A novel function of Extracellular Vesicles produced from rhodopsins-containing Flavobacterium Sediminicola sp. YIK13

Abstract

Diverse marine prokaryotes possess rhodopsin proteins like PR (ProteoRhodopsin) and NaR (SodiumRhodopsin) that interact with light and convert it into bioenergy for growth or into sensory information. One class of energy-harvesting photo proteins called rhodopsins consists of single, membrane-embedded protein covalently bound to a light-sensitive pigment, chromophore retinal. We concentrated and purified the extracellular vesicles (EVs) produced from rhodopsins-containing a parent bacterium, Sediminicola sp. YIK13 (S13), using by ultra membrane filtration followed by CsCl density equilibrium ultracentrifugation. The production rate of S13EVs was estimated by 3.97 × 1013 ml-1 from the total number of parental bacteria, 6.67 × 109 ml-1. The buoyant density of S13EVs ranged from 1.3730 to 1.4065 g cm-3. S13EVs showed a spherical shape without any tail. The range of diameter was between 88 to 227 nm and the median size was 117 nm. Interestingly, S13EVs contained orange color pigment as same as parental cells. The absorbance of S13EVs indicated the presence of carotenoid and PR pigments which were certainly packaged from parental cells. S13EVs showed the light driven proton pump activity as similar as the parental cells although the EVs represented stronger proton inward pump activity rather than that of parental cells. This is the first report of extracellular vesicles of which membrane bound pigments like carotenooteins called rhodopsins consists of single, membrane-embedded protein covalently bound to a light-sensitive pigment, chromophore retinal. We concentrated and purified the extracellular vesicles (EVs) produced from rhodopsins-containing a parent bacterium, Sediminicola sp. YIK13 (S13), using by ultra membrane filtration followed by CsCl density equilibrium ultracentrifugation. The production rate of S13EVs was estimated by 3.97 × 1013 ml-1 from the total number of parental bacteria, 6.67 × 109 ml-1. The buoyant density of S13EVs ranged from 1.3730 to 1.4065 g cm-3. S13EVs showed a spherical shape without any tail. The range of diameter was between 88 to 227 nm and the median size was 117 nm. Interestingly, S13EVs contained orange color pigment as same as parental cells. The absorbance of S13EVs indicated the presence of carotenoid and PR pigments which were certainly packaged from parental cells. S13EVs showed the light driven proton pump activity as similar as the parental cells although the EVs represented stronger proton inward pump activity rather than that of parental cells. This is the first report of extracellular vesicles of which membrane bound pigments like caroteno