Understanding probiotic communication
29 April 2016 – New insight into the way probiotic bacteria communicate with their host is the key outcome of the work by TiFN’s PhD fellow I-Chiao Lee. She defended her thesis at Wageningen University on 31 March 2016. Lee’s work also suggests directions for further investigation into probiotics’ mechanisms of action.
Around the world, probiotics are increasingly popular, as they are seen to be beneficial for health. The effects of these bacteria appear, however, to be highly species and/or strain specific. In-depth research into the molecular structure of probiotics and their communication with host cells is vital to understanding these differences, and to providing molecular-level insight into the mechanisms behind probiotic functions.
Lee’s research focussed on Lactobacillus plantarum WCFS1, a model strain for probiotic lactobacilli with a well-annotated genome sequence and sophisticated genetic engineering tools. It was her model of choice to study how molecules on the bacterial surface – known as envelope-effector molecules –including lipoteichoic acid (LTA), lipo and glycoproteins, and extracellular polysaccharides (EPS), communicate with host cells.
Lee learned that there is great variation between bacterial strains. “Although they all have surface polysaccharides, they occur as different types and in different compositions”, she says. “For example, the Lactobacillus plantarum strains WCFS1 and Lp90 produce very different extracellular polysaccharides (EPS). Lp90 produces about 20x more EPS than WCFS1.” The compositions of EPS are also different. “The EPS of WCFS1 is 65% glucose but that of Lp90 is heavier in glucosamine, galactose, galactosamine and rhamnose. When you remove EPS from WCFS1, the strain becomes more pro-inflammatory.“
Globally, this is the first research that identifies the glycosyltransferases responsible for protein glycosylation in probiotics, including Acm2 – an enzyme, which digests the cell wall of Lactobacillus plantarum. “Until now these experiments have been limited to pathogenic bacteria and it is a real breakthrough to investigate these processes in Lactobacillus.” Therefore, Lee’s research also provides a ‘guideline’ for future studies into these compounds.
Lee, currently available for a post-doc position in industry, enjoyed her time as a PhD fellow at TiFN. “It was exciting to be part of such ground-breaking research”, she says. She also found it interesting to work with other disciplines, though, sometimes, communication was a challenge. “Coming from different fields of expertise, we used different professional terms and looked at issues from different perspectives”, she says. “Therefore we had to put extra effort into explaining things to each other, and always needed to check if the other had the right understanding.”