- Nur Syahidah Zulkefli: Department of Environmental Health Science, Konkuk University, Seoul 05029, Korea.
- Soon-Jin Hwang: Department of Environmental Health Science and Human and Eco-care Center, Konkuk University, Seoul 05029, Korea. ORCID
Nitrogen is globally limiting primary production in the ocean, but some species of cyanobacteria can carry out nitrogen (N) fixation using specialized cells known as heterocysts. However, the effect of N sources and their availability on heterocyst development is not yet fully understood. This study aimed to evaluate the effect of various inorganic N sources on the heterocyst development and cellular growth in an N-fixing cyanobacterium, . Growth rate, heterocyst development, and cellular N content of the cyanobacteria were examined under varying nitrate and ammonium concentrations. exhibited high growth rate both in the presence and absence of N sources regardless of their concentration. Ammonium was the primary source of N in Even the highest concentrations of both nitrate (1.5 g L as NaNO) and ammonium (0.006 g L as Fe-NH-citrate) did not exhibit an inhibitory effect on heterocyst development. Heterocyst production positively correlated with the cell N quota and negatively correlated with vegetative cell growth, indicating that both of the processes were interdependent. Taken together, N deprivation triggers heterocyst production for N fixation. This study outlines the difference in heterocyst development and growth in under different N sources.