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Photoautotrophs are organisms that can utilize light energy from sunlight and elements (such as carbon) from inorganic compounds to produce organic materials needed to sustain their own metabolism (i.e. autotrophy). Such biological activities are known as photosynthesis, and examples of such organisms include plants, algae and cyanobacteria.
Purple bacteria or purple photosynthetic bacteria are Gram-negative proteobacteria that are phototrophic, capable of producing their own food via photosynthesis. [1] They are pigmented with bacteriochlorophyll a or b , together with various carotenoids , which give them colours ranging between purple, red, brown, and orange.
In general, photosynthesis in cyanobacteria uses water as an electron donor and produces oxygen as a byproduct, though some may also use hydrogen sulfide [79] a process which occurs among other photosynthetic bacteria such as the purple sulfur bacteria. Carbon dioxide is reduced to form carbohydrates via the Calvin cycle. [80]
The non-absorbed part of the light spectrum is what gives photosynthetic organisms their color (e.g., green plants, red algae, purple bacteria) and is the least effective for photosynthesis in the respective organisms.
Green plants and photosynthetic bacteria are photoautotrophs. Photoautotrophic organisms are sometimes referred to as holophytic. [3] Oxygenic photosynthetic organisms use chlorophyll for light-energy capture and oxidize water, "splitting" it into molecular oxygen.
Photosynthesis is the main means by which plants, algae and many bacteria produce organic compounds and oxygen from carbon dioxide and water (green arrow). An autotroph is an organism that can convert abiotic sources of energy into energy stored in organic compounds, which can be used by other organisms.
The purple sulfur bacteria (PSB) are part of a group of Pseudomonadota capable of photosynthesis, collectively referred to as purple bacteria. They are anaerobic or microaerophilic , and are often found in stratified water environments including hot springs , stagnant water bodies, as well as microbial mats in intertidal zones.
Purple non-sulfur bacteria, green non-sulfur bacteria, and heliobacteria are examples of bacteria that carry out this scheme of photoheterotrophy. Other organisms, including halobacteria and flavobacteria [8] and vibrios [9] have purple-rhodopsin-based proton pumps that supplement their energy supply.