour, said the team - adding that the discovery is a good example of cross-kingdom communication.
They noted that until now, OMVs have only been observed from pathogenic bacteria looking to invade host cells, this is the first example that benefits both the host and the microbiota.
The IFR team also commented that they want to now investigate the role these bacterial enzymes play in cross-kingdom communication - in order to better find out the consequences of the calcium signalling changes. They noted that because gut bacteria play a role in maintaining this healthy state, with diversions from this implicated in a number of diseases, knowing how bacteria communicate with us opens up new possibilities to investigate this further.
Source: Cell Reports
Published online ahead of print, doi:10.1016/j.celrep.2014.01.021
"A Bacterial Homolog of a Eukaryotic Inositol Phosphate Signaling Enzyme Mediates Cross-kingdom Dialog in the Mammalian Gut"
Authors: Régis Stentz, Samantha Osborne, et al
Decoding Gut Microbiota
Posted by Stella Metsovas,