Project description: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.
Project description:Analysis of marine cyanobacteria and proteobacteria genomes has provided a profound understanding of the life strategies of these organisms and their ecotype differentiation and metabolisms. However, a comparable analysis of the Bacteroidetes, the third major bacterioplankton group, is still lacking. In the present paper, we report on the genome of Polaribacter sp. strain MED152. On the one hand, MED152 contains a substantial number of genes for attachment to surfaces or particles, gliding motility, and polymer degradation. This agrees with the currently assumed life strategy of marine Bacteroidetes. On the other hand, it contains the proteorhodopsin gene, together with a remarkable suite of genes to sense and respond to light, which may provide a survival advantage in the nutrient-poor sun-lit ocean surface when in search of fresh particles to colonize. Furthermore, an increase in CO(2) fixation in the light suggests that the limited central metabolism is complemented by anaplerotic inorganic carbon fixation. This is mediated by a unique combination of membrane transporters and carboxylases. This suggests a dual life strategy that, if confirmed experimentally, would be notably different from what is known of the two other main bacterial groups (the autotrophic cyanobacteria and the heterotrophic proteobacteria) in the surface oceans. The Polaribacter genome provides insights into the physiological capabilities of proteorhodopsin-containing bacteria. The genome will serve as a model to study the cellular and molecular processes in bacteria that express proteorhodopsin, their adaptation to the oceanic environment, and their role in carbon-cycling.
