Phenotypic niche partitioning and transcriptional responses of Microcystis aeruginosa in a spatially heterogeneous environment

Abstract

Variant morphotypes (smooth; S-type and wrinkled; W-type cells) of Microcystis aeruginosa KW strain were observed in bloom samples and during the cultivation of cells in static broth cultures. RNA-seq based whole transcriptome sequencing was performed to examine the pattern of gene expression in these morphotypes. In total 493 differentially expressed transcripts were identified between the two morphotypes. Genes involved in photosynthesis, photosynthesis-related antenna proteins and oxidative phosphorylation were significantly upregulated in W-type cells relative to the control (S-type cells). Here we discussed the roles of these genes and showed that M. aeruginosa responds and acclimates to subtle variations in environmental parameters, especially light, through alteration of the transcript levels of relevant genes. Furthermore, additional physiological experiments such as analyses of photosynthetic activity, redox state and exopolysaccharide production provided further evidence and confirmed the validity of the transcriptomic results. The findings of this study provide greater insight into the metabolic pathways and complex mechanisms that may regulate the interaction and niche adaptation of this important bloom-forming organism in fluctuating environmental conditions.