The effects of light, temperature, and coculture on the intracellular microcystin-LR(MCLR) quota of M icrocystis aeruginosa were evaluated based on coculture experiments with nontoxic Dolichospermum( Anabaena) fl os- ...The effects of light, temperature, and coculture on the intracellular microcystin-LR(MCLR) quota of M icrocystis aeruginosa were evaluated based on coculture experiments with nontoxic Dolichospermum( Anabaena) fl os- aquae. The MC-LR quota and transcription of m cy B and m cy D genes encoding MC synthetases in M. aeruginosa were evaluated on the basis of cell counts, high-performance liquid chromatography, and reverse-transcription quantitative real-time PCR. The MC-LR quotas of M. aeruginosa in coculture with a 1/1 ratio of inoculum of the two species were signifi cantly lower relative to monocultures 6-d after inoculation. Decreased MC-LR quotas under coculture conditions were enhanced by increasing the D. fl os- aquae to M. aeruginosa ratio in the inoculum and by environmental factors, such as temperature and light intensity. Moreover, the transcriptional concentrations of mcy B and mcy D genes in M. aeruginosa were signifi cantly inhibited by D. fl os- aquae competition in coculture(P <0.01), lowered to 20% of initial concentrations within 8 days. These data suggested that coculture effects by D. fl os- aquae not only reduced M. aeruginosa 's intracellular MC-LR quota via inhibition of genes encoding MC synthetases, but also that this effect was regulated by environmental factors, including temperature and light intensities.展开更多
Microcystis aeruginosa is a single-celled cyanobacterium, forming large colonies on the surface of freshwater ecosystems during summer, and producing a toxin (microcystin) that in high concentration can be harmful to ...Microcystis aeruginosa is a single-celled cyanobacterium, forming large colonies on the surface of freshwater ecosystems during summer, and producing a toxin (microcystin) that in high concentration can be harmful to humans and animals. These toxic effects can be governed by abiotic environmental conditions including water temperature, light, nutrient abundance, and fluid motion. We investigated the effect of small-scale turbulence on the growth and metabolism of Microcystis aeruginosa using field measurements and laboratory bioreactor investigations. The laboratory setup included two underwater speakers, generating a quasi-homogeneous turbulent flow with turbulent kinetic energy dissipation rates up to 10<sup>-6</sup> m<sup>2</sup>/s<sup>3</sup>, comparable to field values in the lacustrine photic zone. The role of turbulence is quantified by comparing cell number, dissolved oxygen production/uptake, and inorganic carbon uptake in stagnant condition and two sets of experiments with turbulent conditions, quantified by the Taylor micro-scale Reynolds number at Re<sub>λ</sub> = 15 and Re<sub>λ</sub> = 33. The results suggest that turbulence mediates the metabolism of Microcystis aeruginosa measured by the net oxygen production, oxygen uptake, and inorganic carbon uptake. Furthermore, small-scale turbulence marginally influenced Microcystis growth rate estimated from cell population concentration (-5% and 11% for Re<sub>λ</sub> = 33 and Re<sub>λ</sub> = 15, respectively, as compared to stagnant conditions).展开更多
Phytoplankton including blue-green algal or cyanobacterial blooms frequently occurred in aquaculture ponds. Some cyanobacteria produced cyanotoxins that may accumulate in the food web and eventually in the aquaculture...Phytoplankton including blue-green algal or cyanobacterial blooms frequently occurred in aquaculture ponds. Some cyanobacteria produced cyanotoxins that may accumulate in the food web and eventually in the aquaculture products. In this study, accumulatation of microcystins in Nile tilapia (Oreochromis niloticus) and giant freshwater prawn (Macrobrachium rosenbergii) cultured in green water system was investigated.Nile tilapia was cultured in green water system and fish food;green water system with Microcystis aeruginosa Kützingand fish food and green water system with M. aeruginosa. Giant freshwater prawn was cultured: in green water systems with and without toxic M. aeruginosa. Microcystins of 8.32±0.76 and9.35±1.45μg·kg—1 d.w. were detected in fish cultured in green water system with M. aeruginosa and fish food and in green water system with M. aeruginosa, respectively. Microcystins of 14.42±1.63 μg·kg—1 was found in prawn samples. It implied that aquaculture products were likely to be contaminated with microcystins. This finding is useful for aquaculture in terms of food safety.展开更多
基金Supported by the National Natural Science Foundation of China(Nos.31471810,31272081)the Major Science and Technology Program for Water Pollution Control and Treatment(No.2012ZX07101-013-05(02))the Jiangsu Key Technology R&D Program(No.BE2012372)
文摘The effects of light, temperature, and coculture on the intracellular microcystin-LR(MCLR) quota of M icrocystis aeruginosa were evaluated based on coculture experiments with nontoxic Dolichospermum( Anabaena) fl os- aquae. The MC-LR quota and transcription of m cy B and m cy D genes encoding MC synthetases in M. aeruginosa were evaluated on the basis of cell counts, high-performance liquid chromatography, and reverse-transcription quantitative real-time PCR. The MC-LR quotas of M. aeruginosa in coculture with a 1/1 ratio of inoculum of the two species were signifi cantly lower relative to monocultures 6-d after inoculation. Decreased MC-LR quotas under coculture conditions were enhanced by increasing the D. fl os- aquae to M. aeruginosa ratio in the inoculum and by environmental factors, such as temperature and light intensity. Moreover, the transcriptional concentrations of mcy B and mcy D genes in M. aeruginosa were signifi cantly inhibited by D. fl os- aquae competition in coculture(P <0.01), lowered to 20% of initial concentrations within 8 days. These data suggested that coculture effects by D. fl os- aquae not only reduced M. aeruginosa 's intracellular MC-LR quota via inhibition of genes encoding MC synthetases, but also that this effect was regulated by environmental factors, including temperature and light intensities.
文摘Microcystis aeruginosa is a single-celled cyanobacterium, forming large colonies on the surface of freshwater ecosystems during summer, and producing a toxin (microcystin) that in high concentration can be harmful to humans and animals. These toxic effects can be governed by abiotic environmental conditions including water temperature, light, nutrient abundance, and fluid motion. We investigated the effect of small-scale turbulence on the growth and metabolism of Microcystis aeruginosa using field measurements and laboratory bioreactor investigations. The laboratory setup included two underwater speakers, generating a quasi-homogeneous turbulent flow with turbulent kinetic energy dissipation rates up to 10<sup>-6</sup> m<sup>2</sup>/s<sup>3</sup>, comparable to field values in the lacustrine photic zone. The role of turbulence is quantified by comparing cell number, dissolved oxygen production/uptake, and inorganic carbon uptake in stagnant condition and two sets of experiments with turbulent conditions, quantified by the Taylor micro-scale Reynolds number at Re<sub>λ</sub> = 15 and Re<sub>λ</sub> = 33. The results suggest that turbulence mediates the metabolism of Microcystis aeruginosa measured by the net oxygen production, oxygen uptake, and inorganic carbon uptake. Furthermore, small-scale turbulence marginally influenced Microcystis growth rate estimated from cell population concentration (-5% and 11% for Re<sub>λ</sub> = 33 and Re<sub>λ</sub> = 15, respectively, as compared to stagnant conditions).
文摘Phytoplankton including blue-green algal or cyanobacterial blooms frequently occurred in aquaculture ponds. Some cyanobacteria produced cyanotoxins that may accumulate in the food web and eventually in the aquaculture products. In this study, accumulatation of microcystins in Nile tilapia (Oreochromis niloticus) and giant freshwater prawn (Macrobrachium rosenbergii) cultured in green water system was investigated.Nile tilapia was cultured in green water system and fish food;green water system with Microcystis aeruginosa Kützingand fish food and green water system with M. aeruginosa. Giant freshwater prawn was cultured: in green water systems with and without toxic M. aeruginosa. Microcystins of 8.32±0.76 and9.35±1.45μg·kg—1 d.w. were detected in fish cultured in green water system with M. aeruginosa and fish food and in green water system with M. aeruginosa, respectively. Microcystins of 14.42±1.63 μg·kg—1 was found in prawn samples. It implied that aquaculture products were likely to be contaminated with microcystins. This finding is useful for aquaculture in terms of food safety.
