Varied expression in six cellular processes, including photosynthesis, carbon metabolism, phosphate acquisition, nitrogen acquisition, hli (high-light inducible genes), and phage infection. (a) Expression profiles of six cellular processes. For each gene, the mean expression in ten samples was used as its expression value. For six functional categories, the mean and median expression values were normalized to values of ribosomal genes. (b) Enrichment analysis of four expression subclasses (HEG, MEG, LEG, and VEG) for six functional processes (Fisher’s exact test, one-tailed). Core: the core genome; Flexible: the flexible genome, HEG: highly expressed genes; MEG, moderately expressed genes; LEG, lowly expressed genes; VEG, variably expressed genes.