[Objective] The aim was to study the sequence of aroA gene （synthetic gene in metabolic pathway of aromatic amino acids） of a pathogenic bacterium （Flavobacterium johnsoniae） causing gill-rote disease.[Method] Gen...[Objective] The aim was to study the sequence of aroA gene （synthetic gene in metabolic pathway of aromatic amino acids） of a pathogenic bacterium （Flavobacterium johnsoniae） causing gill-rote disease.[Method] Genomic DNA of strain M165 of F.johnsoniae was used as a template,three specific nested primers of 5＇end and 3＇end and arbitrary primer were used to amplify the aroA gene of strain M165 through Thermal asymmetric interlaced PCR （TAIL-PCR）.And the obtained sequence was analyzed.[Result] The electrophoresis determination result showed that the size of amplified product was consist with the expected product; sequencing analysis suggested that the full-length of aroA gene was 1 230 bp,enconding 410 amino acids.The amino acid sequence of aroA protein showed the highest level of similarity to amino acids sequence of aroA protein of F.johnsoniae.[Conclusion] TAIL-PCR provided a simple and efficient new method for the cloning of the gene sequence.Obtaining of full-length of aroA gene provided a foundation for further investigation on the effects of nutrition correlation factors such as aroA on the virulence of and virulence of F.johnsoniae.展开更多
From the ethyl acetate extract of Murraya koenegii (Rutaceae) leaves, isomahanine (1) and mahanine (2) were isolated that showed antibacterial activity towards Flavobacterium columnare and Streptococcus iniae which ca...From the ethyl acetate extract of Murraya koenegii (Rutaceae) leaves, isomahanine (1) and mahanine (2) were isolated that showed antibacterial activity towards Flavobacterium columnare and Streptococcus iniae which caused columnaris disease and streptococcosis respectively. Isomahanine was found to have the strongest activity against F. columnare (isolate ALM-00-173) and S. iniae (isolate LA94-426) based on 24-h 50% inhibition concentration (IC50) and minimum inhibition concentration (MIC). Although compound (7), a nicotinamide isolated from Amyris texana had the lowest MIC (2.8 ± 0 mg/L) of any of the test compounds against F. columnare, the 24-h IC50 of 14.8 ± 0.6 mg/L was higher than that of isomahanine and subsequently the 24-h IC50 RDC values for (7) were almost a magnitude of order higher than those obtained for isomahanine. Isomahanine also had the strongest activity against S. iniae, with a 24-h IC50 of 1.3 ± 0.1 mg/L and MIC of 3.5 ± 0 mg/L, respectively.展开更多
Flavobacterium columnare causes columnaris disease in freshwater fi sh. In the present study, the antigenic regions of fi ve outer membrane proteins(OMPs), including zinc metalloprotease, prolyl oligopeptidase, thermo...Flavobacterium columnare causes columnaris disease in freshwater fi sh. In the present study, the antigenic regions of fi ve outer membrane proteins(OMPs), including zinc metalloprotease, prolyl oligopeptidase, thermolysin, collagenase and chondroitin AC lyase, were bioinformatically analyzed, fused together, and then expressed as a recombinant fusion protein in Escherichia coli. The expressed protein of 95.6 k Da, as estimated by 10% sodium dodecyl sulfate-polyacrylamide gel electrophoresis, was consistent with the molecular weight deduced from the amino acid sequence. The purifi ed recombinant protein was used to vaccinate the grass carp, C tenopharyngodon idella. Following vaccination of the fi sh their Ig M antibody levels were examined, as was the expression of I g M, Ig D and Ig Z immunoglobulin genes and other genes such as MHC Iα and MHC I I β, which are also involved in adaptive immunity. Interleukin genes( IL), including I L- 1β, IL- 8 and I L- 10, and type I and type II interferon(I FN) genes were also examined. At 3 and 4 weeks post-vaccination(wpv), signifi cant increases in Ig M antibody levels were observed in the fi sh vaccinated with the recombinant fusion protein, and an increase in the expression levels of I g M, Ig D and Ig Z genes was also detected following the vaccinations, thus indicating that an adaptive immune response was induced by the vaccinations. Early increases in the expression levels of IL and IFN genes were also observed in the vaccinated fi sh. At four wpv, the fi sh were challenged with F. column a re, and the vaccinated fi sh showed a good level of protection against this pathogen, with 39% relative percent survival(RPS) compared with the control group. It can be concluded, therefore, that the fi ve OMPs, in the form of a recombinant fusion protein vaccine, induced an immune response in fi sh and protection against F. columnare.展开更多
Flavobacterium columnare is the pathogenic agent of columnaris disease in aquaculture. Using a recently developed gene deletion strategy, two genes that encode the Glyco hydro_19 domain （GH19 domain） containing prot...Flavobacterium columnare is the pathogenic agent of columnaris disease in aquaculture. Using a recently developed gene deletion strategy, two genes that encode the Glyco hydro_19 domain （GH19 domain） containing proteins, ghd-1 and ghd-2, were deleted separately and together from the F. columnare G4 wild type strain. Surprisingly, the single-, Aghd-1 and Aghd-2, and double-gene mutants, Aghd-1 Aghd-2, all had rhizoid and non-rhizoid colony morphotypes, which we named Aghd-1, Aghd-2, Aghd-1 Aghd-2, and NAghd-1, NAghd-2, and NAghd-1 Aghd-2. However, chitin utilization was not detected in either these mutants or in the wild type. Instead, skimmed milk degradation was observed for the mutants and the wild type; the non-rhizoid strain NAghd-2 exhibited higher degradation activity as revealed by the larger transparent circle on the skimmed milk plate. Using zebrafish as the model organism, we found that non-rhizoid mutants had higher LDs0 values and were less virulent because zebrafish infected with these survived longer. Transcriptome analysis between the non-rhizoid and rhizoid colony morphotypes of each mutant, i.e., NAghd-1 versus （vs） Aghd-1, NAghd-2 vs Aghd-2, and NAghd-1 Aghd-2 vs Aghd-1 Aghd-2, revealed a large number of differentially expressed genes, among which 39 genes were common in three of the pairs compared. Although most of these genes encode hypothetical proteins, a few molecules such as phage tail protein, rhs element Vgr protein, thiol-activated cytolysin, and TonB-dependent outer membrane receptor precursor, expression of which was down-regulated in non-rhizoid mutants but up-regulated in rhizoid mutants, may play a role F. columnare virulence.展开更多
The effect of penicillin-G on Flavobacterium psychrophilum, the cause of bacterial coldwater disease, was evaluated in 15 min and overnight exposures. Separate tests evaluated the effect of increasing doses of penicil...The effect of penicillin-G on Flavobacterium psychrophilum, the cause of bacterial coldwater disease, was evaluated in 15 min and overnight exposures. Separate tests evaluated the effect of increasing doses of penicillin-G to rainbow trout Oncorhynchus mykiss eggs, fingerlings, and adults. Rainbow trout eggs were exposed for 1 h to penicillin doses of 0, 250, 500, 1,000, 10,000, 50,000, or 100,000 IU/mL. Mean percent hatch ranged from 64.6% to 75.1%, and did not significantly differ among the treatments. Fingerlings were injected intraperitoneally (i.p.) with 200 μL of 0, 1, 10, 100, 1,000, 10,000, 100,000, or 500,000 IU/mL. Probit analysis resulted in a LD10 (lethal dose for 10% of injected fish) of 52,868 IU/mL (95% confidence limits: 31,522 - 69,490 IU/mL) and a LD50 of 131,466 IU/mL (113,095 - 157,878 IU/mL). Brood stock were injected (i.p.) with 200 μL of penicillin at concentrations of 0 (control), 10,000, 50,000, 100,000, 200,000, 400,000, or 800,000 IU/mL. Mortality ranged from 0% to 7% (50,000 IU/mL treatment) and did not significantly differ among treatments. In 28 h exposure tests, penicillin concentrations of ≥ 333 IU/mL were required to completely suppress growth of F. psychrophilum. In 15 min exposures, ≥ 10,000 IU/mL were needed to achieve the same result. Tests indicated that rainbow trout eggs can tolerate 1 h exposures to penicillin-G concentrations as high as 100,000 IU/mL, and that brood fish can tolerate injections of at least 800,000 IU/mL. Fingerling data however, suggested that injection of doses greater than 10,000 IU/mL can be toxic. The data suggests rainbow trout eggs or brood can tolerate high doses of penicillin-G that could be used for controlling the transfer of F. psychrophilum to hatcheries receiving eggs.展开更多
Flavobacterium columnare, the etiological agent of colunmaris disease, is one of the most important and widespread bacterial pathogens of freshwater fish. In this study, we constructed two artificial selectable marke...Flavobacterium columnare, the etiological agent of colunmaris disease, is one of the most important and widespread bacterial pathogens of freshwater fish. In this study, we constructed two artificial selectable markers （chloramphenicol and spectinomycin resistance） for gene transfer in F. columnare. These two new artificial selectable markers, which were created by placing the chloramphenicol or spectinomycin resistance gene under the control of the native acs regulatory region of F. columnare, were functional in both F. columnare and Escherichia coli. The integrative/conjugative plasmids constructed by using these markers were introduced into F. columnare G4 via electroporation or conjugation. The integrated plasmid DNA was confirmed by Southern blotting and PCR analysis. These two markers can be employed in future investigations into gene deletion and the pathogenicity of virulence factors in F. columnare.展开更多
From time immemorial, human beings have used pigments made from vegetables, fruits, superior plants, animal tissues and cereals. One of the greatest sources of pigments is the bacterium that, with the use of the moder...From time immemorial, human beings have used pigments made from vegetables, fruits, superior plants, animal tissues and cereals. One of the greatest sources of pigments is the bacterium that, with the use of the modern technology, has increased the production of metabolites of interest. The microbiological production of carotenoids has not been optimized to obtain pigment production quantities of pigments and carotenoids recovery that lower production costs. The aim of this work was to design a Zeaxanthin production process with Flavobacterium sp. immobilized cells in a fluidized bed bioreactor. An optimum culture medium for Zeaxanthin production in stirred flasks (2.46 g·L–1) was obtained. Furthermore, optimum process conditions for a maximum yield of Zeaxanthin production, by fluidized bed bioreactor, were established. A statistical analysis showed that the most significant factors were air flow, pH and NaCl concentration (4.5 g·L–1). In this study a maximum Zeaxanthin production of 3.8 g·L–1 was reached. The highest reported yield to date was 0.329 g·L–1.展开更多
Columnaris (caused by Flavobacterium columnare) is one of the most common bacterial diseases affecting the pond-raised channel catfish (Ictalurus punctatus) in the southeastern United States of America resulting in an...Columnaris (caused by Flavobacterium columnare) is one of the most common bacterial diseases affecting the pond-raised channel catfish (Ictalurus punctatus) in the southeastern United States of America resulting in annual losses of millions of dollars. As part of our continuing effort to discover environmentally benign compounds for the control of columnaris disease, acyl derivatives of phloroglucinol were synthesized and tested against F. columnare using a rapid bioassay. Among the analogs that were tested, diacyl analogs showed very high antibacterial activity against F. columnare in the laboratory bioassay. Diisovaleryl and diisobutyryl analogs were found to have the strongest activity against F. columnare (isolate ALM-00-173) based on 24-h 50% inhibitory concentration (IC50) and minimum inhibitory concentration (MIC). Diisovaleryl and diisobutyryl analogs had IC50 values 0.82 mg/L and 0.80 mg/L, respectively, whereas the drug control florfenicol had an IC50 value of 0.81 mg/L. Diisovaleryl and diisobutyryl analogs also had 24-h relative-to- drug-control IC50 values around 1.0 indicating activities similar to florfenicol, which is included in medicated feed and is one of the current management approach for columnaris.展开更多
Objective： The aim of the research was to investigate efficacy of dried bio-floc supplemented with immuno-stimulants as beta-glucan and nucleotide on mortality rate and relative percent survival （RPS） of tilapia in...Objective： The aim of the research was to investigate efficacy of dried bio-floc supplemented with immuno-stimulants as beta-glucan and nucleotide on mortality rate and relative percent survival （RPS） of tilapia infected with Flavobacterium columnare, VETSV01. Materials and Methods： A research was performed in 1-inch long tilapia stimulated its immunity by infection with Flavobacterium columnare, VETSV01. Pathogenesis of 0.2 mL Flavobacterium columnare, VETSV01 in the range of 10^2-10^8 mL-1 fish^-1 was injected into its intraperitoneal injection and intramuscular injection and suitable concentrations were screened to obtain for further experiment in a late restage. Based on data of minimal concentration, 50% mortality rate was caused and it was found the concentration of 108 mL^-1 fish^-1 caused 100% mortality rate and no lethal rate was found in other concentrations. Afterwards, efficacy of bio-floc sediment on survival rate of Tilapia infected with Flavobacterium columnare, VETSV01 was examined. Completely randomized design was employed and experiments were divided into 4 treatment： （1） contxol-commercial feed only, （2） commercial feed attached with dried bio-floc, （3） commercial feed attached with bio-floc and beta-glucan and （4） commercial feed attached with bio-floc and nucleotide. Experiment design was performed as 3 replicates with 10 fishes/replicates in 24 inch glass aquarium. Analysis of difference was performed and determination of mean differences of mortality rate mad relative percent survival was done through Duncan＇s Multiple Range Test （p 〈 0.05）. Results and Discussions： It was demonstrated feeding tilapia with commercial feed in combination with dried bio-floc with or without supplementation of 2 immuno-stimulants could lead to 100% survival rate and 100% relative percent survival rate and it was statistically significant different （p 〈 0.05） compared to control group. Bio-floc product supplemented with beta glucan or nucleotide could effectively stimulate immunity against Flavobacterium columnare, VETSV01 and such high effective performance is viewed as a promising potential product to be further developed and practically employed for sake of aquaculture industry in the near future.展开更多
A bacterium capable of degrading dichlorvos was isolated from the rape phyllosphere and designated YD4. The strain was identified as Flavobacterium sp., based on its phenotypic features and 16S rRNA gene sequence. Str...A bacterium capable of degrading dichlorvos was isolated from the rape phyllosphere and designated YD4. The strain was identified as Flavobacterium sp., based on its phenotypic features and 16S rRNA gene sequence. Strain YD4 was able to utilize dichlorvos as the sole source of phosphorus. In situ enhanced bioremedia- tion of dichlorvos by YD4 was hereafter studied. Chlorpyrifos and phoxim could also be degraded by this strain as the sole phosphorus source. A higher degradation rate of dichlorvos was observed after spraying YD4 onto the surface of rape leaves when compared to the sterilized- YD4 and water-treated samples. The results indicated that pesticide-degrading epiphytic bacterium could become a new way for in situ phyllosphere bioremediation where the hostile niche is unsuitable for other pesticide-degrading bacteria isolated from soil and water.展开更多
基金Supported by The Natural Science Foundation of Guangdong Province(06024033)National Special Fund for the Agricultural Commonweal Industry(200803013)Earmarked Fund for Modern Agroindustry Technology Research System(nycytx-49-14)~~
文摘[Objective] The aim was to study the sequence of aroA gene （synthetic gene in metabolic pathway of aromatic amino acids） of a pathogenic bacterium （Flavobacterium johnsoniae） causing gill-rote disease.[Method] Genomic DNA of strain M165 of F.johnsoniae was used as a template,three specific nested primers of 5＇end and 3＇end and arbitrary primer were used to amplify the aroA gene of strain M165 through Thermal asymmetric interlaced PCR （TAIL-PCR）.And the obtained sequence was analyzed.[Result] The electrophoresis determination result showed that the size of amplified product was consist with the expected product; sequencing analysis suggested that the full-length of aroA gene was 1 230 bp,enconding 410 amino acids.The amino acid sequence of aroA protein showed the highest level of similarity to amino acids sequence of aroA protein of F.johnsoniae.[Conclusion] TAIL-PCR provided a simple and efficient new method for the cloning of the gene sequence.Obtaining of full-length of aroA gene provided a foundation for further investigation on the effects of nutrition correlation factors such as aroA on the virulence of and virulence of F.johnsoniae.
文摘From the ethyl acetate extract of Murraya koenegii (Rutaceae) leaves, isomahanine (1) and mahanine (2) were isolated that showed antibacterial activity towards Flavobacterium columnare and Streptococcus iniae which caused columnaris disease and streptococcosis respectively. Isomahanine was found to have the strongest activity against F. columnare (isolate ALM-00-173) and S. iniae (isolate LA94-426) based on 24-h 50% inhibition concentration (IC50) and minimum inhibition concentration (MIC). Although compound (7), a nicotinamide isolated from Amyris texana had the lowest MIC (2.8 ± 0 mg/L) of any of the test compounds against F. columnare, the 24-h IC50 of 14.8 ± 0.6 mg/L was higher than that of isomahanine and subsequently the 24-h IC50 RDC values for (7) were almost a magnitude of order higher than those obtained for isomahanine. Isomahanine also had the strongest activity against S. iniae, with a 24-h IC50 of 1.3 ± 0.1 mg/L and MIC of 3.5 ± 0 mg/L, respectively.
基金Supported by the National Basic Research Program of China(973 Program)(No.2009CB118703)the Science and Technology Program of Xiamen Southern Oceanographic Center(No.14PYY050SF03)the National Science and Technology Support Program Project of China(No.2012BAD25B02)
文摘Flavobacterium columnare causes columnaris disease in freshwater fi sh. In the present study, the antigenic regions of fi ve outer membrane proteins(OMPs), including zinc metalloprotease, prolyl oligopeptidase, thermolysin, collagenase and chondroitin AC lyase, were bioinformatically analyzed, fused together, and then expressed as a recombinant fusion protein in Escherichia coli. The expressed protein of 95.6 k Da, as estimated by 10% sodium dodecyl sulfate-polyacrylamide gel electrophoresis, was consistent with the molecular weight deduced from the amino acid sequence. The purifi ed recombinant protein was used to vaccinate the grass carp, C tenopharyngodon idella. Following vaccination of the fi sh their Ig M antibody levels were examined, as was the expression of I g M, Ig D and Ig Z immunoglobulin genes and other genes such as MHC Iα and MHC I I β, which are also involved in adaptive immunity. Interleukin genes( IL), including I L- 1β, IL- 8 and I L- 10, and type I and type II interferon(I FN) genes were also examined. At 3 and 4 weeks post-vaccination(wpv), signifi cant increases in Ig M antibody levels were observed in the fi sh vaccinated with the recombinant fusion protein, and an increase in the expression levels of I g M, Ig D and Ig Z genes was also detected following the vaccinations, thus indicating that an adaptive immune response was induced by the vaccinations. Early increases in the expression levels of IL and IFN genes were also observed in the vaccinated fi sh. At four wpv, the fi sh were challenged with F. column a re, and the vaccinated fi sh showed a good level of protection against this pathogen, with 39% relative percent survival(RPS) compared with the control group. It can be concluded, therefore, that the fi ve OMPs, in the form of a recombinant fusion protein vaccine, induced an immune response in fi sh and protection against F. columnare.
基金Supported by the Chinese Academy of Sciences(No.XDA08010207)the National Key Technology R&D Program of China(No.2012BAD25B02)the State Key Laboratory of Freshwater Ecology and Biotechnology(No.2016FBZ04)
文摘Flavobacterium columnare is the pathogenic agent of columnaris disease in aquaculture. Using a recently developed gene deletion strategy, two genes that encode the Glyco hydro_19 domain （GH19 domain） containing proteins, ghd-1 and ghd-2, were deleted separately and together from the F. columnare G4 wild type strain. Surprisingly, the single-, Aghd-1 and Aghd-2, and double-gene mutants, Aghd-1 Aghd-2, all had rhizoid and non-rhizoid colony morphotypes, which we named Aghd-1, Aghd-2, Aghd-1 Aghd-2, and NAghd-1, NAghd-2, and NAghd-1 Aghd-2. However, chitin utilization was not detected in either these mutants or in the wild type. Instead, skimmed milk degradation was observed for the mutants and the wild type; the non-rhizoid strain NAghd-2 exhibited higher degradation activity as revealed by the larger transparent circle on the skimmed milk plate. Using zebrafish as the model organism, we found that non-rhizoid mutants had higher LDs0 values and were less virulent because zebrafish infected with these survived longer. Transcriptome analysis between the non-rhizoid and rhizoid colony morphotypes of each mutant, i.e., NAghd-1 versus （vs） Aghd-1, NAghd-2 vs Aghd-2, and NAghd-1 Aghd-2 vs Aghd-1 Aghd-2, revealed a large number of differentially expressed genes, among which 39 genes were common in three of the pairs compared. Although most of these genes encode hypothetical proteins, a few molecules such as phage tail protein, rhs element Vgr protein, thiol-activated cytolysin, and TonB-dependent outer membrane receptor precursor, expression of which was down-regulated in non-rhizoid mutants but up-regulated in rhizoid mutants, may play a role F. columnare virulence.
文摘The effect of penicillin-G on Flavobacterium psychrophilum, the cause of bacterial coldwater disease, was evaluated in 15 min and overnight exposures. Separate tests evaluated the effect of increasing doses of penicillin-G to rainbow trout Oncorhynchus mykiss eggs, fingerlings, and adults. Rainbow trout eggs were exposed for 1 h to penicillin doses of 0, 250, 500, 1,000, 10,000, 50,000, or 100,000 IU/mL. Mean percent hatch ranged from 64.6% to 75.1%, and did not significantly differ among the treatments. Fingerlings were injected intraperitoneally (i.p.) with 200 μL of 0, 1, 10, 100, 1,000, 10,000, 100,000, or 500,000 IU/mL. Probit analysis resulted in a LD10 (lethal dose for 10% of injected fish) of 52,868 IU/mL (95% confidence limits: 31,522 - 69,490 IU/mL) and a LD50 of 131,466 IU/mL (113,095 - 157,878 IU/mL). Brood stock were injected (i.p.) with 200 μL of penicillin at concentrations of 0 (control), 10,000, 50,000, 100,000, 200,000, 400,000, or 800,000 IU/mL. Mortality ranged from 0% to 7% (50,000 IU/mL treatment) and did not significantly differ among treatments. In 28 h exposure tests, penicillin concentrations of ≥ 333 IU/mL were required to completely suppress growth of F. psychrophilum. In 15 min exposures, ≥ 10,000 IU/mL were needed to achieve the same result. Tests indicated that rainbow trout eggs can tolerate 1 h exposures to penicillin-G concentrations as high as 100,000 IU/mL, and that brood fish can tolerate injections of at least 800,000 IU/mL. Fingerling data however, suggested that injection of doses greater than 10,000 IU/mL can be toxic. The data suggests rainbow trout eggs or brood can tolerate high doses of penicillin-G that could be used for controlling the transfer of F. psychrophilum to hatcheries receiving eggs.
基金Supported by the National Basic Research Program of China(973Program)(No.2009CB118703)
文摘Flavobacterium columnare, the etiological agent of colunmaris disease, is one of the most important and widespread bacterial pathogens of freshwater fish. In this study, we constructed two artificial selectable markers （chloramphenicol and spectinomycin resistance） for gene transfer in F. columnare. These two new artificial selectable markers, which were created by placing the chloramphenicol or spectinomycin resistance gene under the control of the native acs regulatory region of F. columnare, were functional in both F. columnare and Escherichia coli. The integrative/conjugative plasmids constructed by using these markers were introduced into F. columnare G4 via electroporation or conjugation. The integrated plasmid DNA was confirmed by Southern blotting and PCR analysis. These two markers can be employed in future investigations into gene deletion and the pathogenicity of virulence factors in F. columnare.
文摘From time immemorial, human beings have used pigments made from vegetables, fruits, superior plants, animal tissues and cereals. One of the greatest sources of pigments is the bacterium that, with the use of the modern technology, has increased the production of metabolites of interest. The microbiological production of carotenoids has not been optimized to obtain pigment production quantities of pigments and carotenoids recovery that lower production costs. The aim of this work was to design a Zeaxanthin production process with Flavobacterium sp. immobilized cells in a fluidized bed bioreactor. An optimum culture medium for Zeaxanthin production in stirred flasks (2.46 g·L–1) was obtained. Furthermore, optimum process conditions for a maximum yield of Zeaxanthin production, by fluidized bed bioreactor, were established. A statistical analysis showed that the most significant factors were air flow, pH and NaCl concentration (4.5 g·L–1). In this study a maximum Zeaxanthin production of 3.8 g·L–1 was reached. The highest reported yield to date was 0.329 g·L–1.
文摘Columnaris (caused by Flavobacterium columnare) is one of the most common bacterial diseases affecting the pond-raised channel catfish (Ictalurus punctatus) in the southeastern United States of America resulting in annual losses of millions of dollars. As part of our continuing effort to discover environmentally benign compounds for the control of columnaris disease, acyl derivatives of phloroglucinol were synthesized and tested against F. columnare using a rapid bioassay. Among the analogs that were tested, diacyl analogs showed very high antibacterial activity against F. columnare in the laboratory bioassay. Diisovaleryl and diisobutyryl analogs were found to have the strongest activity against F. columnare (isolate ALM-00-173) based on 24-h 50% inhibitory concentration (IC50) and minimum inhibitory concentration (MIC). Diisovaleryl and diisobutyryl analogs had IC50 values 0.82 mg/L and 0.80 mg/L, respectively, whereas the drug control florfenicol had an IC50 value of 0.81 mg/L. Diisovaleryl and diisobutyryl analogs also had 24-h relative-to- drug-control IC50 values around 1.0 indicating activities similar to florfenicol, which is included in medicated feed and is one of the current management approach for columnaris.
文摘Objective： The aim of the research was to investigate efficacy of dried bio-floc supplemented with immuno-stimulants as beta-glucan and nucleotide on mortality rate and relative percent survival （RPS） of tilapia infected with Flavobacterium columnare, VETSV01. Materials and Methods： A research was performed in 1-inch long tilapia stimulated its immunity by infection with Flavobacterium columnare, VETSV01. Pathogenesis of 0.2 mL Flavobacterium columnare, VETSV01 in the range of 10^2-10^8 mL-1 fish^-1 was injected into its intraperitoneal injection and intramuscular injection and suitable concentrations were screened to obtain for further experiment in a late restage. Based on data of minimal concentration, 50% mortality rate was caused and it was found the concentration of 108 mL^-1 fish^-1 caused 100% mortality rate and no lethal rate was found in other concentrations. Afterwards, efficacy of bio-floc sediment on survival rate of Tilapia infected with Flavobacterium columnare, VETSV01 was examined. Completely randomized design was employed and experiments were divided into 4 treatment： （1） contxol-commercial feed only, （2） commercial feed attached with dried bio-floc, （3） commercial feed attached with bio-floc and beta-glucan and （4） commercial feed attached with bio-floc and nucleotide. Experiment design was performed as 3 replicates with 10 fishes/replicates in 24 inch glass aquarium. Analysis of difference was performed and determination of mean differences of mortality rate mad relative percent survival was done through Duncan＇s Multiple Range Test （p 〈 0.05）. Results and Discussions： It was demonstrated feeding tilapia with commercial feed in combination with dried bio-floc with or without supplementation of 2 immuno-stimulants could lead to 100% survival rate and 100% relative percent survival rate and it was statistically significant different （p 〈 0.05） compared to control group. Bio-floc product supplemented with beta glucan or nucleotide could effectively stimulate immunity against Flavobacterium columnare, VETSV01 and such high effective performance is viewed as a promising potential product to be further developed and practically employed for sake of aquaculture industry in the near future.
文摘A bacterium capable of degrading dichlorvos was isolated from the rape phyllosphere and designated YD4. The strain was identified as Flavobacterium sp., based on its phenotypic features and 16S rRNA gene sequence. Strain YD4 was able to utilize dichlorvos as the sole source of phosphorus. In situ enhanced bioremedia- tion of dichlorvos by YD4 was hereafter studied. Chlorpyrifos and phoxim could also be degraded by this strain as the sole phosphorus source. A higher degradation rate of dichlorvos was observed after spraying YD4 onto the surface of rape leaves when compared to the sterilized- YD4 and water-treated samples. The results indicated that pesticide-degrading epiphytic bacterium could become a new way for in situ phyllosphere bioremediation where the hostile niche is unsuitable for other pesticide-degrading bacteria isolated from soil and water.
