Studied On The Purified Effect On Litopenaeus Vannamei Reared Water For The Photosynthetic Bacteria Isolated From Hainan

Photosynthetic bacteria(PSB)is a kind of microorganism that has photosynthetic pigment and could do phosphorylation under anaerobic conditions.They are widely distributed and play an important role in water purification.They are often used in aquaculture for water quality control.Hainan is located in a tropical area with special climate and water quality conditions.The local PSB strains screened from Hainan can better adapt to the aquatic environment in Hainan,and is more effective in water purification.In this study,108 PSB strains were isolated from 85 water and sediment samples collected in the coastal area of Hainan province.Through the analysis of degradation capacity of chemical oxygen demand(COD),10 highly effective strains were screened.According to the results of molecular identification,10 PSB strains were divided into two families and three genera.H21 strain belongs to Rhodospirillum.S6,W4,Y7,Q3 and A1 belong to Rhodopseudomonas.E10,J1,C7 and D1 belong to Rhodobacter.Result of gram stain showed that all the 10 PSB strains were gram-negative bacteria.The absorption spectra showed that 10 PSB strains were found to have bacteriochlorin a absorption peaks near 860 nm and 800 nm,and carotenoid absorption peaks at 590 nm and 380 nm.S6,E10,J1,C7,Q3,A1 and H21 strains have another carotenoid absorption peaks at 500nm,indicating that these strains contain more kinds of carotenoid.Results of salinity tolerance test showed that 10 PSB strains grew best when NaCl concentration was 0%,and they all grew well when NaCl concentration was 0-3%,indicating that all the 10 PSB strains can be used in fresh water and seawater with salinity of less than 30‰.All the 10 PSB strains grow better under strict anaerobic condition superior to aerobic condition,and belong to facultative anaerobe.Results of physiological and biochemical tests showed that 10 PSB strains had the following commonalities:they can use maltose,xylose,glucose,fructose,sucrose and mannitol as carbon source,but can not use glycerol.Starch hydrolysis and gelatin liquefaction tests were negative.Can not use urea as a nitrogen source.Indole tests were positive.Hydrogen sulfide,nitrate reduction and arginine decarboxylase tests were negative.All the 10 PSB strains contain oxidase and catalase activities.Results of genetic stability detection indicate that both 0 generation and 8 generation of Y7 strain had the strongest COD removal ability,and had the best application potential in COD removal.The ammonia nitrogen removal ability between the 10 PSB strains were different.S6,W4,A1,H21,Y7,C7 and D1 had better ammonia nitrogen removal ability.In addition to E10 and Jl,the ammonia nitrogen removal ability of other eight strains was reduced after 8 generations,indicating that the genetic stability of the ammonia nitrogen removal ability of these 8 PSB strains was poor.All the 10 PSB strains showed strong nitrite removal ability,and both 0 generation and 8 generation of A1 strain had the strongest nitrite removal ability.D1,A1 and H21 stains were used for analysis of the optimum growth conditions.Results showed that the optimum carbon source for all these three stains was sodium acetate,and the optimum nitrogen source was yeast extract.The optimum temperatures were 25-30? and pH was 7.0±0.5.The optimum light intensities for D1 and H21 were 1600-2300 lx,and those for A1 were 1000-2300 lx.The optimized medium formula was:anhydrous sodium acetate 1.5 g/L,ammonium chloride 0.9 g/L,hydrogen phosphate 0.3 g/L,magnesium sulfate 0.4 g/L and yeast extract 2.5 g/L.The 10 PSB strains with final dose of 8 × 102 CFU/ml were put into the shrimp reared water respectively to further verify the purifying effect.The shrimp reared water without PSB addition was set for blank control,and that added with commercial PSB was set for positive control.Results showed that,after 5 days,COD growth rates of all the 10 PSB groups significantly lower than that of blank control,and COD growth rates of A1,Y7,J1 and D1 significantly lower than that of positive control.These results indicate that all the 10 strains have strong COD degradation abilities,and could effectively control the growth of COD,among those,COD degradation abilities of A1,Y7,J1 and D1 were better.Does of ammonia nitrogen in blank control increased continuously.Does of ammonia nitrogen in all the 10 PSB groups decreased,and the removal rate were 64.53-98.23%,which significantly higher than that of blank control.These results indicate that all the 10 strains have strong ammonia nitrogen degradation abilities.Does of nitrite in blank control increased continuously.Does of nitrite in all the 10 PSB groups decreased,and the removal rate were 55.00-77.46%,which significantly higher than that of blank control.Nitrite removal rate of A1 significantly higher than that of positive control.These results indicate that all the 10 strains have strong nitrite degradation abilities,and A1 has the strongest.Combined with the above results,the comprehensive purification ability of A1 strain is strongest,and it has a good application potential in aquaculture.The 10 PSB strains with final dose of 107 CFU/ml were put into the shrimp reared water respectively.Survival rate of shrimp were 96.7-100%after 1 week,indicate that all the 10 PSB strains were harmless to the farming shrimp Litopenaeus vannamei.