Electronic Thesis and Dissertation Repository

Degree

Master of Science

Program

Biology

Supervisor

Charles G. Trick

2nd Supervisor

Irena F. Creed

Joint Supervisor

Abstract

The cyanobacterium M. aeruginosa is an important bloom former in freshwater environments. We investigated the growth, photosynthesis and toxin contents of two toxic strains of M. aeruginosa, CPCC 299 and CPCC 300, under a combination of nitrogen supply (nitrate or ammonium) and depleted or replete Molybdenum (Mo) and/or Iron (Fe) concentrations. When Mo and Fe were supplied at growth-replete levels, M. aeruginosa grew equally well on nitrate and ammonium. Reducing Fe dramatically reduced growth rate efficiency when the cells were supplied with nitrate, but not with ammonium. In contrast, the removal of Mo from the medium did not impair growth or nitrogen utilization rates regardless of the form of nitrogen available but impacted negatively photosynthetic capacity. Experiments designed to assess if excess Fe could “mask” the Mo-limitation by replacing key physiological processes with Fe revealed the opposite was true: addition of Mo alleviated the stresses associated with Fe-limitation.


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