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2010 Annual Science Report

Arizona State University Reporting  |  SEP 2009 – AUG 2010

Stoichiometry of Life - Task 1b - Experimental Studies - Microbial Production of Exopolymeric Subtances (EPS)

Project Summary

One way that microscopic plankton affect the Earth system is by producing carbon compounds that can sink to the bottom of the ocean, thus burying C for extended periods. The production of “exopolymeric substances” (EPS), sticky molecules often made from sugars, is such a mechanism. This project seeks to determine some of the basic parameters that affect the production of EPS by marine phytoplankton.

4 Institutions
3 Teams
0 Publications
0 Field Sites
Field Sites

Project Progress

Susanne Neuer and student Amy Hanson refined our methods for quantifying exopolymeric substances (EPS) from liquid cultures of the cyanobacterium Synechococcus sp. WH8102 which we are using as a model organism for the study of aggregation and EPS production by early marine cyanobacteria. Initial experiments indicated that overall carbohydrate concentration followed no trend, but the cell normalized carbohydrate concentration decreased sharply as the culture progressed through exponential phase. We also began using the Alcian Blue (AB) test to quantify acid polysaccharide (APS) production by Synechococcus over time. Our preliminary results showed that, unlike total carbohydrate concentration, APS concentration per cell increased during the exponential growth phase. In the spring, we began using rocker tables in growth chambers with controlled temperature and light conditions to culture Synechococcus. Rocker tables mimic the constant motion cells would experience in the open ocean, conditions which likely affect aggregation by changing the frequency with which cells come into contact with one another, and may also influence production of EPS. Future experiments will include testing the effect of nutrient limitation on EPS production and determining aggregation and sinking rates of the cells in each treatment.

    Susanne Neuer
    Project Investigator
    Amy Hansen
    Doctoral Student

    Alisa Glukhova
    Undergraduate Student

    Kimberly Mohabir
    Undergraduate Student

    Objective 4.1
    Earth's early biosphere.

    Objective 6.1
    Effects of environmental changes on microbial ecosystems