Impact of nitrogen and phosphorus on the growth and microcystin‐related gene expression of Microcystis aeruginosa PCC 7806

Abstract

Harmful algal blooms (HABs) have incurred numerous health problems through drinking water or exposure. A better understanding of the growth kinetics and toxin production under different environmental conditions will help develop tools for early‐warning indicators for predicting HABs. Lab‐scale experiments were performed with Microcystis aeruginosa PCC 7806 under varying N:P ratios and temperatures. We observed different growth behaviors for cultures growing at the three temperatures (20, 25, and 30°C). M. aeruginosa exhibited higher growth rates at higher N:P ratios during the incubation at 25 and 30°C. Microcystis 16S rRNA gene abundance correlated well with the cell growth parameters. Based on RT‐qPCR data, the transcripts of mcyA, mcyD, and mcyE were occasionally detected with N:P of 76.86 showing highest detections of all gene transcripts. Intracellular microcystin (MC) production corresponded well with the presence of gene transcripts, while no extracellular MC was detected. These findings would provide valuable insights and beneficial guidance to further explore and predict the impacts of cyanobacterial blooms in freshwater systems.

Introduction to the topical collection on harmful algal blooms

“…A comprehensive characterization of algal species behavior under different nutrient and temperature conditions, such as for microcystin-producing Microcystis aeruginosa PCC 7806, has been lacking. Jafarzadeh et al (2023) built upon this knowledge by evaluating the physiological and genetic activities of M. aeruginosa by evaluating 16S rRNA gene abundance, cell growth and density, and toxin production under varying nitrogen-to-phosphorus ratios and temperatures. The goal of this study, in addition to advancing our understanding, is to ultimately anticipate and prevent toxin production based on gene expression measurements.…”