[Frontiers in Bioscience 16, 1768-1786, January 1, 2011]

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

Zhao-Lai Dai1, Guoyao Wu2, 3, Wei-Yun Zhu1

1Zhao-lai Dai, Wei-yun Zhu, Laboratory of Gastrointestinal Microbiology, Nanjing Agricultural University, Nanjing 210095, China, 2 Guoyao Wu, Department of Animal Science, Texas A and M University, College Station, TX 77843, USA, 3State Key Laboratory of Animal Nutrition, China Agricultural University, Beijing 100193, China


1. Abstract
2. Introduction
3. Diversity and abundance of the AA-fermenting bacteria in the digestive tract
4. AA metabolism in gut bacteria
4.1. Incorporation of AA into bacterial cells
4.2. Biosynthesis of AA
4.3. Catabolism of AA and production of important metabolites
4.4. Compartmental AA metabolism in gut bacteria
4.5. Metabolic interactions among gut bacteria and host
5. Functional aspects of the AA metabolism in gut bacteria
5.1. Adaptation and survival
5.2. Production of important molecules
6. Dietary modulations of the AA metabolism in gut bacteria
6.1. High protein diet
6.2. Non-digestible carbohydrates and availability of carbon source
6.3. Probiotics and synbiotics
6.4. Phytochemicals
7. Conclusions and perspectives
8. Acknowledgements
9. References


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.