Photoperiodic spectral tuning of carbon metabolism in heterotrophic marine flavobacteria

Influence of the constant full-spectrum light and short-to-long wavelengths of the visible spectrum (red, green and blue lights) and the significance of 12 h photoperiod was tested on heterotrophic marine flavobacteria Siansivirga zeaxanthinifaciens CC-SAMT-1T. RNA-seq analysis revealed remarkable qualitative and quantitative variations in terms of gene expression in CC-SAMT-1T with respect to incident lights. While blue light illumination stimulated expression of genes involved in inorganic carbon metabolism, green?red lights largely upregulated the genes participating in high-molecular-weight (HMW) organic carbon metabolism. Constant full-spectrum light also displayed the upregulation of genes involved in the metabolism of HMW organic carbon. Thus, the short-to-long wavelengths of visible light and the 12 h photoperiod most likely to play a key role in the marine carbon cycle by tuning heterotrophic bacterial metabolism. Overall design: Philips MASTER TL-D De Luxe 18W/965 fluorescent lamps were used as a source of full-spectrum light. Red (620–630 nm), green (520–535 nm) and blue (465–485 nm) light emitting diodes (Cree XLamp XP-E2) were used to assess the impact of short-to-long wavelengths. Lamps were installed inside the temperature-controlled orbital shaker incubator. Genome-wide expression was investigated in cell samples cultured under 36 h full-spectrum light (L36.1 and L36.2) illumination. Cell samples cultured under 36 h constant darkness (D36.1 and D36.2) served as controls. Bacterial cells cultured under darkness for 24 h were exposed to 12 h of red, green and blue light illuminations (D24R12, D24G12 and D24B12, respectively) and subjected to genome-wide expression analysis with reference to 36 h dark-incubated cell sample (D36). Analysis were done in duplicates for each sample.