Virtually all heterotrophs incorporate carbon dioxide by anaplerotic fixation. Little explored, however, is the interdependency of pathways and rates of CO2-fixation on the concurrent usage of organic substrate(s). Potentially, this could reveal which substrates out of a pool of dissolved organic carbon (DOC) are utilised by environmental microorganisms. To explore this possibility, Bacillus subtilis W23 was grown in a minimal medium with normalised amounts of either glucose, lactate or malate as only organic substrates, each together with 1 g/ L NaH13CO3. Incorporation of H13CO3- was traced by elemental analysis-isotope ratio mass spectrometry (EA-IRMS) of biomass and gas chromatography-mass spectrometry (GC-MS) of protein-derived amino acids. Until the late logarithmic phase, 13C-incorporation into the tricarboxylic acid cycle increased with time and occurred via [4-13C]oxaloacetate formed by carboxylation of pyruvate. The levels of 13C-incorporation were highest for growth on glucose and lowest on malate. 13C-Incorporation into gluconeogenesis products was mainly detected in the lactate and malate experiment, whereas glucose down-regulated this path. A proof-of-principle study with a natural groundwater community confirmed the ability to determine incorporation from H13CO3- by natural communities leading to specific labelling patterns. This underlines the potential of the labelling approach to characterise carbon sources of heterotrophic microorganisms in their natural environments.

中文翻译：

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稳定同位素标记揭示了异养细菌中基质依赖的CO2固定。

几乎所有的异养菌都通过无血管固定结合了二氧化碳。然而，很少探讨途径和二氧化碳固定率对有机底物同时使用的相互依赖性。潜在地，这可能揭示环境微生物利用了溶解的有机碳（DOC）库中的哪些底物。为了探索这种可能性，将枯草芽孢杆菌W23在基本量的葡萄糖，乳酸或苹果酸作为有机底物的基础培养基中生长，每种底物均与1 g / L NaH13CO3一起使用。通过生物质的元素分析-同位素比质谱（EA-IRMS）和蛋白质衍生的氨基酸的气相色谱-质谱（GC-MS）追踪H13CO3-的引入。直到对数后期，13 C并入三羧酸循环随时间增加，并通过丙酮酸羧化形成的[4-13C]草酰乙酸发生。葡萄糖生长的13C掺入水平最高，苹果酸最低。在乳酸和苹果酸实验中主要检测到13 C掺入糖异生产物中，而葡萄糖下调了该途径。对天然地下水群落的原理验证研究证实了确定天然群落从H13CO3-掺入的能力，从而导致了特定的标记方式。这强调了标记方法表征自然环境中异养微生物微生物碳源的潜力。葡萄糖生长的13C掺入水平最高，苹果酸最低。在乳酸和苹果酸实验中主要检测到13 C掺入糖原异生产物中，而葡萄糖下调了该途径。对天然地下水群落的原理验证研究证实了确定天然群落从H13CO3-掺入的能力，从而导致了特定的标记方式。这强调了标记方法表征自然环境中异养微生物微生物碳源的潜力。葡萄糖生长的13C掺入水平最高，苹果酸最低。在乳酸和苹果酸实验中主要检测到13 C掺入糖原异生产物中，而葡萄糖下调了该途径。对天然地下水群落的原理验证研究证实了确定天然群落从H13CO3-掺入的能力，从而导致了特定的标记方式。这强调了标记方法表征自然环境中异养微生物微生物碳源的潜力。对天然地下水群落的一项原理验证研究证实了确定天然群落从H13CO3-掺入的能力，从而导致了特定的标记方式。这强调了标记方法表征自然环境中异养微生物微生物碳源的潜力。对天然地下水群落的一项原理验证研究证实了确定天然群落从H13CO3-掺入的能力，从而导致了特定的标记方式。这强调了标记方法表征自然环境中异养微生物微生物碳源的潜力。