New Intracellular Shikimic Acid Biosensor for Monitoring Shikimate Synthesis in Corynebacterium glutamicum

The quantitative monitoring of intracellular metabolites with in vivo biosensors provides an efficient means of identifying high-yield strains and observing product accumulation in real time. In this study, a shikimic acid (SA) biosensor was constructed from a LysR-type transcriptional regulator (ShiR) of Corynebacterium glutamicum. The SA biosensor specifically responded to the increase of intracellular SA concentration over a linear range of 19.5 ± 3.6 to 120.9 ± 1.2 fmole at the single-cell level. This new SA biosensor was successfully used to (1) monitor the SA production of different C. glutamicum strains; (2) develop a novel result-oriented high-throughput ribosome binding site screening and sorting strategy that was used for engineering high-yield shikimate-producing strains; and (3) engineer a whole-cell biosensor through the coexpression of the SA sensor and a shikimate transporter shiA gene in C. glutamicum RES167. This work demonstrated that a new intracellular SA biosensor is a valuable tool facilitating the fast development of microbial SA producer.

First Report of Pantoea agglomerans Causing Brown Apical Necrosis of Walnut in China

Brown apical necrosis (BAN) of walnut (Juglans regia L.) causes premature fruit drop and yield losses and has been reported to be an important walnut production problem in Spain, Italy, France, and Turkey (1,2). A number of organisms have been associated with BAN on walnut: Xanthomonas arboricola pv. juglandis, Fusarium spp., and Alternaria spp. (3). Since the spring of 2007, BAN was observed in 50 to 60% of the trees in walnut orchards in Taian City and Laiwu City, Shandong Province, China. Surface-disinfested tissue from premature walnut fruits was placed onto potato dextrose agar. Alternaria spp., X. arboricola pv. juglandis, and Pantoea agglomerans (formerly Enterobacter agglomerans) were isolated 76, 35, and 45% of the time, respectively. The P. agglomerans cultures formed a yellow lawn and were rod shaped with the body length of 1.5 to 3.0 μm, width of 0.5 to 1.0 μm, and four to six flagella. In biochemical tests, these bacteria were gram negative, lactose positive, and indole negative. Genomic DNA was extracted from one HXJ isolate and the 16S rRNA gene sequence (GenBank Accession No. HM016799) was obtained using universal primers 27F and 1492R. HM016799 had 99% sequence identity with P. agglomerans accessions in GenBank (GU477762, GQ494018, FJ756355, and AB004757). To confirm pathogenicity, HXJ isolate (10⁸ CFU·ml^-1) was inoculated at the bottom of the stigma within 5 days after florescence (DAF) and in premature fruit wounded with a needle within 30 DAF in 2008 to 2010. Stigmas injected with only sterile water served as controls. The bacteria were inoculated into three replicate 9-year-old plants of the walnut cv. Xiangling. Forty nuts on each plant were inoculated. The plants were grown in Shandong Province, China (36°09'59″N, 117°13'30″E). Ten days after inoculation, typical internal BAN symptoms were observed on all treated nuts and the controls were still healthy. In the inoculated stigmas, necrosis of stigma and style spread to internal tissues and reached the kernel. In treated premature fruit, internal tissues became necrotic and blackish and eventually led to nut drop. The same bacterium was reisolated from the inoculated tissue. On the basis of morphological, physiological, and biochemical characteristics and sequencing of the 16S rRNA gene, the bacterium was identified as P. agglomerans. To our knowledge, this is the first report of P. agglomerans causing internal type BAN of walnut in China or worldwide. References: (1) A. Belisario et al. Plant Dis. 6:599, 2002. (2) G. Bouvet. Acta Hortic. 705:447, 2005. (3) C. Moragrega and H. Özaktan. J. Plant Pathol. 92:S1.67, 2010.

Jadomycin B, an Aurora-B kinase inhibitor discovered through virtual screening

Aurora kinases have emerged as promising targets for cancer therapy because of their critical role in mitosis. These kinases are well-conserved in all eukaryotes, and IPL1 gene encodes the single Aurora kinase in budding yeast. In a virtual screening attempt, 22 compounds were identified from nearly 15,000 microbial natural products as potential small-molecular inhibitors of human Aurora-B kinase. One compound, Jadomycin B, inhibits the growth of ipl1-321 temperature-sensitive mutant more dramatically than wild-type yeast cells, raising the possibility that this compound is an Aurora kinase inhibitor. Further in vitro biochemical assay using purified recombinant human Aurora-B kinase shows that Jadomycin B inhibits Aurora-B activity in a dose-dependent manner. Our results also indicate that Jadomycin B competes with ATP for the kinase domain, which is consistent with our docking prediction. Like other Aurora kinase inhibitors, Jadomycin B blocks the phosphorylation of histone H3 on Ser10 in vivo. We also present evidence suggesting that Jadomycin B induces apoptosis in tumor cells without obvious effects on cell cycle. All the results indicate that Jadomycin B is a new Aurora-B kinase inhibitor worthy of further investigation.

TPR repeats and ELTR pattern: length variation as a function evolution mechanism

TPR repeat was originally defined as a 34 amino acid structural repeat (TPR-34). Equal length tandem repeats (ELTR) was proposed to represent the ancestral repeat pattern. Length polymorphism of TPR repeats was analyzed using PATTINPROT, two new versions of TPR repeat of 40 and 42 amino acids were identified. These 'long' TPRs endow new functional capacities to the resulting proteins. A strong correlation between varied lengths and new functions supports the hypothesis that length variation is an underlying mechanism for the function evolution of repeat containing proteins.

Engineering a regulatory region of jadomycin gene cluster to improve jadomycin B production in Streptomyces venezuelae

Streptomyces venezuelae ISP5230 produces a group of jadomycin congeners with cytotoxic activities. To improve jadomycin fermentation process, a genetic engineering strategy was designed to replace a 3.4-kb regulatory region of jad gene cluster that contains four regulatory genes (3' end 272 bp of jadW2, jadW3, jadR2, and jadR1) and the native promoter upstream of jadJ (P(J)) with the ermEp* promoter sequence so that ermEp* drives the expression of the jadomycin biosynthetic genes from jadJ in the engineered strain. As expected, the mutant strain produced jadomycin B without ethanol treatment, and the yield increased to about twofold that of the stressed wild-type. These results indicated that manipulation of the regulation of a biosynthetic gene cluster is an effective strategy to increase product yield.

Sample preparation for two-dimensional blue native/SDS polyacrylamide gel electrophoresis in the identification of Streptomyces coelicolor cytoplasmic protein complexes

Ammonium sulfate precipitation was tested as a sample preparation step for BN-PAGE analyses of S. coelicolor cytoplasmic protein complexes. A procedure of sample preparation compatible with two-dimensional BN/SDS-PAGE was established and used to visualize protein complexes. To validate the sample preparation procedure, representative protein complexes were identified. Several previously characterized protein complexes were rediscovered and their reported oligomeric states reconfirmed. In addition, we identified new but plausible interactions that have never been reported before. Our work provides useful reference for the wide application of BN-PAGE in protein interaction study.

Characterization of a hyperthermostable Fe-superoxide dismutase from hot spring

A new gene encoding a thermostable Fe-superoxide dismutase (tcSOD) was identified from a metagenomic library prepared from a hot spring sample. The open reading frame of tcSOD encoded a 211 amino acid protein. The recombinant protein was overexpressed in Escherichia coli and confirmed to be a Fe-SOD with a specific activity of 1,890 U/mg using the pyrogallol method. The enzyme was highly stable at 80 degrees C and retained 50% activity after heat treatment at 95 degrees C for 2 h. It showed striking stability across a wide pH span from 4 to 11. The native form of the enzyme was determined as a homotetramer by analytical ultracentrifugation and gradient native polyacrylamide gel electrophoresis. Fe(2+) was found to be important to SOD activity and to the stability of tcSOD dimer. Comparative modeling analyses of tcSOD tetramer indicate that its high thermostability is mainly due to the presence of a large number of intersubunit ion pairs and hydrogen bonds and to a decrease in solvent accessible hydrophobic surfaces.

[Construction and analysis of a metagenomic library from Tengchong hot spring soil in Yunnan Province]

By a combination of freezing/thawing/ proteinase K-based method and SDS/high-salt/heating treatment, the mixed environmental genomic DNA was isolated directly from a hot spring soil in Tengchong, Yunnan, China. With this method, The DNA yield was up to 1 - 2 microg/g soil. After purification with the Wizard DNA clean up system (Promega, Madison, Wis), the mixed genomic DNA was partially digested with restriction enzyme Pst I. Digested DNA fragments of 3 - 8 kb were recovered from agrose gel and ligated to the pSK (+) vector. The ligation mixture was transformed into DH10B strain, resulting in the construction of a metagenomic library with about 2.5 x 10(4) clones. Restriction enzyme analysis revealed that the average insert is about 4.6 kb. Some novel sequences were identified via sequencing and gene annotation analysis of 30 clones randomly chosen from this library.

Development of a multifunctional and efficient conjugal plasmid for use in Streptomyces spp

A plasmid, pGB112, has recently been developed to transfer DNA from Escherichia coli to Streptomyces spp via conjugation. This technique made use of (A) E. coli replicon, (B) ampicillin (amp) resistance gene for selection in E. coli and thiostrepton (tsr) resistance gene for selection in Streptomyces, (C) a fragment of SCP2* replicon, (D) a 2.6 kb fragment of tra-cassette which consists of pIJ101 transfer gene (tra) and two ermE promoters, (E) a 0.8 kb fragment of oriT of (IncP) RK2. The results showed that this plasmid was able to transfer plasmid DNA from E. coli to Streptomyces coelicolor via conjugation, and that it could also transfer DNA between Streptomyces strains. Since this plasmid has both pBR322 and SCP2* replicons, it may provide a novel and useful method for genetic operation in E. coli and Streptomyces.

Cytotoxic activities of new jadomycin derivatives

Cytotoxic activities of jadomycin B and five new jadomycin derivatives against four cancer cell lines (HepG2, IM-9, IM-9/Bcl-2 and H460) were evaluated. Jadomycin S was most potent against HepG2, IM-9 and IM-9/Bcl-2 while jadomycin F was most potent against H460. Their potencies correlated with the degrees of apoptosis induced. Structure-activity-relationship analyses clearly demonstrate that the side chains of the oxazolone ring derived from the incorporated amino acids make a significant impact on biological activity. Therefore, jadomycin offers an ideal scaffold to manipulate structure and could be exploited to make many novel bioactive compounds with altered activities.

C-terminus mutations of Acremonium chrysogenum deacetoxy/deacetylcephalosporin C synthase with improved activity toward penicillin analogs

Deacetoxy/deacetylcephalosporin C synthase (acDAOC/DACS) from Acremonium chrysogenum is a bifunctional enzyme that catalyzes both the ring-expansion of penicillin N to deacetoxycephalosporin C (DAOC) and the hydroxylation of the latter to deacetylcephalosporin C (DAC). Three residues N305, R307 and R308 located in close proximity to the C-terminus of acDAOC/DACS were each mutated to leucine. The N305L and R308L mutant acDAOC/DACSs showed significant improvement in their ability to convert penicillin analogs. R308 was identified for the first time as a critical residue for DAOC/DACS activity. Kinetic analyses of purified R308L enzyme indicated its improved catalytic efficiency is due to combined improvements of K(m) and k(cat). Comparative modeling of acDAOC/DACS supports the involvement of R308 in the formation of substrate-binding pocket.

[Analyses of Streptomyces coelicolor inner membrane proteome by multidimentional protein identification technology]

Streptomyces coelicolor is the model species among streptomycetes. Until now, proteomic analyses of S. coelicolor have been conducted using two-dimensional polyacrylamide gel electrophoresis and matrix-assisted laser desorption ionization time-of-flight mass spectrometry method, few integral membrane proteins were identified due to the hydrophobic and low-abundance nature of these proteins. In this work, 154 possible inner membrane proteins from S. coelicolor were identified using high pH-proteinase K sample preparation method and multidimensional protein identification technology, among them 44 are integral membrane proteins containing at least one transmembrane domain, most peptides and their corresponding proteins were identified experimentally for the first time.

Functional analyses of oxygenases in jadomycin biosynthesis and identification of JadH as a bifunctional oxygenase/dehydrase

A novel angucycline metabolite, 2,3-dehydro-UWM6, was identified in a jadH mutant of Streptomyces venezuelae ISP5230. Both UWM6 and 2,3-dehydro-UWM6 could be converted to jadomycin A or B by a ketosynthase alpha (jadA) mutant of S. venezuelae. These angucycline intermediates were also converted to jadomycin A by transformant of the heterologous host Streptomyces lividans expressing the jadFGH oxygenases in vivo and by its cell-free extracts in vitro; thus the three gene products JadFGH are implicated in catalysis of the post-polyketide synthase biosynthetic reactions converting UWM6 to jadomycin aglycone. Genetic and biochemical analyses indicate that JadH possesses dehydrase activity, not previously associated with polyketide-modifying oxygenase. Since the formation of aromatic polyketides often requires multiple dehydration steps, bifunctionality of oxygenases modifying aromatic polyketides may be a general phenomenon.

[Construction and characterization of TetR and GFP fusion protein]

Tetracycline repressor gene (tetR) from E. coli transposon Tn10 was fused in frame with green fluorescent protein gene (gfp) from jellyfish Aequorea Victoria on an E. coli expression vector and the fusion protein (TR::GFP) was purified. The binding of TR::GFP with tetracycline (tc) was demonstrated by nitrocellulose filter binding assay. TR::GFP also maintained the fluorescence property of GFP. Most significantly, fluorescence emission intensity of TR::GFP increased by 2-fold in the presence of tc, from 1.132 to 2.214, while those of GFP and TetR showed little change under similar conditions. The results indicated TR::GFP possesses characteristics of a tetracycline biosensor.

[Construction of efficient conjugal plasmids between Escherichia coli and Streptomycetes]

Conjugal plasmid pGH112 has been developed based on the replicons of Streptomyces coelicolor plasmid SCP2 and E. coli ColE. The plasmid contains ampicilin resistance gene(amp) for selection in E. coli and thiostrepton resistance gene (tsr) for selection in Streptomycetes, and a 0.76 kb oriT fragment of (IncP) RK2. Conjugal transfer of pGH112 was performed from E. coli to S. coelicolor A3(2), S. avermitilis, S. lividans TK54, S. toxytricini NNRL15443, S. venezuelae ISP5230 and Sacc. erythraea by conjugation, results show that the plasmid was able to transfer efficenctly from E. coli to Streptomycetes, was stably inherited in the recipients. pGH113 was constructed from pGH112 by combining the constitutive ermE promoter with green fluorescent protein gene(gfp).

[Filling blood vessels with latex and its application]

The purpose of this study is to find out the better conditions for filling blood vessels of the body with latex. We test it on 500 bodies. Our data show that the temperature for storing the latex, filling positions, the wash of blood vessels prior to filling and filling pressure are all important in this process. A good filling increases elasticity of vessels, makes vessels stronger and facilitates dissection of vessel. It is of importance in the study of cardiovascular system.

Use of arsenic trioxide (As2O3) in the treatment of acute promyelocytic leukemia (APL): II. Clinical efficacy and pharmacokinetics in relapsed patients

The therapeutic effect of arsenic trioxide (As2O3) in the treatment of acute promyelocytic leukemia (APL) was evaluated among 15 APL patients at relapse after all-trans retinoic acid (ATRA) induced and chemotherapy maintained complete remission (CR). As2O3 was administered intravenously at the dose of 10 mg/d. Clinical CR was achieved in nine of 10 (90%) patients treated with As2O3 alone and in the remaining five patients treated by the combination of As2O3 and low-dose chemotherapeutic drugs or ATRA. During the treatment with As2O3, there was no bone marrow depression and only limited side effects were encountered. Pharmacokinetic studies, which were performed in eight patients, showed that after a peak level of 5.54 micromol/L to 7.30 micromol/L, plasma arsenic was rapidly eliminated, and the continuous administration of As2O3 did not alter its pharmacokinetic behaviors. In addition, increased amounts of arsenic appeared in the urine, with a daily excretion accounting for approximately 1% to 8% of the total daily dose administered. Arsenic contents in hair and nail were increased, and the peak content of arsenic could reach 2.5 to 2.7 microg/g tissue at CR. On the other hand, a decline of the arsenic content in hair and nail was observed after withdrawal of the drug. We conclude that As2O3 treatment is an effective and relatively safe drug in APL patients refractory to ATRA and conventional chemotherapy.

[Observation and measurement of coronary arteries of goat]

The coronary arteries of 50 goats were studied by means of angiography and dissection. The results were as follows: The right coronary artery (RCA) and left coronary artery (LCA) arose from the right and left aortic sinuses respectively. At the beginning, the average external diameter of RCA (2.98 +/- 1.02 mm) was smaller than that of LCA (3.42 +/- 0.74 mm). An independent inter ventricular septal artery (in 94%) supplied the upper two-thirds of the inter ventricular septum. The arterial distributive types were divided into three: The LCA was dominant in 96%, symmetrical in 4%, RCA dominant in 0%. Sixty two percent of the S-A node arteries arose from the RCA, 28% from LCA, 10% from both RCA and LCA. All the A-V node arteries originated from the LCA.

[Clinical significance of congenital fusion of cervical vertebrae: a report of 87 cases]

Based on clinical analysis of 87 cases with congenital fusion of cervical vertebrae, the clinical significance of these lesions was discussed in detail. It was found that the C 2-3 and then the C 3-4 were the sites of frequent involvement. Fusion of 2 to 3 segments was common and showed no clinical signs of abnormality, nor associated with any other malformations. While fusion of multiple segments, though rare, was often associated with other anomalies such as short neck, lowered posterior hair line, webbed neck and malformation of internal organs and other bones. Single lesion does not give rise to symptoms until late when degenerative changes have taken place in the unfused vertebrae in most cases, or following trauma in occasional patients, usually of neurologic upsets. However, fusion at several especially levels, fusion of C 2-3 with occipitalization of atlas predisposes the nerve to damage. In short, remedy is only necessary for cases with symptoms: conservative treatment for those with symptoms caused by radiculopathy, and operation for those with symptoms of myelopathy.