Hehemann et al. first discovered a new type of glycoside hydrolase in Zobellia galactinovorans.
Algae comports unique sulphated polysaccharides and marine bacteria have evolved a biochemical toolkit of their own to digest them. The enzyme the French group noticed is able to able to cleave L6S saccharide links, particular to porphyran, a polysaccharide rich in Porphyra algae. Where b-agarases present a Tyr residue, the b-porphyranases comport variable, smaller amino acids, opening a positively charged binding pocket for the SO4- moiety.
When the group searched the databases for amino acid signature specific to b-porphyranase, they retrieved them in only one type of organism apart of marine Bacteroidetes: B. plebeius, a gut Bacteroides. Moreover, b-porphyranases are only observed in Bacteroides from Japanese gut microflora, not in North American microflora. The high homology (35%-55%) of sequence between the genes from marine and gut bacteria indicates the Japanese bugs got their hydrolase by horizontal gene transfer.
Algae, especially of the Porphyra genre (on which Z. galactinovorans thrives) are a staple of Japanese cuisine. Nori comes to mind immediately: Porphyra is grown in marine farms, and processed in sheets, which are used as a condiment on noodles... and to prepare sushi. Bacteroides in Japaneses’ guts has thus been in contact with their porphyran-digesting cousin and inherited the gene that would help them make the most of the Japanese diet.
Further reading :
Hehemann JH, Correc G, Barbeyron T, Helbert W, Czjzek M, Michel G. (2010) Transfer of carbohydrate-active enzymes from marine bacteria to Japanese gut microbiota. Nature 464, 908-912
