All the regulations that define a maximum concentration of metals in the receiving soil are based on total soil metal concentration. However, the potential toxicity of a heavy metal in the soil depends on its speciati...All the regulations that define a maximum concentration of metals in the receiving soil are based on total soil metal concentration. However, the potential toxicity of a heavy metal in the soil depends on its speciation and availability. We studied the effects of heavy metal speciation and availability on soil microorganism activities along a Cu/Zn contamination gradient. Microbial biomass and enzyme activity of soil contaminated with both Cu and Zn were investigated. The results showed that microbial biomass was negatively affected by the elevated metal levels. The microbial biomass-C (Cmic)/organic C (Corg) ratio was closely correlated to heavy metal stress. There were negative correlations between soil microbial biomass, phosphatase activity and NH4NO3 extractable heavy metals. The soil microorganism activity could be predicted using empirical models with the availability of Cu and Zn. We observed that 72% of the variation in phosphatase activity could be explained by the NH4NO3-extractable and total heavy metal concentration. By considering different monitoring approaches and different viewpoints, this set of methods applied in this study seemed sensitive to site differences and contributed to a better understanding of the effects of heavy metals on the size and activity of microorganisms in soils. The data presented demonstrate the relationship between heavy metals availability and heavy metal toxicity to soil microorganism along a contamination gradient.展开更多
Black soybeans [Glycine max(L.) Merrill] were fermented with various GRAS(generally recognized as safe) microorganisms,including Aspergillus sp.,Bacillus sp.and yeast(Issatchenkia orientalis) at 30°C for 3 ...Black soybeans [Glycine max(L.) Merrill] were fermented with various GRAS(generally recognized as safe) microorganisms,including Aspergillus sp.,Bacillus sp.and yeast(Issatchenkia orientalis) at 30°C for 3 d.The antioxidant contents,including total phenolics and total flavonoids,and the antioxidant activities of 1,1-diphenyl-2-picrylhydrazine(DPPH),ferric reducing antioxidant power(FRAP) and HO.scavenging were analyzed in preparations of fermented black soybeans.Fermented cultures proved to yield significant levels of antioxidants compared with non-fermented cultures(P 〈 0.05).Fermented black soybean preparations possessed antioxidant activities could be attributed to the total phenolics and flavonoids present.展开更多
A strain saccharomycete STSM-1 with high flocculanting activity was isolated from activated sludge with conventional methods. The high production rate and the low cost STSM-1 medium was obtained by selecting different...A strain saccharomycete STSM-1 with high flocculanting activity was isolated from activated sludge with conventional methods. The high production rate and the low cost STSM-1 medium was obtained by selecting different kinds of media, carbon source, nitrogen source and inorganic salt ion. The best flocculant-producing conditions were found by changing medium initial pH, culture temperature and ventilation flow. The best flocculating effect was obtained by changing positive ion types, density and concentration of flocculant.展开更多
The environmental risk of chromium pollution is pronounced in soils adjacent to chromate industry. It is important to investigate the functioning of soil microorganisms in ecosystems exposed to long-term contamination...The environmental risk of chromium pollution is pronounced in soils adjacent to chromate industry. It is important to investigate the functioning of soil microorganisms in ecosystems exposed to long-term contamination by chromium. 45 soil samples obtained from different places of the slag heap in a steel alloy factory were analyzed for chromium contamination level and its effect on soil microorganisms and enzyme activities. The results show that the average concentrations of total Cr in the soil under the slag heap, adjacent to the slag heap and outside the factory exceed the threshold of Secondary Environmental Quality Standard for Soil in China by 354%, 540% and 184%, respectively, and are 15, 21 and 9 times higher than the local background value, respectively. Elevated chromium loadings result in changes in the activity of the soil microbe, as indicated by the negative correlations between soil microbial population and chromium contents. Dehydrogenase activity is greatly depressed by chromium in the soil. The results imply that dehydrogenase activity can be used as an indicator for the chromium pollution level in the area of the steel alloy factory.展开更多
The efforts of heavy metals on activated sludge microorganisms are reviewed. Although some heavy metals play an important role in the life of microorganism, heavy metals concentrations above toxic levels inhibit biolo...The efforts of heavy metals on activated sludge microorganisms are reviewed. Although some heavy metals play an important role in the life of microorganism, heavy metals concentrations above toxic levels inhibit biological processes. Copper, zinc, nickel,cadmium and chromium were mostly studied because of their toxicity and widely used, regardless of single or combination. The microorganism response to these heavy metals varied with species and concentrations of metals,factors such as pH, sludge age, MLSS etc. also affect toxicity on the microorganism. The acclimation could extend the microorganism tolerance of heavy metals. The effects of heavy metals on sludge microorganisms could be described with different models, such as Sigmoidal and Monod equation. The kinetic constants are the useful indexes to estimate the heavy metals inhibition on activated sludge system. Methods to measure the toxicity and effects on microorganism community were also reviewed.展开更多
[Objectives] To study the changes in active components before and after microorganism fermentation of Rhizoma Paridis( Chonglou). [Methods]Analytical methods using total saponins and total flavonoids as indicators wer...[Objectives] To study the changes in active components before and after microorganism fermentation of Rhizoma Paridis( Chonglou). [Methods]Analytical methods using total saponins and total flavonoids as indicators were established. UV spectrophotometry was used to determine the changes in active components before and after fermentation of Rhizoma Paridis. [Results] The content of total saponins decreased after fermentation,while the content of total flavonoids increased. [Conclusions]The content of total saponins decreased after fermentation and the content of total flavonoids increased. The fermentation process of Monascus purpureus Went. needs further optimization.展开更多
Analysis of a gravity-induced film flow of a fluid containing both nanoparticles and gyrotactic microorganisms along a convectively heated vertical surface is presented.The Buongiorno model is applied. Two kinds of bo...Analysis of a gravity-induced film flow of a fluid containing both nanoparticles and gyrotactic microorganisms along a convectively heated vertical surface is presented.The Buongiorno model is applied. Two kinds of boundary conditions, the passive and the active boundary conditions, are considered to investigate this film flow phenomenon.Through a set of similarity variables, the ordinary differential equations that describe the conservation of the momentum, the thermal energy, the nanoparticles, and the microorganisms are derived and then solved numerically by an efficient finite difference technique.The effects of various physical parameters on the profiles of momentum, thermal energy,nanoparticles, microorganisms, local skin friction, local Nusselt number, local wall mass flux, and local wall motile microorganisms flux are investigated. It is expected that the passively controlled nanofluid model can be much more easily achieved and applied in real circumstances than the actively controlled model.展开更多
Soil nitrification is mediated by ammonia-oxidizing archaea (AOA) and bacteria (AOB), which occupy different specialized ecological niches. However, little is known about the diversification of AOA and AOB communities...Soil nitrification is mediated by ammonia-oxidizing archaea (AOA) and bacteria (AOB), which occupy different specialized ecological niches. However, little is known about the diversification of AOA and AOB communities in a large geographical scale. Here, eight paddy soils collected from different geographic regions in China were selected to investigate the spatial distribution of AOA and AOB, and their potential nitrification activity (PNA). The result showed that the abundance of AOA was predominant over AOB, indicating that the rice fields favor the growth of AOA. PNA highly varied from 0.43 to 3.57 μg NOX-N·g·dry·soil·h-1, and was positively related with soil NH3 content, the abundance of AOA community, and negatively related with the diversity of AOB community (P amoA genes revealed remarkable differences in the compositions of AOA and AOB community. Phylogenetic analyses of amoA genes showed that Nitrosospiracluster-3-like and Nitrosomonas cluster 7-like AOB extensively dominated the AOB communities, and 54d9-like AOA within the soil group 1.1b predominated in AOA communities in paddy soils. Redundancy analysis suggested that the spatial variations of AOA community structure were influenced by soil TN content (P < 0.01), while no significant correlation between AOB community structure and soil properties was found. Findings highlight that ammonia oxidizers exhibit spatial variations in complex paddy fields due to the joint influence of soil variables associated with N availability.展开更多
Vegetable oil Spills are becoming frequent and are potentially more challenging than petroleum hydrocarbon spills. Microbial lipases occupy a place of prominence among biocatalysts are often used for remediation of ve...Vegetable oil Spills are becoming frequent and are potentially more challenging than petroleum hydrocarbon spills. Microbial lipases occupy a place of prominence among biocatalysts are often used for remediation of vegetable oil-polluted sites. This work was carried out to isolate microorganisms from oil-polluted sites and screen them for their lipolytic activity. Microorganisms were isolated from eight experimental soil samples contaminated with different types of vegetable oil, soil from an oil mill in Ibadan, and normal uncontaminated soil as a control. The isolates were characterized, identified and those common to at least one of the experimental sites and oil mill sites were screened for their lipolytic activity. Data obtained were analysed using Duncan Multiple Range Test. Seventy three microorganisms were isolated from the polluted soil and identified as species of Bacillus (16), Pseudomonas (12), Flavobacterium (6), Alcaligenes (2), Proteus (3), Micrococcus (1), Aspergillus (9), Penicillium (6), Saccharomyces (4), Geotrichum (1), Kluveromyces (1). Bacillus subtilis, Bacillus licheniformic, Pseudomonas cepacia, Pseudomonas fluorescens, Flavobacterium sp., Alcaligenes sp. and Candida parapsilosis which were common to at least one of the experimental site and oil mill site were preliminarily screened for lipolytic activity and all nine confirmed by presence of halos around the colonies. These screened organisms have potential for the degradation of fatty waste. They could therefore be employed in environmental clean-up of vegetable oil spill site.展开更多
<span style="font-family:Verdana;">Object: </span><span style="font-family:Verdana;">To isolate and identify the microorganisms from the burn patients admitted to the National Ins...<span style="font-family:Verdana;">Object: </span><span style="font-family:Verdana;">To isolate and identify the microorganisms from the burn patients admitted to the National Institute of Burn and Plastic Surgery Unit in Tertiary Medical College Hospital, Bangladesh. A total number of fifty wound surface swab samples of first and second-degree burn patients were collected and the microbial analysis as well </span><span style="font-family:Verdana;">as </span><span style="font-family:Verdana;">the study of antibacterial susceptibility was conducted. The study showed the bacterial isolates were found.</span><span style="font-family:Verdana;"> 45 (90%) of wound swab were positive among 50 and only 5 samples (10%) were negative in bacterial growth, </span><span style="font-family:""><span style="font-family:Verdana;">which presented invasive burn wound infection from both sex age groups marked 12 - 60 years. The total viable count TVC-11651 CFU/plate was found and the highest amount in the second-degree burn patients. The results showed that </span><i><span style="font-family:Verdana;">Pseudomonas aeruginosa </span></i><span style="font-family:Verdana;">was common in all positive samples 6636 CFU/plate</span></span><span style="font-family:""> </span><span style="font-family:Verdana;">(57%)</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">followed by </span><i><span style="font-family:Verdana;">Staphylococcus aureus</span></i><span style="font-family:Verdana;"> 4070 CFU/plate (35%), </span><i><span style="font-family:Verdana;">Klebsiella </span></i><span style="font-family:Verdana;">spp</span></span><span style="font-family:Verdana;">.</span><span style="font-family:""><span style="font-family:Verdana;"> 450 </span><span style="font-family:Verdana;">CFU/plate</span></span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">(5%),</span><i><span style="font-family:Verdana;"> Proteus </span></i><span style="font-family:Verdana;">spp</span></span><span style="font-family:Verdana;">.</span><span style="font-family:""><span style="font-family:Verdana;"> 243 CFU/plate (2%), and </span><i><span style="font-family:Verdana;">E</span></i><span style="font-family:Verdana;">.</span></span><i><span style="font-family:""> </span></i><i><span style="font-family:Verdana;">coli</span></i><span style="font-family:Verdana;"> 162 CFU/plate (1%). Most of the pathogens were found to be drug-resistant while several isolates were noted to be multi-drug resistant. The growth of multidrug-resistant organisms </span><span style="font-family:Verdana;">should be considered as a serious risk factor in a burn unit. Aggressive infection control measures should be applied to limit the emergence and spread of multidrug-resistant pathogens.展开更多
Microorganisms (bacteria and fungi) were isolated from different parts of yellow maize (stem, cob, husk, leaf, root) as well as from rhizosphere and non-rhizosphere soil of maize using conventional microbiological tec...Microorganisms (bacteria and fungi) were isolated from different parts of yellow maize (stem, cob, husk, leaf, root) as well as from rhizosphere and non-rhizosphere soil of maize using conventional microbiological techniques. A total number of twenty-six bacteria and thirteen fungi were isolated. The antagonistic efficacies of these isolates were tested against Sclerotium rolfsii, Aspergillus repens, Penicillium notatum and Pythium sp. using streak bioassay, food poisoning and dual culture techniques. None of the bacteria was antagonistic to the test fungi at 25°C on PDA using streak bioassay. However, there was reduction in the population density of the test fungi using food poisoning technique. The fungal isolates were antagonistic to the test fungi in varying degrees. Generally, S. rolfsii was susceptible to seven out of the eight fungal antagonists while P. notatum was least susceptible. The percentage reduction of S. rolfsii ranged from 40.00 ± 5.78 to 64.07 ± 2.31. Efficacies of chemical fungicides;mancozeb, camazeb and red force at 3 different concentrations— 0.05%, 0.1% and 1.0% (w/v) on the test fungi were also determined. No growth of the test fungi was observed at 1% (w/v) of all the fungicides while at lower concentration (0.05%), red force did not have any inhibitory effect. The growth of S. rolfsii was completely inhibited at 0.05% of mancozeb whereas there was reduction in mycelial growth of A. repens. Effect of inoculation time and nutrients (PDA and MEA) was determined on the antagonistic activities of Trichoderma viride. There were significant differences in inhibitory potentials of the two isolates of Trichoderma viride when pre-inoculated on the culture medium. The antagonistic potentials were more pronounced on malt extract agar than potato dextrose agar.展开更多
基金Project supported by the National Natural Science Foundation of Chi-na (No. 40432004, 40601086) the Natural Science Foundationof Zhejiang Province (No. Y504109).
文摘All the regulations that define a maximum concentration of metals in the receiving soil are based on total soil metal concentration. However, the potential toxicity of a heavy metal in the soil depends on its speciation and availability. We studied the effects of heavy metal speciation and availability on soil microorganism activities along a Cu/Zn contamination gradient. Microbial biomass and enzyme activity of soil contaminated with both Cu and Zn were investigated. The results showed that microbial biomass was negatively affected by the elevated metal levels. The microbial biomass-C (Cmic)/organic C (Corg) ratio was closely correlated to heavy metal stress. There were negative correlations between soil microbial biomass, phosphatase activity and NH4NO3 extractable heavy metals. The soil microorganism activity could be predicted using empirical models with the availability of Cu and Zn. We observed that 72% of the variation in phosphatase activity could be explained by the NH4NO3-extractable and total heavy metal concentration. By considering different monitoring approaches and different viewpoints, this set of methods applied in this study seemed sensitive to site differences and contributed to a better understanding of the effects of heavy metals on the size and activity of microorganisms in soils. The data presented demonstrate the relationship between heavy metals availability and heavy metal toxicity to soil microorganism along a contamination gradient.
基金supproted by a grant from the Korea Institute of Planning and Evaluation for Technology of Food,Agriculture,Forestry and Fishes (i PET)
文摘Black soybeans [Glycine max(L.) Merrill] were fermented with various GRAS(generally recognized as safe) microorganisms,including Aspergillus sp.,Bacillus sp.and yeast(Issatchenkia orientalis) at 30°C for 3 d.The antioxidant contents,including total phenolics and total flavonoids,and the antioxidant activities of 1,1-diphenyl-2-picrylhydrazine(DPPH),ferric reducing antioxidant power(FRAP) and HO.scavenging were analyzed in preparations of fermented black soybeans.Fermented cultures proved to yield significant levels of antioxidants compared with non-fermented cultures(P 〈 0.05).Fermented black soybean preparations possessed antioxidant activities could be attributed to the total phenolics and flavonoids present.
文摘A strain saccharomycete STSM-1 with high flocculanting activity was isolated from activated sludge with conventional methods. The high production rate and the low cost STSM-1 medium was obtained by selecting different kinds of media, carbon source, nitrogen source and inorganic salt ion. The best flocculant-producing conditions were found by changing medium initial pH, culture temperature and ventilation flow. The best flocculating effect was obtained by changing positive ion types, density and concentration of flocculant.
基金Project(K0802144-31) supported by the Program of Science and Technology of Changsha, ChinaProjects(2006AA06Z374, 2007AA021304) supported by the National Hi-tech Research and Development Program of China
文摘The environmental risk of chromium pollution is pronounced in soils adjacent to chromate industry. It is important to investigate the functioning of soil microorganisms in ecosystems exposed to long-term contamination by chromium. 45 soil samples obtained from different places of the slag heap in a steel alloy factory were analyzed for chromium contamination level and its effect on soil microorganisms and enzyme activities. The results show that the average concentrations of total Cr in the soil under the slag heap, adjacent to the slag heap and outside the factory exceed the threshold of Secondary Environmental Quality Standard for Soil in China by 354%, 540% and 184%, respectively, and are 15, 21 and 9 times higher than the local background value, respectively. Elevated chromium loadings result in changes in the activity of the soil microbe, as indicated by the negative correlations between soil microbial population and chromium contents. Dehydrogenase activity is greatly depressed by chromium in the soil. The results imply that dehydrogenase activity can be used as an indicator for the chromium pollution level in the area of the steel alloy factory.
文摘The efforts of heavy metals on activated sludge microorganisms are reviewed. Although some heavy metals play an important role in the life of microorganism, heavy metals concentrations above toxic levels inhibit biological processes. Copper, zinc, nickel,cadmium and chromium were mostly studied because of their toxicity and widely used, regardless of single or combination. The microorganism response to these heavy metals varied with species and concentrations of metals,factors such as pH, sludge age, MLSS etc. also affect toxicity on the microorganism. The acclimation could extend the microorganism tolerance of heavy metals. The effects of heavy metals on sludge microorganisms could be described with different models, such as Sigmoidal and Monod equation. The kinetic constants are the useful indexes to estimate the heavy metals inhibition on activated sludge system. Methods to measure the toxicity and effects on microorganism community were also reviewed.
基金Supported by Innovating Research Program of Postgraduates of Southwest Minzu University in 2017(CX2017SZ099)the Funds of Basic Research for Application of Sichuan Province(18YYJC0230)
文摘[Objectives] To study the changes in active components before and after microorganism fermentation of Rhizoma Paridis( Chonglou). [Methods]Analytical methods using total saponins and total flavonoids as indicators were established. UV spectrophotometry was used to determine the changes in active components before and after fermentation of Rhizoma Paridis. [Results] The content of total saponins decreased after fermentation,while the content of total flavonoids increased. [Conclusions]The content of total saponins decreased after fermentation and the content of total flavonoids increased. The fermentation process of Monascus purpureus Went. needs further optimization.
基金Project supported by the Program for New Century Excellent Talents in University(No.NCET-12-0347)
文摘Analysis of a gravity-induced film flow of a fluid containing both nanoparticles and gyrotactic microorganisms along a convectively heated vertical surface is presented.The Buongiorno model is applied. Two kinds of boundary conditions, the passive and the active boundary conditions, are considered to investigate this film flow phenomenon.Through a set of similarity variables, the ordinary differential equations that describe the conservation of the momentum, the thermal energy, the nanoparticles, and the microorganisms are derived and then solved numerically by an efficient finite difference technique.The effects of various physical parameters on the profiles of momentum, thermal energy,nanoparticles, microorganisms, local skin friction, local Nusselt number, local wall mass flux, and local wall motile microorganisms flux are investigated. It is expected that the passively controlled nanofluid model can be much more easily achieved and applied in real circumstances than the actively controlled model.
文摘Soil nitrification is mediated by ammonia-oxidizing archaea (AOA) and bacteria (AOB), which occupy different specialized ecological niches. However, little is known about the diversification of AOA and AOB communities in a large geographical scale. Here, eight paddy soils collected from different geographic regions in China were selected to investigate the spatial distribution of AOA and AOB, and their potential nitrification activity (PNA). The result showed that the abundance of AOA was predominant over AOB, indicating that the rice fields favor the growth of AOA. PNA highly varied from 0.43 to 3.57 μg NOX-N·g·dry·soil·h-1, and was positively related with soil NH3 content, the abundance of AOA community, and negatively related with the diversity of AOB community (P amoA genes revealed remarkable differences in the compositions of AOA and AOB community. Phylogenetic analyses of amoA genes showed that Nitrosospiracluster-3-like and Nitrosomonas cluster 7-like AOB extensively dominated the AOB communities, and 54d9-like AOA within the soil group 1.1b predominated in AOA communities in paddy soils. Redundancy analysis suggested that the spatial variations of AOA community structure were influenced by soil TN content (P < 0.01), while no significant correlation between AOB community structure and soil properties was found. Findings highlight that ammonia oxidizers exhibit spatial variations in complex paddy fields due to the joint influence of soil variables associated with N availability.
文摘Vegetable oil Spills are becoming frequent and are potentially more challenging than petroleum hydrocarbon spills. Microbial lipases occupy a place of prominence among biocatalysts are often used for remediation of vegetable oil-polluted sites. This work was carried out to isolate microorganisms from oil-polluted sites and screen them for their lipolytic activity. Microorganisms were isolated from eight experimental soil samples contaminated with different types of vegetable oil, soil from an oil mill in Ibadan, and normal uncontaminated soil as a control. The isolates were characterized, identified and those common to at least one of the experimental sites and oil mill sites were screened for their lipolytic activity. Data obtained were analysed using Duncan Multiple Range Test. Seventy three microorganisms were isolated from the polluted soil and identified as species of Bacillus (16), Pseudomonas (12), Flavobacterium (6), Alcaligenes (2), Proteus (3), Micrococcus (1), Aspergillus (9), Penicillium (6), Saccharomyces (4), Geotrichum (1), Kluveromyces (1). Bacillus subtilis, Bacillus licheniformic, Pseudomonas cepacia, Pseudomonas fluorescens, Flavobacterium sp., Alcaligenes sp. and Candida parapsilosis which were common to at least one of the experimental site and oil mill site were preliminarily screened for lipolytic activity and all nine confirmed by presence of halos around the colonies. These screened organisms have potential for the degradation of fatty waste. They could therefore be employed in environmental clean-up of vegetable oil spill site.
文摘<span style="font-family:Verdana;">Object: </span><span style="font-family:Verdana;">To isolate and identify the microorganisms from the burn patients admitted to the National Institute of Burn and Plastic Surgery Unit in Tertiary Medical College Hospital, Bangladesh. A total number of fifty wound surface swab samples of first and second-degree burn patients were collected and the microbial analysis as well </span><span style="font-family:Verdana;">as </span><span style="font-family:Verdana;">the study of antibacterial susceptibility was conducted. The study showed the bacterial isolates were found.</span><span style="font-family:Verdana;"> 45 (90%) of wound swab were positive among 50 and only 5 samples (10%) were negative in bacterial growth, </span><span style="font-family:""><span style="font-family:Verdana;">which presented invasive burn wound infection from both sex age groups marked 12 - 60 years. The total viable count TVC-11651 CFU/plate was found and the highest amount in the second-degree burn patients. The results showed that </span><i><span style="font-family:Verdana;">Pseudomonas aeruginosa </span></i><span style="font-family:Verdana;">was common in all positive samples 6636 CFU/plate</span></span><span style="font-family:""> </span><span style="font-family:Verdana;">(57%)</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">followed by </span><i><span style="font-family:Verdana;">Staphylococcus aureus</span></i><span style="font-family:Verdana;"> 4070 CFU/plate (35%), </span><i><span style="font-family:Verdana;">Klebsiella </span></i><span style="font-family:Verdana;">spp</span></span><span style="font-family:Verdana;">.</span><span style="font-family:""><span style="font-family:Verdana;"> 450 </span><span style="font-family:Verdana;">CFU/plate</span></span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">(5%),</span><i><span style="font-family:Verdana;"> Proteus </span></i><span style="font-family:Verdana;">spp</span></span><span style="font-family:Verdana;">.</span><span style="font-family:""><span style="font-family:Verdana;"> 243 CFU/plate (2%), and </span><i><span style="font-family:Verdana;">E</span></i><span style="font-family:Verdana;">.</span></span><i><span style="font-family:""> </span></i><i><span style="font-family:Verdana;">coli</span></i><span style="font-family:Verdana;"> 162 CFU/plate (1%). Most of the pathogens were found to be drug-resistant while several isolates were noted to be multi-drug resistant. The growth of multidrug-resistant organisms </span><span style="font-family:Verdana;">should be considered as a serious risk factor in a burn unit. Aggressive infection control measures should be applied to limit the emergence and spread of multidrug-resistant pathogens.
文摘Microorganisms (bacteria and fungi) were isolated from different parts of yellow maize (stem, cob, husk, leaf, root) as well as from rhizosphere and non-rhizosphere soil of maize using conventional microbiological techniques. A total number of twenty-six bacteria and thirteen fungi were isolated. The antagonistic efficacies of these isolates were tested against Sclerotium rolfsii, Aspergillus repens, Penicillium notatum and Pythium sp. using streak bioassay, food poisoning and dual culture techniques. None of the bacteria was antagonistic to the test fungi at 25°C on PDA using streak bioassay. However, there was reduction in the population density of the test fungi using food poisoning technique. The fungal isolates were antagonistic to the test fungi in varying degrees. Generally, S. rolfsii was susceptible to seven out of the eight fungal antagonists while P. notatum was least susceptible. The percentage reduction of S. rolfsii ranged from 40.00 ± 5.78 to 64.07 ± 2.31. Efficacies of chemical fungicides;mancozeb, camazeb and red force at 3 different concentrations— 0.05%, 0.1% and 1.0% (w/v) on the test fungi were also determined. No growth of the test fungi was observed at 1% (w/v) of all the fungicides while at lower concentration (0.05%), red force did not have any inhibitory effect. The growth of S. rolfsii was completely inhibited at 0.05% of mancozeb whereas there was reduction in mycelial growth of A. repens. Effect of inoculation time and nutrients (PDA and MEA) was determined on the antagonistic activities of Trichoderma viride. There were significant differences in inhibitory potentials of the two isolates of Trichoderma viride when pre-inoculated on the culture medium. The antagonistic potentials were more pronounced on malt extract agar than potato dextrose agar.