Department of Systems Biology, Søltofts Plads, Technical University of Denmark, DK-2800 Kgs Lyngby, Denmark.
BMC Microbiol. 2009 Dec 10;9:255. doi: 10.1186/1471-2180-9-255.
Aspergillus niger is a filamentous fungus found in the environment, on foods and feeds and is used as host for production of organic acids, enzymes and proteins. The mycotoxin fumonisin B2 was recently found to be produced by A. niger and hence very little is known about production and regulation of this metabolite. Proteome analysis was used with the purpose to reveal how fumonisin B2 production by A. niger is influenced by starch and lactate in the medium.
Fumonisin B2 production by A. niger was significantly increased when lactate and starch were combined in the medium. Production of a few other A. niger secondary metabolites was affected similarly by lactate and starch (fumonisin B4, orlandin, desmethylkotanin and pyranonigrin A), while production of others was not (ochratoxin A, ochratoxin alpha, malformin A, malformin C, kotanin, aurasperone B and tensidol B). The proteome of A. niger was clearly different during growth on media containing 3% starch, 3% starch + 3% lactate or 3% lactate. The identity of 59 spots was obtained, mainly those showing higher or lower expression levels on medium with starch and lactate. Many of them were enzymes in primary metabolism and other processes that affect the intracellular level of acetyl-CoA or NADPH. This included enzymes in the pentose phosphate pathway, pyruvate metabolism, the tricarboxylic acid cycle, ammonium assimilation, fatty acid biosynthesis and oxidative stress protection.
Lactate added in a medium containing nitrate and starch can increase fumonisin B2 production by A. niger as well as production of some other secondary metabolites. Changes in the balance of intracellular metabolites towards a higher level of carbon passing through acetyl-CoA and a high capacity to regenerate NADPH during growth on medium with starch and lactate were found to be the likely cause of this effect. The results lead to the hypothesis that fumonisin production by A. niger is regulated by acetyl-CoA.
黑曲霉是一种丝状真菌，存在于环境、食物和饲料中，被用作生产有机酸、酶和蛋白质的宿主。最近发现黑曲霉会产生真菌毒素伏马菌素 B2，因此对这种代谢产物的产生和调控知之甚少。本研究采用蛋白质组学分析的方法，旨在揭示黑曲霉产生伏马菌素 B2的过程是如何受到培养基中淀粉和乳酸影响的。
当培养基中同时含有乳酸和淀粉时，黑曲霉产生伏马菌素 B2的量显著增加。乳酸和淀粉对几种其他黑曲霉次级代谢物的产生也有类似的影响（伏马菌素 B4、奥兰丁、去甲基可他宁和吡喃黑曲霉 A），而对其他代谢物则没有影响（赭曲霉毒素 A、赭曲霉毒素 α、马尔福明 A、马尔福明 C、可他宁、奥来素 B 和 tensidol B）。在含有 3%淀粉、3%淀粉+3%乳酸或 3%乳酸的培养基中，黑曲霉的蛋白质组明显不同。获得了 59 个斑点的身份，主要是那些在含有淀粉和乳酸的培养基上表达水平较高或较低的斑点。其中许多是参与初级代谢和其他过程的酶，这些过程会影响细胞内乙酰辅酶 A 或 NADPH 的水平。这包括戊糖磷酸途径、丙酮酸代谢、三羧酸循环、铵同化、脂肪酸生物合成和氧化应激保护中的酶。
在含有硝酸盐和淀粉的培养基中添加乳酸可以增加黑曲霉产生伏马菌素 B2以及其他一些次级代谢物的产量。在含有淀粉和乳酸的培养基上生长时，细胞内代谢物的平衡向更高水平的碳通过乙酰辅酶 A 和更高的能力再生 NADPH 转变，这可能是这种效应的原因。研究结果提出了黑曲霉产生伏马菌素的调控可能与乙酰辅酶 A 有关的假说。
