Rainwater contains substantial bacteria and rain is an efficient pathway for the dissemination of bacteria from the atmosphere to land and water surfaces.However,quantitative information on rainwater bacteria is very ...Rainwater contains substantial bacteria and rain is an efficient pathway for the dissemination of bacteria from the atmosphere to land and water surfaces.However,quantitative information on rainwater bacteria is very limited due to the lack of a reliable method.In this study,the epifluorescence microscopy enumeration with the LIVE/DEAD BacLight Bacterial Viability Kit stain was verified to quantify the abundance of viable and non-viable bacterial cells in rainwater,with the 4',6-diamidino-2-phenylindole(DAPI) stain for the reference of total cell counts.Results showed that the total counts of bacterial cells by LIVE/DEAD BacLight staining were consistent with those by DAPI staining,and the average detection efficiency was(109 ± 29)%.The ratio of cell count with glutaraldehyde fixation to that without fixation was(106 ± 5)%on average.The bacterial concentration in negative control was usually an order of magnitude lower than that in rainwater samples.However,in case of small precipitation,the abundance in negative control could be more than that in rainwater samples.These results indicate that the enumeration with LIVE/DEAD BacLight bacterial viability assay coupled with glutaraldehyde fixation and careful negative control investigation is an approach applicable to the measurement of the concentration and viability of bacterial cells in rainwater.展开更多
Fildes Peninsula, in King George Island, Antarctica, has a great concentration of international facilities, and it has clearly been affected by human activities. The objective of this 5-year study was to assess the im...Fildes Peninsula, in King George Island, Antarctica, has a great concentration of international facilities, and it has clearly been affected by human activities. The objective of this 5-year study was to assess the impact of anthropogenic activities on the bacterial abundance in water bodies close to Artigas Antarctic Scientific Base (BCAA, in Spanish Base Cientifica Antdrtica Artigas). Water samples from areas under different human influence (Uruguay Lake, nearby ponds, and meltwater from Collins Glacier) were aseptically collected and refrigerated until processed. The number of heterotrophic bacteria and Pseudomonas spp. was analyzed using a culture-dependent approach. Physico-chemical properties of the water samples (temperature, pH, and conductivity) were also determined. Results showed that water from the highly affected area, Uruguay Lake, where the pump that provides water to the BCAA is located, did not suffer significant fluctuations in heterotrophie bacterial abundance (10^4- 10^5 CFU.mL^-1); however, Pseudomonas abundance increased until becoming the predominant population. In other water samples, the number of heterotrophie bacteria and Pseudomonas gradually increased during this 5-year study, by 2014 reaching similar values to those observed for Uruguay Lake. The implications of human activities on Antarctic bacterial abundance are discussed.展开更多
Low availability of phosphorus(P) is a major constraint for optimal crop production, as P is mostly present in its insoluble form in soil. Therefore,phosphate-solubilizing bacteria(PSB) from paddy field soils of the I...Low availability of phosphorus(P) is a major constraint for optimal crop production, as P is mostly present in its insoluble form in soil. Therefore,phosphate-solubilizing bacteria(PSB) from paddy field soils of the Indo-Gangetic Plain, India were isolated, and their abundance was attempted to be correlated with the physicochemical characteristics of the soils. Ninety-four PSB were isolated on Pikovskaya’s agar medium, and quantitative phosphate solubilization was evaluated using NBRIP medium. The isolates solubilized P up to a concentration of 1 006 μg mL-1 from tricalcium phosphate with the secretion of organic acids. These isolates were identified by 16 S rRNA gene sequence comparison, and they belonged to Gammaproteobacteria(56 isolates),Firmicutes(28 isolates), Actinobacteria(8 isolates), and Alphaproteobacteria(2 isolates). Phylogenetic analysis confirmed the identification by clustering the isolates in the clade of the respective reference organisms. The correlation analysis between PSB abundance and physicochemical characteristics revealed that the PSB population increased with increasing levels of soil organic carbon, insoluble P, K+, and Mg2+. The promising PSB explored in this study can be further evaluated for their biofertilizer potential in the field and for their use as potent bio-inoculants.展开更多
Fluoride(F^(-))is widespread in aquatic environments;however,it is not clear whether the fluctuation of F^(-)concentrations in overlying lake water affects the composition and migration of dissolved organic matter(DOM...Fluoride(F^(-))is widespread in aquatic environments;however,it is not clear whether the fluctuation of F^(-)concentrations in overlying lake water affects the composition and migration of dissolved organic matter(DOM)from sediment.A case study was presented in Sand Lake,China,and an experiment was conducted to analyze the influence of different F^(-)concentrations in overlying water on DOM characteristics.Diffusion resulted in similarities in DOM components between overlying and pore waters,and bacterial activities and enzyme variation resulted in differences between them.Higher F^(-)concentrations in overlying water resulted in a higher pH of pore water,which favored the enrichment of protein-like substances.Higher F^(-)concentrations caused lower DOM concentrations and lower maximum fluorescence intensities(Fmax)of protein-like components in pore water.The F^(-)concentrations had significantly negative correlations with Shannon indexes(P<0.05).Thiobacillus influenced the migration of tyrosinelike substances by decreasing the pH of pore water.Trichococcus and Fusibacter altered the Fmax of protein-like,humic-like,and fulvic-like substances.The F^(-)concentrations affected the DOM composition and migration due to the response of functional bacterial communities,which were positively correlated with the relative abundance of Thiobacillus and negatively correlated with the relative abundances of Trichococcus and Fusibacter.The high F^(-)concentrations influenced the biosynthesis and degradation of protein-like substances by shifting the abundances of the relevant enzymes.The results of this study may provide ideas for investigating DOM cycling under the influence of F^(-),especially in lakes with fluctuations in F^(-)concentrations.展开更多
基金supported by a Grant-in-Aid for Challenging Exploratory Research(No.15K12192)from the Japan Society for the Promotion of Science(JSPS)The State Scholarship Fund of Chinese Scholarship Council(CSC No.201406010350)provides Mr.Wei Hu the scholarship for his study and stay at the Prefectural University of Kumamoto
文摘Rainwater contains substantial bacteria and rain is an efficient pathway for the dissemination of bacteria from the atmosphere to land and water surfaces.However,quantitative information on rainwater bacteria is very limited due to the lack of a reliable method.In this study,the epifluorescence microscopy enumeration with the LIVE/DEAD BacLight Bacterial Viability Kit stain was verified to quantify the abundance of viable and non-viable bacterial cells in rainwater,with the 4',6-diamidino-2-phenylindole(DAPI) stain for the reference of total cell counts.Results showed that the total counts of bacterial cells by LIVE/DEAD BacLight staining were consistent with those by DAPI staining,and the average detection efficiency was(109 ± 29)%.The ratio of cell count with glutaraldehyde fixation to that without fixation was(106 ± 5)%on average.The bacterial concentration in negative control was usually an order of magnitude lower than that in rainwater samples.However,in case of small precipitation,the abundance in negative control could be more than that in rainwater samples.These results indicate that the enumeration with LIVE/DEAD BacLight bacterial viability assay coupled with glutaraldehyde fixation and careful negative control investigation is an approach applicable to the measurement of the concentration and viability of bacterial cells in rainwater.
基金supported by the Program for the Development of Basic Sciences (Programa de Desarrollo de las Ciencias Básicas, PEDECIBA)provided by the Uruguayan Antarctic Institute (Instituto Antártico Uruguayo, IAU)
文摘Fildes Peninsula, in King George Island, Antarctica, has a great concentration of international facilities, and it has clearly been affected by human activities. The objective of this 5-year study was to assess the impact of anthropogenic activities on the bacterial abundance in water bodies close to Artigas Antarctic Scientific Base (BCAA, in Spanish Base Cientifica Antdrtica Artigas). Water samples from areas under different human influence (Uruguay Lake, nearby ponds, and meltwater from Collins Glacier) were aseptically collected and refrigerated until processed. The number of heterotrophic bacteria and Pseudomonas spp. was analyzed using a culture-dependent approach. Physico-chemical properties of the water samples (temperature, pH, and conductivity) were also determined. Results showed that water from the highly affected area, Uruguay Lake, where the pump that provides water to the BCAA is located, did not suffer significant fluctuations in heterotrophie bacterial abundance (10^4- 10^5 CFU.mL^-1); however, Pseudomonas abundance increased until becoming the predominant population. In other water samples, the number of heterotrophie bacteria and Pseudomonas gradually increased during this 5-year study, by 2014 reaching similar values to those observed for Uruguay Lake. The implications of human activities on Antarctic bacterial abundance are discussed.
文摘Low availability of phosphorus(P) is a major constraint for optimal crop production, as P is mostly present in its insoluble form in soil. Therefore,phosphate-solubilizing bacteria(PSB) from paddy field soils of the Indo-Gangetic Plain, India were isolated, and their abundance was attempted to be correlated with the physicochemical characteristics of the soils. Ninety-four PSB were isolated on Pikovskaya’s agar medium, and quantitative phosphate solubilization was evaluated using NBRIP medium. The isolates solubilized P up to a concentration of 1 006 μg mL-1 from tricalcium phosphate with the secretion of organic acids. These isolates were identified by 16 S rRNA gene sequence comparison, and they belonged to Gammaproteobacteria(56 isolates),Firmicutes(28 isolates), Actinobacteria(8 isolates), and Alphaproteobacteria(2 isolates). Phylogenetic analysis confirmed the identification by clustering the isolates in the clade of the respective reference organisms. The correlation analysis between PSB abundance and physicochemical characteristics revealed that the PSB population increased with increasing levels of soil organic carbon, insoluble P, K+, and Mg2+. The promising PSB explored in this study can be further evaluated for their biofertilizer potential in the field and for their use as potent bio-inoculants.
基金the Innovative team project of Nanjing Institute of Environmental Sciences,MEE(GYZX200101)the National Natural Science Foundation of China(No.51778265)Key R&D Program of Ningxia Hui Autonomous Region(2019BFG02028,2021BEG01002).
文摘Fluoride(F^(-))is widespread in aquatic environments;however,it is not clear whether the fluctuation of F^(-)concentrations in overlying lake water affects the composition and migration of dissolved organic matter(DOM)from sediment.A case study was presented in Sand Lake,China,and an experiment was conducted to analyze the influence of different F^(-)concentrations in overlying water on DOM characteristics.Diffusion resulted in similarities in DOM components between overlying and pore waters,and bacterial activities and enzyme variation resulted in differences between them.Higher F^(-)concentrations in overlying water resulted in a higher pH of pore water,which favored the enrichment of protein-like substances.Higher F^(-)concentrations caused lower DOM concentrations and lower maximum fluorescence intensities(Fmax)of protein-like components in pore water.The F^(-)concentrations had significantly negative correlations with Shannon indexes(P<0.05).Thiobacillus influenced the migration of tyrosinelike substances by decreasing the pH of pore water.Trichococcus and Fusibacter altered the Fmax of protein-like,humic-like,and fulvic-like substances.The F^(-)concentrations affected the DOM composition and migration due to the response of functional bacterial communities,which were positively correlated with the relative abundance of Thiobacillus and negatively correlated with the relative abundances of Trichococcus and Fusibacter.The high F^(-)concentrations influenced the biosynthesis and degradation of protein-like substances by shifting the abundances of the relevant enzymes.The results of this study may provide ideas for investigating DOM cycling under the influence of F^(-),especially in lakes with fluctuations in F^(-)concentrations.