THE ROLE OF CYANOPHYCIN SYNTHETASE AND CYANOPHYCINASE WITH RESPECT TO NITROGEN AVAILABILITY IN PLANKTOTHRIX AGARDHII

• Published in: The Ohio journal of science Vol. 118; no. 1; p. A44
• Main Authors: Kern, Nicole M, Durham, Kathryn A, Cairns, Jessica, Cintron, Dulce, Cintron, Eleana, Diaz, Arianna, Diaz, Mia, Jeon, Sijoon, Leatherwood, Deanna A, Plantado, Alexa, Webber, Taylor, Wyatt, Jacob R, Dickerson, Sunny S, Neudeck, Michelle J, Bullerjahn, George S, McKay, R Michael
• Format: Journal Article
• Language: English
• Published: Columbus Ohio Academy of Science 01.04.2018
• Subjects: Algal blooms; Arginine; Aspartic acid; Chlorophyll; Chlorosis; Culture; Cyanobacteria; Cyanophycin synthase; Depletion; Enzymes; Eutrophication; Fluorometers; Gene expression; Genes; Nitrogen; Phosphorus; Planktothrix agardhii; Polymerase chain reaction; Primers; Ribonucleic acid; RNA; Storage; Lake Erie
• ISSN: 0030-0950

Unlike the phosphorus dependent algal blooms of western Lake Erie, Sandusky Bay's cyanobacterium Planktothrix agardhii blooms are often dependent on nitrogen inputs. Nitrogen levels of the bay drop significantly by midsummer, but the blooms persist, despite the fact that P. agardhii is a nondiazatrophic organism. Certain strains of cyanobacteria house 2 genes that are responsible for nitrogen storage and utilization. cphA encodes the enzyme cyanophycin synthetase that synthesizes a nitrogen storage polymer of arginine and aspartic acid called cyanophycin. cphB encodes the enzyme cyanophycinase that breaks down cyanophycin. The presence of these 2 genes in Sandusky Bay Pa strain was demonstrated through PCR. It is expected that cphA should be expressed when nitrogen is replete and that cphB should be expressed during nitrogen depletion. In this experiment, 2 cultures of P. agardhii were grown in BG-11 media. The culture was divided, centrifuged and resuspended: one in BG-11 and one in nitrogen-free BG-11. Every 3 days a portion of each culture was filtered for chlorophyll a and RNA was extracted. Furthermore, the color of the cultures was observed daily for signs of nutrient stress. The experiment continued until the nitrogen free culture showed significant signs of chlorosis. The levels of chlorophyll a were determined using a fluorometer to measure any difference between the 2 cultures. RT-PCR was performed on the RNA extracted from the cultures using primers for cphA and cphB to monitor the expression of those genes.