Nitrogen and iron interactions in filamentous cyanobacteria

Abstract

Also investigated was the relationship between siderophore-mediated iron uptake and diazotrophy in Anabaena. It was found that the strain of Anabaena used in these experiments (PCC strain 7120) is unable to make siderophores and fix nitrogen simultaneously, suggesting that previous work linking these two capabilites to competitive dominance may be in error or misinterpreted.The final aspect of this problem which was examined was the possibilty 2 of gratuitous repression of Anabaena siderophore production by manganese in the manner previously described by other investigators in E. coli. No evidence for this type of molecular regulation was found, although maganese did appear to bind to siderophore in the water.

Changes in Proteins Associated with Nitrogen Fixation and Iron Nutrition in the Marine Cyanobacterium Trichodesmium

“…Chemical was used for the spectrophotometric determination of protein in colonies of Trichodesmium. The assay was performed as described in Hutchins (1989) for Trichodesmium colonies and the assay itself as described by the manufacturer for the "Enhanced Protocol". The BCA reagent creates a complex with protein and Cu2 + (the biuret reaction) that results in a colorimetric detection for reduced copper ions (Cul+).…”

“…Ferrozine, a spectrophotometric reagent for iron, was used to determine acid leachable iron content in field collected Trichodesmium colonies. The assay was preformed as described by Hutchins (1989) for Trichodesmium colonies. The assay is a modification of Stookey (1970) and Gibbs (1979).…”

“…Due to the considerable variability in protein and iron content per colony, protein-N to iron ratios were calculated from the di el measurements. The mol to mol protein-N to iron ratios were plotted in Figure 10 which includes the boundaries of the upper and lower limits determined previously by Hutchins (1989) for Trichodesmium samples in the Caribbean Sea. The data indicate that at times, Trichodesmium populations have a higher limit of protein-N to uon ratio of up to 3000.…”

“…Protein nitrogen ·to iron ratios in Trichodesmium colonies from the Caribbean Sea. The N :Fe ratio limits (200 and 700) are taken fromHutchins (1989). filtration apparatus and millipore HA filter to remove salt from the colonies(Figure 11, lanes 7, 8).…”