Regulatory role for l-arginine in the utilization of amino acids by pig small-intestinal bacteria
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We recently reported that bacteria from the pig small intestine rapidly utilize and metabolize amino acids (AA). This study investigated the effect of l-arginine on the utilization of AA by pure bacterial strains (Streptococcus sp., Escherichia coli and Klebsiella sp.) and mixed bacterial cultures derived from the pig small intestine. Bacteria were incubated at 37°C for 3 h in anaerobic AA media containing 0–5 mmol/L of arginine to determine the effect of arginine on the bacterial utilization of AA. Amino acids in the medium plus cell extracts were analyzed by high-performance liquid chromatography. Results indicated concentration-dependent increases in the bacterial utilization of arginine and altered fluxes of arginine into ornithine and citrulline in the bacteria. Net glutamine utilization increased in pure bacterial strains with increased concentrations of arginine. With the addition of arginine, net utilization of threonine, glycine, phenylalanine and branched-chain AA increased (P < 0.05) in Streptococcus sp. and Klebsiella sp., but decreased in E. coli. Net utilization of lysine, threonine, isoleucine, leucine, glycine and alanine by jejunal or ileal mixed bacteria decreased (P < 0.05) with the addition of arginine. Complete utilization of asparagine, aspartate and serine were observed in pig small-intestinal bacteria after 3 h of incubation. Overall, the addition of arginine affected the metabolism of the arginine-family of AA and the serine- and aspartate-family of AA in small-intestinal bacteria and reduced the utilization of most AA in ileal mixed bacteria. These novel findings indicate that arginine exerts its beneficial effects on swine nutrition partially by regulating AA utilization and metabolism in the small-intestinal microbiota.
KeywordsAmino acids Intestinal bacteria Nutrition Small intestine Swine
Acid resistance system
Nutritionally essential amino acids
Colony forming unit
This work was supported by the Natural Science Foundation of China (30810103909), the National Basic Research Program of China (2004CB117500-4), National Research Initiative Competitive Grants from the Animal Growth and Nutrient Utilization Program (2008-35206-18764) of the USDA National Institute of Food and Agriculture, and Texas AgriLife Research Hatch Project (H-8200). We are grateful to Dr. J. Fleming for technical assistance, Dr. H. J. Gao and Dr. J. J. Wang for helpful discussion, and Dr. T. A. Davis for critical reading of the manuscript. Z.-L. Dai thanks the China Scholarship Council for support of his study at Texas A&M University between 17 February 2009 and 28 February 2010.
Conflict of interest
The authors declare that they have no conflict of interest.
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