Environmental Microbiology: You Are What You

ReseaRch highlights

ENvIRONmENtAL mICRObIOLOGy You are what you eat

The bacteria in the human gut used this information to screen provide their host with energy by sequence databases for other putative degrading dietary polysaccharides. β-porphyranases. They found six contact with Writing in Nature, Hehemann et al. candidates, five of which were present now show that bacteria present in in marine bacteria. Interestingly, one environmental the gut of Japanese individuals have candidate (Bp1689) originated from microorganisms acquired a carbohydrate-degrading Bacteroides plebius, a bacterium iso- associated enzyme from marine bacteria that lated from the intestinal microbiota of with ingested allows them to degrade a polysaccha- Japanese individuals. To test whether ride found only in seaweed. porphyranases are common in food tailors While investigating the carbo- Japanese gut bacteria, Hehemann et the metabolic hydrate-active enzymes present in al. analysed the gut metagenome data capabilities of Zobellia galactanivorans, a member of from 13 Japanese individuals, iden- the marine Bacteroidetes, Hehemann tifying 7 different β-porphyranases our resident et al. identified five putative enzymes in 4 individuals. By contrast, the gut microbiota that distantly resembled glycoside gut metagenomes of 18 individuals hydrolases of the GH16 family but from North America contained no lacked the residues that provide β-porphyranases. Therefore, bacteria specificity for carbohydrates such that have acquired porphyran- as agarose or κ-carrageenan that are degrading enzymes, most likely found in marine algae. Two of these through horizontal gene transfer from enzymes were cloned and purified a marine bacterium, are common and then screened against a range in the gut microbiota of Japanese of natural polysaccharides extracted individuals, whose daily diet includes from various marine macrophytes. porphyran-containing seaweeds. The authors found that the enzymes These findings suggest that con- were active only against extracts from tact with environmental microorgan- red algae of the genus Porphyra, which isms associated with ingested food contain high levels of the polysaccha- tailors the metabolic capabilities of ride porphyran, leading the authors our resident gut microbiota, meaning to classify these enzymes as the first that there is some truth in the old β-porphyranases to be identified and adage, ‘you are what you eat’. to name them PorA and PorB. Andrew Jermy The authors then determined

the crystal structures of PorA and ORIGINAL RESEARCH PAPER Hehemann, J. H. PorB, identified the key regions of et al. Transfer of carbohydrate-active enzymes the proteins that were important from marine bacteria to Japanese gut microbiota. Nature 464, 908–912 (2010) for binding to porphyran and GETTY