[Show abstract][Hide abstract] ABSTRACT: Lactobacillus brevis alcohol dehydrogenase (Lb-ADH) catalyzes reduction of prochiral carbonyl compounds to chiral alcohol and meanwhile consumes its cofactor NADH into NAD(+), while the cofactor regeneration can be catalyzed by Candida boidinii formate dehydrogenase (Cb-FDH). This work presents three different Escherichia coli whole-cell biocatalyst systems expressing recombinant ADH/FDH, FDH-LIN1-ADH and FDH-LIN2-ADH, respectively, all of which display very high efficacies of prochiral carbonyl conversion with respect to conversion rates and enantiomeric excess values. ADH/FDH represents co-expression of Lb-ADH and Cb-FDH under different promoters in a single vector. Fusion of Lb-ADH and Cb-FDH by a linker peptide LIN1 (GGGGS)2 or LIN2 (EAAAK)2 generates the two bifunctional enzymes FDH-LIN1-ADH and FDH-LIN2-ADH, which enable efficient asymmetric reduction of prochiral ketones in whole-cell biotransformation.
[Show abstract][Hide abstract] ABSTRACT: Aim:
To examine whether the novel cyclic lipopeptide antibiotic daptomycin could be used to treat anthrax and to study the mechanisms underlying its bactericidal action against Bacillus anthracis.
Spore-forming B anthracis AP422 was tested. MIC values of antibiotics were determined. Cell membrane potential was measured using flow cytometric assays with membrane potential-sensitive fluorescent dyes. Cell membrane integrity was detected using To-Pro-3 iodide staining and transmission electron microscopy. K(+) efflux and Na(+) influx were measured using the fluorescent probes PBFI and SBFI-AM, respectively.
Daptomycin exhibited rapid bactericidal activity against vegetative B anthracis with a MIC value of 0.78 μg/mL, which was comparable to those of ciprofloxacin and penicillin G. Furthermore, daptomycin prevented the germinated spores from growing into vegetative bacteria. Daptomycin concentration-dependently dissipated the membrane potential of B anthracis and caused K(+) efflux and Na(+) influx without disrupting membrane integrity. In contrast, both ciprofloxacin and penicillin G did not change the membrane potential of vegetative bacteria or spores. Penicillin G disrupted membrane integrity of B anthracis, whereas ciprofloxacin had no such effect.
Daptomycin exerts rapid bactericidal action against B anthracis via reducing membrane potential without disrupting membrane integrity. This antibiotic can be used as an alternate therapy for B anthracis infections.
[Show abstract][Hide abstract] ABSTRACT: Infections with bacterial or fungal biofilms have emerged as a major public heath concern because biofilm-growing cells are highly resistant to both antibiotics and host immune defenses. This review focuses on the progress in understanding the mechanisms of biofilm-specific antimicrobial resistance and in developing innovative therapeutic measures based on novel antibiofilm agents.
[Show abstract][Hide abstract] ABSTRACT: AphA is a small PadR-family DNA-binding regulator in vibrios. AphA has been shown to be involved in transcriptional auto-repression, intestinal colonization and lethality in mice, biofilm formation, and quorum sensing in Vibrio cholerae. The AphA protein of Vibrio parahaemolyticus has 85% identity to that of V. cholerae with the same number of amino acids. In this work, the aphA null mutant was constructed from a wild-type pandemic strain of V. parahaemolyticus for characterization of the phenotypic changes. AphA is required for biofilm formation in V. parahaemolyticus, and a decreased production of biofilm exopolysaccharide matrix in the aphA mutant relative to the wild-type parent strain accounts for its reduced biofilm formation. AphA is also necessary for the optimal swimming and swarming motility of V. parahaemolyticus. In addition, AphA is essential for lethality in mice and cytotoxic activity, but the aphA deletion did not have effect on enterotoxicity.
International journal of food microbiology 01/2013; 160(3):245-51. DOI:10.1016/j.ijfoodmicro.2012.11.004 · 3.08 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Sepsis represents a systemic inflammatory response to infection and its sequelae include severe sepsis, septic shock, multiple organ dysfunction syndrome (MODS) and death. Studies in mice and humans indicate that the inducible nitric oxide synthase (iNOS, NOS2) plays an important role in the development of sepsis and its sequelae. It was reported that several single nucleotide polymorphisms (SNPs) within NOS2 could influence the production or activity of NOS2. In this study, we assessed whether SNPs within NOS2 gene were associated with severity of sepsis in Chinese populations. A case-control study was conducted, which included 299 and 280 unrelated patients with sepsis recruited from Liaoning and Jiangsu provinces in China, respectively. Six SNPs within NOS2 were genotyped using Sequenom MassARRAY system. The associations between the SNPs and risk of sepsis complications were estimated by a binary logistic regression model adjusted for confounding factors. Functional assay was performed to assess the biological significance. The GA + AA genotype of a non-synonymous SNP in the exon 16 of NOS2 (rs2297518: G>A) was significantly associated with increased susceptibility to septic shock compared with GG genotype in Liaoning population (OR = 3.29, 95 % CI = 1.40-7.72, P = 0.0047). This association was confirmed in the Jiangsu population (OR = 3.49, 95 % CI = 1.57-7.79, P = 0.0019). Furthermore, the functional assay performed in the immortalized lymphocyte cell lines indicated that the at-risk GA genotype had a tendency of higher NOS2 activity than the GG genotype (P = 0.32). Our findings suggest that the NOS2 rs2297518 may play a role in mediating the susceptibility to septic shock in patients with sepsis in Chinese populations.
Human Genetics 11/2012; 132(3). DOI:10.1007/s00439-012-1253-4 · 4.82 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To analyze the sequence of STK11 gene coding region in 20 patients with Peutz-Jeghers syndrome and identify the point mutations in STK11 gene associated with the occurrence of the disease.
Blood samples were collected from 20 inpatients with Peutz-Jeghers syndrome treated in our center between January 2009 and October 2010. The sequence of STK11 gene coding region was analyzed using PCR and DNA sequencing and compared with the normal sequence of STK11 gene.
Of the 20 patients with Peutz-Jeghers syndrome, 14 showed STK11 gene mutations in the coding region, including 1 patient having two mutations and 13 patients with a single mutation site. In one case, sequence analysis of the STK11 gene identified a novel type of STK11 germline mutation, in which the cytosine (C)460 was substituted by guanine (G) in exon 3 to result in a new amino acid at codon 154. Four patients from 2 families were found to have a common mutation. The remaining 6 patients were not found to have mutations in STK11 gene coding region.
Mutations of STK11 gene is a major cause of Peutz-Jeghers syndrome. The missense mutation of 460 C→G in exon 3 of STK11 gene is a novel mutation associated with Peutz-Jeghers syndrome.
Nan fang yi ke da xue xue bao = Journal of Southern Medical University 04/2012; 32(4):511-4.
[Show abstract][Hide abstract] ABSTRACT: Coxsackievirus B (CVB) can cause aseptic meningitis, myocarditis and respiratory disease, especially in newborn infants. To compare the susceptibility to CVB infection of fetal and adult mice, we prepared primary alveolar epithelial cells (AECs) from lungs of BALB/c mice. In contrast to fetal mouse AECs, those of adults were less susceptible to CVB3 infection, as indicated by decreased cytopathic effects, and reduced levels of viral particles bound at the cell surface. In adult mouse AECs, amplification of the viral genome and virus capsid protein VP1 synthesis were concomitantly reduced. In addition, the cell-surface expression of coxsackievirus and adenovirus receptor (CAR), which plays a key role in the initiation of CVB and pulmonary infection, was downregulated in adult mouse AECs. These findings demonstrate that adult mouse AECs are less susceptible to CVB3 due to decreased CAR levels. Thus, these findings strongly indicate that the level of virus receptors on AECs is one of the crucial determinants for the age-dependence of CVB virulence in the mouse lung.
Archives of Virology 03/2012; 157(6):1101-11. DOI:10.1007/s00705-012-1254-6 · 2.39 Impact Factor