Is an organism which uses the sun's light to directly power its metabolic pathways and which type of microorganism derives nutrition from organic compounds?
Organisms using light as energy source are called phototrophic (as opposed with chemotropic organisms which need to degrade organic compound for energy supply). Among the phototrophs, there are the photolithotropic organisms which take redox equivalents (= electrons) for both energy metabolism and biosynthesis from inorganic donors. Examples are the plants or cyanobacteria, which use water as electron donor, as well as green sulfur bacteria (Chlorobia) or sulfur-dependent purple bacteria (Chromaticeae) using H2S or certain strains of green non-sulfur bacteria (Chloroflexaceae) which can use H2 as electron source. Most of these organisms are simultaneously autotrophic, i.e. reduce CO2 as only C-source to biomass, however, even among these organisms, there are examples where they employ photolithotrophy and still use some organic compounds for biosynthesis (hetertrophy or mixotrophy). Furthermore, there are many known photoorganotrophic bacteria which depend on the presence of organic compounds as electron donor for phototrophic energy conservation as well as for biosynthesis. These are e.g. the sulfur-independent purple bacteria (Genera Rhodobacter, Rhodospirillum, Rhodocyclus, etc), which always need organics (e.g. malate, acetate, benzoate) to re-plenish the bacteriochlorphylls after they lost electrons due to the light-activated intramolecular transfer from BChl to quinone (even with cyclic electron transport, some electrons are lost for synthesis of NADPH and the reduced quuinone pool has to be filled up with electrons from organic substrates). The elctrons from oxidising the organics are provided to the quinone pool via the usual metabolic pathways (e.g. via NADH and respiratory complex I).
Autotrophs are the producers in the food chain, meaning they create their own nutrients and energy. Kelp, like most autotrophs, creates energy through a process called photosynthesis. An autotroph is an organism that can produce its own food using light, water, carbon dioxide, or other chemicals. They introduce chemical energy and fixed carbon into ecosystems by using light to synthesize sugars. Since these organisms produce their own food that is, fix their own carbon using light energy, they are photoautotrophs. Producers such as plants, algae, and cyanobacteria use the energy from sunlight to make organic matter from carbon dioxide and water. An autotroph is an organism that can produce its own food using light, water, carbon dioxide, or other chemicals. Because autotrophs produce their own food, they are sometime producers. Plants are called autotrophs because they can use energy from light to synthesize, or make, their own food source. Many people believe they are “feeding” a plant when they put it in soil, water it, or place it outside in the Sun, but none of these things are considered food. Chemoheterotrophs: microbes that use organic chemical substances as sources of energy and organic compounds as the main source of carbon. Autotrophic organisms take inorganic substances into their bodies and transform them into organic nourishment. Chemoautotrophs are able to synthesize their own organic molecules from the fixation of carbon dioxide. These organisms are able to produce their own source of food, or energy. The energy required for this process comes from the oxidation of inorganic molecules such as iron, sulfur or magnesium. Because most autotrophs transform sunlight to make food, we call the process they use photosynthesis. Only three groups of organisms plants, algae, and some bacteria - are capable of this life-giving energy transformation. Autotrophs make food for their own use, but they make enough to support other life as well.
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