Screening,identification and antagonistic effect of antagonistic bacteria JTFM1001 against aflatoxin contamination in corn

Aflatoxin is a strong carcinogenic and toxic fungal toxin produced by Aspergillus flavus and other Aspergillus species,and can seriously threaten the health of consumers,thus becoming a global concern.Corn,as an important oil and economic crop,is highly susceptible contaminated by aflatoxin.In this study,antagonistic bacteria with strong inhibitory effect on aflatoxin were screened to provide support for the treatment aflatoxin contamination control in corn.Ten strains which have strong antagonistic effects against A.flavus were isolated from healthy corn from different corn producing areas in China.Among them,the antagonistic bacteria JTFM1001 through corn kernels in vivo and field experiment,the inhibition effect of aflatoxin contamination reached above 70%and 55%,respectively.And the strain was identified as Bacillus subtilis based on its morphological,physiological and biochemical characteristics and phylogenetic analysis of 16S rDNA.In addition,our data showed that it can colonize in the rhizosphere and survive for a long time,forming the dominant flora,with broad application prospect.Finally,we were surprised to find that the antibacterial metabolites secreted by the antagonistic bacteria was one of the mechanisms of its inhibition of A.flavus and aflatoxin.This will provide us with new ideas and perspectives on the effective prevention and control of aflatoxin contamination in corn and corn oil.

Screening antagonistic microbes for seedling blight of rice and study on antagonistic mechanisms

It is shown by the result of the dual-cultured experiment that the inhibitory rate of DZW-47 was 60.42%, and the inhibitory rates of R.solani by actinomyces ZLR-2 and ZLR-11 were 43.75% and 43.05%, lower than that of DZW-47. The inhibitory mycelia growth mechanism of different strains on R.solani was quite different, with DZW-3 mainly on the aspect of hyperparasitism, DZW-21 on the synergism of hyperparasitism and metabolite, DZW-47 on the synergism of nutrient competition and secondary metabolite, ZLR-2 and ZLR-11 on producing secondary metabolite. Controlling efficiency of seedling bed accorded basically with that of the broth. The controlling efficiency of DZW-47, ZLR-2, ZLR-11, DZW-21 and DZW-3 were 97.20%, 95.7%, 94.6%, 93.6% and 89.20%, respectively.

Antagonistic Potential against Pathogenic Microorganisms and Hydrogen Peroxide Production of Indigenous Lactobacilli Isolated from Vagina of Chinese Pregnant Women

Objective To investigate the indigenous lactobacilli from the vagina of pregnant women and to screen the isolates with antagonistic potential against pathogenic microorganisms. Methods The strains were isolated from pregnant women＇s vagina and identified using the API50CH system. The ability of the isolates to produce hydrogen peroxide was analyzed semi-quantitatively using the TMB-HRP-MRS agar. The antagonistic effects of the isolates on pathogenic microorganisms were determined with a double layer agar plate. Results One hundred and three lactobacilli strains were isolated from 60 samples of vaginal secretion from healthy pregnant women. Among them, 78 strains could produce hydrogen peroxide, in which 68%, 80%, 80%, and 88% had antagonistic effects against Candida albicans CMCC98001, Staphylococcus aureus CMCC26003, Escherichia coli CMCC44113, and Pseudomonas aeruginosa CMCC10110, respectively. Conclusion The recovery of hydrogen peroxide-producing lactobacilli decreases with the increasing pregnant age and time. The most commonly isolated species from vagina of Chinese pregnant women are Lactobacillus acidophilus and Lactobacillus crispatus. Most of L. acidophilus and L. crispatus produce a high H2O2 level.

Dynamic Multi-team Antagonistic Games Model with Incomplete Information and Its Application to Multi-UAV

At present, the studies on multi-team antagonistic games(MTAGs) are still in the early stage, because this complicated problem involves not only incompleteness of information and conflict of interests, but also selection of antagonistic targets.Therefore, based on the previous researches, a new framework is proposed in this paper, which is dynamic multi-team antagonistic games with incomplete information(DMTAGII) model.For this model, the corresponding concept of perfect Bayesian Nash equilibrium(PBNE) is established and the existence of PBNE is also proved. Besides, an interactive iteration algorithm is introduced according to the idea of the best response for solving the equilibrium. Then, the scenario of multiple unmanned aerial vehicles(UAVs) against multiple military targets is studied to solve the problems of tactical decision making based on the DMTAGII model. In the process of modeling, the specific expressions of strategy, status and payoff functions of the games are considered, and the strategy is coded to match the structure of genetic algorithm so that the PBNE can be solved by combining the genetic algorithm and the interactive iteration algorithm.Finally, through the simulation the feasibility and effectiveness of the DMTAGII model are verified. Meanwhile, the calculated equilibrium strategies are also found to be realistic, which can provide certain references for improving the autonomous ability of UAV systems.

Mechanism of antagonistic effects of Andrographis paniculata methanolic extract against Staphylococcus aureus

Objective: To investigate the effects of Andrographis paniculata(Burm.f.) Wall. Ex Nees(A. paniculata) on expressions and activities of catalase, superoxide dismutase and alkylhydroperoxide reductase C in Staphylococcus aureus(S. aureus) with respect to its survival in vitro. Methods: Antioxidative property of methanolic leaves extract of A. paniculata(0.06 mg/m L). Minimum inhibitory concentration(MIC) was determined by its ability to reduce hydrogen peroxide(H_2O_2) toxicity against S. aureus ATCC 25923(3.8×10~8 cfu/m L). Effects of the extract on expressions of kat A(encoding catalase), sod A and sod M [encoding superoxide dismutases(SODs)], and ahp C [encoding alkylhydroperoxide reductase C(AhpC)] in S. aureuswere determined by RT-q PCR and corresponding enzyme activity assays were performed. Nitroblue tetrazolium reduction(NBT) assay was performed to determine effects of the extract on intracellular and extracellular levels of O_2-in S. aureus. Results: Cells challenged with 7.5 mmol/L H_2O_2 showed 0% survival in 30 min whereas 25% survived after treatment with the extract and H_2O_2. Cells that were treated with the extract alone had 43% survival in the same exposure period. Expressions of sod A and sod M genes in extract-treated cells were lowered 0.8-fold and 0.7-fold, respectively with decrease in total SOD activity of 26.8 U compared to untreated cells, 32.4 U(P<0.05). In contrast, extract-treated S. aureus cells showed 3.3-fold increase in kat A expression with corresponding increase in catalase activity of 1.828 U compared to untreated cells which was 1.248 U,(P<0.05). More profoundly, ahp C expression was increased 61-fold in extract-treated cells,(P<0.05) with corresponding increase in Ahp C activity of 0.018 U compared to untreated cells, 0.012U,(P<0.05). Extract-treated cells had significantly lower intra-and extracellular O_2-levels with absorbance readings(A_(575nm)) of 0.340 and 0.524 compared to untreated cells which were 0.516 and 0.928(P<0.05), respectively. Conclusions: Taken together these results suggest that the low MIC of A. paniculatamethanolic leaves extract(0.06 mg/m L) reduce H_2O_2 toxicity and more importantly, was in itself effectively inhibitory against S. aureus. Further, our observations suggest that a probable mode of its inhibitory mechanism against S. aureus is by reducing total SOD activity through downregulation of sod A and sod M expressions.

Responses of marine-derived Trichoderma fungi to seawater and their potential antagonistic behaviour

To explore the metabolic responses of marine-derived Trichoderma fungi to environmental stresses, the survivability, metabolism, and antagonism of ten marine isolates have been examined. Their survival in both freshwater and seawater indicates them to be facultative marine fungi, but they are more adaptable to marine environment. Most of them feature strain-specific and positive metabolic responses to seawater, which also usually result in the higher proportions of heteroatom-bearing and unsaturated units in mycelial constituents. Seawater factors can promote many strains to produce bioactive metabolites, including plant pathogen- and marine phytoplankton-inhibitory and marine animal-toxic ones, but the eff ects of NaCl are often weak or negative. The inhibition of marine phytoplankton corresponds to the intracellular accumulation of heteroatom-bearing and unsaturated units under seawater condition, and the varied toxicities to marine animals further signify the divergences of lipophilic exudates under diff erent conditions. The results may contribute to further understanding and mining the structural diversity and biological activity of secondary metabolites from marine-derived Trichoderma fungi.

Antagonistic formation motion of cooperative agents

This paper investigates a new formation motion problem of a class of first-order multi-agent systems with antagonistic interactions.A distributed formation control algorithm is proposed for each agent to realize the antagonistic formation motion.A sufficient condition is derived to ensure that all of the agents make an antagonistic formation motion in a distributed manner.It is shown that all of the agents can be spontaneously divided into several groups and that agents in the same group collaborate while agents in different groups compete.Finally,a numerical simulation is included to demonstrate our theoretical results.

Sensitivity of Four Yeasts to Fungicides and CO2 Concentrations and Their Antagonistic Ability in Combination with Fungicide to Pathogenic Fungi in vitro

The yeasts Cryptococcus laurentii, Trichosporon pullulans, Rhodotorula glutinis andTrichosporon sp.were used to investigate their sensitivity to four fungicides anddifferent concentrations of CO2, as well as their antagonistic ability to Penicilliumexpansumand Alternariaalternata in vitro when applied with fungicide. There were significantdifferences in sensitivity to the fungicides among the different yeasts(P=0.05). R.glutinis was more sensitive to Deccocil, Iprodione and Stroby as compared to otheryeasts. Combination antagonistic yeasts with fungicide could more significantly enhancebiocontrol ability of the yeasts against the pathogenic fungi in vitro(P = 0.05). C.laurentii was the most effective antagonist among the four yeasts and could completelycontrol spore germination of P.expansum and A.alternata when combined with Stroby at theconcentration of 100 L L-1. The yeasts, except R.glutinis, could grow well on nutrientyeast dextrose agar (NYDA) after 8 d incubation even at 20% CO2 concentration at 25℃.Particularly Trichosporon sp. showeda better adaptability to low temperature as comparedto other antagonists.

In Vitro Assessment of Probiotic Potential of Lactobacilus acidophilus and Antagonistic Activity Against Escherichia coli O157:H7

The antagonistic activity of Lactobacillus acidophilus KLDS1.0901, KLDS1.0902, KLDSI.1003 and NCFM against Escherichia coli O157 ： H7 were investigated in this study. The culture supematants of all the L. acidophilus stains showed high bacteriostatic activities against E. coli O 157 ： H7 and the bacteriostatic substances of their Cell-Free Supernatants （CFS） were preliminarily determined from organic acids. The bacteriostatic activity from CFS or viable L. acidophilus against E. coli O157 ： H7 was also assessed by using co-incubation methods, CFS had high bactericidal activity against E. coli O157 ： H7, no viable E. coli O157 ： H7 was detected when 5×10^7 CfU ofE. coli O157 ： H7 was added to 5 mL of CFS and incubated at 37℃ for 2 h. However, L. acidophilus themselves had no bacteriostatic activity after directly contacted with E. coli O157 ： H7. The inhibition E. coli O157 ： H7 adhesion and colonization of L. acidophilus were also investigated based on competition, exclusion and displacement assays. L. acidophilus KLDS1.0901, KLDSI.1003 and NCFM strains were effective to displace E. coli O157 ： H7 from a Caco-2 cell layer in competition and exclusion assays. However, in displacement assay, all of the strains showed no significant antagonistic activities. Meanwhile, the probiotic potential of L. acidophilus strains was investigated based on adhesion assay to Caco-2 cells and anti- inflammatory effects by IL-8 produced in Caco-2 cells. The adhesion ability and anti-inflammatory effects of L. acidophilus strains showed a strain-dependent manner. In general, L. acidophilus KLDS 1.0901 and NCFM showed better probiotic potential than KLDS1.0902 and KLDSI.1003. Thus, the use ofL. acidophilus KLDS1.0901 and NCFM to prevent or treat of diseases associated induced E. coli O157 ： H7 in vivo was suggested.

Antagonistic Effects of Sphingomonas and Pseudomonas aeruginosa on 4 Kinds of Pathogenic Bacteria of Ginseng

[Objectives]To explore effective biocontrol methods for diseases in the process of ginseng cultivation,and develop an efficient and environmentally friendly biocontrol agent.[Methods]In this study,2 strains were isolated from biogas slurry,and Cylindrocarpon destructans(XF),Fusarium solani(GF),Botrytis cinerea Pers(HM)and Alternaria panax Whetz(HB)were used as test materials.The strains were isolated and identified by dilution plate method,16S rDNA sequence identification method,confrontation culture method,filter paper method and ultraviolet spectrophotometer method,and the bacteriostatic activity and bacteriostatic rate were tested.[Results]Strain 15(Sphingomonas)and strain 19(Pseudomonas aeruginosa)were screened out through identification and analysis,and they grew stably within 8-10 d.The bacteriostatic rates of strain 15 against A.panax and B.cinerea were 47.37%and 43.40%,respectively,and the bacteriostatic rates of strain 19 against A.panax and B.cinerea were 62.30%and 63.27%,respectively.The bacteriostatic activity of the extract of strain 19 increased with the increase of OD_(600) value,and the bacteriostatic effect was optimal when the OD_(600) value was in the range of 0.8-1.0,up to 70%,so it had a strong biocontrol potential.[Conclusions]This experiment provides convenience for more effective inoculation,establishes a fast,simple and accurate method for the determination of the best bacteriostatic rate of P.aeruginosa culture solution to HM,and lays a foundation for large-scale culture of P.aeruginosa culture solution.Besides,it is expected to provide a theoretical basis for the efficient control of ginseng B.cinerea in field production,use it for the prevention and control of ginseng shoot diseases,and provide a reference for the efficient and diverse development of biocontrol agents for ginseng shoot diseases.

Isolation,Screening and Identification of Antagonistic Actinomycetes against Ustilago scitaminea Syd

[Objectives] This study was conducted to obtain actinomycetes strains having antagonistic effect on Ustilago scitaminea Syd.[Methods] At first, actinomycetes strains were isolated from 22 soil samples in Hainan sugarcane regions. Then, antagonistic actinomycetes against U. scitaminea were screened by confrontation culture. Finally, the taxonomic status of antagonistic actinomycetes was determined using 16S rDNA.[Results] From the 22 samples, 984 actinomycetes strains were isolated. From all the isolated strains, 23 antagonistic actinomycetes strains were obtained through primary screening, and one strains with better antagonistic effect was then obtained through secondary screening, and designated FAS. 16S rDNA identification showed that strain FAS shared 99% sequence similarity with Streptomyces cealestis US24. A phylogenetic tree was built with MAGE 7.0 software, and the results showed that strain FAS had the shortest genetic distance with S. caelestis US24. Therefore, the actinomycetes FAS was determined as S. caelestis .[Conclusions] This study provides a new biocontrol method for the biological control of sugarcane smut, thereby ensuring sustainable development of sugarcane industry and sugar industry.

Biocontrol Efficacy of Two Antagonistic Yeasts Against Postharvest Diseases in Peach Fruits During Storage Periods

Two antagonistic yeasts, Thichosporon pullulans and Cryptococcus laurentii, were investigated for their biocontrol potential to blue mold rot and rhizopus rot on harvested peach fruits(Prunus persica L. Batsch, cv. Okubao), alone or in combination with a low dose of iprodione(50 μg ml-1). The results indicated that T. pullulans and C. laurentii were effective at reducing disease incidence and severity of blue mold rot and rhizopus rot in peach fruits. Biocontrol efficacy of C. laurentii and T. pullulans were significantly enhanced by combination with a low dose of iprodione(50 μg ml-1)against blue mold and rhizopus rot in peach fruits. T. pullulans and C. laurentii combined with a low dose of iprodione(50 μg ml-1)resulted in better disease control than either iprodione or the yeasts used alone. Dipping fruits in suspensions of antagonist cells showed the similar control effect as the treatment with iprodione(500μg ml-1).

Screening of Antagonistic Bacillus spp. Strains against Phytophthora infestans (Mont.) de Bary and Isolation of lipopeptide Substances

[ Objective] The paper was to screen the antagonistic Bacillus spp. strains against Phytophthora infestans （Mont.） de Bary and analyze its lipepeptide substances. [ Methods] Using flat isolation and culture method, the bacteria that could produce Bacillus spp. were isolated from rhizosphere soil, and carried out primary and secondary screening by confrontation culture. The lipopeptide substances of Y-3 strain with better antifungal effect were carried out I-IPLC analysis. [Result] Nine strains of bacteria had certain antagonistic effects against P. infestans in primary screening, Y-1 and Y-3 strains had significant inhibition effect against the growth of P. infestans in secondary screening, with inhibition rate higher than 80% ; the crude extract of lipepeptide produced by Y-3 strain had better antagonistic effect against P. infestans, with inhibition rate higher than 90%. HPLC analysis showed that the crude extract of lipepeptide mainly contained 8 components. [ Conclusion] The lipopeptide substances produced by Y-3 strain had significant inhibition effect, which had potential application value for biological control of potato late blight.

Isolation of Antagonistic Bacteria against Fusarium graminearum and Its Antagonistic Activity

[ Objective] To develop biological control resources of endophytic bacteria in wheat, the bacteria with antagonistic effect against Fusarium graminearum were screened and their antagonistic activity was studied. [ Method] The endophytic bacteria of wheat with antagonistic effect were screened using plate confrontation method; the antagonistic bacteria were identified through physiological and biochemical characteristics and 16S rDNA sequence analysis; the antagonistic spectrum of antagonistic bacteria was studied using plate confrontation method. [ Result] The antagonistic bacterium XY-3 was isolated from wheat leaves, and was identified as Bacillus amyloliquefaciens according to the physiological and biochemical characteristics and 16S rDNA sequence analysis. [ Conclusion] XY-3 had antagonistic effect against four kinds of common pathogenic fungi, presenting broad spectrum antagonistic activity against plant pathogenic fungi.

Evaluation of Antibacterial and Synergistic/Antagonistic Effect of Some Medicinal Plants Extracted by Microwave and Conventional Methods

The purpose of the study was to evaluate the efficiency of the microwave (MW) extraction method by comparing it with a conventional method through evaluation of antimicrobial and synergism/antagonism activity of each aquatic and ethanolic extracts samples, which were extracted from the dried plants (Ficus sycomorus leaves, Lawsonia inermis leaves and Glycerrhiza glabra Linn.). Nine samples of each plant for both solvents were irradiated with MW at several power outputs (180 w, 360 w, and 540 w) in several interval times (1, 2 and 3 minutes). The antibacterial activities of extracts and the synergistic effect between plants and antibiotics were evaluated using disk diffusion method against clinical isolated Staphylococcus aureus and Escherichia coli. The result revealed that the inhibition zone for more than 50% using aquatic and ethanolic samples results (extracted in two minutes and MW power 180 w) had shown the optimum extract and better antibiotic activity for each plant. Also, the results of ethanolic extracts used against selected microorganisms showed antimicrobial and synergistic effect with most antibiotics better than aquatic extracts. Our results indicate the possibility of using MW apparatus as an extractor to obtain bioactive compounds from plants and thus used in the treatment of bacterial infections, and some results of this study were encouraging. However, the antagonistic reactions of some extracts with some antibiotics and their use in combination should be further studied for in vitro activities. It is clearly a need to be furthermore evaluated, to identify the effective components, the mode of action and the possible toxic effect in-vivo of these ingredients.

<i>In vitro</i>antagonistic potential of <i>Streptomyces</i>sp. AM-S1 against plant and human pathogens

In the present investigation, a total number of 132 different actinomycetes strains were isolated from the humus soil samples. Out of 132 isolates, 52 showed inhibitory activity against the fungal pathogen Rhizoctonia solani. Among the antagonists, the isolate designated as AM-S1 exhibited maximum inhibitory activity against the test pathogen R. solani (41 mm). Further, the light microscopic observations of the co-cultures showed severe structural alterations in the mycelia of R. solani near the zone of inhibition. The isolate AM-S1 was identified as Streptomyces sp. by morphological and 16S rDNA sequence analysis. The color of the aerial and substrate mycelia produced by the Streptomyces sp. AM-S1 varied with different media. The isolate Streptomyces sp. AM-S1 also effectively inhibited the growth of various plant and human pathogens. Further works are needed on optimization of this strain’s antagonistic activity, isolation and characterization of the antimicrobial metabolite.

Prediction of Antagonistic Activity of <i>β</i>-Carboline and Its Derivatives Using Topological Descriptors

Prediction of antagonistic activity of β-carboline and its thirteen derivatives has been made using topological descriptors viz, connectivity index, and kappa shape index of different orders. For evaluation of values of descriptor, molecular modeling and geometry optimization of all the compounds were carried out with CAChe Pro software by opting semiempirical PM3 method using MOPAC 2002. For prediction of activity multiple linear regression analysis (MLR) was performed. MLR analysis has been made by Project Leader Software associated with CAChe by using the above descriptors as independent variables and biological activity as dependent variables. We were performed leave-one-out methods and the result reflected a direct relationship between biological activity and connectivity index of zero order, while indirect relationship with connectivity index of second order and thus connectivity index is a reliable descriptor to predict the biological activity of β-carboline and its various derivatives.

Studies of the antagonistic effect of BQ-123 on cerebral vasospasm induced by intracisternal injection of endothelin-1 and subarachnoid hemorrhage

To clarify whether the endothelin A (ETA)-receptor antagonist BQ-123 can prevent the development of cerebral vasospasm (CVS) induced by endothelin (ET-1) and subarachnoid hemorrhage (SAH), which has been controversia11y reported by various authors. We have performed investigations in anesthetized Sprague-Dawley rats- Intracisternal injection (i. c. ) of ET-l (10-11, 10-10, 10-9 mol/kg) could induce acute dose-dependent CVS, furthermore, the highest dose of ET-l (lO-’ mo1/kg) had a biphasic response in CVS of a 24-hour duration. However, the CVS by ET-1 (10-9 mol/kg) could be prevented effectively by previous i. c. of BQ-123 in a dose-dependent manner (10-9, 10-8, 10-7 mol/kg), of which the i. c- of BQ-123 (10-7mol/kg) could abolish the CVS completely. i. c. of BQ-123 (10-7 mol/kg) before SAH induced by a single i. c, of 150 pl autologous fresh blood directly to the Willis circle cou1d prevent the following CVS largely, which was a biphasic response and long-lasting (duration of 72 h). We conclude that subarachnoid application of ETA-receptor antagonist can effecti vely prevent CVS induced by ET-1 and SAH, and ET-1 may be the major mediator responsible for the CVS following SAH.

Small Molecular Weight Compounds Antagonistic to Amyloid Peptide_25-35

High levels of the neurotoxic beta-amyloid protein (Aβ) in patients with Alzheimer’s disease present a significant therapeutic target, although the protein is unlikely to be the sole instigator of this condition. Aβ initiates cell receptor and synapse dysfunction, and causes mitochondrial damage within neurons. Neurotransmitters and various small molecular weight compounds ameliorate the effects of Aβ on cell membranes. This study uses a molecular modeling technique to compare the structures of Aβ25-35 and compounds known to antagonize properties of the polypeptide. Compounds provide good fits to the peptide amino acid residues, revealing planarity in their linear structures and fitting points. Compounds and polypeptide share relative molecular similarity, affinity for receptors and apoptosis modulating properties indicative of their potential for competition at neuron membrane sites. The therapeutic targeting of Aβ by small molecular weight compounds may benefit from a multi-drug approach.