The invasive red alga Grateloupia turuturu Yamada could turn Vibrio parahaemolyticus into nonculturable state in live algal culture.In order to elucidate the mechanism of such an effect,a series of culture experiments...The invasive red alga Grateloupia turuturu Yamada could turn Vibrio parahaemolyticus into nonculturable state in live algal culture.In order to elucidate the mechanism of such an effect,a series of culture experiments were performed in this investigation based on three hypothesized causes,namely bacterial attachment,production of reactive oxygen species （ROS） and the discharge of water soluble secondary metabolic compounds.The results reveal that attachment to the thallus surface of G.turuturu was the major reason for the decrease of V.parahaemolyticus in seawater.Further investigations show that V.parahaemolyticus attachment to the surface of algal thallus in live cultures of seaweeds was a common phenomenon.However,the disappearance of the culturability of V.parahaemolyticus occurred only on the thallus of G.turuturu over 72 h among all six algal species tested.Electron microscopic scanning shows that most of V.parahaemolyticus attached to G.turuturu changed from the initial normal bacilli to coccoid-shape after 72 h.The enclosure experiments by enclosing the algal thallus in tubes demonstrate that the nonculturability of V.parahaemolyticus in the water of live culture of G.turuturu occurred after the physical contact of the V.parahaemolyticus to the alga.The capacity of G.turuturu in affecting the culturability of V.parahaemolyticus was not influenced after inhibition of photosynthesis by treatment of 3（3,4dichlorophenyl）-1 ,1dimethyl urea （DCMU） at non-lethal levels.Production of reactive oxygen species after addition of live culture of bacteria was excluded by on-line analyzing the oxidation of dichlorohydrofluorescein （DCFH） to dichlorofluorescein （DCF） in the presence of peroxidase on a VersaFluor fluorometer.展开更多
Solar radiation varies quantitatively and qualitatively while penetrating through the seawater column and thus is one of the most important environmental factors shaping the vertical distribution pattern of phytoplank...Solar radiation varies quantitatively and qualitatively while penetrating through the seawater column and thus is one of the most important environmental factors shaping the vertical distribution pattern of phytoplankton.The haploid and diploid life-cycle phases of coccolithophores might have different vertical distribution preferences.Therefore,the two phases respond differently to high solar photosynthetically active radiation(PAR,400-700 nm)and ultraviolet radiation(UVR,280-400 nm).To test this,the haploid and diploid Emiliania huxleyi were exposed to oversaturating irradiance.In the presence of PAR alone,the effective quantum yield was reduced by 10%more due to the higher damage rate of photosystem Ⅱ in haploid cells than in diploid cells.The addition of UVR resulted in further inhibition of the quantum yield for both haploid and diploid cells in the first 25 min,partly because of the increased damage of photosystem Ⅱ.Intriguingly,this UVR-induced inhibition of the haploid cells completely recovered half an hour later.This recovery was confirmed by the comparable maximum quantum yields,maximum relative electron transport rates and yields of the haploid cells treated with PAR and PAR+UVR.Our data indicated that photosynthesis of the haploid phase was more sensitive to high visible light than the diploid phase but resistant to UVR-induced inhibition,reflecting the ecological niches to which this species adapts.展开更多
基金The National Natural Science Foundation of China under contract No.30671596
文摘The invasive red alga Grateloupia turuturu Yamada could turn Vibrio parahaemolyticus into nonculturable state in live algal culture.In order to elucidate the mechanism of such an effect,a series of culture experiments were performed in this investigation based on three hypothesized causes,namely bacterial attachment,production of reactive oxygen species （ROS） and the discharge of water soluble secondary metabolic compounds.The results reveal that attachment to the thallus surface of G.turuturu was the major reason for the decrease of V.parahaemolyticus in seawater.Further investigations show that V.parahaemolyticus attachment to the surface of algal thallus in live cultures of seaweeds was a common phenomenon.However,the disappearance of the culturability of V.parahaemolyticus occurred only on the thallus of G.turuturu over 72 h among all six algal species tested.Electron microscopic scanning shows that most of V.parahaemolyticus attached to G.turuturu changed from the initial normal bacilli to coccoid-shape after 72 h.The enclosure experiments by enclosing the algal thallus in tubes demonstrate that the nonculturability of V.parahaemolyticus in the water of live culture of G.turuturu occurred after the physical contact of the V.parahaemolyticus to the alga.The capacity of G.turuturu in affecting the culturability of V.parahaemolyticus was not influenced after inhibition of photosynthesis by treatment of 3（3,4dichlorophenyl）-1 ,1dimethyl urea （DCMU） at non-lethal levels.Production of reactive oxygen species after addition of live culture of bacteria was excluded by on-line analyzing the oxidation of dichlorohydrofluorescein （DCFH） to dichlorofluorescein （DCF） in the presence of peroxidase on a VersaFluor fluorometer.
基金funded by the National Key Research and Development Program(2019YFB1503904)National Natural Science Foundation of China(42076206)+1 种基金Guangdong Basic and Applied Basic Research Foundation(2020A1515011073,2016A030313066)Department of Science and Technology of Guangdong Province(2021B1212050025 and STKJ2021125).
文摘Solar radiation varies quantitatively and qualitatively while penetrating through the seawater column and thus is one of the most important environmental factors shaping the vertical distribution pattern of phytoplankton.The haploid and diploid life-cycle phases of coccolithophores might have different vertical distribution preferences.Therefore,the two phases respond differently to high solar photosynthetically active radiation(PAR,400-700 nm)and ultraviolet radiation(UVR,280-400 nm).To test this,the haploid and diploid Emiliania huxleyi were exposed to oversaturating irradiance.In the presence of PAR alone,the effective quantum yield was reduced by 10%more due to the higher damage rate of photosystem Ⅱ in haploid cells than in diploid cells.The addition of UVR resulted in further inhibition of the quantum yield for both haploid and diploid cells in the first 25 min,partly because of the increased damage of photosystem Ⅱ.Intriguingly,this UVR-induced inhibition of the haploid cells completely recovered half an hour later.This recovery was confirmed by the comparable maximum quantum yields,maximum relative electron transport rates and yields of the haploid cells treated with PAR and PAR+UVR.Our data indicated that photosynthesis of the haploid phase was more sensitive to high visible light than the diploid phase but resistant to UVR-induced inhibition,reflecting the ecological niches to which this species adapts.
