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Metabolic cross-feeding relationship gains probiotic status Sarah Wettstadt Estación Experimental del Zaidín Granada, Spain
A diet rich in plant polymers challenges the human digestive system and is highly nutritious fodder for our gut microbiota. However, even in the gut environment where these molecules are highly abundant, species have been identified that are unable to digest the sometimes highly complex plant polymers. This means these species depend on other members of the community to break down their food for them – called ‘syntrophy’. In the study by Muñoz et al. discussed here, a novel syntrophic relationship was
identified in which Bacteroides cellulosilyticus breaks down side chains of a highly complex plant peptidoglycan. Bifidobacterium breve can then use these degradation products as sole carbon sources for growth. As such, the list of probiotic organisms is being extended by a syntrophic relationship while more plant components gain the status of prebiotics. Unprocessed plant products contain the complex and sturdy molecules that make up the plant cell wall, which our digestive enzymes are unable to deal with. Generally, plant polymers like cellulose, hemicellulose or lignin are meant to stabilise and protect the plant from physical breakage and enzymatic digestion. One such polymer that is omnipresent in plant cell walls is an extracellular proteoglycan called arabinogalactan protein (AGP). Almost all vegetal foods contain AGPs, with gum arabic (Arabic gum) from the Acacia senegal tree being the best known and most widely used natural gum. The food industry discovered the emulsifying properties of AGPs and use them in fruit syrups, marshmallows, confectionary sugar, icings, chewing gum, soft drinks and in edible decorative ingredients. Due to the vital roles AGPs play in our diet
The list of probiotic organisms is being extended
28
microbiologist
|
December 2020
www.sfam.org.uk
