MICROBIAL METABOLISMS OF REDUCED PHOSPHOROUS COMPOUNDS

拟议研究的长期目标是鉴定参与磷化合物氧化还原反应的微生物代谢过程，并对其进行分子、遗传和生化表征。这些反应很少被研究，代表了这种重要元素的生物化学的新方面，这种重要元素在所有活着的有机体的新陈代谢中起着核心作用。已知，包括人类在内的许多生物体中都存在还原P化合物的产生和消费。这些化合物的代谢对于这些化合物在发现它们的生物体中的自然作用以及对于广泛用于工业、农业和军事目的的人造还原P化合物的毒性和环境持久性具有重要意义。此外，磷是许多生态系统中的限制性营养物质。磷的氧化还原反应可能在这一所需养分的生物利用度和全球循环中发挥重要作用。为了进一步了解这些过程，我们分离了一些微生物，它们具有涉及P化合物氧化还原化学的新的生化途径。这里提出的实验涉及在遗传和生化水平上对这些反应进行鉴定和表征。这些实验的具体目标是：1)用标准的生化方法纯化和鉴定斯氏假单胞菌P氧化途径中的两种新的酶，2)利用突变分析和转录报告基因研究来鉴定参与该P氧化途径的14个基因的功能和遗传调控，3)大肠杆菌氧化亚磷酸盐的新途径的分子、遗传和生化特征，4)一种新的细菌分离株对次磷酸盐厌氧氧化的新途径的分子遗传学特征，以及5)具有其他涉及P氧化还原反应的新代谢途径的生物体的分离和鉴定。

The long-term objective of the proposed research is the identification and molecular, genetic and biochemical characterization of microbial metabolic processes involved in oxidation-reduction reactions of phosphorus compounds. These reactions have been little studied and represent novel aspects of the biochemistry of this important element, which plays a central role in the metabolism of all living organisms. The production and consumption of reduced P compounds are known to occur in many organisms, including humans. The metabolism of these compounds has importance with respect to the natural roles of these compounds in the organisms where they are found, and with respect to the toxicity and environmental persistence of man-made reduced P compounds, which are widely used for industrial, agricultural and military purposes. Further, phosphorus is the limiting nutrient in many ecosystems. Redox reactions of phosphorus may play an important role in the bioavailability and global cycling of this required nutrient. To further our understanding of these processes we have isolated a number of microorganisms that possess novel biochemical pathways involving redox chemistry of P compounds. The experiments proposed here involve identification and characterization of these reactions at the genetic and biochemical levels. The specific goals of these experiments are: 1) purification and characterization by standard biochemical approaches of two novel enzymes involved in a P oxidation pathway in Pseudomonas stutzeri, 2) characterization of the functions and genetic regulation of the 14 genes (at least) involved in this P. stutzeri pathway using mutant analysis and transcriptional reporter gene studies, 3) molecular, genetic, and biochemical characterization of a novel pathway for oxidation of phosphite by Escherichia coli, 4) molecular genetic characterization of a novel pathway for anaerobic hypophosphite oxidation by a new bacterial isolate, and 5) isolation and characterization of organisms that possess other novel metabolic pathways involving P redox reactions.