2012 Annual Science Report
Arizona State University Reporting | SEP 2011 – AUG 2012
Stoichiometry of Life - Task 1 - Laboratory Studies in Biological Stoichiometry
This project component involves a diverse set of studies of various microorganisms with which we are trying to better understand how living things use chemical elements (nitrogen, phosphorus, iron, etc) and how they cope, in a physiological sense, with shortages of such elements. For example, how does the “elemental recipe of life” change when an organism is starved for phosphorus or nitrogen or iron? Is this change similar for diverse species of microorganisms? Furthermore, how does an organism shift its patterns of gene expression when it is starved by various nutrients? This will help in interpreting studies of gene expression in natural environments, including extreme environments relevant to astrobiology.
Effects of nutrient limitation on microbial stoichiometry and metabolism: During September-October 2011 we established 30 batch cultures grouped in 4 different treatments. Led by Albert Rivas (visiting PhD student from Autonomous University of Barcelona), we grew the cyanobacterium Synechocystis sp. PCC6803 under different nutrient conditions: Complete (media rich in all nutrients; N/P ratio of 100), Nitrogen-limited; media with low concentration of N; N/P ratio of 10), Phosphorus-limited; (media with low concentrations of P; N/P ratio of 1000); and Iron-limited (media with low concentration of Fe; 10 times less Fe than complete media).
After several generations of growth, all cultures were harvested to obtain data on various response parameters such as elemental stoichiometry (C:N:P:etc), metabolomics, and quantification of DNA and RNA, protein, chlorophyll, and cell counts.
Regarding the metabolomic analyses, the harvested cyanobacteria were first lyophilized, avoiding any enzymatic reaction. The extractions for the samples were performed in April and May 2012 to prepare them for LC-MS Q-TOF analysis (Liquid Chromatography with Time-of-Flight Mass Spectrometry) and for NMR spectroscopy analyses. The extractions of LC-MS were aimed mainly at detecting polar and semi-polar compounds while the extracts for NMR analyses followed a protocol developed by Rivas aimed mainly at polar compounds such as sugars and amino acids. Metabolomic analyses are still in process. LC-MS analyses were performed at King’s College London and NMR analyses were recently performed at the Autonomous University of Barcelona. Elemental and macromolecular data are available and await integration with the metabolomic data.
Interactions of molybdenum with other biogeochemical cycles.
In order to determine the regulation of the putative Mo storage protein “Mop” in freshwater heterocystous cyanobacteria, Glass and undergraduate research assistant Eric Hughes performed various experiments manipulating Mo supplies to with the model organism Nostoc sp. PCC 7120. A manuscript reporting results from this study has been submitted.
PROJECT INVESTIGATORS:James Elser
PROJECT MEMBERS:Ariel Anbar
RELATED OBJECTIVES:Objective 5.2
Co-evolution of microbial communities
Biochemical adaptation to extreme environments
Effects of environmental changes on microbial ecosystems
Adaptation and evolution of life beyond Earth