Cyanobacteria have evolved effective adaptive mechanisms to improve photosynthesis and CO 2 fixation. The central CO 2 -fixing machinery is the carboxysome, which is composed of an icosahedral proteinaceous shell encapsulating the key carbon fixation enzyme, Rubisco, in the interior. Controlled biosynthesis and ordered organization of carboxysomes are vital to the CO 2 -fixing activity of cyanobacterial cells. However, little is known about how carboxysome biosynthesis and spatial positioning are physiologically regulated to adjust to dynamic changes in the environment. Here, we used fluorescence tagging and live-cell confocal fluorescence imaging to explore the biosynthesis and subcellular localization of b-carboxysomes within a model cyanobacterium, Synechococcus elongatus PCC7942, in response to light variation. We demonstrated that b-carboxysome biosynthesis is accelerated in response to increasing light intensity, thereby enhancing the carbon fixation activity of the cell. Inhibition of photosynthetic electron flow impairs the accumulation of carboxysomes, indicating a close coordination between b-carboxysome biogenesis and photosynthetic electron transport. Likewise, the spatial organization of carboxysomes in the cell correlates with the redox state of photosynthetic electron transport chain. This study provides essential knowledge for us to modulate the b-carboxysome biosynthesis and function in cyanobacteria. In translational terms, the knowledge is instrumental for design and synthetic engineering of functional carboxysomes into higher plants to improve photosynthesis performance and CO 2 fixation.

The spatial protein organization, topography and physical mechanics of native carboxysomes, the self-assembling carbon-fixation machinery in cyanobacteria, were characterized.

The structural dynamics and flexibility of cell membranes play fundamental roles in the functions of the cells, i.e., signaling, energy transduction, and physiological adaptation. The cyanobacterial thylakoid membrane represents a model membrane that can conduct both oxygenic photosynthesis and respiration simultaneously. In this study, we conducted direct visualization of the global organization and mobility of photosynthetic complexes in thylakoid membranes from a model cyanobacterium, Synechococcus elongatus PCC 7942, using high-resolution atomic force, confocal, and total internal reflection fluorescence microscopy. We visualized the native arrangement and dense packing of photosystem I (PSI), photosystem II (PSII), and cytochrome (Cyt) b6f within thylakoid membranes at the molecular level. Furthermore, we functionally tagged PSI, PSII, Cyt b6f, and ATP synthase individually with fluorescent proteins, and revealed the heterogeneous distribution of these four photosynthetic complexes and determined their dynamic features within the crowding membrane environment using live-cell fluorescence imaging. We characterized red light-induced clustering localization and adjustable diffusion of photosynthetic complexes in thylakoid membranes, representative of the reorganization of photosynthetic apparatus in response to environmental changes. Understanding the organization and dynamics of photosynthetic membranes is essential for rational design and construction of artificial photosynthetic systems to underpin bioenergy development. Knowledge of cyanobacterial thylakoid membranes could also be extended to other cell membranes, such as chloroplast and mitochondrial membranes.

Burning mouth syndrome (BMS) is an idiopathic condition that manifests itself primarily with the onset of a burning sensation. The aim of this research was to perform photobiomodulation therapy (PBM) using a diode laser on the oral mucosa of BMS patients, followed by an objective evaluation of the morphological changes in the vascular bed underlying the mucosa using polarized light videocapillaroscopy. A group of 40 patients were included in the study. The patients were randomly divided into two groups (using simple randomization) as follows: 20 patients were assigned to the laser group and 20 patients were assigned to the placebo group. Each patient of the laser group received eight irradiations (with 4 Watt of power, wavelength 800 nm, energy 1200 Joules, irradiation time of 300 s, energy density 50 J/cm2, 60 mW continuous wave laser, and irradiance 180 mW/cm2), twice a week, blinded to the type of irradiation administered, for four consecutive weeks. The patients in the placebo group underwent the same sessions as the other patients, the only difference was the non-emission of the laser. An initial check of the vascular bed was performed with a polarized light videocapillaroscope. This was followed by treatment with a therapeutic diode laser and a subsequent check with a videocapillaroscope. We observed that in the group of patients who underwent laser therapy, there was a lasting improvement in symptoms. The capillary oral bed of patients in the placebo group did not show any statistically significant difference (p > 0.05). In the laser group we observed the following: in the buccal mucosa the diameter of the capillary had a reduction of 3 μm; in the upper lip mucosa, there was a reduction of 3 μm; in the lower lip mucosa, there was a reduction of 3 μm; and in the dorsal lingual surface, there was a reduction of 2 μm. An increase in capillary length was also obtained in all irradiated regions in the laser group patients (p < 0.05). PBM induces microcirculatory changes that are still present over a long period of time, such as an improvement in the clinical picture. The improvement in the symptoms has been correlated to the reduction of the capillary diameter. The placebo effect only led to a temporary improvement in symptoms that were unrelated to changes in the microcirculatory pattern.

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