2010 Annual Science Report
Arizona State University Reporting | SEP 2009 – AUG 2010
Stoichiometry of Life, Task 1a: Experimental Studies - Cellular Stoichiometry Under Nutrient Limitation in Chemostats
In this project we are raising several species of “extremophile” microbes at different growth rates under different kinds of element limitation (N, P, and Fe) in order to determine how their “elemental recipes” (in terms of C, N, P, Fe, and other metals) change with environmental conditions. These data will help us understand similar data to be obtained from microbes in natural ecosystems.
This year our chemostat research included work on two species: a cyanobacterium Synechocystis sp. PCC 6803 and a mesophilic bacterium isolated from Cuatro Cienegas, Mexico called Bacillus sp. m3-13. Synechocystis sp. PCC 6803 is a mesophilic, non-nitrogen-fixing photoautotroph and Bacillus sp. m3-13 is a mesophilic heterotroph adapted to low phosphorus environments. This work involved Postdoc Amisha Poret-Peterson, Technician Marcia Kyle, Graduate Student Michelle Knowlton, James Elser, and Ariel Anbar. Synechocystis sp. PCC 6803 chemostats were maintained at two growth rates (10% and 50% of the maximum growth rate) under four treatment conditions (nutrient-replete, phosphorus-limited, nitrogen-limited, and iron-limited). We have analyzed media and biomass samples from these chemostats for content of chlorophyll (biomass only), phosphorus, nitrogen, carbon, and trace elements. Cell counts of each chemostat were done and RNA, DNA, and protein concentrations of cells were quantified. These data are currently being analyzed. Further work planned for Synechocystis sp. PCC 6803 includes analysis of lipid concentrations, assessment of cellular and extracellular alkaline phosphatase activity, and completion of the final growth rate testing. Our work on chemostats this year has also included the design, fabrication, and plumbing/heating of 3 water baths to maintain the temperatures required by Bacillus sp. m3-13 and other thermophilic prokaryotes we plan to grow in chemostats. We are also working on developing an appropriate defined medium for this species.
PROJECT INVESTIGATORS:James Elser
PROJECT MEMBERS:Amisha Poret-Peterson
RELATED OBJECTIVES:Objective 5.1
Environment-dependent, molecular evolution in microorganisms
Co-evolution of microbial communities
Biochemical adaptation to extreme environments
Effects of environmental changes on microbial ecosystems
Adaptation and evolution of life beyond Earth
Biosignatures to be sought in Solar System materials