by Roberto
From its humble beginnings as an inhabitant of the Japanese corbicula clam alimentary canal to center stage attention-getter as a cholesterol-lowering resident of the human gut, Oscillibacter has experienced a meteoric rise to stardom. First described in 2007, this genus received little attention for over a decade. Now, a mere 17 years after its discovery and thus still a relative newcomer in the bacterial world (as far as time humans have studied it), its role as a beneficial member of the human gut microbiome seems to have it on track to becoming a superstar.
Fig. 1. Rod-shaped Oscillibacter sp. take up fluorescently labeled cholesterol (shown in green). Photo credit: Ahmed Mohamed. Source
A recent and gargantuan study provides strong evidence that members of the Oscillibacter genus (phylum Bacillota, class Clostridia) metabolize cholesterol and consequently reduce both fecal and serum cholesterol level in humans. The work started by metagenomic and metabolomic profiling of stool samples from nearly 1500 Framingham Heart Study participants with the aim of finding associations between the gut microbiome and cardiovascular health. The results revealed many associations, with the most tantalizing one being Oscillibacter's effect on cholesterol. The authors pursued this further by growing several Oscillibacter isolates in the presence of cholesterol. These experiments were not straightforward; it was not as simple as detecting growth in minimal medium with cholesterol as sole carbon source. Not by a long shot. Nonetheless, coupling of bioinformatic and mass spec analyses pointed to several possible enzymes, all able to metabolize cholesterol to multiple products. Interestingly, some of these products might be metabolized further, suggesting that within the gut microbial community other members might be acting in synergy with Oscillibacter to reduce cholesterol levels even more. As large and detailed as this study was, it is only the beginning and there is much work still to be done to iron out the wrinkles of how Oscillibacter metabolizes cholesterol. Doubtless, we will see continued increase in the interest on members of this genus in the coming years.
Will ingestion of Oscillibacter strains someday replace daily doses of cholesterol-lowering statins? Only time will tell. But the consequences of an easily accessible bacterium safely replacing the world's best-selling drugs are worth pondering upon.
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