Plant growth-promoting properties and anti-fungal activity of endophytic bacterial strains isolated from Thymus altaicus and Salvia deserta in arid lands

Endophytes,as crucial components of plant microbial communities,significantly contribute to enhancing the absorption of nutrients such as nitrogen and phosphorus by their hosts,promote plant growth,and degrade pathogenic fungal mycelia.In this study,an experiment was conducted in August 2022 to explore the growth-promoting potential of endophytic bacterial strains isolated from two medical plant species,Thymus altaicus and Salvia deserta,using a series of screening media.Plant samples of Thymus altaicus and Salvia deserta were collected from Zhaosu County and Habahe County in Xinjiang Uygur Autonomous Region,China,in July 2021.Additionally,the inhibitory effects of endophytic bacterial strains on the four pathogenic fungi(Fusarium oxysporum,Fulvia fulva,Alternaria solani,and Valsa mali)were determined through the plate confrontation method.A total of 80 endophytic bacterial strains were isolated from Thymus altaicus,while a total of 60 endophytic bacterial strains were isolated from Salvia deserta.The endophytic bacterial strains from both Thymus altaicus and Salvia deserta exhibited plant growth-promoting properties.Specifically,the strains of Bacillus sp.TR002,Bacillus sp.TR005,Microbacterium sp.TSB5,and Rhodococcus sp.TR013 demonstrated strong cellulase-producing activity,siderophore-producing activity,phosphate solubilization activity,and nitrogen-fixing activity,respectively.Out of 140 endophytic bacterial strains isolated from Thymus altaicus and Salvia deserta,104 strains displayed anti-fungal activity against Fulvia fulva,Alternaria solani,Fusarium oxysporum,and Valsa mali.Furthermore,the strains of Bacillus sp.TR005,Bacillus sp.TS003,and Bacillus sp.TSB7 exhibited robust inhibition rates against all the four pathogenic fungi.In conclusion,the endophytic bacterial strains from Thymus altaicus and Salvia deserta possess both plant growth-promoting and anti-fungal properties,making them promising candidates for future development as growth-promoting agents and biocontrol tools for plant diseases.

Research Progress on Economic Forest Water Stress Based on Bibliometrics and Knowledge Graph

This study employed the bibliometric software CiteSpace 6.1.R6 to analyze the correlation between thermal infrared,spectral remote sensing technology,and the estimation of economic forest water stress.It aimed to review the development and current status of this field,as well as to identify future research trends.A search was conducted on the China National Knowledge Infrastructure(CNKI)database using the keyword“water stress”for relevant studies from 2003 to 2023.The visual analysis function of CNKI was used to generate the distribution of annual publication volume,and CiteSpace 6.1.R6 was utilized to create network maps illustrating collaboration among authors and institutions.The study also analyzed the hotspots and frontiers of economic forest water stress.As a result,a total of 6664 academic journal articles related to water stress were retrieved.Considerable collaboration networks were observed among scholars and institutions,with a focus on using crown temperature monitoring to diagnose crop water stress.Based on the research findings,it was evident that the primary research trend involved the use of thermal infrared and spectral remote sensing technology for estimating water stress,making it a future research hotspot.

Biochemical and microbial properties of rhizospheres under maize/ peanut intercropping

Maize/peanut intercropping system shows the significant yield advantage. Soil microbes play major roles in soil nutrient cycling and were affected by intercropping plants. This experiment was carried out to evaluate the changing of rhizosphere microbial community composition, and the relationship between microbial community and soil enzymatic activities, soil nutrients in maize/peanut intercropping system under the following three treatments： maize （Zea mays L.） and peanut （Arachis hypogaea L.） were intercropped without any separation （NS）, by half separation （HS） using a nylon net （50 μm） and complete separation （CS） by using a plastic sheet, respectively. The soil microbial communities were assessed by phospholipid fatty acid （PLFA）. We found that soil available nutrients （available nitrogen （Avail N） and available phosphorus （Avail P）） and enzymatic activities （soil urase and phosphomonoesterase） in both crops were improved in NS and HS treatments as compared to CS. Both bacterial and fungal biomasses in both crops were increased in NS followed by HS. Furthermore, Gram-positive bacteria （G＋） in maize soils were significant higher in NS and HS than CS, while the Gram-negative （G-） was significant higher in peanut soil. The ratio of normal saturated to monounsaturated PLFAs was significantly higher in rhizosphere of peanut under CS treatment than in any other treatments, which is an indicator of nutrient stress. Redundancy analysis and cluster analysis of PLFA showed rhizospheric microbial community of NS and HS of both plants tended to be consistent. The urase and Avail N were higher in NS and HS of both plants and positively correlated with bacteria, fungi （F） and total PLFAs, while negatively correlated with G＋/G- and NS/MS. The findings suggest that belowground interactions in maize/peanut intercropping system play important roles in changing the soil microbial composition and the dominant microbial species, which was closely related with the improving of soil available nutrients （N and P） and enzymatic activities.

Construction of multiform scFv antibodies using linker peptide

Multiform single chain variable fragments （scFvs） including different length linker scFvs and bispecific scFv were constructed. The linker lengths of 0, 3, 5, 8, 12, and 15 amino acids between VH and VL of antideoxynivalenol （anti-DON） scFv were used to analyze the affinities of scFvs. The affinity constants of these scFvs increased when the linker was lower than 12 amino acids. The affinity constant would not change when the linker was longer than 12 amino acids. Fusion gene of anti-DON scFv and antizearalenone （anti-ZEN） scFv was also constructed through connection by a short peptide linker DNA to express a bispecific scFv. The affinity constants assay showed that the two scFvs of fusion bispecific scFv remained their own affinity compared to their parental scFvs. Competitive direct enzyme linked immunosorbent assay was used to detect DON and ZEN in contaminated wheat （Triticum aestivum L.） samples, and the results indicated that this bispecific scFv was applicable in DON and ZEN detection. This work confirmed that bispecific scFv could be successfully obtained, and might also have an application in diagnosing fungal infection, and breeding transgenic plants.

Isolation and identification of Sclerotinia stem rot causal pathogen in Arabidopsis thaliana

A new stem rot disease is found to occur naturally on Arabidopsis plants in greenhouses of Fuzhou, China. In order to identify its pathogen, we conducted a series of fungal isolation and purification, plant reinoculation, and ascus and ascospore induction from the sclerotia. The isolate caused typical water-soaked lesions after reinoculation and produced sclerotia both on Arabidopsis plants and culture medium plates, and the sclerotia could be induced to produce discal apothecia and 8 binucleate ascospores per ascus. These disease symptom and fungal morphology data revealed that the fungus Sclerotinia sclerotiorum (Lib.) de Bary was the pathogen for Arabidopsis stem rot. To confirm this, we further amplified its large subunit ribosomal DNA (LSU rDNA) by polymerase chain reaction (PCR), and compared the sequence with the known LSU rDNA sequences in GenBank. The results show that the sequence shares the highest identities with the LSU rDNAs of different S. sclerotiorum strains. Taking all these data together, we concluded that the fungus that caused the Arabidopsis stem rot is S. sclerotiorum (Lib.) de Bary. This is the first report that Arabidopsis is naturally infected by S. sclerotiorum.

Evolutionary analysis of plant jacalin-related lectins(JRLs)family and expression of rice JRLs in response toMagnaporthe oryzae

Jacalin-related lectins （JRLs） are widely distributed carbohydrate-binding proteins in the plant kingdom, which play key roles in development and pathogen defense. In this study, we profiled evolutionary trajectory of JRLs family in 30 plant species and identified domain diversification and recombination leading to different responsive patterns of JRLs in rice during defense against rice blast. All of 30 plant species analyzed in our study have two types of JRLs by containing either a single jacalin or repeated jacalin domains, while chimeric jacalins exist in more than half of the species, especially in the Poaceae family. Moreover, Poaceae species have evolved two types of unique chimeric JRLs by fusing the jacalin domain（s） with dirigent or NB_ARC domain, some of which positively regulate plant immunity. Seven Poaceae-specific JRLs are found in the rice genome. We further found expression of rice JRLs, including four Poaceae-specific JRLs, are induced by Magnaporthe oryzae infections at either early or late infection stages. Overall, the results present the evolutionary trajectory of JRLs in plant and highlight essential roles of Poaceae specific JRLs against pathogen attacks in rice.

Comparative analysis of the genome of the field isolate V86010 of the rice blast fungus Magnaporthe oryzae from Philippines

Genome dynamics of pathogenic organisms are driven by plant host and pathogenic organism co-evolution, in which patho- gen genomes areused to overcome stresses imposed by hosts with various genetic backgrounds through generation of a range of field isolates. This model also applies to the rice host and its fungal pathogen Magnaporthe oryzae. To better understand genetic variation of M. oryzae in nature, the field isolate V86010 from the Philippines was sequenced and ana- lyzed. Genome annotation found that the assembled V86010 genome was composed of 1 931 scaffolds with a combined length of 38.9 Mb. The average GC ratio is 51.3% and repetitive elements constitute 5.1% of the genome. A total of 11 857 genes including 616 effector protein genes were predicted using a combined analysis pipeline. All predicted genes and effector protein genes of isolate V86010 distribute on the eight chromosomes when aligned with the assembled genome of isolate 70-15. Effector protein genes are located disproportionately at several chromosomal ends. The Pot2 elements are abundant in V86010. Seven V86010-specific effector proteins were found to suppress programmed cell death induced by BAX in tobacco leaves using an Agrobacterium-mediated transient assay. Our results may provide useful information for further study of the molecular and genomic dynamics in the evolution of M. oryzae and rice host interactions, and for characterizing novel effectors and AVR genes in the rice blast pathogen.

Toxicity of Five Insecticides to Culicoides oxystoma Kieffer (Diptera:Ceratopogonidae)

Field-collected Culicoides oxystoma adults were exposed to different concentrations of commercial insecticides including chlorpyrifos, DDVP, deltamethyrin, beta-cypermethrin and beta--cypermethrin · emamectin benzoate via filter paper method, to determine toxicity of different insecticides on C. oxystoma. Results showed that toxicities varied significantly among insecticides. Biting midges were the most susceptible to deltamethyrin （0. 060 mg/L）, followed by chlorpyrifos （0. 588 mg/L）, beta-cypermethrin （ 1. 741 rag/L）, beta-cypermethrin · emamectin benzoate （99.670 mg/L）, and DDVP （600. 496 mg/L）. After exposed to insecticides for 1 h, tested midges were transferred to recovery chamber and observed for another 24 h ; increased mortality within this period was different under different concentrations of each insecticide. Relative toxicity index of dehamethrin was maximal when used as the standard reagent.

Preparation and characterization of atrazine-loaded biodegradable PLGA nanospheres

Atrazine is the second mostly used herbicide in USA,but low utilization ratio causes severe environmental problem,so controlled release system is highly needed in order to minimize the negative impact on environment.In this paper,a herbicide delivery system,atrazine-loaded poly(lactic-co-glycolic acid)(PLGA)nanoparticles(NPs)were prepared by forming an oilin-water emulsion using the emulsion-solvent evaporation method.By varying the preparation conditions of PLGA-NPs,such as sonication time,surfactant content,solvent fraction,and polymer content,the particle sizes of the PLGA-NPs were well controlled from 204 to 520 nm.The morphology and size distribution of PLGA-NPs were evaluated using dynamic light scattering(DLS)and scanning electron microscopy(SEM).Both the encapsulation efficiency and release profile of the herbicide from the PLGA-NPs were typically evaluated by using 2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine(atrazine,ATZ)as the model.ATZ encapsulation efficiency within the PLGA-NPs was ranged from 31.6 to 50.5%.The release profiles of ATZ-loaded PLGA-NPs exhibited a much slower release rate in comparison with that of pure herbicide.The results demonstrated that the prepared PLGA-NPs had a high encapsulation efficiency and slow release rate,which could be used as a promising herbicide release system in agriculture to diminish the impact on the environment and minimize the potential harm to the farmers.

Synthesis and Crystal Structure of 3-(4-Chlorophenyl)-8-cyano-2-(di-isopropylamino)-5-methyl-7-(methylthio)-pyrido[4,3-d]pyrimidine-4(3H)-one

The crystal structure of the new title compound 3-（4-chlorophenyl）-8-cyano-2-（di-iso-propylamino）-5-methyl-7-（methylthio）-pyrido[4,3-d]pyrimidine-4（3H）-one（C22H24ClN5OS,Mr = 441.97）has been determined by single-crystal X-ray diffraction. The crystal is of orthorhombic,space group Pna21 with a = 7.6721（5）,b = 18.9370（11）,c = 15.6260（9）A,V = 2270.2（2）A^3,Z = 4,Dc = 1.293 g/cm^3,F（000）= 928,μ = 0.283 mm^-1,MoKa radiation（λ = 0.71073 A）,R = 0.0494 and wR = 0.1062 for 3278 observed reflections with I 〉 2σ（I）. X-ray diffraction analysis reveals that all ring atoms in the py-ridopyrimidinone moiety are almost coplanar. Intramolecular C（20）-H（20）···N（4）,C（19）-H（19A）···N（3）,C（18）-H（18C）···N（3）and C（16）-H（16B）···O（5）hydrogen bonds together with weak C···π interactions are found in the structure.

Expression,Purification,Crystallization and Preliminary Crystallographic Analysis of Nucleoside Diphosphate Kinase(NDK)from Aspergillus Flavus

Aspergillus flavus causes serious disease on important agriculture crops, and its secondary metabolic products-aflatoxins are most potent toxin and carcinogen for animal and human, Structural and functional studies ofA. flavus proteins may provide insights into the identification of potential therapeutic targets and prevention of damage caused by A. flavus. Here, we report the expression, purification, crystallization and preliminary crystallographic analysis of NDK protein from A. flavus. The NDK protein was expressed in E. coli and purified by using a series of chromatographic methods to 〉98% purity. The recombinant protein was crystallized and the crystals diffracted to 2.4 A^° resolution. The crystal of NDK is in space group of C121 with a = 190.84, b = 169.47, c = 146.94 A^°. Preliminary data analysis indicated that the NDK molecule assembles into a multimer in the asymmetric unit.

Changing Roles of Traditional Small Urban Green Spaces (<i>Telajakan</i>) in Bali, Indonesia

Bali Island, Indonesia is undergoing rapid land use changes due to heavy development pressure and its fast growing urban population. One such urbanization phenomenon is the shrinkage, deterioration, and disappearance of traditional small urban green spaces in Denpasar, Bali. Focusing on telajakan, a strip of traditional green space between the wall of a housing compound and a ditch/pedestrian path in a roadside, the study aims 1) to investigate and document the changes that are occurring with regards to telajakan and 2) to assess the functions (roles) of telajakan in Denpasar. The research methods include vegetation assessment at a lot scale and in-depth homeowner and village leader interviews with the help of local experts. The results show that telajakan space is often paved over to give way to more front space for the property owner and to ease maintenance. It is also minimized or destroyed as the owner builds a more “western” style house. Traditionally telajakan has multiple functions such as provision of plant and flower materials for Balinese daily rituals, regu-lation of stormwater from the property, and offering semi-public space for street vendors and neighbours. However, the results show that: diversity of planted species is decreasing;only a couple of functions such as aesthetics and economics are strongly favored;and the semi-public nature of telajakan is being lost. Since telajakan is as much traditional green open space as part of the aesthetics of the Balinese architecture, its loss, minimization, and degradation lead to the loss of Balinese culture and identity. On the other hand, new meaning is given to telajakan’s functions such as neighborhood beautification and exhibition of the owner’s pride in the modern context. Therefore, policy recommendations to conserve telajakan in the changing urban fabric need to balance these changing needs of telajakan for its use and conservation of traditional rituals and culture of Bali.

Antioxidant and Anti-Tyrosinase Activity from Olea Leaf Extract Depended on Seasonal Variations and Chromagraphy Treatment

In the present study, olive leaf extract, harvested from four seasons, extracted with solvent (methanol and water), was treated by D101 and Sephadex LH-20, and divided into 10 fractions by TLC detection. The antioxidant activity was evaluated using DPPH, superoxide anion scavenging and reducing power assays. Tyrosinase inhibitory activity was also performed with L-DOPA as substrate. On extraction method, there is no significant difference in methanol and water. Among 12 months, autumn showed the best harvest time in whole. OLE showed 90% tyrosinase inhibitory activity and inhibition type was non-competitive competition. By chromagraphy treatment, the ingredients of polysacchmaride and protein showed high bioactivity towards antioxidant and anti-tyrosinase activity, the rest part showed different extent of activity and prove some effect by chromatography treatment indirectly. OLE might be a valuable bioactive source and can be applicable in both the cosmetic and medical use.

Detection and identification of Vibrio parahaemolyticus by multiplex PCR and DNA-DNA hybridization on a microarray

In this paper, we developed a rapid and accurate method for the detection of Vibrio parahaemolyticus strains, using multiplex PCR and DNA--DNA hybridization. Multiplex PCR was used to simultaneously amplify three diagnostic genes （tlh, tdh andfla） that serve as molecular markers of V. parahaemolyticus. Biotinylated PCR products were hybridized to primers immobilized on a microarray, and detected by chemiluminesce with avidin-conjugated alkaline phosphatase. With this method, forty-five samples were tested. Eight known virulent strains （tlh＋/tdh＋/fla＋） and four known avirulent strains （tlh＋/tdh /fla＋） of the V. parahaemolyticus were successfully detected, and no non-specific hybridization and cross-hybridization reaction were found from fifteen closely-related strains （tlh-/tdh-/fla＋） of the Vibrio spp. In addition, all the other eighteen strains of non-Vibrio bacteria （tlh-/tdh /fla-） gave negative results. The DNA microarray successfully distinguished V. parahaemolyticus from other Vibrio spp. The results demonstrated that this was an efficient and robust method for identifying virulent strains of V. parahaemolyticus.

Rice allelopathy and its properties of molecular ecology

Crop allelopathy is a promising and environmentally friendly method in weed control;however,the inducible genetic trait for allelopathy in the suppression of weeds needs to be overcome for practical use.Further study needs to be directed to this end to elucidate the molecular genetics and its physiologic mechanism.In this paper,the authors review recent advances in the investigation of rice allelopathy and its molecular regulatory mechanism,especially in responses to stressful conditions including biotic and abiotic factors in China.Previous studies show that rice allelopathy could be enhanced when the rice accession was exposed to stressful conditions,and further analysis by the transcriptomics and proteomics approaches conducted in our laboratory indicated that the increase in allelopathic potential of rice,when exposed to the stresses,was attributed to increased expression level of genes involved in phenolic synthetic metabolism.The increasing phenolic compounds have been confirmed as the main allelochemicals and they jointly act to suppress the target,especially in responses to stressful condition,but it seems to be the primary effect in phenolic allelopathy.We still wonder how the exudates from rice root,which were released into rhizosphere soil,are transformed by soil microorganism to produce the higher secondary effect of phenolic allelopathy in the suppression of weeds.Therefore,the authors suggest that rhizosphere biologic properties of allelopathy in rice and its mechanism are being the key research areas in the world now,and systems biology and its approaches,such as metagenomics and metaproteomics,would be helpful to reveal the process and its molecular ecological mechanism regarding rhizospheric biology of rice allelopathy.

Identification and characterization of a cytochrome P450 C YP6CX1 putatively associated with insecticide resistance in Bemisia tabaci

The novel full length of cytochrome P450 gene has been isolated in insecticideresistant （named CYP6CXlvl） and -susceptible （named CYP6CXlv2） Bemisia tabaci, which was identified as B biotype, in Shangjie, Fujian, China （Sj）. CYP6CX1 （1 940 bp contained a 1 557 bp open reading frame） included conserved domains common to CYP6 members, such as heme-binding motif PFGEGPRFCIA, putative ＂meander＂-binding sequence ETLR and PERF in helix-K, oxygen-binding motif AGLDPV and conserved sequence PEKFNP near the carboxyl end. There were four different replacements of amino acid residues between R and S B. tabaci （Thr300 Ala, Thr354Pro, Arg486His and Ile503Thr）, among which the substitution Ile503Thr was located in the substrate recognition sites region. The mRNA transcription level of CYP6CXlvl was 2.38-fold as high as that of CYP6CXlv2. The results indicated that the CFP6CX1 from the B biotype B. tabaci in Sj was one of the CYP6 members, and enhanced CYP6CX1 expression and substitute of amino acid residues might be involved in the resistance mechanisms in field B. tabaci.

Positive correlation of methamidophos resistance between Lipaphis erysimi and Diaeretilla rapae and effects of methamidophos ingested by host insect on the parasitoid

Temporal and spatial correlated variations on the methamidophos resistance and biomolecular rate constant of acetylcholinesterase to insecticides were found between the turnip aphid, Lipaphis erysimi and its endoparasitoid, Diaeretilla rapae, collected from field colonies and an insecticide-free field insectarium in Fujian, China. Compared to the related susceptible insectarium population, L. erysimi and D. rapae displayed 7.4-29.2- and 2.6- 9.2-fold resistance ratios, respectively. In addition, two populations ofL. erysimi with different methamidophos resistance levels, that is, a field （with 5.8-fold resistance ratio） and an insectarium population, were used to study the effects of methamidophos ingested by the host insect on D. rapae development. The percentage of D. rapae cocoon formation decreased significantly when the parasitized L. erysimi were fed on cauliflower leaves treated with methamidophos at lethal concentration dosages 10 （LC50） or LC520. At LC50 dosages the percentage of D. rapae cocoon formation and adult emergence decreased significantly. When the parasitized L. erysimi were fed on methamidophos at LC50 dosage, no D. rapae cocoons were found. When the field or insectarium L. erysimi were treated with methamidophos at LC50, the susceptibility to methamidophos in the adult D. rapae emerged from the treated host insect was similar to the control. However, the susceptibility to methamidophos in the adult D. rapae became lower than the control when the host insects were treated at LC50 dosages. The data thus suggested that the methamidophos ingested by the host insect L. erysimi could be an important factor in the endoparasitoids＇ insecticide resistance development. The natural selectivity would favor the parasitoids that had developed an insensitivity to the insecticide（s）.

Seasonal changes of resistance to fenvalerate and cypermethrin in the larval parasitoid Cotesia plutellae （Hymenoptera： Braconidae）

在 hymenopteranCotesia plutellae 的杀虫药剂抵抗和稳定性的季节的变化，从 Jianxin， Fuzhou 城市，和 Shangjie 镇定， Minhou 县，福建，中国，被使用一个干燥剩余电影方法估计。抵抗到在 C 的地人口的二杀虫药剂。plutellae 不在在养虫室的没有杀虫药剂的条件下面是稳定的。与 C 的易受影响的 F_(11 ) 子孙相比。在养虫室的 plutellae ，在 F_0 父母的抵抗比率( RR )为氰戊菊酯是 18.4 并且 11.4 为氯氰菊酯基于在 9 个小时的LC_( 50 )，并且 32.8 为氰戊菊酯并且 28.5 分别地在 第9a 24 个小时为基于在 24 点的LC_( 50 )， theparasitoids 是左的在的小时与杀虫药剂联系 1 个小时和死亡的氯氰菊酯被记录。然而，在 C 的一张地人口的 RR。plutellae 是 9.2 forfenvalerate 并且 12.7 为氯氰菊酯，如果 parasitoids 在与杀虫药剂的接触是左的 24 个小时了。到在另外的地人口的二 pyrethroids 的电阻从 2000 年 11 月收集了 fromJianxin 和 Shangjie， 2004 年 7 月也被决定。到在 C 的地人口的二杀虫药剂的抵抗的重要季节变化。plutellae 被发现。RR 是 3.0—18.4 为氰戊菊酯并且 4.8—20.6 为在到 2002 年 4 月的从 2000 年 11 月的 Jianxin 人口的氯氰菊酯基于在为在到 2004 年 7 月的从 2002 年 5 月的 Shangjie 人口的氰戊菊酯和 3.6-16.0for 氯氰菊酯的 9 h，和 2.3-13.6 的 LC_(50 ) 基于在 24 个小时的 LC_(50 ) 。抵抗层次在春天和秋天高并且在夏天严厉地减少了。另外，重要恢复从组合式由杀虫药剂引起了在 F_0 和 C 的地人口被发现。如果 parasitoidswere 在与 pyrethroids 的接触离开了 1 个小时，对氰戊菊酯和氯氰菊酯抵抗的 plutellae。然而，没有恢复在 susceptibleF_(11 ) 被发现子孙。

American fall webworm in China:A new case of global biological invasions

Season of mists and mellow fruitfulness-a wonderful autumn scene was described by the poet John Keats.Unfortunately,in multiple locations in China,this picturesque scenery has been nibbled away by an invasive insect,fall webworm,Hyphantria cunea(Lepidoptera:Arctiidae).By the end of September in 2021,outbreaks were detected in 607 counties in 14 provinces,resulting in cumulative damage of 10,427,300 acres and increasing the amount of infested area by 6.15%than last year(Data from Biological Disaster Prevention and Control Center,China).

Aerobic Cr(VI) Reduction by an Indigenous Soil Isolate Bacillus thuringiensis BRC-ZYR2

Chromium(Cr) may cause losses in the yield of field plant, which is one of the favorite habitats of Bacillus thuringiensis(Bt). The purposes of our study were to assess the Cr(VI)-resistance and Cr(VI)-reducing abilities of an indigenous soil isolate of Bt and to determine the factors governing Cr(VI) reduction. Towards this end a novel dichromate-reducing Bt BRC-ZYR2, characterized with insecticidal crystal proteins(ICPs), was isolated from a uranium deposit. Minimum inhibitory concentrations(MICs) of Cr(VI) were determined by broth dilution method and the concentrations of Cr(VI) and total Cr in the supernatant were quantified colorimetrically using 1,5-diphenylcarbazide(DPC) reagent and a mixture of sulfuric-nitric acids, respectively. The isolate contained five ICP genes(cry1Ba, cry1 Bb, cry1Be/cry1 Bf, cry9 Ca and cry9Da) and exhibited a high level of Cr(VI) resistance with MICs of 150 mg L-1at pH 7.0 and 30?C, and 500 mg L-1under optimal conditions(pH 9.0 and 40?C). The total Cr concentration was similar to initial concentration of Cr(VI) under the optimal condition, suggesting that the essential removal of the Cr(VI) was dependent on Bt reduction. Under optimal conditions, the initial Cr(VI) concentrations from 25 to 75 mg L-1significantly decreased in 24 h after incubation. Addition of Mn2+, Co2+, Mo2+and Cu2+activated Bt-mediated Cr(VI) reduction, while Zn2+, Ni2+and glucose were found to inhibit the reduction. Our results indicated that this isolate could be a promising biopesticide with the potential for both insect biocontrol and Cr bioremediation in the field.