Isolation of 2,4-dichlorophenol degrading bacterium strain and cloning and expression of its 2,4-dichlorophenol hydroxylase gene / 生物工程学报

2,4-Dichlorophenol is toxic and biorefratory organic pollutant. A 2,4-dichlorophenol degrading bacterial strain GT241-1, identified as Pseudomonas sp., was isolated from soil samples which was collected from drainage area of several 2,4-dichlorophenol producing factories. Strain GT241-1 had strong 2,4-dichlorophenol degrading ability, it could decompose 91% 2, 4-dichlorophenol of 90 mg/L within 48 hours at 25 - 30 degrees C, and could utilize 2,4-dichlorophenol, 2,4-dichlorophenoxyacetic acid (2,4-D), benzoate and catechol as sole carbon and energy source. Southern blot showed that 2,4-dichlorophenol hydroxylase gene (dcpA) of strain GT241-1 locates on the about 10kb EcoR I/Xba I fragment. This fragment was recovered, linked to the vecter pUC19 and transformed into the E. coli DH5alpha. A aim transformant, Z539, was obtained by dot blotting from about 1200 transformants. PCR and the sequencing results shew that the whole dcpA gene is contained within the 10kb EcoR I /Xba I fragment of pZ539. This fragment was shortened to about 2.4kb by HindmIII. The shorted fragment was subcloned to vecter pRSET-B to get a transformant BS1-12. The subcloned fragment was sequenced. Sequencing results showed that the whole length of the subcloned fragment containing dcpA is 2389bp and the nucleotide span of coding region is from number 276 to number 2072 (1797 bp), with ATG and TAA as start and stop codon respectively. The sequence analysis of dcpA and the deduced amino acid encoded by dcpA showed that they are different from the relative sequences registered in the GenBank. The subcloned fragment carry the promoter of dcpA, this can deduce from the fact that the upflow length of dcpA coding region is 275bp, and further confirmed by the 2,4-dichlorophenol hydroxylase activity measurement results. The 2,4-dichlorophenol hydroxylase activity of transformant Z539 and BS1-12 were detected, the results showed these transformants have 2,4-dichlorophenol hydroxylase activity. By comparison, the activity of these transformants were lower than that of the strain GT241-1.

Expression of gene aiiA carrying the promoter of gene cry3Aa in Bacillus thuringiensis / 生物工程学报

N-acyl-homoserine lactones (AHLs), are widely conserved signal molecules present in quorum-sensing systems of many Gram-negative bacteria. AHLs molecules mediate the expression of virulence genes of a range of bacterial pathogens. Recently, it has been reported that AiiA protein, which widely exists in Bacillus species, can inactivate the AHLs by hydrolyzing the lactone bond of AHLs, thus attenuate the diseases caused by the expression of virulence genes of bacterial pathogens. Bacillus thuringiensis, a type of Gram-positive bacteria, has been used extensively as a microbial insecticide in the last few decades. However, most of important insecticidal B. thuringiensis strains have not been exploited for bacterial disease control because they usually do not produce antibiotics that are effective against bacteria and fungi. The discovery of AiiA protein in B. thuringiensis shows the application potential of B. thuringiensis on biocontrol against bacterial diseases. In this study, in order to construct the B. thuringiensis recombinant strain that has high expression of AiiA protein, the promoter of insecticidal crystal protein coding gene cry3Aa of B. thuringiensis was selected. The promoter of gene cry3Aa is a non-sporulation promoter, it promotes the transcription earlier and longer than the promoters of other cry genes. The promoter of AiiA protein coding gene aiiA was replaced with the promoter of gene cry3Aa by overlapping PCR, resulting fusion gene pro3A-aiiA. The gene pro3A-aiiA was inserted into shuttle vector pHT304 at site BamH I / Sph I , resulting recombinant plasmid pBMB686. The plasmid pBMB686 was introduced into B. thuringiensis acrystalliferous strain BMB171, the resulting strain BMB686 had a higher and more stable expression level of protein AiiA comparing with the parental strain BMB171. Furthermore, the strain BMB686 exhibited stronger ability of AHLs inactivation and much more effective restraint to the potato's soft rot disease caused by Erwinia carotovora than those of the parental strain BMB171. From these results, it was concluded that the B. thuringiensis strain harvesting the fusion gene pro3A-aiiA may be utilized in the future to control bacterial diseases which are mediated by the AHL quorum-sensing signals.

A novel resolution vector with Bacillus thuringiensis plasmid replicon ori44 / 生物工程学报

The resolution recognization sites of transposon Tn4430 of Bacillus thuringiensis was inserted into cloning vector pRSET B and pUC19, resulting recombinant plasmids pBMB1201 and pBMB1202. Both of the mini res fragments, BamHI/HindIII fragment in pBMB1201 and EcoRI/HindIII fragment in pBMB1202, were ligated to the 3.3 kb EcoRI/HindIII fragment of shuttle vector pHT3101, which contained the ori. Ec, ampr and emr antibiotic resistant genes, resulting recombinant plasmid pBMB1203. After deleted the BamHI and EcoRI sites which located ouside the two res sites, resolution vector pBMB1204 was resulted. There are multiple cloning sites between two copies of resolution sites which have the same direction. The plasmid replication origin ori44, which come from B. thuringiensis sub sp. kurstaki strain YBT-1520, was inserted into the multiple cloning sites of pBMB1204 and then resolution shuttle vector pBMB1205 was obtained. With spectinomycin resistant gene as target, it was found that the resolution rate is 100% and the stability of the resolved plasmid is 93%. Using this shuttle vector, antibiotic resistance markers and other non-B. thuringiensis DNA can be selectively eliminated after the selection of transformants by antibiotic resistance marker. This vector is very useful to solve the gene safety problem while has no effect on target gene expression.

The analysis of Bacillus thuringiensis vegetative insecticical protein gene cloning and expression / 生物工程学报

Three kinds of Bacillus thuringiensis serotype-subsp. Leesis(H33) strain YBT-833, subsp. Aizawai(H7) strain YBT-1416 and subsp. Kurstaki(H3ab) strain YBT-1535, which were isolated by our lab, are chosen as original strain to clone vegetative insecticidal protein gene. Southern hybridization showed that vip genes are all localized at roughly 4-5 kb size-fractionated XbaI fragments of total DNA from YBT-833, YBT-1416 and YBT-1535. Three subgenomic libraries containing the vip gene fragment, were constructed with pUC19 as vector. Then, three vegetative insecticidal protein gene vip83, vip14 and vip15 are obtained from the libraries through the methods of colony-blot-in-situ screening and enzyme-cut detection. Comparision of DNA sequence made out that only vip83 gene exist five different base pairs with known vip genes. Because the sequences of vip14 and vip15 are the same, two of the three genes, vip83 and vip14, were subcloned to shuttle vehicle pHT315 to get recombinant plasmids pBMB8901 and pBMB8902 in turn. The plasmids were separately transformed into vip Bt. receptors BMB171 and 4Q7 to obtain four engineered strains BMB8901-171, BMB8902-171, BMB8901-4Q7 and BMB8902-4Q7. SDS-PAGE results indicated that all recombinant strains express 88 kD vegetative insecticidal protein. Bioassay also showed that the proteins of genes vip83 and vip14 both have certain toxicity to Lepidopteran insect larvae such as Heliochis armigera, Spodotera exigua and Plutella xylostella. While the toxicity of vip protein from four engineered strains to Plutella xylostellas are highest, whose LC50 value is 28.6, 31.6, 45.4 and 37.6 microL/mL respectively. This study will contributed to construct high efficacy and wide spectrum engineered strains on theory and reality.

Study on Separation and Purification of Zwittermicin A and its Stability / 微生物学通报

Zwittermicin A was purified by ion exchange resin and HPLC from supernatants of Bacillus thuringiensis.subsp.kurstaki strain D1-23 cultivation.2.89mg pure Zwittermicin A was acquired,proved by HPLC-MS.Results show that the optimized wash concentration of NH_ 4 H_ 2 PO_ 4 is 5mmol/L at first step.Next step CH_ 3 COONH_ 4 concentration is 30 mmol/L,the gradient pH is 8.0～9.5.Totally 93% Zwittermicin A can be reserved with ion exchange resin.The temperature and pH stability experiments show the half life of Zwittermicin A is 48.22 minutes in 100℃,and it is more stable in lower pH in pH 2.0～12.0.

Gloning and Sequence Analysis of Dienelactone Hydrolase Gene / 微生物学通报

A 2,4 -dichlorophenol degrading Pseudomonas strain GI241-1 was isolated from a soil sample. The dienelactone hydrolase gene, designated as dcpD which encodes dienelactone hydrolase involved in transforming cis-2-chloro-dienelactone into 2-chloromaleylacetic acid, was cloned from this bacterium strain. The gene cloning strategy was to construct genomic library after location of its neighbouring gene by Southem blot and to screen the aim transformant by dot blotting. Sequencing results showed that length of dcpD is 702bp. The sequence of dcpD and the deduced amino acid are different from the relative sequences registered in the GenBank.

THE SYNERGISM OF VEGETATIVE INSECTICIDAL PROTEIN VIP AND CRY PROTEIN FROM BACILLUS THURINGIENSIS / 微生物学通报

In this paper, vegetative( vip83 ) and crystal(cry1Ac10 and cry1Ca) insecticidal protein genes from Bacillus thuri ngiensis were simultaneously electrospored into the plasmid-free strain BMB17 1. By the means of the specific P CR detection, the recombinant strains BMB2830-171 contained cry 1Ac10 and vip83, and BMB2 882-171 had cry1Ca and vip83 , were obtained respectively. Under the control of r ecombinant strains with one gene, bioassay of the synergism between vegetative V ip83 and crystal Cry1Ac10( or Cry1Ca )insecticidal proteins to three important Lepidopteran pests were done. The results, by analysis of statistic bio-so ft, showed that the synergia relation of vegetative Vip83 and crystal Cry1Ac10 i nsecticidal protein toxic to Heliothis armigera wascounteracted, while Plu tella xylostella and Spodotera exigua unobservable. There was no synergis tic action between Vip83 and Cry1Ca insecticidal proteins with Spodotera exigu a as tested insect. Bu t their cooperation to Heliothis armigera was minus, and the counterpart to Plutella xylostella plus, whose cotoxicity factor is 32.6. The experiment of bi-g ene genetic stability also suggested that the synergia effection had certain molecu lar genetic stability in the same cell. This performance can be contributed to construct high-effect and wide-spectrum engineered strain.