Charles T. Campbell Laboratory of Ophthalmic Microbiology, Department of Ophthalmology, University of Pittsburgh Eye Center, Pittsburgh, Pennsylvania, USA.
Appl Environ Microbiol. 2012 Sep;78(17):6225-35. doi: 10.1128/AEM.01778-12. Epub 2012 Jun 29.
Serratia marcescens is a model organism for the study of secondary metabolites. The biologically active pigment prodigiosin (2-methyl-3-pentyl-6-methoxyprodiginine), like many other secondary metabolites, is inhibited by growth in glucose-rich medium. Whereas previous studies indicated that this inhibitory effect was pH dependent and did not require cyclic AMP (cAMP), there is no information on the genes involved in mediating this phenomenon. Here we used transposon mutagenesis to identify genes involved in the inhibition of prodigiosin by glucose. Multiple genetic loci involved in quinoprotein glucose dehydrogenase (GDH) activity were found to be required for glucose inhibition of prodigiosin production, including pyrroloquinoline quinone and ubiquinone biosynthetic genes. Upon assessing whether the enzymatic products of GDH activity were involved in the inhibitory effect, we observed that d-glucono-1,5-lactone and d-gluconic acid, but not d-gluconate, were able to inhibit prodigiosin production. These data support a model in which the oxidation of d-glucose by quinoprotein GDH initiates a reduction in pH that inhibits prodigiosin production through transcriptional control of the prodigiosin biosynthetic operon, providing new insight into the genetic pathways that control prodigiosin production. Strains generated in this report may be useful in large-scale production of secondary metabolites.
粘质沙雷氏菌是研究次生代谢物的模式生物。生物活性色素灵菌红素（2-甲基-3-戊基-6-甲氧基普洛托京）与许多其他次生代谢物一样，受到富含葡萄糖的培养基中生长的抑制。虽然以前的研究表明这种抑制作用依赖于 pH 值，并且不需要环腺苷酸（cAMP），但对于介导这种现象的基因没有信息。在这里，我们使用转座子诱变来鉴定参与葡萄糖抑制灵菌红素产生的基因。发现与醌蛋白葡萄糖脱氢酶（GDH）活性相关的多个遗传基因座都需要参与葡萄糖抑制灵菌红素产生，包括吡咯喹啉醌和泛醌生物合成基因。在评估 GDH 活性的酶产物是否参与抑制作用时，我们观察到 d-葡萄糖-1,5-内脂和 d-葡萄糖酸，但不是 d-葡萄糖酸盐，能够抑制灵菌红素的产生。这些数据支持这样一种模型，即醌蛋白 GDH 氧化 d-葡萄糖引发 pH 降低，通过转录控制灵菌红素生物合成操纵子来抑制灵菌红素的产生，为控制灵菌红素产生的遗传途径提供了新的见解。本报告中生成的菌株可能在次生代谢物的大规模生产中有用。
