Amino acid metabolism in intestinal bacteria: links between gut ecology and host health

Abstract

Bacteria in the gastrointestinal (GI) tract play an important role in the metabolism of dietary substances in the gut and extraintestinal tissues. Amino acids (AA) should be taken into consideration in the development of new strategies to enhance efficiency of nutrient utilization because they are not only major components in the diet and building blocks for protein but also regulate energy and protein homeostasis in organisms. The diversity of the AA-fermenting bacteria and their metabolic redundancy make them easier to survive and interact with their neighboring species or eukaryotic host during transition along GI tract. The outcomes of the interactions have important impacts on gut health and whole-body homeostasis. The AA-derived molecules produced by intestinal bacteria affect host health by regulating either host immunity and cell function or microbial composition and metabolism. Emerging evidence shows that dietary factors, such as protein, non-digestible carbohydrates, probiotics, synbiotics and phytochemicals, modulate AA utilization by gut microorganisms. Interdisciplinary research involving nutritionists and microbiologists is expected to rapidly expand knowledge about crucial roles for AA in gut ecology and host health.

Microbial and metabolic interactions between the gastrointestinal tract andClostridium difficileinfection

“…27 Additionally, Clostridium species are the most common amino acid fermenting bacteria found in the gut. 29 It is estimated that 20 to 60 g of undigested carbohydrates enter the colon each day. 30,31 The colonic microbiota plays a major functional role by fermenting these complex carbohydrates and antibiotics disturb the gastrointestinal tract microbiota and in turn reduce colonization resistance against Clostridium difficile.…”

“…[32][33][34] SCFAs, especially butyrate, are the main energy source for the colonic mucosa. SCFAs also play key roles in the regulation of host gene expression, inflammation, differentiation and apoptosis.…”

Functional amino acids in nutrition and health

“…Dietary requirements of AA depend on species, developmental stage, physiological status, the microbiota in the lumen of the small intestine, environmental factors, and pathological states (Dai et al 2011(Dai et al , 2012aWu et al 2013). Thus, some of the AA that are synthesized by animals have been classified as conditionally essential because rates of their utilization are greater than rates of their synthesis under certain conditions (e.g., early weaning, lactation, pregnancy, burns, injury, infection, heat stress, and cold stress) (Wu 2009).…”

Bromochloromethane, a Methane Analogue, Affects the Microbiota and Metabolic Profiles of the Rat Gastrointestinal Tract

“…The interaction between the host and its resident microbiota results in the mutually beneficial environment that contributes to gut health (17). This contribution consists of host-microbe metabolic flux, exemplified by the production of short-chain fatty acids (SCFA) (17), amino acids (19), lipids (17), and polyamines (19). Thus, variation in the gut microbiota might lead to changes in intestinal and host systemic metabolism.…”