Boyer, G. L.. State University of New York, glboyer@esf.edu
Szmyr, D. L.. State University of New York, dbszmyr@mailbox.syr.edu
Alexander, J. A.. State University of New York, jealexan@mailbox.syr.edu
La Roche, J. Brookhaven National Laboratory, laroche@sun2.bnl.gov

 
METABOLIC MARKERS FOR THE STUDY OF IRON LIMITATION IN THE BROWN TIDE ALGA AUREOCOCCUS ANOPHAGEFFERENS
 
Blooms of the pelagophyte, Aureococcus anophagefferens are responsible for the brown tides that occur in the Peconic Estuary on Long Island. The trace element Fe has been implicated in controlling this bloom formation. A. anophagefferens (CCMP1708) was grown in trace-metal defined artificial seawater, and iron, chelated with EDTA, was added at concentrations of 0, 1, 11, 110, 1100, and 11000 nM. Cells were serially transferred through 5 culture cycles, and the several different indicators of iron limitation were examined. No difference in growth yield or growth rate, as determined by in vivo fluorescence or cell number, was observed with decreasing amounts of added iron. However two physiological indicators of iron limitation, chlorophyll per cell and Fv/Fm (e.g. DCMU-enhanced fluorescence) decreased when added iron concentrations dropped below 100 nM. The cultures did not produce siderophores as determined using the HPLC-55Fe binding assay but did have constitutive levels of ferric chelate reductase activity (2-23 nmols FeHEDTA reduced min-1 mg protein-1). This reductase activity did not increase with decreasing added iron. Low levels of added iron did induce formation of the iron-replacement protein flavodoxin. These results suggest A. anophagefferens has a low iron requirement, with the minimal iron quota between 10-20 nM. Aureococcus has developed efficient mechanisms (reductive uptake and iron-sparing) to obtain sufficient iron to support maximal growth during bloom formation. (This work was supported by New York Sea Grant, the National Oceanic and Atmospheric Administration's Coastal Ocean Program, and by the Suffolk County Department of Health Services.)
 
Day: Friday, Feb. 5
Time: 03:30 - 03:45pm
Location: Eldorado Hotel
 
Code: SS42FR0330E