Nutrient cross-feeding in the microbial world

Abstract

The stability and function of a microbial community depends on nutritional interactions among community members such as the cross-feeding of essential small molecules synthesized by a subset of the population. In this review, we describe examples of microbe-microbe and microbe-host cofactor cross-feeding, a type of interaction that influences the forms of metabolism carried out within a community. Cofactor cross-feeding can contribute to both the health and nutrition of a host organism, the virulence and persistence of pathogens, and the composition and function of environmental communities. By examining the impact of shared cofactors on microbes from pure culture to natural communities, we stand to gain a better understanding of the interactions that link microbes together, which may ultimately be a key to developing strategies for manipulating microbial communities with human health, agricultural, and environmental implications.

Keywords: cofactor; corrinoid; microbial communities; microbial interactions; nutrient cross-feeding.

FIGURE 1

Nutritional interactions between microbes. Nutritional interactions may shape a microbe’s metabolic capacity within a microbial community. Three general categories of nutritional interactions are illustrated. (A) Nutrient competition. The ability of a microbe to compete for limiting nutrients such as iron (red triangles) may determine survival and persistence within a particular niche. (B) Syntrophic metabolism. The consumption of an intermediate or end product such as hydrogen (green squares) by a partner organism allows an otherwise energetically unfavorable reaction, for example, propionate (blue hexagons) to acetate (orange circles) to support growth. (C) Nutrient cross-feeding. The presence of a microbe that produces an essential nutrient such as folate (yellow squares) enables auxotrophs to survive.

FIGURE 2

Microbial strategies for fulfilling corrinoid requirements. Microbes employ various strategies to obtain specific corrinoids from environments that contain a variety of corrinoids and corrinoid precursors. The structure of cobalamin, a corrinoid with the lower ligand 5,6- dimethylbenzimidazole (boxed) is shown, as are the structures of the three classes of lower ligand bases of other corrinoids. Specific strategies for obtaining corrinoids are illustrated with representative bacteria listed in parentheses. (A) Corrinoid transport in Bacteroides thetaiotaomicron. (B) Cobinamide salvaging in Escherichia coli. (C) Corrinoid remodeling in Dehalococcoides mccartyi. (D) α-ribazole salvaging in Listeria innocua.