Biomedical subjects

Shouwen Chen

Publications and source records attributed to Shouwen Chen.

6 recordsLinked to original sources

PubMed2007

Identification of three Zwittermicin A biosynthesis-related genes from Bacillus thuringiensis subsp. kurstaki strain YBT-1520.

Zwittermicin A (ZwA) is a novel, broad-spectrum linear aminopolyol antibiotic produced by some Bacillus cereus and Bacillus thuringiensis. However, only part of its biosynthesis cluster has been identified and characterized from B. cereus UW85. To better understand the biosynthesis cluster of ZwA, a bacterial artificial chromosome (BAC) library of B. thuringiensis subsp. kurstaki strain YBT-1520, a ZwA-producing strain, was constructed. Two BAC clones, 1F8 and 5E2, were obtained by PCR, which overlap the known ZwA biosynthesis cluster of B. cereus UW85. This ZwA biosynthesis cluster is at least 38.6 kb and is located on the chromosome, instead of the plasmid. Partial DNA sequencing revealed both BAC clones carry three new ZwA biosynthesis-related genes, zwa6, zwa5A and zwa5B, which were found at the corresponding location of B. cereus UW85. Putative amino acid sequences of these genes shown that ZWA6 is homologous to a typical carbamoyltransferase from Streptomyces avermitilis, while ZWA5A and ZWA5B are homologs of cysteine synthetase and ornithine cyclodeaminase which jointly synthesize 2,3-diaminopropionate in the viomycin biosynthesis pathway, respectively. The identification of these three genes further supports the hypothesized ZwA biosynthesis pathway.

Bacillus thuringiensis↗

PubMed2007

Fusion of the genes for AHL-lactonase and S-layer protein in Bacillus thuringiensis increases its ability to inhibit soft rot caused by Erwinia carotovora.

Two genes, ctc and ctc2, responsible for surface layer (S-layer) protein synthesis in Bacillus thuringiensis CTC, were mutated and resulted in B. thuringiensis Tr5. To synthesize and express the N-acyl-homoserine lactonase (AHL-lactonase) in the extracellular space of B. thuringiensis, the aiiA ( 4Q7 ) gene (an AHL-lactonase gene from B. thuringiensis 4Q7), which confers the ability to inhibit plant soft rot disease in B. thuringiensis 4Q7, was fused with the upstream sequence of the ctc gene, which in turn is essential for S-layer protein secretion and anchoring on the cell surface. The resulting fusion gene, slh-aiiA, was expressed in B. thuringiensis Tr5 to avoid competition for the extracellular space with the native S-layer protein. Our results indicate that B. thuringiensis Tr5 containing the fusion gene slh-aiiA displayed high extracellular AHL-degrading activity. When compared with wild-type B. thuringiensis strains, the ability of the constructed strain to inhibit soft rot disease caused by Erwinia carotovora SCG1 was markedly increased. These findings provide evidence for a significant advance in our ability to inhibit soft rot disease caused by E. carotovora.

Antibiosis↗

PubMed2006

Microbial transformation of androst-4-ene-3,17-dione by Beauveria bassiana.

The microbial transformation of androst-4-ene-3,17-dione (I) by the fungus Beauveria bassiana CCTCC AF206001 has been investigated using pH 6.0 and 7.0 media. Two hydroxylated metabolites were obtained with the pH 6.0 medium. The major product was 11alpha-hydroxyandrost-4-ene-3,17-dione (II) whereas the minor product was 6beta,11alpha-dihydroxyandrost-4-ene-3,17-dione (III). On the other hand, four hydroxylated and/or reduced metabolites were obtained with the pH 7.0 medium. The major product was 11alpha,17beta-dihydroxyandrost-ene-3-one (V) and the minor products were 17beta-hydroxyandrost-ene-3-one (IV), 6beta,11alpha,17beta-trihydroxyandrost-ene-3-one (VI) and 3alpha,11alpha,17beta-trihydroxy-5alpha-androstane (VII). The products were purified by chromatographic methods, and were identified on the basis of spectroscopic methods. This fungus strain is clearly an efficient biocatalyst for 11alpha-hydroxylation and reduction of the 17-carbonyl group.

Androstenedione↗

PubMed2005

High yield of poly-gamma-glutamic acid from Bacillus subtilis by solid-state fermentation using swine manure as the basis of a solid substrate.

Solid-state fermentations (SSF), using swine manure as the basis of a solid substrate, were carried out for high yield of poly-gamma-glutamic acid (gamma-PGA) by Bacillus subtilis CCTCC202048. Fermentation medium and process parameters were optimized through three orthogonal array designs. The optimal medium consisted of 62.3% (w/w, dry weight basis) swine manure, 25.0% soybean cake, 5.0% wheat bran, 5.0% glutamic acid, 2.5% citric acid and 0.2% MnSO4.H2O. The optimal process parameters were 15.0 g medium with initial moisture content 60% and initial pH 9.0 in 250 ml flask, inoculation at mid-log phase with a 4% inoculum level and cultivation for 48 h at 37 degrees C. The average-PGA yield (6.0%) in triplicate under optimal conditions was obtained on the laboratory scale while it was 4.5% at compost experiment. These would lay a foundation for lessening the pollution of swine manure, increasing fertilizer efficiency and exploring a late-model organic fertilizer that retains water and nutrients.

Animals↗

PubMed2003

Determination of spore concentration in Bacillus thuringiensis through the analysis of dipicolinate by capillary zone electrophoresis.

A new capillary zone electrophoresis (CZE) method for the analysis of dipicolinic acid, a specific component found in spores but not in vegetative cells, was used to determine spore concentration in Bacillus thuringiensis according to the relationship between the spore concentration and the content of dipicolinate. The quantitative relationship was established by using purified spores. Electrolyte conditions that affected the separation efficiency of dipicolinate and the reproducibility were investigated. With 10 mM phosphate, 10 mM ethylenediaminetetraacetic acid and 0.25 mM tetradecyltrimethylammonium bromide at pH 6.2 as the carrier electrolyte, dipicolinate can be determined within 8 min at an applied voltage of -25 kV (anode at detector) and a capillary temperature of 25 degrees C. The method has a high separation efficiency with which the number of theoretical plates is above 300,000 plates m(-1). The relative standard deviations for migration time and peak area are less than 0.5% and 2.0%, respectively. The detection limit for dipicolinate was 10 ng ml(-1), which corresponds to 7.2 x 10(5) spores ml(-1). The method was used to determine spores in fermentation broths, and the results obtained agreed well with the values obtained by plate counting.

Bacillus thuringiensis↗

PubMed2002

Determination of poly-beta-hydroxybutyric acid in Bacillus thuringiensis by capillary zone electrophoresis with indirect ultraviolet absorbance detection.

A new capillary electrophoresis method for determining poly-beta-hydroxybutyric acid (PHB) in Bacillus thuringiensis was established. Poly-beta-hydroxybutyric acid in samples was hydrolyzed by sulphuric acid and neutralized by Ba(OH)2. The content of produced beta-hydroxybutyrate was then determined by capillary zone electrophoresis (CZE) with indirect UV detection at 254 nm. With 5 mM p-hydroxybenzoate and 0.5 mM tetradecyltrimethylammonium bromide (TTAB) at pH 8.0 as carrier electrolyte, beta-hydroxybutyrate can be determined within 6 min. Standard regression equation was made by beta-hydroxybutyrate, and the linear range was 2-1000 microg/ml. The relative standard deviations (RSDs) for migration time and peak area are both less than 1.0%. The detection limit for beta-hydroxybutyrate was 0.2 microg/ml, which is two to three orders of magnitude lower than that of the gas chromatography (GC) method. The capillary electrophoresis method was successfully applied to determine poly-beta-hydroxybutyric acid in fermentation broth and single colony. The added standard recovery was 96%.

Bacillus thuringiensis↗