School of Medicine, National Yang Ming Chiao Tung University, Yangming Campus, Taipei, Taiwan.
Program in Molecular Medicine, National Yang Ming Chiao Tung University, Yangming Campus, Taipei, Taiwan.
Appl Environ Microbiol. 2024 Aug 21;90(8):e0114824. doi: 10.1128/aem.01148-24. Epub 2024 Jul 31.
spp. are nitrate-reducing bacteria with anaerobic respiratory activity that reduce nitrate to nitrite. They are obligate anaerobic, Gram-negative cocci that ferment lactate as the main carbon source and produce short-chain fatty acids (SCFAs). Commensal reside in the human body site where lactate level is, however, limited for growth. In this study, nitrate was shown to promote the anaerobic growth of in the lactate-deficient media. We aimed to investigate the underlying mechanisms and the metabolism involved in nitrate respiration. Nitrate (15 mM) was demonstrated to promote growth and viability in the tryptone-yeast extract medium containing 0.5 mM L-lactate. Metabolite and transcriptomic analyses revealed nitrate enabled to actively utilize glutamate and aspartate from the medium and secrete tryptophan. Glutamate or aspartate was further supplemented to a medium to investigate individual catabolism during nitrate respiration. Notably, nitrate was demonstrated to elevate SCFA production in the glutamate-supplemented medium, and further increase tryptophan production in the aspartate-supplemented medium. We proposed that the increased consumption of glutamate provided reducing power for nitrate respiration and aspartate served as a substrate for fumarate formation. Both glutamate and aspartate were incorporated into the central metabolic pathways reverse tricarboxylic acid cycle and were linked with the increased production of acetate, propionate, and tryptophan. This study provides further understanding of the promoted growth and metabolic mechanisms by commensal utilizing nitrate and specific amino acids to adapt to the lactate-deficient environment.IMPORTANCENitrate is a pivotal ecological factor influencing microbial community and metabolism. Dietary nitrate provides health benefits including anti-diabetic and anti-hypertensive effects microbial-derived metabolites such as nitrite. Unraveling the impacts of nitrate on the growth and metabolism of human commensal bacteria is imperative to comprehend the intricate roles of nitrate in regulating microbial metabolism, community, and human health. are lactate-utilizing, nitrate-reducing bacteria that are frequently found in the human body site where lactate levels are low and nitrate is at millimolar levels. Here, we comprehensively described the metabolic strategies employed by to thrive in the lactate-deficient environment using nitrate respiration and catabolism of specific amino acids. The elevated production of SCFAs and tryptophan from amino acids during nitrate respiration of further suggested the potential roles of nitrate and in the promotion of human health.
种属是具有厌氧呼吸活性的硝酸盐还原细菌，可将硝酸盐还原为亚硝酸盐。它们是严格的厌氧菌，革兰氏阴性球菌，以发酵乳酸作为主要碳源，并产生短链脂肪酸（SCFAs）。共生菌存在于人体中乳酸水平有限的部位。在这项研究中，硝酸盐被证明可以促进乳酸缺乏培养基中 的厌氧生长。我们旨在研究硝酸盐呼吸涉及的潜在机制和代谢。硝酸盐（15 mM）被证明可以在含有 0.5 mM L-乳酸的胰蛋白胨酵母提取物培养基中促进 的生长和活力。代谢物和转录组分析表明，硝酸盐使 能够从培养基中主动利用谷氨酸和天冬氨酸，并分泌色氨酸。进一步向培养基中补充谷氨酸或天冬氨酸来研究硝酸盐呼吸过程中的个别分解代谢。值得注意的是，硝酸盐被证明可以提高谷氨酸补充培养基中的 SCFA 产量，并进一步增加天冬氨酸补充培养基中的色氨酸产量。我们提出，谷氨酸的消耗增加为硝酸盐呼吸提供了还原力，而天冬氨酸则作为富马酸形成的底物。谷氨酸和天冬氨酸都被纳入 反向三羧酸循环的中心代谢途径，并与乙酸盐、丙酸盐和色氨酸产量的增加有关。这项研究进一步了解了共生菌利用硝酸盐和特定氨基酸来适应乳酸缺乏环境的促进生长和代谢机制。
硝酸盐是影响微生物群落和代谢的关键生态因素。饮食中的硝酸盐提供了健康益处，包括抗糖尿病和抗高血压作用，这些作用是由微生物衍生的代谢物如亚硝酸盐介导的。揭示硝酸盐对人体共生细菌生长和代谢的影响对于理解硝酸盐在调节微生物代谢、群落和人类健康方面的复杂作用至关重要。 是一种利用乳酸的、硝酸盐还原的细菌，经常存在于乳酸水平低且硝酸盐处于毫摩尔水平的人体部位。在这里，我们全面描述了 利用硝酸盐呼吸和特定氨基酸分解代谢在乳酸缺乏环境中茁壮成长的代谢策略。在 利用硝酸盐呼吸过程中，氨基酸产生的 SCFAs 和色氨酸的增加进一步表明了硝酸盐和 在促进人类健康方面的潜在作用。
