Ruminococcus bromii is a keystone species for the degradation of resistant starch in the human colon

Abstract

The release of energy from particulate substrates such as dietary fiber and resistant starch (RS) in the human colon may depend on the presence of specialist primary degraders (or 'keystone species') within the microbial community. We have explored the roles of four dominant amylolytic bacteria found in the human colon in the degradation and utilization of resistant starches. Eubacterium rectale and Bacteroides thetaiotaomicron showed limited ability to utilize RS2-and RS3-resistant starches by comparison with Bifidobacterium adolescentis and Ruminococcus bromii. In co-culture, however, R. bromii proved unique in stimulating RS2 and RS3 utilization by the other three bacterial species, even in a medium that does not permit growth of R. bromii itself. Having previously demonstrated low RS3 fermentation in vivo in two individuals with undetectable populations of R. bromii-related bacteria, we show here that supplementation of mixed fecal bacteria from one of these volunteers with R. bromii, but not with the other three species, greatly enhanced the extent of RS3 fermentation in vitro. This argues strongly that R. bromii has a pivotal role in fermentation of RS3 in the human large intestine, and that variation in the occurrence of this species and its close relatives may be a primary cause of variable energy recovery from this important component of the diet. This work also indicates that R. bromii possesses an exceptional ability to colonize and degrade starch particles when compared with previously studied amylolytic bacteria from the human colon.

Modulation of the gut microbiota by prebiotic fibres and bacteriocins

“…populations in the gut of different animal models and humans [16,55,56]. Moreover, R. bromii was suggested to be a keystone species in resistant starch degradation, particularly type 3, which is required for the other bacteria to utilize the products from resistant starch [57]. Concordantly to the other studies [16,55,56], the Ruminococcus genus (including R. bromii ) increased in relative abundance in growing pigs that were fed with a type 3 resistant starch-containing diet [30].…”

Production of Butyrate from Lactate by a Newly Isolated Clostridium sp. BPY5

“…The medium (YCFAL), modified based on YCFA medium [17], consists of the following: 10 g casitone, 2.5 g yeast extract, 5.0 g DL-sodium lactate, 4.0 g NaHCO 3 , 1.0 g cysteine, 0.45 g K 2 HPO 4 , 0.45 g KH 2 PO 4 , 0.9 g (NH4) 2 SO4, 0. 9 g NaCl, 0.09 g MgSO 4 ·7H 2 O, 0.09 g CaCl 2 , 1 mg resazurin, 10 mg haemin, 10 μg biotin, 10 μg cobalamin, 30 μg p-aminobenzoic acid, 50 μg folic acid, and 150 μg pyridoxamine per liter.…”

Human gut microbiota: does diet matter?

“…SCFA have been implicated to have both local and systemic beneficial biological effects in the human body; acetate is readily absorbed and transported to the liver; propionate is a substrate for hepatic gluconeogenesis; butyrate is the preferred fuel of the colonocytes and also plays a major role in the regulation of cell proliferation and differentiation (7) . Several excellent review-papers already exist (130,(142)(143)(144)(145)(146)(147) , and therefore we will not go into detail with the dietary interventions with fibre.…”