In addition, cells also contain carbon storage substances such as glycogen, poly-β-hydroxybutyric acid, coenzyme Q, antiviral substances and growth promoting factors, which have high feed value and broad application prospects in aquaculture. Under anaerobic illumination, PSB can use low-molecular-weight organic compounds such as low-molecular-weight fatty acids, various dicarboxylic acids, alcohols, sugars, aromatic compounds, etc. as electron acceptors of photosynthesis, and carry out heterotrophic growth of light energy. Under dark conditions, organic substances can be used as respiratory substrates for aerobic or heterotrophic growth. Photosynthetic bacteria can not only assimilate CO2 by light energy under anaerobic illumination, but also nitrogen fixation and hydrogen production under certain conditions. In addition, some strains can also produce hydrogen through pyruvate metabolism system under dark anaerobic conditions. Photosynthetic bacteria can also use many organic substances, such as organic acids. Alcohol and sugar can transform some toxic substances, such as H2S and some aromatic compounds. Through biotransformation, PSB can synthesize bacterial proteins with no toxic side effects and rich in various nutrients, which not only improves the ecological environment, but also provides high-quality feed materials for aquaculture. The contents of vitamin B 12, biotin, pantothenic acid, carotenoid, chlorophyll and folic acid related to hematopoiesis and hemoglobin formation in PSB bacteria are much higher than those in general microorganisms, especially the D- isomer of biotin which cannot be synthesized artificially. These substances have important physiological activities in animals. In aquaculture, according to the content of dissolved oxygen in water, the aquaculture pond can be divided into aerobic zone and anaerobic zone from surface to bottom. Surface organisms are flourishing and the water quality is generally good; The excrement of fish and shrimp and unconsumed food residues are piled up on the bottom layer, which is rich in organic matter, which leads to the proliferation of microorganisms and consumes a lot of oxygen in the water, leading to the formation of anaerobic environment on the bottom layer, and the proliferation of sulfate-reducing bacteria, which produces hydrogen sulfide and acidic substances toxic to fish and shrimp. The environment at the bottom of the culture ground is just the right condition for photosynthetic bacteria to survive. One is anaerobic conditions, and the other is that light passes through a filter covering an aerobic water layer, so that photosynthetic bacteria can absorb light with a wavelength of 450-550 nm suitable for growth. Photosynthetic bacteria take underground fish and shrimp excreta, food residues, toxic and harmful hydrogen sulfide and acidic substances as substrates, multiply in large quantities, increase the dissolved oxygen content in water, adjust pH, reduce the contents of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen, and reduce the accumulation of sludge at the bottom of the pond, which is beneficial to the increase of algae and microorganisms and the purification of water quality. PSB can perform physiological functions such as photosynthesis, aerobic respiration, nitrogen fixation and carbon fixation. , rich in protein, vitamins, growth promoting factors, immune factors and other nutrients. It is equivalent to antibiotics in function and safer, and it is one of the promising research fields in bioengineering. Photosynthetic bacteria preparation also has unique function of resisting diseases and promoting growth, which greatly improves the production performance and shows great potential in application. Others have broad application prospects in water purification, fish and shrimp breeding, livestock and poultry breeding, organic fertilizer and new energy development.