2014 Annual Science Report
Arizona State University Reporting | SEP 2013 – DEC 2014
Stoichiometry of Life - Task 1 - Laboratory Studies in Biological Stoichiometry
This project component involves a set of studies of 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 different species of microorganisms? Are the changes the same if the organism is limited by a different key nutrient? 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.
Effects of nutrient limitation on microbial stoichiometry and metabolism:
In previous project years, batch cultures of the freshwater unicellular cyanobacterium, Synechocystis sp. PCC 6803 were grown under different nutrient conditions: Complete (media rich in all nutrients; N/P ratio of 100, 18 uM Fe) and Iron-limited (N/P ratio of 100; 1.8 uM Fe). During the exponential phase of growth, all cultures were subjected to analysis of elemental stoichiometry (C:N:P:S:metals), biological macromolecule composition (DNA, RNA, protein, and chlorophyll), transcriptome profiles, and metabolome profiles. The elemental composition of cultures was determined via EA-IRMS (C and N) and ICP-MS (P and metals) and biological macromolecule composition using fluorescent or spectrophotometric methods. Metabolome profiling was conducted using for LC-MS Q-TOF (Liquid Chromatography with Time-of-Flight Mass Spectrometry) and for NMR spectroscopy analyses. Transcriptome profiling was conducted by Ion Torrent sequencing of cDNA derived from rRNA-subtracted RNA extractions.
In the final project year, the findings from these studies, reported in last year’s report, were incorporated into manuscripts in advanced states of preparation.
PROJECT MEMBERS:James Elser
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