Abstract Title

Characterization of nitrate reductase in Microcystis aeruginosa PCC7806 wild type and non-toxic mutant strain

Start Date

24-5-2022 11:30 AM

End Date

24-5-2022 11:45 AM

Abstract

Nitrogen is an essential element for the growth of cyanobacteria. Runoff of nitrate fertilizers into freshwater systems can contribute to the proliferation of cHABS and their toxicity. Characterizing the enzyme activity of nitrate reductase (NR) in Microcystis aeruginosa is an important step to understanding the bloom dynamics of this organism when nitrate is present. Nitrate reductase isolated from the toxin-producing wild type (WT) strain Microcystis aeruginosa PCC7806 and in its non-toxic -mcyB mutant was characterized for suitable electron donors, pH optimum, and substrate affinity. Suitable electron donors for WT strain included ferredoxin reduced by ferredoxin-NADP+ reductase and methyl viologen. No NR activity was detected using NADH, NADPH, FADH2 or ferredoxin reduced by sodium dithionite. Using methyl viologen as the electron donor the WT NR activity showed Michaelis Menten kinetics with a Km(nitrate) of 3.4-7.40 μM. The pH optimum was 8.5 for ferredoxin reduced by ferredoxin-NADP+ reductase, and 10.5 for methyl viologen. These results indicate M. aeruginosa WT NR activity is typical of a bacterial NR and very different from purified NR obtained from Arabidopsis thaliana and Aspergillus nidulans. Differences NR activity between WT and its –mcyB mutant under laboratory conditions will be presented.

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May 24th, 11:30 AM May 24th, 11:45 AM

Characterization of nitrate reductase in Microcystis aeruginosa PCC7806 wild type and non-toxic mutant strain

Nitrogen is an essential element for the growth of cyanobacteria. Runoff of nitrate fertilizers into freshwater systems can contribute to the proliferation of cHABS and their toxicity. Characterizing the enzyme activity of nitrate reductase (NR) in Microcystis aeruginosa is an important step to understanding the bloom dynamics of this organism when nitrate is present. Nitrate reductase isolated from the toxin-producing wild type (WT) strain Microcystis aeruginosa PCC7806 and in its non-toxic -mcyB mutant was characterized for suitable electron donors, pH optimum, and substrate affinity. Suitable electron donors for WT strain included ferredoxin reduced by ferredoxin-NADP+ reductase and methyl viologen. No NR activity was detected using NADH, NADPH, FADH2 or ferredoxin reduced by sodium dithionite. Using methyl viologen as the electron donor the WT NR activity showed Michaelis Menten kinetics with a Km(nitrate) of 3.4-7.40 μM. The pH optimum was 8.5 for ferredoxin reduced by ferredoxin-NADP+ reductase, and 10.5 for methyl viologen. These results indicate M. aeruginosa WT NR activity is typical of a bacterial NR and very different from purified NR obtained from Arabidopsis thaliana and Aspergillus nidulans. Differences NR activity between WT and its –mcyB mutant under laboratory conditions will be presented.