Regulation of Pyrroloquinoline Quinone-Dependent Glucose Dehydrogenase Activity in the Model Rhizosphere-Dwelling Bacterium Pseudomonas putida KT2440
Regulation of Pyrroloquinoline Quinone-Dependent Glucose Dehydrogenase Activity in the Model Rhizosphere-Dwelling Bacterium Pseudomonas putida KT2440
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DOI：
10.1128/aem.00813-16
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发表时间：
2016-08-01
影响因子：
4.4
通讯作者：
Moe, Luke A.
中科院分区：
文献类型：
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作者：
An, Ran;Moe, Luke A.
土壤微生物通过分泌葡萄糖酸来溶解无机磷酸盐，葡萄糖酸是由周质葡萄糖脱氢酶（GDH）从葡萄糖产生的，所述周质葡萄糖脱氢酶需要吡咯喹啉醌（PQQ）作为氧化还原辅酶。虽然在许多细菌中观察到GDH依赖性磷酸盐增溶，但对调节该过程的机制知之甚少。在这里，我们使用的模式根际细菌恶臭假单胞菌KT 2440探讨GDH活性和PQQ合成，以及GDH编码基因（gcd）和PQQ生物合成基因（pqq操纵子）的基因表达，而在不同的生长条件下。我们还使用逆转录-PCR来鉴定来自pqq操纵子的转录物，以更准确地映射操纵子结构。GDH比活性和PQQ水平根据生长条件而变化，当葡萄糖用作唯一碳源时和在低可溶性磷酸盐的条件下两者的水平最高。然而，在这些条件下，PQQ水平限制了体外磷酸盐溶解。GDH比活性数据与gcd基因表达数据相关性良好，并且pqqF和pqqB基因的表达水平反映了PQQ合成的水平，这表明这些基因中的一个或两个可以根据生长条件调节PQQ水平。pqq基因簇（pqqFABCDEG）编码至少两个独立的转录物，并且pqqF基因的表达似乎是在独立的启动子和终止子的控制下。重要的是植物生长促进可以通过许多不同的方法由土壤和根际居住的细菌增强。一种方法是促进从土壤中获取养分。磷是植物通过土壤获得的必需营养素，但在许多情况下，它被锁定在植物无法吸收的形式。细菌如模式细菌恶臭假单胞菌KT 2440可以通过分泌葡萄糖酸来溶解不溶性土壤磷酸盐。这种化学物质是由葡萄糖通过细菌酶葡萄糖脱氢酶的活性产生的，这需要一种称为PQQ的辅酶。在这里，我们研究了葡萄糖脱氢酶和PQQ辅酶是如何根据细菌生长条件的差异进行调节的。我们确定，葡萄糖脱氢酶活性和PQQ生产是最佳的条件下，当细菌生长与葡萄糖作为唯一的碳源和低可溶性磷酸盐的条件下。
Soil-dwelling microbes solubilize mineral phosphates by secreting gluconic acid, which is produced from glucose by a periplasmic glucose dehydrogenase (GDH) that requires pyrroloquinoline quinone (PQQ) as a redox coenzyme. While GDH-dependent phosphate solubilization has been observed in numerous bacteria, little is known concerning the mechanism by which this process is regulated. Here we use the model rhizosphere-dwelling bacterium Pseudomonas putida KT2440 to explore GDH activity and PQQ synthesis, as well as gene expression of the GDH-encoding gene (gcd) and PQQ biosynthesis genes (pqq operon) while under different growth conditions. We also use reverse transcription-PCR to identify transcripts from the pqq operon to more accurately map the operon structure. GDH specific activity and PQQ levels vary according to growth condition, with the highest levels of both occurring when glucose is used as the sole carbon source and under conditions of low soluble phosphate. Under these conditions, however, PQQ levels limit in vitro phosphate solubilization. GDH specific activity data correlate well with gcd gene expression data, and the levels of expression of the pqqF and pqqB genes mirror the levels of PQQ synthesized, suggesting that one or both of these genes may serve to modulate PQQ levels according to the growth conditions. The pqq gene cluster (pqqFABCDEG) encodes at least two independent transcripts, and expression of the pqqF gene appears to be under the control of an independent promoter and terminator.IMPORTANCEPlant growth promotion can be enhanced by soil-and rhizosphere-dwelling bacteria by a number of different methods. One method is by promoting nutrient acquisition from soil. Phosphorus is an essential nutrient that plants obtain through soil, but in many cases it is locked up in forms that are not available for plant uptake. Bacteria such as the model bacterium Pseudomonas putida KT2440 can solubilize insoluble soil phosphates by secreting gluconic acid. This chemical is produced from glucose by the activity of the bacterial enzyme glucose dehydrogenase, which requires a coenzyme called PQQ. Here we have studied how the glucose dehydrogenase enzyme and the PQQ coenzyme are regulated according to differences in bacterial growth conditions. We determined that glucose dehydrogenase activity and PQQ production are optimal under conditions when the bacterium is grown with glucose as the sole carbon source and under conditions of low soluble phosphate.