• Proceedings of the Zoological Society Korea Conference
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• 2000.10a
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• pp.230.2-230
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• 2000

No Abstract, See Full Text

• Molecules and Cells
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• v.28 no.4
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• pp.389-395
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• 2009

We previously observed that the transcription of some flagellar genes decreased in Salmonella Typhimurium tdcA mutant, which is a gene encoding the transcriptional activator of the tdc operon. Since flagella-mediated bacterial motility accelerates the invasion of Salmonella, we have examined the effect of tdcA mutation on the invasive ability as well as the flagellar biosynthesis in S. Typhimurium. A tdcA mutation caused defects in motility and formation of flagellin protein, FliC in S. Typhimurium. Invasion assays in the presence of a centrifugal force confirmed that the defect of flagellum synthesis decreases the ability of Salmonella to invade into cultured epithelial cells. In addition, we also found that the expression of Salmonella pathogenicity island 1 (SPI1) genes required for Salmonella invasion was down-regulated in the tdcA mutant because of the decreased expression of fliZ, a positive regulator of SPI1 transcriptional activator, hilA. Finally, the virulence of a S. Typhimurium tdcA mutant was attenuated compared to a wild type when administered orally. This study implies the role of tdcA in the invasion process of S. Typhimurium.

• IMMUNE NETWORK
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• v.12 no.6
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• pp.284-290
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• 2012

Innate immune cells sense and respond to the cytoplasmic infection of bacterial pathogens through NLRP3, NLRC4 or AIM2 inflammasome depending on the unique molecular pattern of invading pathogens. The infection of flagellin- or type III secretion system (T3SS)-containing Gram-negative bacteria such as Salmonella enterica serovar Typhimurium (S. typhimurium) or Pseudomonas aeruginosa (P. aeruginosa) triggers NLRC4-dependent caspase-1 activation leading to the secretion of proinflammatory cytokines such as interleukin-1-beta (IL-$1{\beta}$) and IL-18. Previous studies have shown that apoptosis-associated speck-like protein containing a CARD (ASC) is also required for Salmonella-induced caspase-1 activation, but it is still unclear how ASC contributes to the activation of NLRC4 inflammasome in response to S. typhimurium infection. In this study, we demonstrate that S. typhimurium triggers the formation of ASC oligomer in a potassium depletion-independent manner as determined by in vitro crosslinking and in situ fluorescence imaging. Remarkably, inhibition of potassium efflux failed to block Salmonella-promoted caspase-1 activation and macrophage cell death. These results collectively suggest that ASC is substantially oligomerized to facilitate the activation of caspase-1 in response to S. typhimurium infection. Contrary to NLRP3 inflammasome, intracellular potassium depletion is not critical for NLRC4 inflammasome signaling by S. typhimurium.

• Molecules and Cells
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• v.43 no.12
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• pp.989-1001
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• 2020

Salmonella enterica serovar Typhimurium (S. Typhimurium) is a facultative intracellular pathogen that causes salmonellosis and mortality worldwide. S. Typhimurium infects macrophages and survives within phagosomes by avoiding the phagosome-lysosome fusion system. Phagosomes sequentially acquire different Rab GTPases during maturation and eventually fuse with acidic lysosomes. Lysophosphatidylcholine (LPC) is a bioactive lipid that is associated with the generation of chemoattractants and reactive oxygen species (ROS). In our previous study, LPC controlled the intracellular growth of Mycobacterium tuberculosis by promoting phagosome maturation. In this study, to verify whether LPC enhances phagosome maturation and regulates the intracellular growth of S. Typhimurium, macrophages were infected with S. Typhimurium. LPC decreased the intracellular bacterial burden, but it did not induce cytotoxicity in S. Typhimurium-infected cells. In addition, combined administration of LPC and antibiotic significantly reduced the bacterial burden in the spleen and the liver. The ratios of the colocalization of intracellular S. Typhimurium with phagosome maturation markers, such as early endosome antigen 1 (EEA1) and lysosome-associated membrane protein 1 (LAMP-1), were significantly increased in LPC-treated cells. The expression level of cleaved cathepsin D was rapidly increased in LPC-treated cells during S. Typhimurium infection. Treatment with LPC enhanced ROS production, but it did not affect nitric oxide production in S. Typhimurium-infected cells. LPC also rapidly triggered the phosphorylation of IκBα during S. Typhimurium infection. These results suggest that LPC can improve phagosome maturation via ROS-induced activation of NF-κB pathway and thus may be developed as a therapeutic agent to control S. Typhimurium growth.

• Journal of Radiation Industry
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• v.2 no.3
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• pp.111-119
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• 2008

Microarrays can measure the expression of thousands of genes to identify the changes in expression between different biological states. To survey the change of whole Salmonella genes after a relatively high dose of gamma radiation (1 kGy), transcriptome dynamics were examined in the cells by using DNA microarrays. At least 75 genes were induced and 89 genes were reduced two-fold or more after irradiation. Several genes located in pSLT plasmid, cyo operon, and Gifsy prophage were induced along with many genes encoding uncharacterized proteins.While, the expression of genes involved in the virulence of Salmonella as well as metabolic functions were decreased. Although the radiation response as a whole could not be illustrated by using DNA microarrays, the data suggest that the response to high dose of irradiation might be more complex than the SOS response.

• Journal of Microbiology and Biotechnology
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• v.17 no.9
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• pp.1452-1459
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• 2007

The Dps protein, which is overexpressed in harsh environments, is known to playa critical role in the protection of DNA against oxidative stresses. In this study, the roles of Fur in the expression of the dps gene in Salmonella and the protection mechanisms against oxidative stress in Salmonella cells preexposed to iron-stress were investigated. Two putative Fur boxes were predicted within the promoter region of the S. typhimurium dps gene. The profile of dps expression performed by the LacZ reporter assay revealed growth-phase dependency regardless of iron-status under the culture conditions. The fur mutant, $_X4659$, evidenced a reduced level of ${\beta}$-galactosidase as compared to the wild-type strain. The results observed after the measurement of the Dps protein in various Salmonella regulatory mutants were consistent with the results acquired in the reporter assay. This evidence suggested that Fur performs a function as a subsidiary regulator in the expression of dps. The survival ability of Salmonella strains after exposure to oxidative stress demonstrated that the Dps protein performs a pivotal function in the survival of stationary-phase S. typhimurium against oxidative stress. Salmonella cells grown in iron-restricted condition required Dps for full protection against oxidative stress. The CK24 (${\Delta}dps$) cells grown in iron-replete condition survived at a rate similar to that observed in the wild-type strain, thereby suggesting the induction of an unknown protection mechanism(s) other than Dps in this condition.

• Korean Journal of Veterinary Research
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• v.50 no.3
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• pp.213-220
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• 2010

Salmonella (S.) Enterica infection ranks among the most common food borne bacterial infections worldwide. Although there are six subspecies of S. Enterica, the vast majority of human and animal infections are caused by strains belonging to subspecies 1 serovar Typhimurium and Enteritidis. Recent reports on antibiotic resistance of Salmonella spp. are rising steadily. The increasing problem of antibiotic resistance has rekindled interest in bacteriophage to therapy. Therefore, we investigated the efficacy of bacteriophage in S. enterica serovar Enteritidis infected mice and pigs by measuring of body condition, body weight, bacterial colonization and weight of organs based on the in vitro analysis. In vitro experiment, phage cultured with S. Enteritidis showed clear lysis pattern, the plaque forming unit (PFU) of our phage culture was $1.5{\times}10^{11}PFU/mL$, and phage showed its maximum activity at 4 h post inoculation. In mouse experiment, there was no significant difference among experimental groups in the general body conditions and body weight of mice. However, there was difference in weight of liver and spleen depending on the experimental group (p < 0.05). The weight of liver and spleen were reduced by the phage treatment. Also bacterial colonization in spleen and liver were significantly reduced by the phage treatment. In pig experiment, the general body conditions and body temperature exhibited not much difference among the pigs except few pigs in group 3 which showed poor body conditions. From the feces in each group, we could isolate the S. Enteritidis only from group 3. Bacterial enrichment culture was necessary for isolating the bacteria from 5 dpi and 10 dpi, however direct isolation was possible from 15 dpi feces. In phage treated group, postmortem lesion was better than non-phage treated group. Recently, antibiotic resistance concerns on the food-borne bacterial pathogens have been increasing because of the wide spread of the antibiotics resistance genes. This concern is widely transmitted to the human related public health. As one of the alternative treatments on the bacterial pathogens, attempt using phages have been made to control the bacterial diseases. The positive possibility of the trail using phage was observed to control the S. enterica serovar Enteritidis in this study even though the further analysis has been remained.

• Korean Journal of Food Science and Technology
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• v.43 no.4
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• pp.446-452
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• 2011

Total 480 lactic acid-producing bacteria were isolated from five kinds of kimchi, and their antibacterial activity was tested against Salmonella enterica serovar Typhimurium, Bacillus subtilis, and Pseudomonas aeruginosa using an agar diffusion assay. Among them, 340 isolates showed a halo on MRS agar against one or more indicator strains, which were identified using multiplex PCR, an API 50CHL kit, and a 16S rDNA sequence analysis. As a result, 169 Lactobacillus plantarum, 20 Lactobacillus fermentum, two Lactobacillus paracasei ssp. paracasei, two Lactobacillus sp., and 15 Pediococcus sp. were identified. This may be the first report on the isolation of antibacterial Lactobacillus fermentum from kimchi.

• Journal of Life Science
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• v.11 no.5
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• pp.432-438
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• 2001

Various lactic acid bacteria were isolated from Korean Dongchimi (whole radish Kimichi with added water) in order to study their antimutagenic activity. Ames test using Salmonella enterica serovar typhimurium TA98 and TA100 showed the strain DLAB19 to have the highest antimutagenic activity among the 300 isolated strains against MNNG(N-methyl-N-nitro-N-nitrosoguanidine), NPD (4-nitro-O-phenylenediamine), 4-NQO(4-nitroquinoline-1-oxide) and AFB$_{1}$(aflatoxin B$_{1}$). The strain was identified as Leuconostoc mesenteroides subsp. cremoris according to the Bergeys Mannual Systematic Bscteriology based on its morphological, cultural, physiological characteristics and biological system Antimutagenic activity of Leu. mesenteroides subsp. cremoris DLAB19 was found in the culture supernatant suggesting the bacterium secretes, the antimutagenic substance in the media. The antimutagenic activity of Leu. mesenteroides subsp. cremoris DLAB19 was reconfirmed by the spore-rec assay using spores of Bacillus subtilis H17 (Rec$^{+}$) and M45 (Rec$^{[-10]}$ ).).

• Journal of Microbiology and Biotechnology
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• v.23 no.12
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• pp.1664-1672
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• 2013

In Salmonella enterica serovar Typhimurium, many genes encoded within Salmonella pathogenicity island 1 (SPI1) are required to induce intestinal/diarrheal disease. In this study, we compared the expression of four SPI1 genes (hilA, invF, prgH, and sipC) under shaking and standing culture conditions and found that the expression of these genes was highest during the transition from the exponential to stationary phase under shaking conditions. To identify regulators associated with the stationary phase-dependent activation of SPI1, the effects of selected regulatory genes, including relA/spoT (ppGpp), luxS, ihfB, hfq, and arcA, on the expression of hilA and invF were compared under shaking conditions. Mutations in the hfq and arcA genes caused a reduction in hilA and invF expression (more than 2-fold) in the early stationary phase only, whereas the lack of ppGpp and IHF decreased hilA and invF gene expression during the entire stationary phase. We also found that hfq and arcA mutations caused a reduction of hilD expression upon entry into the stationary phase under shaking culture conditions. Taken together, these results suggest that Hfq and ArcA regulate the hilD promoter, causing an accumulation of HilD, which can trigger a stationary phase-dependent activation of SPI1 genes under shaking culture conditions.