Milligan, A. J. University of British Columbia, allenm@unixg.ubc.ca
Harrison, P. J. University of British Columbia, pharrisn@unixg.ubc.ca

 
THE INFLUENCE OF IRON AVAILABILITY ON NITROGEN ASSIMILATION IN A MARINE DIATOM
 
Iron limitation has been suspected to influence the ability of diatoms to utilize nitrate as a nitrogen source based on the requirement of iron in the enzymes nitrate (NR) and nitrite reductase (NiR). To investigate the influence of iron limitation on these enzymes, in vitro enzyme assays were used to measure activity in cultures of Thalassiosira weissflogii grown under iron-limiting and replete conditions. Under iron limitation, cultures excreted up to 100 fmol NO2- cell-1 h-1 and NiR activities declined by 50-fold while internal NO2- pools remained relatively constant. Activity of both NR and NiR remained well in excess of nitrogen assimilation rates throughout iron-limited growth. Both C:N ratios and GLN:GLU ratios indicate that iron limitation does not reduce a cell's ability to assimilate nitrate. Rather, it appears that diatoms are limited in their ability to process photons within the photosynthetic electron transport chain which results in nitrite reduction becoming the rate limiting step in nitrogen assimilation.
 
Day: Thursday, Feb. 4
Time: 02:45 - 03:00pm
Location: Sweeney Center
 
Code: SS28TH0245S