EAGER: Exploratory Studies of Metabolic Water in Plants and Microorganisms

Northern Arizona University, Flagstaff AZ

Investigators

Abstract

Water is produced in the cells of organisms during respiration. This project seeks to understand the importance of this water for plants and soil microorganisms. This metabolic water is potentially of vital importance when external water supply is low. The project will test the idea that metabolic water is important to plants in withstanding drought and repairing drought-induced damage to the plant water transport system. The project will also test the idea that metabolic water provides a means for soil microbes to sustain activity in dry soils. The project will employ novel techniques based on providing a tracer for metabolic water via a chemically distinct form of oxygen that allows distinguishing metabolic water from water that is not produced by metabolism. The techniques developed in this study to monitor metabolism in complex living tissues have potential applications for studying mitochondrial disorders underlying human disease and cancer detection. Undergraduate students will be active participants in the research, receiving training in microbial and plant ecology, and respiratory metabolism. Metabolic water is produced during respiratory metabolism in animals, plants, and aerobic microorganisms. Although its vital importance is well recognized in some animals, virtually nothing is known about the physiological or ecological significance of metabolic water in microorganisms and plants. The project hypothesizes that metabolic water contributes importantly to the water balance of soil microorganisms, prolonging activity in drying soils by providing an internal source of water that slows desiccation and delays the onset of dormancy. For plants, it's hypothesized that metabolic water contributes to the recovery of water transport function in embolized vascular cells by providing a local source of water under positive pressure that contributes to refilling of embolized cells. To test these hypotheses, the project uses a suite of innovative observations, experiments, and modeling activities. A key experimental methodology involves incubations in air containing oxygen gas enriched in the stable isotope of oxygen, 18-O, resulting in 18-O enriched metabolic water that can be distinguished from environmental water by its distinctive isotopic composition. The 18-O studies are augmented with two cutting-edge imaging techniques: high-resolution x-ray computed tomography to visualize refilling of embolized vessels, and stable isotope Raman spectroscopy to locate 18-O labeled metabolic water within cells and tissues. New insights from these studies will be transformational in terms of understanding the interaction of central energy metabolism and water relations in plants and microorganisms.