Molecular epidemiology of norovirus in asymptomatic food handlers in Busan, Korea, and emergence of genotype GII.17.

The molecular epidemiology of norovirus infections was studied in food handlers without any symptoms from January to December 2015 in Busan city, Korea. A total of 2,174 fecal specimens from asymptomatic food handlers were analyzed, and 2.3% (49/2,174) were norovirus-positive. Fourteen of 335 samples (4.2%) were positive in January; fifteen of 299 samples (5.0%) in February, and seven of 189 samples (3.7%) in December. However, norovirus was rarely detected in other months. From sequencing analysis, 11 genotypes (five GI and six GII genotypes) were detected. Among the 42 capid gene sequences identified, 14 were from the GI genogroup, while 28 were from the GII genogroup. The most commonly detected genotype was GII.17, comprising 15 (35.7%) of positive samples. From January 2012 to December 2015, 5,138 samples were collected from gastroenteritis patients and outbreaks in Busan. The most detected genotype in 2012, 2013, and 2014 was GII.4 (121, 24, and 12 cases, respectively), but in 2015, GII.17 (25 cases) was the most common. The GII.4 genotype was the major cause of acute gastroenteritis from 2012 to 2014, but the GII.17 genotype became the most prevalent cause in 2015. Continued epidemiological surveillance of GII.17 is needed, together with assessment of the risk of norovirus infection.

The hrp pathogenicity island of Pseudomonas syringae pv. tomato DC3000 is induced by plant phenolic acids.

Plants produce a wide array of antimicrobial compounds, such as phenolic compounds, to combat microbial pathogens. The hrp PAI is one of the major virulence factors in the plant pathogen, Pseudomonas syringae. A major role of hrp PAI is to disable the plant defense system during bacterial invasion. We examined the influence of phenolic compounds on hrp PAI gene expression at low and high concentrations. There was approximately 2.5 times more hrpA and hrpZ mRNA in PtoDC3000 that was grown in minimal media (MM) supplemented with 10 -M of ortho-coumaric acid than in PtoDC3000 grown in MM alone. On the other hand, a significantly lower amount of hrpA mRNA was observed in bacteria grown in MM supplemented with a high concentration of phenolic compounds. To determine the regulation pathway for hrp PAI gene expression, we performed qRTPCR using gacS, gacA, and hrpS deletion mutants.

Functional analysis of the aefR mutation and identification of its binding site in Pseudomonas syringae pv. tabaci 11528.

The TetR family transcriptional regulator AefR contributes to the regulation of the quorum-sensing system. However, the role of AefR in the regulatory network of the phytopathogen Pseudomonas syringae pathovars is not known. In this study, the phenotype of a P. syringae pv. tabaci 11528 aefR deletion mutant strain was examined. The aefR gene expression and AefR DNA-binding affinity were examined by quantitative real-time polymerase chain reaction and electrophoretic mobility shift assay, respectively. AefR was found to control quorum-sensing genes as well as the efflux genes mexE, mexF, and oprN via an indirect mechanism. AefR binds to its own operator site as well as to the palindromic sequence between positions -28 and -2 corresponding to the transcription start site of aefR, as determined by dye primer sequencing. These results suggest that P. syringae AefR modulates quorum sensing and efflux as well as its own expression, which can be exploited by strategies developed to manage this plant parasite.

Protein-protein interactions between histidine kinases and response regulators of Mycobacterium tuberculosis H37Rv.

Using yeast two-hybrid assay, we investigated protein-protein interactions between all orthologous histidine kinase (HK)/response regulator (RR) pairs of M. tuberculosis H37Rv and identified potential protein-protein interactions between a noncognate HK/RR pair, DosT/NarL. The protein interaction between DosT and NarL was verified by phosphotransfer reaction from DosT to NarL. Furthermore, we found that the DosT and DosS HKs, which share considerable sequence similarities to each other and form a two-component system with the DosR RR, have different cross-interaction capabilities with NarL: DosT interacted with NarL, while DosS did not. The dimerization domains of DosT and DosS were shown to be sufficient to confer specificity for DosR, and the different cross-interaction abilities of DosS and DosT with NarL were demonstrated to be attributable to variations in the amino acid sequences of the α2-helices of their dimerization domains.

GacA directly regulates expression of several virulence genes in Pseudomonas syringae pv. tabaci 11528.

A two-component system comprising GacS and GacA affects a large number of traits in many Gram-negative bacteria. However, the signals to which GacS responds, the regulation mechanism for GacA expression, and the genes GacA controls are not yet clear. In this study, several phenotypic tests and tobacco-leaf pathogenicity assays were conducted using a gacA deletion mutant strain (BL473) of Pseudomonas syringae pv. tabaci 11528. To determine the regulation mechanism for gacA gene expression and to identify GacA-regulated genes, we conducted quantitative RT-PCR and electrophoretic mobility shift assay (EMSA) experiments. The results indicated that virulence traits related to the pathogenesis of P. syringae pv. tabaci 11528 are regulated coordinately by GacA and iron availability. They also revealed that several systems coordinately regulate gacA gene expression in response to iron concentration and bacterial cell density and that GacA and iron together control the expression of several virulence genes. EMSA results provided genetic and molecular evidence for direct control of virulence genes by GacA.

Negative regulation of pathogenesis in Pseudomonas syringae pv. tabaci 11528 by ATP-dependent Lon protease.

Pseudomonas syringae pv. tabaci causes wildfire disease in tobacco plants. The hrp pathogenicity island (hrp PAI) of P. syringae pv. tabaci encodes a type III secretion system (TTSS) and its regulatory system, which are required for pathogenesis in plants. Three important regulatory proteins-HrpR, HrpS, and HrpL-have been identified to activate hrp PAI gene expression. The bacterial Lon protease regulates the expression of various genes. To investigate the regulatory mechanism of the Lon protease in P. syringae pv. tabaci 11528, we cloned the lon gene, and then a Δlon mutant was generated by allelic exchange. lon mutants showed increased UV sensitivity, which is a typical feature of such mutants. The Δlon mutant produced higher levels of tabtoxin than the wild-type. The lacZ gene was fused with hrpA promoter and activity of ß-galactosidase was measured in hrp-repressing and hrp-inducing media. The Lon protease functioned as a negative regulator of hrp PAI under hrp-repressing conditions. We found that strains with lon disruption elicited the host defense system more rapidly and strongly than the wild-type strain, suggesting that the Lon protease is essential for systemic pathogenesis.

Changes of physiological and biochemical properties of Salmonella enterica serovar Typhimurium by deletion of cpxR and lon genes using allelic exchange method.

To construct a novel Salmonella attenuated live vaccine, the cpxR and lon genes were deleted from a wild-type Salmonella enterica serovar Typhimurium (S. Typhimurium) using allelic exchange method, resulting in S. Typhimurium CK31 (DeltacpxR), CK38 (Deltalon), and CK111 (DeltacpxR/lon). These mutated strains were grown normally, as was the wild-type strain. The biochemical properties of the mutants remained highly similar to those of the wild-type. In comparison with the wild-type, 1.5 to 3.3-fold increases of fimbrial products such as Agf, Fim, and Pef fimbria in the mutants CK31, CK38, and CK111 were observed by using a transmission electron microscope and dot blotting. Furthermore, CK38 and CK111 morphologically appeared elongated in shape and produced 2.0- and 3.2-fold increases, respectively, of capsular polysaccharide, which is a major antigenic component. Approximately 10(4)-fold attenuation assessed by analysis of LD(50) of BALB/c mouse was observed by deleting the lon/cpxR (CK111) genes. This result indicated that deletion of lon and cpxR genes induced significant attenuation.

Lysophosphatidylcholine enhances oxidative stress via the 5-lipoxygenase pathway in rat aorta during aging.

Lysophosphatidylcholine (LPC) is a lysolipid, acting as a potent cellular mediator of various biological processes. The purpose of this study was to define the role of LPC as a possible causative factor of disrupted redox balance in aged aorta from rats. In this study, we found elevated serum LPC levels in 24-month-old rats that were correlated with the age-related increase in cytosolic phospholipase A(2) (PLA(2)) activity. We also found that aortas from old rats showed increased 5-lipoxygenase (5-LO) activity. With the LPC-treated endothelial cells (YPEN-1 cells), we observed a rapid generation of reactive species, leading to enhanced oxidative stress. Our further investigations using specific 5-LO inhibitors led to the identification of a 5-LO pathway as the reactive species production source in the LPC-treated cells. Additional validation of this 5-LO pathway was made by the detection of increased leukotriene B4 generation in the LPC-treated cells. These in vitro data supported findings of increased expression and activation of aortic 5-LO in old rats by LPC. Together, our data strongly suggested that LPC caused the enhancement of oxidative stress in aged aorta through reactive species generation by an activated 5-LO pathway. LPC may well be an important contributor to age-related oxidative stress in aging aorta.

O2- and NO-sensing mechanism through the DevSR two-component system in Mycobacterium smegmatis.

The DevS histidine kinase of Mycobacterium smegmatis contains tandem GAF domains (GAF-A and GAF-B) in its N-terminal sensory domain. The heme iron of DevS is in the ferrous state when purified and is resistant to autooxidation from a ferrous to a ferric state in the presence of O(2). The redox property of the heme and the results of sequence comparison analysis indicate that DevS of M. smegmatis is more closely related to DosT of Mycobacterium tuberculosis than DevS of M. tuberculosis. The binding of O(2) to the deoxyferrous heme led to a decrease in the autokinase activity of DevS, whereas NO binding did not. The regulation of DevS autokinase activity in response to O(2) and NO was not observed in the DevS derivatives lacking its heme, indicating that the ligand-binding state of the heme plays an important role in the regulation of DevS kinase activity. The redox state of the quinone/quinol pool of the respiratory electron transport chain appears not to be implicated in the regulation of DevS activity. Neither cyclic GMP (cGMP) nor cAMP affected DevS autokinase activity, excluding the possibility that the cyclic nucleotides serve as the effector molecules to modulate DevS kinase activity. The three-dimensional structure of the putative GAF-B domain revealed that it has a GAF folding structure without cyclic nucleotide binding capacity.

Functional analysis of the role of Fur in the virulence of Pseudomonas syringae pv. tabaci 11528: Fur controls expression of genes involved in quorum-sensing.

In most bacteria, Fur (ferric uptake regulator) is a crucial global regulator known to operate not only in the regulation of iron homeostasis but also in a variety of other cellular processes. In an effort to characterize the role of Fur in the virulence of plant pathogens, a fur homolog was isolated from Pseudomonas syringae pv. tabaci 11528. Phenotype assays showed that a fur deletion mutant (BL33) constitutively produced siderophore(s) and exhibited decreases in swarming motility as well as the synthesis of tabtoxin and N-acyl homoserine lactones. Consistent with the results of TLC, quantitative real-time RT-PCR of the QS associated genes psyR and psyI demonstrated that Fur up-regulates these genes at the transcriptional level. Finally, the effects of a fur mutation on plant virulence indicated that Fur-regulated traits are relevant to plant-pathogen interactions.

Tbx3, a transcriptional factor, involves in proliferation and osteogenic differentiation of human adipose stromal cells.

Tbx3 is a transcription factor, the mutation of which causes ulnar mammary syndrome (UMS) characterized by abnormality and hypoplasia of the mammary gland, teeth, limbs, hair and genitalia. Tbx3 has been reported to be related to apoptosis and proliferation of rat bladder carcinoma cell and to regulate proliferation and differentiation of mouse osteoblast cells. Human adipose tissue stromal cells (hADSC) have been defined as multipotential adult stem cells, capable of differentiating into a variety of cell types such as osteoblasts, chondrocytes, adipocytes, muscle cells, and neural cells. To determine the functional roles of Tbx3 expression in hADSC, we used lentivirus siRNA vector. Expression of Tbx3 was downregulated during culture expansion. Downregulation of Tbx3 in hADSC by transduction of siTbx3 lentivirus decreased proliferation and osteogenic differentiation of hADSC. Expression of Tbx3 and the ratio of Tbx3 + 2a to Tbx3 increased during osteogenic differentiation. This report shows that Tbx3 plays an important role on osteogenic differentiation and proliferation of human mesenchymal stem cell derived from adipose tissue.

Characterization, cloning and expression of the ferritin gene from the Korean polychaete, Periserrula leucophryna.

Ferritin is a major eukaryotic protein and in humans is the protein of iron storage. A partial gene fragment of ferritin (255 bp) taken from the total RNA of Periserrula leucophryna, was amplified by RT-PCR using oligonucleotide primers designed from the conserved metal binding domain of eukaryotic ferritin and confirmed by DNA sequencing. Using the 32P-labeled partial ferritin cDNA fragment, 28 different clones were obtained by the screening of the P. leucophryna cDNA library prepared in the Uni-ZAP XR vector, sequenced and characterized. The longest clone was named the PLF (Periserrula leucophryna ferritin) gene and the nucleotide and amino acid sequences of this novel gene were deposited in the GenBank databases with accession numbers DQ207752 and ABA55730, respectively. The entire cDNA of PLF clone was 1109 bp (CDS: 129-653), including a coding nucleotide sequence of 525 bp, a 5'-untranslated region of 128 bp, and a 3'-noncoding region of 456 bp. The 5'-UTR contains a putative iron responsive element (IRE) sequence. Ferritin has an open reading frame encoding a polypeptide of 174 amino acids including a hydrophobic signal peptide of 17 amino acids. The predicted molecular weights of the immature and mature ferritin were calculated to be 20.3 kDa and 18.2 kDa, respectively. The region encoding the mature ferritin was subcloned into the pT7-7 expression vector after PCR amplification using the designed primers and included the initiation and termination codons; the recombinant clones were expressed in E. coli BL21(DE3) or E. coli BL21(DE3)pLysE. SDS-PAGE and western blot analysis showed that a ferritin of approximately 18 kDa (mature form) was produced and that by iron staining in native PAGE, it is likely that the recombinant ferritin is correctly folded and assembled into a homopolymer composed of a single subunit.

The influence of the nucleotide sequences of random Shine-Dalgarno and spacer region on bovine growth hormone gene expression.

To investigate the effects of the nucleotide sequences in Shine-Dalgarno (SD) and the spacer region (SD-ATG) on bovine growth hormone (bGH) gene expression, the expression vectors under the control of the T7 promoter (pT7-7 vector) were constructed using bGH derivatives (bGH1 & bGH14) which have different 5'-coding regions and were induced in E. coli BL21(DE3). Oligonucleotides containing random SD sequences and a spacer region were chemically synthesized and the distance between the SD region and the initiation codon were fixed to nine bases in length. The oligonucleotides were annealed and fused to the bGH1 and bGH14 cDNA, respectively. When the bGH gene was induced with IPTG in E. coli BL21(DE3), some clones containing only bGH14 cDNA produced considerable levels of bGH in the range of 6.9% to 8.5% of total cell proteins by SDS-PAGE and Western blot. Otherwise, the bGH was not detected in any clones with bGH1 cDNA. Accordingly, the nucleotide sequences of SD and the spacer region affect on bGH expression indicates that the sequences sufficiently destabilize the mRNA secondary structure of the bGH14 gene. When the free energy was calculated from the transcription initiation site to the +51 nucleotide of bGH cDNA using a program of nucleic acid folding and hybridization prediction, the constructs with values below -26.3 kcal/mole (toward minus direction) were not expressed. The constructs with the original sequence of bGH cDNA also did not show any expression, regardless of the free energy values. Thus, the disruption of the mRNA secondary structure may be a major factor regulating bGH expression in the translation initiation process. Accordingly, the first stem-loop among two secondary structures present in the 5'-end region of the bGH gene should be disrupted for the effective expression of bGH.

Evaluation of PCR-based assay for diagnosis of spotted fever group rickettsiosis in human serum samples.

A nested PCR assay was developed for the detection of spotted fever group (SFG) rickettsiae in serum samples. The assay was based on specific primers derived from the rickettsial outer membrane protein B gene (rompB) of Rickettsia conorii. An SFG rickettsia-specific signal is obtained from R. akari, R. japonica, R. sibirica, and R. conorii. Other bacterial species tested did not generate any signal, attesting to the specificity of the assay. As few as seven copies of the rompB gene of R. conorii could be detected in 200 microl of serum sample. The assay was evaluated with a panel of sera obtained from patients with acute-phase febrile disease tested by immunofluorescent antibody assay (IFA). The SFG rickettsia-specific DNA fragment was detected in 71 out of 100 sera, which were proven to have immunoglobulin M antibodies against SFG rickettsial antigen by IFA. The results were further confirmed by restriction fragment length polymorphism and sequencing analysis of the DNA fragments. The results indicated that this PCR assay is suitable for the diagnosis of spotted fever group rickettsiosis in Korea.

Purification and characterization of complement-activating acidic polysaccharides from the fruits of Capsicum annuum.

Hot water-soluble crude polysaccharide (HCAP-0) that was obtained from the fruits of Capsicum annuum showed potent anti-complementary activity. The activity was unchanged by pronase digestion, but decreased by periodate oxidation. The HCAP-0 was fractionated by DEAE ion-exchange chromatography to give two major fractions, HCAP-II and III. These two fractions were finally purified by gel filtration to give HCAP-IIa, HCAPIIIa1, and IIIa2 fractions that had high anti-complementary activities. The HCAP-IIIa1 and IIIa2 consisted of homogeneous polysaccharides. The anti-complementary activities were unaffected by treatment with polymyxin B, indicating that the modes of complement activation were not due to preexisting lipopolysaccharide. The molecular weight and sugar content of HCAP-IIIa2 had potent anti-complementary activity. The highest yields were 55 kDa and 75.9%, and the molar ratio of galactose (Ara:Gal, 1.0:4.6) was higher than other sugars. The crossed immuno-electrophoresis showed that both classical and alternative pathways were activated by HCAP-IIIa2.