Mapping and cloning of the gene coding for beta-glucanase from various bacilli

Beta-glucanase gene from Bacillus subtilis 168 has been mapped by bacteriophage pBS1 transduction technique between sacA and purA genes. The stimulating effect of pleiotropic mutations pap, amyB and sacUh on beta-glucanase production in Bacillus subtilis and Bacillus amyloliquefaciens has been described. Beta-glucanase gene from Bacillus amyloliquefaciens has been cloned ona Charon 4A vector. Expression of the gene in E. coli cells depended on the orientation of the cloned DNA on a pBR322 vector plasmid. Maximal enzymatic activity was registered in periplasm. Beta-glucanase gene was recloned in Bacillus subtilis cells. Bacillus subtilis strain, harbouring pBG1, produces 500 times more beta-glucanase as compared with the wild type strain of Bacillus subtilis.     

Construction of a Bacillus subtilis double mutant deficient in extracellular alkaline and neutral proteases

A mutant strain of Bacillus subtilis carrying lesions in the structural genes for extracellular neutral (nprE) and serine (aprA) proteases was constructed by the gene conversion technique. This mutant had less than 4% of the extracellular protease activity of the wild type and sporulated normally, indicating that neither of these sporulation-associated proteases is essential for development.     

Isolation and characterization of a cis-acting mutation conferring catabolite repression resistance to alpha-amylase synthesis in Bacillus subtilis.

Bacillus subtilis 168GR10 was shown to contain a mutation, gra-10, which allowed normal temporal activation of alpha-amylase synthesis in the presence of a concentration of glucose that is inhibitory to activation of amylase synthesis in the parent strain, 168. The gra-10 mutation was mapped by phage PBS-1-mediated transduction and by transformation to a site between lin-2 and aroI906, very tightly linked to amyE, the alpha-amylase structural gene. The gra-10 mutation did not pleiotropically affect catabolite repression of sporulation or of the synthesis of extracellular proteases or RNase and was unable to confer glucose-resistance to the synthesis of chloramphenicol acetyltransferase encoded by the cat-86 gene driven by the amyE promoter region (amyR1) inserted into the promoter-probe plasmid pPL603B. It therefore appears that gra-10 defines a cis-regulatory site for catabolite repression, but not for temporal activation, of amyE expression. The evidence shows that temporal activation and glucose-mediated repression of alpha-amylase synthesis in B. subtilis 168 are distinct phenomena that can be separated by mutation.     

Stability of the recombinant plasmid carrying theBacillus amyloliquefaciens α-amylase gene inB. subtilis

Summary Theα-amylase gene ofBacillus amyloliquefaciens has previously been cloned into pUB110 to give the recombinant plasmid, pKTH10 (Palva 1982. Gene 19:81–87). Strains transformed by this plasmid are promising candidates for industrialα-amylase production. The stability of pKTH10 was determined in variousB. subtilis strains possessing specific alleles which affect the level ofα-amylase secretion.B. subtilis strains carrying pKTH10 were cultivated in starch-containing medium for up to 50 generations without antibiotic selection and then screened for the presence of pKTH10. The plasmid proved stable enough (< 1.0% cured after 50 generations) for industrial batchwise enzyme production in two strains, but in asacU9 strain (thesacU9 mutation increases concominantly the production ofα-amylase levansucrase and proteases) 99.9% of cells had lost pKTH10 after 50 generations, although the parental plasmid (pUB110) was stable in this strain (0.09% cured after 50 generations). The instability of pKTH10 in thesacU9 strain seems somehow to be related to high expression of the clonedα-amylase gene: when grown in a medium restrictingα-amylase production, only 0.53% ofsacU9 cells had lost pKTH10 after 50 generations.     

Improving the production of E. coli beta-lactamase in Bacillus subtilis: the effect of glucose, pH and temperature on the production level.

Bacillus subtilis has been considered a promising host for the production of foreign proteins. However, proteases released by the host organism can often cause rapid breakdown of secreted heterologous proteins. Here we report that the addition of 6% glucose and 100 mM potassium phosphate to the growth medium significantly reduces the degradation of E. coli TEM beta-lactamase secreted from B. subtilis, when applying an expression system based on B. amyloliquefaciens alpha-amylase. The yield of beta-lactamase was increased 10-20-fold when compared to the yield in Luria medium. The promoter of B. amyloliquefaciens alpha-amylase gene is repressed by glucose. However, here we show that the repression does not take place in a multicopy plasmid, thus enabling our approach to efficiently reduce the protease action by catabolite repression. We have also studied the role of pH and temperature on the beta-lactamase production in laboratory scale bioreactors. Low temperature and low pH are both favorable for a high level beta-lactamase production by the high copy plasmid construction.     

Molecular cloning of alpha-amylase gene from Bacillus amyloliquefaciens and its expression in B. subtilis

The gene coding for alpha-amylase from Bacillus amyloliquefaciens was isolated by direct shotgun cloning using B. subtilis as a host. The genome of B. amyloliquefaciens was partially digested with the restriction endonuclease MboI and 2- to 5-kb fragments were isolated and joined to plasmid pUB110. Competent B. subtilis amylase-negative cells were transformed with the hybrid plasmids and kanamycin-resistant transformants were screened for the production of alpha-amylase. One of the transformants producing high amounts of alpha-amylase was characterized further. The alpha-amylase gene was shown to be present in a 2.3-kb insert. The alpha-amylase production of the transformed B. subtilis could be prevented by inserting lambda DNA fragments into unique sites of EcoRI, HindIII and KpnI in the insert. Foreign DNA inserted into a unique ClaI site failed to affect the alpha-amylase production. The amount of alpha-amylase activity produced by this transformed B. subtilis was about 2500-fold higher than that for the wild-type B. subtilis Marburg strain, and about 5 times higher than the activity produced by the donor B. amyloliquefaciens strain. Virtually all of the alpha-amylase was secreted into the culture medium. The secreted alpha-amylase was shown to be indistinguishable from that of B. amyloliquefaciens as based on immunological and biochemical criteria.     

Alpha-amylase genes (amyR2 and amyE+) from an alpha-amylase-hyperproducing Bacillus subtilis strain: molecular cloning and nucleotide sequences.

amyR2, amyE+, and aroI+ alleles from an alpha-amylase-hyperproducing strain, Bacillus subtilis NA64, were cloned in temperate B. subtilis phage p11, and the amyR2 and amyE+ genes were then recloned in plasmid pUB110, which was designated pTUB4. The order of the restriction sites, ClaI-EcoRI-PstI-SalI-SmaI, found in the DNA fragment carrying amyR2 and amyE+ from the phage genome was also found in the 2.3-kilobase insert of pTUB4. Approximately 2,600 base pairs of the DNA nucleotide sequence of the amyR2 and amyE+ gene region in pTUB4 were determined. Starting from an ATG initiator codon, an open reading frame was composed of a total 1,776 base pairs (592 amino acids). Among the 1,776 base pairs, 1,674 (558 amino acids) were found in the cloned DNA fragment, and 102 base pairs (34 amino acids) were in the vector pUB110 DNA. The COOH terminal region of the alpha-amylase of pTUB4 was encoded in pUB110. The electrophoretic mobility in a 7.5% polyacrylamide gel of the alpha-amylase was slightly faster than that of the parental alpha-amylases. The NH2 termination portion of the gene encoded a 41-amino acid-long signal sequence (Ohmura et al., Biochem. Biophys. Res. Commun. 112:687-683, 1983). The DNA sequence of the mature extracellular alpha-amylase, a potential RNA polymerase recognition site and Pribnow box (TTGATAGAGTGATTGTGATAATTTAAAAT), and an AT-rich inverted repeat structure which has free energy of -8.2 kcal/mol (-34.3 kJ/mol) were identified. The AT-rich inverted repeat structure seemed to correspond to the hyperproducing character. The nucleotide sequence around the region was quite different from the promoter region of the B. subtilis 168 alpha-amylase gene which was cloned in the Escherichia coli vector systems.     

The gene amyE(TV1) codes for a nonglucogenic alpha-amylase from Thermoactinomyces vulgaris 94-2A in Bacillus subtilis.

We isolated the gene amyE(TV1) from Thermoactinomyces vulgaris 94-2A encoding a nonglucogenic alpha-amylase (AmyTV1). A chromosomal DNA fragment of 2,247 bp contained an open reading frame of 483 codons, which was expressed in Escherichia coli and Bacillus subtilis. The deduced amino acid sequence of the AmyTV1 protein was confirmed by sequencing of several peptides derived from the enzyme isolated from a T. vulgaris 94-2A culture. The amino acid sequence was aligned with several known alpha-amylase sequences. We found 83% homology with the 48-kDa alpha-amylase part of the Bacillus polymyxa beta-alpha-amylase polyprotein and 50% homology with Taka amylase A of Aspergillus oryzae but only 45% homology with another T. vulgaris amylase (neopullulanase, TVA II) recently cloned from strain R-47. The putative promoter region was characterized with primer extension and deletion experiments and by expression studies with B. subtilis. Multiple promoter sites (P3, P2, and P1) were found; P1 alone drives about 1/10 of the AmyTV1 expression directed by the native tandem configuration P3P2P1. The expression levels in B. subtilis could be enhanced by fusion of the amyE(TV1) coding region to the promoter of the Bacillus amyloliquefaciens alpha-amylase gene.     

Two-codon mutagenesis of alpha-amylase gene of Bacillus amyloliquefaciens

The oligonucleotide encoding Bam HI recognition site having the structure pCGGGATC had been inserted into the recognition sites MspI of the B. amyloliquefaciens alpha-amylase gene, which was cloned in pTG29B plasmid. The alpha-amylase gene had no BamHI sites before mutagenesis. The set of pNSBamHI plasmids with BamHI site at four different positions was obtained. It was shown that all the mutant alpha-amylases possess different specific activities. One of the mutant proteins possesses reduced thermostability. The mutant alpha-amylases can be used for further experiments on protein-engineering of liquefying-type alpha-amylases.     

The transition state regulator Hpr of Bacillus subtilis is a DNA-binding protein

The synthesis of a variety of proteins, including the well characterized degradative enzymes, which occurs during the transition state between vegetative growth and the onset of sporulation in Bacillus subtilis is controlled by a class of molecules known as transition state regulators. One of these regulators is the product of the hpr gene, first identified by mutations affecting the synthesis of extracellular proteases. We have purified the Hpr protein and found that it binds specifically to DNA fragments carrying the promoters and the upstream regions of the alkaline (aprE) and neutral (nprE) protease genes of B. subtilis. DNase I protection experiments revealed that the Hpr protein is able to bind at four and two regions of the aprE and nprE promoters, respectively. We have also located two Hpr binding sites in the promoter region of a gene of unknown function which is nevertheless known to be developmentally regulated during the transition state and which occurs in the same operon as the gene encoding another transition state regulator, Sin. The location of one of the Hpr binding sites on the aprE gene occurs adjacent to a region to which the Sin protein binds. However, in mixing competition experiments we have shown that Hpr and Sin binding occurred independently, and no visible alterations of protected regions were detected.     

Cloning the alpha-amylase gene of Bacillus amyloliquefaciens in cyanobacteria cells

The recombinant plasmids of pIAH4amy series were constructed containing the alpha-amylase gene of Bacillus amyloliquefaciens A50 with its own promoter and leading sequence within an integrative vector plasmid pIAH4 (CmR) for cyanobacterium Anacystis nidulans R2. At Anacystis nidulans transformation the hybrid plasmids integrate into cyanobacterium chromosome with high efficiency and all CmR transformants produce alpha-amylase. Expression of bacillar alpha-amylase gene in cyanobacterium cells is independent of the cloned gene orientation in the vector plasmid. Secretion of alpha-amylase into the cyanobacterial periplasm has been demonstrated.     

肺炎克雷伯菌KP1＿4563基因突变株的构建及其生物膜表型分析

KP1_4563基因是肺炎克雷伯菌NTUH-K2044中假设的蛋白编码基因,与Ⅲ型菌毛的功能有关。本实验首先采用同源重组基因敲除方法构建肺炎克雷伯菌KP1_4563基因缺失的突变株(Kp-△4563),然后PCR扩增KP1_4563基因片段,克隆到质粒p BAD33上,将重组质粒导入Kp-△4563获得回补株(Kpc-△4563)。分别测定野生株、突变株、回补株用普通LB培养基,改良Minka培养基以及含胆汁盐的LB培养基培养时生物膜形成能力,以此来探讨KP1_4563基因以及不同培养基对肺炎克雷伯菌体外生物膜形成的影响。我们成功构建KP1_4563基因缺失的突变株和回补株Kpc-△4563。与野生株相比,突变株Kp-△4563生物膜形成能力减弱,回补株介于野生株和突变株之间。使用改良Minka培养基使菌株菌毛化以及加入胆汁盐可以增加生物膜的形成能力。这些分析表明肺炎克雷伯菌KP1_4563基因能正调控细菌生物膜的形成。体外培养使细菌菌毛化以及加入胆汁盐可以促进生物膜的形成。     

啤酒酵母DNA修复基因RAD24温度敏感突变株的分离及其特性的初步研究

以ＹＣｐｌａｃ系列带Ｔｒｐ、Ｈｉｓ和Ｕｒａ标志基因的载体为骨架构建含野生型和经羟胺处理的突变型的啤酒酵母ＲＡＤ２４基因质粒,用质粒替换方法分离ＲＡＤ２４基因温度敏感突变株（ｒａｄ２４－ｔｓ３）．紫外生存试验发现,ｒａｄ２４－ｔｓ３对紫外线敏感;同位素（３Ｈ－ＴｄＲ,３Ｈ－ＵＲ,３Ｈ－Ｌｅｕ）参入试验表明,该突变株ＤＮＡ、ＲＮＡ及蛋白质合成均较野生型明显降低．     

Directed evolution of a bacterial alpha-amylase: toward enhanced pH-performance and higher specific activity

alpha-Amylases, in particular, microbial alpha-amylases, are widely used in industrial processes such as starch liquefaction and pulp processes, and more recently in detergency. Due to the need for alpha-amylases with high specific activity and activity at alkaline pH, which are critical parameters, for example, for the use in detergents, we have enhanced the alpha-amylase from Bacillus amyloliquefaciens (BAA). The genes coding for the wild-type BAA and the mutants BAA S201N and BAA N297D were subjected to error-prone PCR and gene shuffling. For the screening of mutants we developed a novel, reliable assay suitable for high throughput screening based on the Phadebas assay. One mutant (BAA 42) has an optimal activity at pH 7, corresponding to a shift of one pH unit compared to the wild type. BAA 42 is active over a broader pH range than the wild type, resulting in a 5-fold higher activity at pH 10. In addition, the activity in periplasmic extracts and the specific activity increased 4- and 1.5-fold, respectively. Another mutant (BAA 29) possesses a wild-type-like pH profile but possesses a 40-fold higher activity in periplasmic extracts and a 9-fold higher specific activity. The comparison of the amino acid sequences of these two mutants with other homologous microbial alpha-amylases revealed the mutation of the highly conserved residues W194R, S197P, and A230V. In addition, three further mutations were found K406R, N414S, and E356D, the latter being present in other bacterial alpha-amylases.     

Highly efficient gene expression of a fibrinolytic enzyme (subtilisin DFE) in Bacillus subtilis mediated by the promoter of α-amylase gene from Bacillus amyloliquefaciens

Subtilisin DFE is a fibrinolytic enzyme produced by Bacillus amyloliquefaciens DC-4. The promoter and signal peptide-coding sequence of alpha-amylase gene from B. amyloliquefaciens was cloned and fused to the sequence coding for pro-peptide and mature peptide of subtilisin DFE. This hybrid gene was inserted into the Escherichia coli/Bacillus subtilis shuttle plasmid vector, pSUGV4. Recombinant subtilisin DFE gene was successfully expressed in B. subtilis WB600 with a fibrinolytic activity of 200 urokinase units ml(-1).     

Designed gene amplification on the Bacillus subtilis chromosome

We previously reported the cloning of a 1.6 kb HindIII fragment (containing the junction of the repeating unit) from chromosomal DNA of Bacillus subtilis strain B7 in which tandem amplification of a 16 kb region occurred, and the induction of B7-type gene amplification by competence transformation with this cloned fragment. Based on this result, we designed, on the B. subtilis chromosome, a gene amplification of the 22 kb repeating unit containing the alpha-amylase structural gene (amyE), the tunicamycin-resistance gene (tmrB) and the shikimate kinase structural gene (aroI). We cloned only two short DNA fragments from both termini of the 22 kb region, constructed a junction structure of the designed repeating unit on pBR327 and transformed a B. subtilis wild-type strain by this constructed plasmid. As a result, we succeeded in obtaining tunicamycin-resistant (Tmr) transformants in which the designed gene amplification of 22 kb occurred on the chromosome. The Tmr transformants showed high productivity of alpha-amylase and shikimate kinase. The copy number of the repeating unit was estimated to be 10-20. This system may provide an effective means of amplifying long (greater than 20 kb) DNA regions on the chromosome.