Production and quality of vinegar from mango juice was evaluated using a two steps production procedure. The first step of fermentation was done using Saccharomyces cerevisae KVL013 for 7 days. The second step, an ace...Production and quality of vinegar from mango juice was evaluated using a two steps production procedure. The first step of fermentation was done using Saccharomyces cerevisae KVL013 for 7 days. The second step, an acetic fermentation was realized using two acetic acid bacteria: A. tropicalis CRSBAN-BVA1 and A. tropicalis CRSBAN-BVK2 for 21 days. Several parameters of the vinegar produced such as physico-chemical and sensory properties were determined. Microbial density during each step was monitored. Results showed that pH, alcoholic and acetic acid contents of vinegar were respectively 2.97%, 7% and 4.54% g/ml respectively by using A. tropicalis CRSBAN-BVA1 and 3.02%, 7% and 4.32% g/ml with A. tropicalis CRSBAN-BVK2. Sensory evaluation revealed that the vinegar was acceptable to the panellists. Results of microbial density showed that the maximum concentration of cell biomass produced was 4.32 × 10<sup>8</sup> and 4.25 × 10<sup>8</sup> CFU/ml respectively for CRSBAN-BVA1 and CRSBAN-BVK2.展开更多
Candida endocarditis is extremely rare in term neonates,and gall bladder involvement due to candidemia has never been reported amongst neonates and infants.A term,appropriate for gestational age neonate developed Cand...Candida endocarditis is extremely rare in term neonates,and gall bladder involvement due to candidemia has never been reported amongst neonates and infants.A term,appropriate for gestational age neonate developed Candida tropicalis blood stream infection in second week of life.He was started on conventional amphotericin B.However,he failed to show any clinical improvement,and candidemia keep on persisting.Repeat sanctuary sites screening revealed multiple echogenic masses in heart(vegetations) and gall bladder.On changing the treatment to liposomal amphotericin B and fluconazole,he recovered clinically,echogenic masses in gall bladder disappeared,and intracardiac vegetations decreased in size.展开更多
Xylose reductase (EC 1.1.1.21) of Candida tropicalis IEC5-ITV, an indigenous xylitol-producing strain, was partially purified by reversed micelles and characterized, an 8.1 fold purification factor being obtained. The...Xylose reductase (EC 1.1.1.21) of Candida tropicalis IEC5-ITV, an indigenous xylitol-producing strain, was partially purified by reversed micelles and characterized, an 8.1 fold purification factor being obtained. The XR present in the crude extract exhibited its highest specific activity at pH 6.0 and 40℃, while in that obtained by reverse micelles, this occurs at pH 6.0 and 30℃. XR before and after extraction is stable within a range of 30 to 40℃, pH 7 after one hour of incubation under these conditions. After two months’storage at –18℃, the enzyme obtained by reverse micelles lost 76.60% specific activity. The estimated molecular weight by PAGE-SDS was 32.42 kD. KM for xylose was higher for the XR extracted by reverse micelles (0.026 M) than that obtained for the enzyme before extraction (0.0059 M), while KM for cofactor NADPH was lower after than before extraction (1.85 mM to 12.0 mM respectively). There was no activity with NADH as a cofactor. Variations in pH and temperature optima, as well as kinetic parameters before and after partial XR purification by reverse micelles are probably due to an alteration in enzyme molecule structure caused by the solvents used during extraction.展开更多
[Objectives] The fermentation conditions of Candida tropicalis 1798-pxa1 were optimized to further improve its yield of long-chain dibasic acids. [Methods] The strains used in the study were C. tropicalis 1798, C. tro...[Objectives] The fermentation conditions of Candida tropicalis 1798-pxa1 were optimized to further improve its yield of long-chain dibasic acids. [Methods] The strains used in the study were C. tropicalis 1798, C. tropicalis 1798-pxa1 and C. tropicalis 1798-pxa1 p2. First, through single factor experiments, the activated three fungi were cultured in different carbon sources, and the absorbance was measured every 2 h. The growth curve was drawn by software, and finally the most suitable substance for the substrate was selected, i.e., dodecane. Then, the composition of the fermentation medium and the fermentation process parameters were determined through the PB experiment of the single-deletion C. tropicalis 1798-pxa1. [Results] The experiment determined the important components affecting the synthesis of long-chain dibasic acids, namely(NH_4)_2SO_4, NaCl and dodecane. After optimization of the culture conditions, the yield of long-chain dibasic acids of C. tropicalis 1798-pxa1 increased from 5.6 to 10.1 g/L. [Conclusions] The scheme has been verified to be capable of greatly increasing the yield of the corresponding long-chain dibasic acids of the C. tropicalis engineering strain.展开更多
Phenol is an important commodity for the chemical industry, used for many processes and deemed to be a major pollutant due its xenobiotic nature and high toxicity. For the purpose of phenol bioremediation a biotechnol...Phenol is an important commodity for the chemical industry, used for many processes and deemed to be a major pollutant due its xenobiotic nature and high toxicity. For the purpose of phenol bioremediation a biotechnological set up consisting of a continuous packed column bioreactor with Candida tropicalis adhered onto activated carbon beads has been previously described. In this work, we show how the integration of available experimental data of such a biotechnological set up into a mathematical model, can lead both to a better comprehension of the underlying physiological mechanisms operating in the cell culture, and to the identification of the system parameters optimum performance. The model so constructed describes the dynamics of phenol uptake and growth rates by the adhered and suspended biomass;the lethality rates;the adhered biomass removal into suspension or adherence onto carbon beads rates and the phenol and biomass (adhered and suspended) concentrations. It also serves to identify different physiological states for the adhered and the suspended biomass;its predictions being verified by comparing with experimental observations. Based on the model description, different optimization strategies are proposed, some of which have been experimentally tested, encompassing changes in bioreactor operation conditions, process development and strain development.展开更多
To investigate the chemical structure of cell wall mannan obtained from pathogenic yeast, Candida tropicalis NBRC 1400 (former antigenic standard strain, IFO 1400). As a result of two-dimensional NMR analysis, it was ...To investigate the chemical structure of cell wall mannan obtained from pathogenic yeast, Candida tropicalis NBRC 1400 (former antigenic standard strain, IFO 1400). As a result of two-dimensional NMR analysis, it was shown that the mannan of this strain is composed of α-1,6-, α-1,3-, α-1,2- and β-1,2-linked mannose residues. In this research, the mannan was subjected to three degradation procedures, acid-treatment, α-mannosidase, and acetolysis under two conditions in order to determine the chemical structure of the antigenic oligomannosyl side chains in this molecule. The 1H-nuclear magnetic resonance spectra of resultant oligosaccharides, pentaose and hexaose, demonstrated the existence of the oligomannosyl side chains corresponding to Manα1-3Manα1-2Manα1-2Manα1-2Man and Manα1-3Manα1-2Manα1-2Manα1-2Manα1-2Man, respectively, which have previously also been found in Candida albicans serotype A strain mannans. These findings indicate that C. tropicalis and C. albicans serotype A have no significant difference in the chemical structure of these cell wall mannans. Therefore, it can be interpreted that it is extremely difficult to distinguish both species by targeting the antigenic group in these mannans.展开更多
Microorganism resistance to the existing products is yet another difficulty that agriculturalists have to deal with. In this context, the search for new agricultural products that can fight phytopathogens has become i...Microorganism resistance to the existing products is yet another difficulty that agriculturalists have to deal with. In this context, the search for new agricultural products that can fight phytopathogens has become increasingly important. Plants have played an important role in this process, because they can serve as a source of new compounds for drug discovery. Plants belonging to the genus Pinus produce an oleoresin that protects the plant against herbivores and pathogens. With a view to developing products that can combat fungal pathogens without harming the environment, this work aimed to evaluate the antifungal activity of the oleoresins and fractions of Pinus elliottii Engelm and Pinus tropicalis against phytopathogens. The methodology based on NCCLS M38-A standards aided antifungal activity assessment. The microdilution method helped to determine the Minimum Inhibitory Concentration (MIC) and Minimum Fungicidal Concentration (MFC). The oleoresins of P. elliottii and P. tropicalis afforded the most significant results—they displayed fungicidal activity against all the tested species. MIC values were promising, especially the MIC of the oleoresin of P. elliottii against S. rolfsii (1.95 μg·mL-1). The MIC values of the oleoresins of P. elliottii and P. tropicalis ranged from 1.95 to 1000 μg·mL-1 and from 31.25 to 250 μg·mL-1, respectively. Fraction PT2 of P. tropicalis furnished the best results among all the assayed fractions: MIC values lay between 125 and 500 μg·mL-11. In conclusion, the oleoresin of P. tropicalis is a promising source of new antifungal agents for application in the treatment of phytopathogenic infections.展开更多
Direct discharge of aquaculture wastewater may have toxic effects,due to the presence of heavy metals,antibiotics,and even resistant pathogens,but little attention has been given.Here,tanks simulating a wild ecosystem...Direct discharge of aquaculture wastewater may have toxic effects,due to the presence of heavy metals,antibiotics,and even resistant pathogens,but little attention has been given.Here,tanks simulating a wild ecosystem were built to study the effects of long-term exposure to duckwastewater containing oxytetracycline(OTC)and/or arsenic(As)on the growth,physiological function,and gut microbiota evolution of Xenopus tropicalis.The results showed that duck wastewater had no apparent impact on X.tropicalis,but the impact increased significantly(P<0.05)with exposure to OTC and/or As,especially the impact on body weight and growth rate.Biochemical indicators revealed varying degrees of oxidative stress damage,hepatotoxicity(inflammation,necrosis,and sinusoids),and collagen fibrosis of X.tropicalis in all treated groups after 72 days of exposure,which indirectly inhibited X.tropicalis growth.Moreover,16S rDNA amplicon sequencing results showed that the gut microbiota structure and metabolic function were perturbed after chronic exposure,which might be the leading cause of growth inhibition.Interestingly,the abundance of intestinal resistance genes(RGs)increased with exposure time owing to the combined direct and indirect effects of stress factors in duck wastewater.Moreover,once the RGs were expressed,the resistance persisted for at least 24 days,especially that conferred by tetA.These results provide evidence of the toxic effects of DW containing OTC(0.1–4.0 mg/L)and/or As(0.3–3.5μg/L)on amphibians and indicate that it is vital to limit the usage of heavy metals and antibiotics on farms to control the biotoxicity of wastewater.展开更多
Statistical experimental designs were used to optimize the process of phenol degradation by Candida tropicalis Z-04, isolated from phenol-degrading aerobic granules. The most important factors influencing phenol degra...Statistical experimental designs were used to optimize the process of phenol degradation by Candida tropicalis Z-04, isolated from phenol-degrading aerobic granules. The most important factors influencing phenol degradation (p 〈 0.05), as identified by a two-level Plackett-Burman design with 11 variables, were yeast extract, phenol, inoculum size, and temperature. Steepest ascent method was undertaken to determine the optimal regions of these four significant factors. Central composite design (CCD) and response surface analysis were adopted to further investigate the mutual interactions between these variables and to identify their optimal values that would generate maximum phenol degradation. The analysis results indicated that interactions between yeast extract and temperature, phenol and temperature, inocuhim size and temperature affected the response variable (phenol degradation) significantly. The predicted results showed that the maximum removal efficiency of phenol (99.10%) could be obtained under the optimum conditions of yeast extract 0.41 g/L, phenol 1.03 g/L, inoculum size 1.43% (V/V) and temperature 30.04℃. These predicted values were further verified by validation experiments. The excellent correlation between predicted and experimental values confirmed the validity and practicability of this statistical optimum strategy. This study indicated the excellent ability of C. tropicalis Z-04 in degrading high-strength phenol. Optimal conditions obtained in this experiment laid a solid foundation for further use of this microorganism in the treatment of highstrength phenol effluents.展开更多
Aniline-degrading microbes were cultivated and acclimated with the initial activated sludge collected from a chemical wastewater treatment plant. During the acclimation processes, aerobic granular sludge being able to...Aniline-degrading microbes were cultivated and acclimated with the initial activated sludge collected from a chemical wastewater treatment plant. During the acclimation processes, aerobic granular sludge being able to effectively degrade aniline was successfully formed, from which a preponderant bacterial strain was isolated and named as AN1. Effects of factors including pH, temperature, and second carbon/nitrogen source on the biodegradation of aniline were investigated. Results showed that the optimal conditions for the biodegradation of aniline by the strain AN1 were at pH 7.0 and 28–35°C. At the optimal pH and temperature, the biodegradation rate of aniline could reach as high as 17.8 mg/(L·hr) when the initial aniline concentration was 400 mg/L. Further studies revealed that the addition of 1 g/L glucose or ammonium chloride as a second carbon or nitrogen source could slightly enhance the biodegradation efficiency from 93.0% to 95.1%–98.5%. However, even more addition of glucose or ammonium could not further enhance the biodegradation process but delayed the biodegradation of aniline by the strain AN1. Based on morphological and physiological characteristics as well as the phylogenetic analysis of 26S rDNA sequences, the strain AN1 was identified as Candida tropicalis.展开更多
Background: Adhesion, biofilm formation, yeast-hyphal transition, secretion of enzymes, and hemolytic activity are all considered important factors in Candida tropicalis infection. However, DNA sequence data for this ...Background: Adhesion, biofilm formation, yeast-hyphal transition, secretion of enzymes, and hemolytic activity are all considered important factors in Candida tropicalis infection. However, DNA sequence data for this pathogen are limited. In this study, the polymorphism and heterogeneity of genes agglutinin-like sequences (ALS)2, Lipase (LIP)1, LIP4, and secretory aspartyl proteinase tropicalis (SAPT)1-4 as well as the relationship between phenotype and genotype were analyzed. Methods: This study started in August 2013, and ended in July 2017. The complete length of ALS2, LIP1, LIP4, and SAPT1-4 of 68 clinical C. tropicalis isolates was sequenced. Single nucleotide polymorphisms (SNPs) as well as insertions and deletions (indels) were identified within these genes. In addition, phenotypic characteristics of the virulent factors, including adhesion and the secretion of aspartyl proteinases and phospholipases, were determined. Results: There were 73, 24, 17, 16, 13, and 180 SNPs in the genes LIP1, LIP4, SAPT1, SAPT2, SAPT3, and SAPT4, respectively. Furthermore, 209 SNPs were identified in total for the gene ALS2. Interestingly, large fragment deletions and insertions were also found in ALS2. Isolate FXCT 01 obtained from blood had deletions on all 4 sites and showed the lowest adhesion ability on the polymethylpentene surface. In addition, isolates with deletions in the regions 1697 to 1925 and 2073 to 2272 bp displayed relatively low abilities for adhesion and biofilm formation, and this phenotype correlated with the deletions found in ALS2. LIP1, SAPT4, and ALS2 displayed great heterogeneity among the isolates. Large deletions found in gene ALS2 appeared to be associated with the low ability of adhesion and biofilm formation of C. tropicalis. Conclusion: This study might be useful for deeper explorations of gene function and studying the virulent mechanisms of C. tropicalis.展开更多
Tributyltin(TBT),a biocide used in antifouling paints,has shown strong teratogenic effects on Xenopus tropicalis embryos at environmentally relevant concentrations.X.tropicalis embryos were exposed to 50,100 and 200...Tributyltin(TBT),a biocide used in antifouling paints,has shown strong teratogenic effects on Xenopus tropicalis embryos at environmentally relevant concentrations.X.tropicalis embryos were exposed to 50,100 and 200 ng/L tributyltin chloride for 72 hr.The histological changes were further observed on abnormal eyes,enlarged trunks,enlarged proctodaeums and absence of fins induced by TBT.The lens and the retinal layers of abnormal eyes were slightly or barely differentiated,and that the pigment epithelium was neither continuous nor smooth.The abdomens were full of undifferentiated gut tissue with yolk-rich inclusions in the tadpoles with enlarged trunks.The proctodaeums formed a bump-like or columnar structure.The mass of yolk-rich cells occupied the lumen,blocked the opening and even turned inside out of the proctodaeum.Both the ventral and dorsal fins in trunks and tails became narrow or even disappeared totally.Our results suggest that great changes of histology took place corresponding to the unique phenotypes.The gut tissue was poorly differentiated,which led to the failed elongation of the guts and subsequently the enlarged trunks.The enlarged proctodaeums were due to the undifferentiation of inner layer,the expansion of outer epidermal part and the absence of fins around them.In brief,the histological observations provided insights into the reason of the unique external malformations in some degree.展开更多
Temperature is important to determine physiological status of ectotherms. However, it is still not fully understood how amphibians and their symbiotic microbiota acclimate to ambient temperature. In this study, we inv...Temperature is important to determine physiological status of ectotherms. However, it is still not fully understood how amphibians and their symbiotic microbiota acclimate to ambient temperature. In this study, we investigated the changes of gut microbiota of Xenopus tropicalis at different temperatures under controlled laboratory conditions. The results showed that microbial communities were distinct and shared only a small overlap among froglet guts, culture water and food samples.Furthermore, the dominant taxa harbored in the gut exhibited low relative abundance in water and food. It indicates that bacterial taxa selected by amphibian gut were generally of low abundance in the external environment. Temperature could affect betadiversity of gut microbiota in terms of phylogenetic distance, but it did not affect alpha diversity. The composition of gut microbiota was similar in warm and cool treatments. However, signature taxa in different temperature environments were identified. The relationships between temperature, gut microbiota and morphology traits of X. tropicalis revealed in this study help us to predict the consequences of environmental changes on ectothermic animals.展开更多
Background According to data from the China Hospital Invasive Fungal Surveillance Net (CHIF-NET) 2010, Candida tropica/is (C. tropica/is) is the third most common pathogen causing invasive candidiasis. Moreover, t...Background According to data from the China Hospital Invasive Fungal Surveillance Net (CHIF-NET) 2010, Candida tropica/is (C. tropica/is) is the third most common pathogen causing invasive candidiasis. Moreover, the majority of fluconazole-resistant C. tropicalis isolates were from a single hospital. Therefore, a molecular epidemiological survey is necessary to investigate the genetic relatedness of C. tropica/is isolates in China. Methods In this study, 48 C. tropicalis isolates causing invasive fungal infections from four tertiary hospitals in China were studied. All the isolates were identified by sequencing the internal transcribed spacer region. Antifungal susceptibility to triazoles, amphotericin B, and caspofungin was determined by the Clinical and Laboratory Standards Institute standard broth microdilution method. Multilocus sequence typing (MLST) was performed, and phylogenetic analysis was further performed by the eBURST and maximum parsimony (MP) methods to characterize the genetic relatedness of isolates. Results MLST discriminated 40 diploid sequence types (DSTs) among 48 isolates, including 36 novel DSTs, and the XYR1 gene showed the highest discriminatory power. The DSTs obtained from this study were compared with those of previously reported C. tropicalis isolates, and there was poor type alignment with regional strains. Nine groups and 11 singletons were identified by eBURST, whereas two groups and 10 subgroups were clustered by MP analysis. Generally, there were no obvious correlations between clonal clusters generated and the specimen source or hospital origin. Seven fiuconazole-resistant isolates were confirmed and assigned to three distinguishable branches. Conclusions The results suggested diverse origins of invasive C. tropicalis isolates in China. Although most invasive C. tropicalis strains in the mainland of China were clustered with previously characterized Asian isolates, major C. tropicalis clusters identified in this study were genetically distinct from those of other geographic regions.展开更多
Xenopus tropicalis embryos were exposed for 48 hr to the mixtures of 5 μg Sn/L triphenyltin (TPT), which is a well-known endocrine disruptor, and 0.25-5 μg/L 9-cis retinoic acid (9c-RA), which is the natural lig...Xenopus tropicalis embryos were exposed for 48 hr to the mixtures of 5 μg Sn/L triphenyltin (TPT), which is a well-known endocrine disruptor, and 0.25-5 μg/L 9-cis retinoic acid (9c-RA), which is the natural ligand of retinoid X receptor. The phenotypes induced by combined exposure were more variable than those resulting from single exposure to either TPT or 9c-RA. The prominent phenotypes included underdeveloped head structures, abnormal eyes, narrow fins, enlarged proctodaeum, etc. Especially, combined exposure induced unexpected notochord malformations, which ranged from small swellings of the surface of the tails to the extension and extrusion of notochord out of the posterior tails. Compared with the 5 μg Sn/L TPT-treated group, the index of fin deficiency was not affected, and the index of axis deficiency was significantly increased with increasing RA concentrations in the mixtures. Our results suggest that combined exposure to TPT and 9c-RA induced not only more variable phenotypes of malformations than exposure to single compound but also some new and unexpected phenotypes.展开更多
文摘Production and quality of vinegar from mango juice was evaluated using a two steps production procedure. The first step of fermentation was done using Saccharomyces cerevisae KVL013 for 7 days. The second step, an acetic fermentation was realized using two acetic acid bacteria: A. tropicalis CRSBAN-BVA1 and A. tropicalis CRSBAN-BVK2 for 21 days. Several parameters of the vinegar produced such as physico-chemical and sensory properties were determined. Microbial density during each step was monitored. Results showed that pH, alcoholic and acetic acid contents of vinegar were respectively 2.97%, 7% and 4.54% g/ml respectively by using A. tropicalis CRSBAN-BVA1 and 3.02%, 7% and 4.32% g/ml with A. tropicalis CRSBAN-BVK2. Sensory evaluation revealed that the vinegar was acceptable to the panellists. Results of microbial density showed that the maximum concentration of cell biomass produced was 4.32 × 10<sup>8</sup> and 4.25 × 10<sup>8</sup> CFU/ml respectively for CRSBAN-BVA1 and CRSBAN-BVK2.
文摘Candida endocarditis is extremely rare in term neonates,and gall bladder involvement due to candidemia has never been reported amongst neonates and infants.A term,appropriate for gestational age neonate developed Candida tropicalis blood stream infection in second week of life.He was started on conventional amphotericin B.However,he failed to show any clinical improvement,and candidemia keep on persisting.Repeat sanctuary sites screening revealed multiple echogenic masses in heart(vegetations) and gall bladder.On changing the treatment to liposomal amphotericin B and fluconazole,he recovered clinically,echogenic masses in gall bladder disappeared,and intracardiac vegetations decreased in size.
文摘Xylose reductase (EC 1.1.1.21) of Candida tropicalis IEC5-ITV, an indigenous xylitol-producing strain, was partially purified by reversed micelles and characterized, an 8.1 fold purification factor being obtained. The XR present in the crude extract exhibited its highest specific activity at pH 6.0 and 40℃, while in that obtained by reverse micelles, this occurs at pH 6.0 and 30℃. XR before and after extraction is stable within a range of 30 to 40℃, pH 7 after one hour of incubation under these conditions. After two months’storage at –18℃, the enzyme obtained by reverse micelles lost 76.60% specific activity. The estimated molecular weight by PAGE-SDS was 32.42 kD. KM for xylose was higher for the XR extracted by reverse micelles (0.026 M) than that obtained for the enzyme before extraction (0.0059 M), while KM for cofactor NADPH was lower after than before extraction (1.85 mM to 12.0 mM respectively). There was no activity with NADH as a cofactor. Variations in pH and temperature optima, as well as kinetic parameters before and after partial XR purification by reverse micelles are probably due to an alteration in enzyme molecule structure caused by the solvents used during extraction.
文摘[Objectives] The fermentation conditions of Candida tropicalis 1798-pxa1 were optimized to further improve its yield of long-chain dibasic acids. [Methods] The strains used in the study were C. tropicalis 1798, C. tropicalis 1798-pxa1 and C. tropicalis 1798-pxa1 p2. First, through single factor experiments, the activated three fungi were cultured in different carbon sources, and the absorbance was measured every 2 h. The growth curve was drawn by software, and finally the most suitable substance for the substrate was selected, i.e., dodecane. Then, the composition of the fermentation medium and the fermentation process parameters were determined through the PB experiment of the single-deletion C. tropicalis 1798-pxa1. [Results] The experiment determined the important components affecting the synthesis of long-chain dibasic acids, namely(NH_4)_2SO_4, NaCl and dodecane. After optimization of the culture conditions, the yield of long-chain dibasic acids of C. tropicalis 1798-pxa1 increased from 5.6 to 10.1 g/L. [Conclusions] The scheme has been verified to be capable of greatly increasing the yield of the corresponding long-chain dibasic acids of the C. tropicalis engineering strain.
文摘Phenol is an important commodity for the chemical industry, used for many processes and deemed to be a major pollutant due its xenobiotic nature and high toxicity. For the purpose of phenol bioremediation a biotechnological set up consisting of a continuous packed column bioreactor with Candida tropicalis adhered onto activated carbon beads has been previously described. In this work, we show how the integration of available experimental data of such a biotechnological set up into a mathematical model, can lead both to a better comprehension of the underlying physiological mechanisms operating in the cell culture, and to the identification of the system parameters optimum performance. The model so constructed describes the dynamics of phenol uptake and growth rates by the adhered and suspended biomass;the lethality rates;the adhered biomass removal into suspension or adherence onto carbon beads rates and the phenol and biomass (adhered and suspended) concentrations. It also serves to identify different physiological states for the adhered and the suspended biomass;its predictions being verified by comparing with experimental observations. Based on the model description, different optimization strategies are proposed, some of which have been experimentally tested, encompassing changes in bioreactor operation conditions, process development and strain development.
文摘To investigate the chemical structure of cell wall mannan obtained from pathogenic yeast, Candida tropicalis NBRC 1400 (former antigenic standard strain, IFO 1400). As a result of two-dimensional NMR analysis, it was shown that the mannan of this strain is composed of α-1,6-, α-1,3-, α-1,2- and β-1,2-linked mannose residues. In this research, the mannan was subjected to three degradation procedures, acid-treatment, α-mannosidase, and acetolysis under two conditions in order to determine the chemical structure of the antigenic oligomannosyl side chains in this molecule. The 1H-nuclear magnetic resonance spectra of resultant oligosaccharides, pentaose and hexaose, demonstrated the existence of the oligomannosyl side chains corresponding to Manα1-3Manα1-2Manα1-2Manα1-2Man and Manα1-3Manα1-2Manα1-2Manα1-2Manα1-2Man, respectively, which have previously also been found in Candida albicans serotype A strain mannans. These findings indicate that C. tropicalis and C. albicans serotype A have no significant difference in the chemical structure of these cell wall mannans. Therefore, it can be interpreted that it is extremely difficult to distinguish both species by targeting the antigenic group in these mannans.
基金CNPq(Brazilian National Research Council)which has awarded us a grant for this research
文摘Microorganism resistance to the existing products is yet another difficulty that agriculturalists have to deal with. In this context, the search for new agricultural products that can fight phytopathogens has become increasingly important. Plants have played an important role in this process, because they can serve as a source of new compounds for drug discovery. Plants belonging to the genus Pinus produce an oleoresin that protects the plant against herbivores and pathogens. With a view to developing products that can combat fungal pathogens without harming the environment, this work aimed to evaluate the antifungal activity of the oleoresins and fractions of Pinus elliottii Engelm and Pinus tropicalis against phytopathogens. The methodology based on NCCLS M38-A standards aided antifungal activity assessment. The microdilution method helped to determine the Minimum Inhibitory Concentration (MIC) and Minimum Fungicidal Concentration (MFC). The oleoresins of P. elliottii and P. tropicalis afforded the most significant results—they displayed fungicidal activity against all the tested species. MIC values were promising, especially the MIC of the oleoresin of P. elliottii against S. rolfsii (1.95 μg·mL-1). The MIC values of the oleoresins of P. elliottii and P. tropicalis ranged from 1.95 to 1000 μg·mL-1 and from 31.25 to 250 μg·mL-1, respectively. Fraction PT2 of P. tropicalis furnished the best results among all the assayed fractions: MIC values lay between 125 and 500 μg·mL-11. In conclusion, the oleoresin of P. tropicalis is a promising source of new antifungal agents for application in the treatment of phytopathogenic infections.
基金supported by the National Natural Science Foundation of China(No.41977340)the Key-Area Research and Development Program of Guangdong Province(No.2020B1111350003).
文摘Direct discharge of aquaculture wastewater may have toxic effects,due to the presence of heavy metals,antibiotics,and even resistant pathogens,but little attention has been given.Here,tanks simulating a wild ecosystem were built to study the effects of long-term exposure to duckwastewater containing oxytetracycline(OTC)and/or arsenic(As)on the growth,physiological function,and gut microbiota evolution of Xenopus tropicalis.The results showed that duck wastewater had no apparent impact on X.tropicalis,but the impact increased significantly(P<0.05)with exposure to OTC and/or As,especially the impact on body weight and growth rate.Biochemical indicators revealed varying degrees of oxidative stress damage,hepatotoxicity(inflammation,necrosis,and sinusoids),and collagen fibrosis of X.tropicalis in all treated groups after 72 days of exposure,which indirectly inhibited X.tropicalis growth.Moreover,16S rDNA amplicon sequencing results showed that the gut microbiota structure and metabolic function were perturbed after chronic exposure,which might be the leading cause of growth inhibition.Interestingly,the abundance of intestinal resistance genes(RGs)increased with exposure time owing to the combined direct and indirect effects of stress factors in duck wastewater.Moreover,once the RGs were expressed,the resistance persisted for at least 24 days,especially that conferred by tetA.These results provide evidence of the toxic effects of DW containing OTC(0.1–4.0 mg/L)and/or As(0.3–3.5μg/L)on amphibians and indicate that it is vital to limit the usage of heavy metals and antibiotics on farms to control the biotoxicity of wastewater.
基金supported by the National Natural Science Foundation of China (No.50778110)
文摘Statistical experimental designs were used to optimize the process of phenol degradation by Candida tropicalis Z-04, isolated from phenol-degrading aerobic granules. The most important factors influencing phenol degradation (p 〈 0.05), as identified by a two-level Plackett-Burman design with 11 variables, were yeast extract, phenol, inoculum size, and temperature. Steepest ascent method was undertaken to determine the optimal regions of these four significant factors. Central composite design (CCD) and response surface analysis were adopted to further investigate the mutual interactions between these variables and to identify their optimal values that would generate maximum phenol degradation. The analysis results indicated that interactions between yeast extract and temperature, phenol and temperature, inocuhim size and temperature affected the response variable (phenol degradation) significantly. The predicted results showed that the maximum removal efficiency of phenol (99.10%) could be obtained under the optimum conditions of yeast extract 0.41 g/L, phenol 1.03 g/L, inoculum size 1.43% (V/V) and temperature 30.04℃. These predicted values were further verified by validation experiments. The excellent correlation between predicted and experimental values confirmed the validity and practicability of this statistical optimum strategy. This study indicated the excellent ability of C. tropicalis Z-04 in degrading high-strength phenol. Optimal conditions obtained in this experiment laid a solid foundation for further use of this microorganism in the treatment of highstrength phenol effluents.
基金supported by the National Natural Science Foundation of China (No. 20977048)the National High Technology and Development Program (863) of China (No. 2009AA06Z317)a Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)
文摘Aniline-degrading microbes were cultivated and acclimated with the initial activated sludge collected from a chemical wastewater treatment plant. During the acclimation processes, aerobic granular sludge being able to effectively degrade aniline was successfully formed, from which a preponderant bacterial strain was isolated and named as AN1. Effects of factors including pH, temperature, and second carbon/nitrogen source on the biodegradation of aniline were investigated. Results showed that the optimal conditions for the biodegradation of aniline by the strain AN1 were at pH 7.0 and 28–35°C. At the optimal pH and temperature, the biodegradation rate of aniline could reach as high as 17.8 mg/(L·hr) when the initial aniline concentration was 400 mg/L. Further studies revealed that the addition of 1 g/L glucose or ammonium chloride as a second carbon or nitrogen source could slightly enhance the biodegradation efficiency from 93.0% to 95.1%–98.5%. However, even more addition of glucose or ammonium could not further enhance the biodegradation process but delayed the biodegradation of aniline by the strain AN1. Based on morphological and physiological characteristics as well as the phylogenetic analysis of 26S rDNA sequences, the strain AN1 was identified as Candida tropicalis.
基金the National Natural Science Foundation of China (Youth Project No.81301409)the National Sci-Tech Key Project (No.2013ZX10004203-002).
文摘Background: Adhesion, biofilm formation, yeast-hyphal transition, secretion of enzymes, and hemolytic activity are all considered important factors in Candida tropicalis infection. However, DNA sequence data for this pathogen are limited. In this study, the polymorphism and heterogeneity of genes agglutinin-like sequences (ALS)2, Lipase (LIP)1, LIP4, and secretory aspartyl proteinase tropicalis (SAPT)1-4 as well as the relationship between phenotype and genotype were analyzed. Methods: This study started in August 2013, and ended in July 2017. The complete length of ALS2, LIP1, LIP4, and SAPT1-4 of 68 clinical C. tropicalis isolates was sequenced. Single nucleotide polymorphisms (SNPs) as well as insertions and deletions (indels) were identified within these genes. In addition, phenotypic characteristics of the virulent factors, including adhesion and the secretion of aspartyl proteinases and phospholipases, were determined. Results: There were 73, 24, 17, 16, 13, and 180 SNPs in the genes LIP1, LIP4, SAPT1, SAPT2, SAPT3, and SAPT4, respectively. Furthermore, 209 SNPs were identified in total for the gene ALS2. Interestingly, large fragment deletions and insertions were also found in ALS2. Isolate FXCT 01 obtained from blood had deletions on all 4 sites and showed the lowest adhesion ability on the polymethylpentene surface. In addition, isolates with deletions in the regions 1697 to 1925 and 2073 to 2272 bp displayed relatively low abilities for adhesion and biofilm formation, and this phenotype correlated with the deletions found in ALS2. LIP1, SAPT4, and ALS2 displayed great heterogeneity among the isolates. Large deletions found in gene ALS2 appeared to be associated with the low ability of adhesion and biofilm formation of C. tropicalis. Conclusion: This study might be useful for deeper explorations of gene function and studying the virulent mechanisms of C. tropicalis.
基金supported by the National Natural Science Foundation of China (No. 20877023,20507007)
文摘Tributyltin(TBT),a biocide used in antifouling paints,has shown strong teratogenic effects on Xenopus tropicalis embryos at environmentally relevant concentrations.X.tropicalis embryos were exposed to 50,100 and 200 ng/L tributyltin chloride for 72 hr.The histological changes were further observed on abnormal eyes,enlarged trunks,enlarged proctodaeums and absence of fins induced by TBT.The lens and the retinal layers of abnormal eyes were slightly or barely differentiated,and that the pigment epithelium was neither continuous nor smooth.The abdomens were full of undifferentiated gut tissue with yolk-rich inclusions in the tadpoles with enlarged trunks.The proctodaeums formed a bump-like or columnar structure.The mass of yolk-rich cells occupied the lumen,blocked the opening and even turned inside out of the proctodaeum.Both the ventral and dorsal fins in trunks and tails became narrow or even disappeared totally.Our results suggest that great changes of histology took place corresponding to the unique phenotypes.The gut tissue was poorly differentiated,which led to the failed elongation of the guts and subsequently the enlarged trunks.The enlarged proctodaeums were due to the undifferentiation of inner layer,the expansion of outer epidermal part and the absence of fins around them.In brief,the histological observations provided insights into the reason of the unique external malformations in some degree.
基金the National Key Program of Research and Development, Ministry of Science and Technology of China (2016YFC0503200)Sichuan Province Science and Technology Project (2017SZ0004)+2 种基金the 13th Five-year Informatization Plan of Chinese Academy of Sciences (XXH13503-03-106)Open Fund of Key Laboratory of Environmental and Applied Microbiology CAS (KLCAS-2017-3, KLCAS2016-03)China Biodiversity Observation Networks (Sino BON)。
文摘Temperature is important to determine physiological status of ectotherms. However, it is still not fully understood how amphibians and their symbiotic microbiota acclimate to ambient temperature. In this study, we investigated the changes of gut microbiota of Xenopus tropicalis at different temperatures under controlled laboratory conditions. The results showed that microbial communities were distinct and shared only a small overlap among froglet guts, culture water and food samples.Furthermore, the dominant taxa harbored in the gut exhibited low relative abundance in water and food. It indicates that bacterial taxa selected by amphibian gut were generally of low abundance in the external environment. Temperature could affect betadiversity of gut microbiota in terms of phylogenetic distance, but it did not affect alpha diversity. The composition of gut microbiota was similar in warm and cool treatments. However, signature taxa in different temperature environments were identified. The relationships between temperature, gut microbiota and morphology traits of X. tropicalis revealed in this study help us to predict the consequences of environmental changes on ectothermic animals.
文摘Background According to data from the China Hospital Invasive Fungal Surveillance Net (CHIF-NET) 2010, Candida tropica/is (C. tropica/is) is the third most common pathogen causing invasive candidiasis. Moreover, the majority of fluconazole-resistant C. tropicalis isolates were from a single hospital. Therefore, a molecular epidemiological survey is necessary to investigate the genetic relatedness of C. tropica/is isolates in China. Methods In this study, 48 C. tropicalis isolates causing invasive fungal infections from four tertiary hospitals in China were studied. All the isolates were identified by sequencing the internal transcribed spacer region. Antifungal susceptibility to triazoles, amphotericin B, and caspofungin was determined by the Clinical and Laboratory Standards Institute standard broth microdilution method. Multilocus sequence typing (MLST) was performed, and phylogenetic analysis was further performed by the eBURST and maximum parsimony (MP) methods to characterize the genetic relatedness of isolates. Results MLST discriminated 40 diploid sequence types (DSTs) among 48 isolates, including 36 novel DSTs, and the XYR1 gene showed the highest discriminatory power. The DSTs obtained from this study were compared with those of previously reported C. tropicalis isolates, and there was poor type alignment with regional strains. Nine groups and 11 singletons were identified by eBURST, whereas two groups and 10 subgroups were clustered by MP analysis. Generally, there were no obvious correlations between clonal clusters generated and the specimen source or hospital origin. Seven fiuconazole-resistant isolates were confirmed and assigned to three distinguishable branches. Conclusions The results suggested diverse origins of invasive C. tropicalis isolates in China. Although most invasive C. tropicalis strains in the mainland of China were clustered with previously characterized Asian isolates, major C. tropicalis clusters identified in this study were genetically distinct from those of other geographic regions.
基金supported by the National Natural Science Foundation of China(No.21277049)the State Key Laboratory of Estuarine and Coastal Research(No.2012KYYW04)
文摘Xenopus tropicalis embryos were exposed for 48 hr to the mixtures of 5 μg Sn/L triphenyltin (TPT), which is a well-known endocrine disruptor, and 0.25-5 μg/L 9-cis retinoic acid (9c-RA), which is the natural ligand of retinoid X receptor. The phenotypes induced by combined exposure were more variable than those resulting from single exposure to either TPT or 9c-RA. The prominent phenotypes included underdeveloped head structures, abnormal eyes, narrow fins, enlarged proctodaeum, etc. Especially, combined exposure induced unexpected notochord malformations, which ranged from small swellings of the surface of the tails to the extension and extrusion of notochord out of the posterior tails. Compared with the 5 μg Sn/L TPT-treated group, the index of fin deficiency was not affected, and the index of axis deficiency was significantly increased with increasing RA concentrations in the mixtures. Our results suggest that combined exposure to TPT and 9c-RA induced not only more variable phenotypes of malformations than exposure to single compound but also some new and unexpected phenotypes.