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Biomedical subjects

Sungsu Park

Publications and source records attributed to Sungsu Park.

10 recordsLinked to original sources
PubMed2006

Bacterial metapopulations in nanofabricated landscapes.

We have constructed a linear array of coupled, microscale patches of habitat. When bacteria are inoculated into this habitat landscape, a metapopulation emerges. Local bacterial populations in each patch coexist and weakly couple with neighbor populations in nearby patches. These spatially distributed bacterial populations interact through local extinction and colonization processes. We have further built heterogeneous habitat landscapes to study the adaptive dynamics of the bacterial metapopulations. By patterning habitat differences across the landscape, our device physically implements an adaptive landscape. In landscapes with higher niche diversity, we observe rapid adaptation to large-scale, low-quality (high-stress) areas. Our results illustrate the potential lying at the interface between nanoscale biophysics and landscape evolutionary ecology.

Adaptation, Biological↗
PubMed2006

Multilayer transfer printing on microreservoir-patterned substrate employing hydrophilic composite mold for selective immobilization of biomolecules.

In this study, we introduce a hydrophilic composite mold with elasticity and moderate water permeability, suitable for transferring water-soluble polar molecules such as polyelectrolyte multilayer. This composite mold is constructed from two UV-curable polymers-Norland Optical Adhesives (NOA) 63, a urethane-related polymer, and poly(ethylene glycol) diacrylate (PEGDA). The mixture of inherently hard NOA 63 and hydrogel precursor, PEGDA, resulted in an optically transparent mold with some degree of elasticity and enhanced water permeability upon UV polymerization. Employing the NOA 63-PEGDA composite mold, a polyelectrolyte multilayer comprising alternate thin layers of poly(acrylic acid) (PAA) and poly(acrylamide) (PAAm) was transfer-printed onto arrays of microreservoir-patterned substrate to selectively prevent unwanted adsorption of biomolecules on the protruding surface. Antibody was immobilized selectively inside the microreservoirs where multilayer was not transferred, and a specific antibody binding reaction was detected inside the microreservoirs. Furthermore, the potential of this composite mold as a convenient tool for constructing a biosensor for detecting Escherichia coli (E. coli) O157:H7 was explored.

Antibodies↗
PubMed2006

Protein kinase Calpha can undergo membrane localization via an alternative phosphatidylinositol 4,5-bisphosphate-dependent pathway.

Protein kinase Calpha (PKCalpha) activation is known to be dependent on the metabolic product of phosphatidylinositol 4,5-bisphosphate (PIP2) by phospholipase C (PLC). Here we report that fibroblasts may have an additional PIP2-dependent mechanism for membrane localization of PKCalpha. We observed PKCalpha membrane localization in both wild type and PLCgamma1 -/- mouse embryonic fibroblasts. Treatment of cells with a specific PLC inhibitor U73122 resulted in increased PIP2 levels and enhanced membrane localization of PKCalpha. PKCalpha levels in the membrane fraction decreased following incubation with PLCgamma, but increased following treatment with U73122 or addition of exogenous PIP2 in vitro. In addition, PKCalpha interacted with PIP2-conjugate bead and mixed micelles containing PIP2. Finally, we found that PIP2 is involved in syndecan-4-mediated membrane localization of PKCalpha. Taken together, these data suggest that PIP2 might contribute to directly regulating the membrane localization of PKCalpha.

Animals↗
PubMed2006

The role of periplasmic antioxidant enzymes (superoxide dismutase and thiol peroxidase) of the Shiga toxin-producing Escherichia coli O157:H7 in the formation of biofilms.

This study examined the role of the periplasmic oxidative defense proteins, copper, zinc superoxide dismutase (SodC), and thiol peroxidase (Tpx), from the Shiga toxin-producing Escherichia coli O157:H7 (STEC) in the formation of biofilms. Proteomic analyses have shown significantly higher expression levels of both periplasmic antioxidant systems (SodC and Tpx) in STEC cells grown under biofilm conditions than under planktonic conditions. An analysis of their growth phase-dependent gene expression indicated that a high level of the sodC expression occurred during the stationary phase and that the expression of the tpx gene was strongly induced only during the exponential growth phase. Exogenous hydrogen peroxide reduced the aerobic growth of the STEC sodC and tpx mutants by more than that of their parental strain. The two mutants also displayed significant reductions in their attachment to both biotic (HT-29 epithelial cell) and abiotic surfaces (polystyrene and polyvinyl chloride microplates) during static aerobic growth. However, the growth rates of both wild-type and mutants were similar under aerobic growth conditions. The formation of an STEC biofilm was only observed with the wild-type STEC cells in glass capillary tubes under continuous flow-culture conditions compared with the STEC sodC and tpx mutants. To the best of our knowledge, this is the first mutational study to show the contribution of sodC and tpx gene products to the formation of an E. coli O157:H7 biofilm. These results also suggest that these biofilms are physiologically heterogeneous and that oxidative stress defenses in both the exponential and stationary growth stages play important roles in the formation of STEC biofilms.

Aerobiosis↗
PubMed2006

Effect of bacteriocin produced by Lactococcus sp. HY 449 on skin-inflammatory bacteria.

This study was carried out to evaluate the effect of bacteriocin produced by Lactococcus sp. HY 449 against skin-inflammatory bacteria such as Staphylococcus epidermidis ATCC 12228, Staphylococcus aureus ATCC 65389, Streptococcus pyogenes ATCC 21059, and Propionibacterium acnes ATCC 6919. The spot-on-the-lawn method was used to determine the antimicrobial activity of bacteriocin against indicator strains on the human skin. The bacteriocin produced by Lactococcus sp. HY 449 inhibited the growth of S. epidermidis ATCC 12228, S. aureus ATCC 65389, Strep. pyogenes ATCC 21059, and P. acnes ATCC 6919. The treatment of crude bacteriocin caused a rapid inactivation of P. acnes ATCC 6919. The LC50 of bacteriocin on human fibroblast was ca. 50mg/ml at which the inhibition of cell proliferation was not observed. Neither any irritations nor allergic reactions by the bacteriocin were evident in a human patch test. The bacteriocin produced by Lactococcus sp. HY 449 may be a useful antimicrobial substance to control the growth of P. acnes and to prevent skin inflammation and acne.

Adult↗
PubMed2005

Effect of bacteriocin produced by Lactococcus sp. HY 449 on skin-inflammatory bacteria.

This study was carried out to evaluate the effect of bacteriocin produced by Lactococcus sp.HY 449 against skin-inflammatory bacteria such as Staphylococcus epidermidis ATCC 12228, Staphylococcus aureus ATCC 65389, Streptococcus pyogenes ATCC 21059, and Propionibacterium acnes ATCC 6919. The spot-on-the-lawn method was used to determine the antimicrobial activity of bacteriocin against indicator strains on the human skin. The bacteriocin produced by Lactococcus sp. HY 449 inhibited the growth of S. epidermidis ATCC 12228, S. aureus ATCC 65389, Strep. pyogenes ATCC 21059, and P. acnes ATCC 6919. The treatment of crude bacteriocin caused a rapid inactivation of P. acnes ATCC 6919. The LC(50) of bacteriocin on human fibroblast was approximately 50mg/ml at which the inhibition of cell proliferation was not observed. Neither any irritations nor allergic reactions by the bacteriocin were evident in a human patch test. The bacteriocin produced by Lactococcus sp. HY 449 may be a useful antimicrobial substance to control the growth of P. acnes and to prevent skin-inflammation and acne.

Acne Vulgaris↗
PubMed2005

Rapid identification of Lactobacillus acidophilus by restriction analysis of the 16S-23S rRNA intergenic spacer region and flanking 23S rRNA gene.

A rapid molecular approach was developed for the initial identification of Lactobacillus acidophilus strains which are difficult to identify using a single biochemical test. The 16S-23S rRNA intergenic spacer regions and flanking 23S rRNA genes of 19 strains of lactobacilli were amplified and the nucleotide sequences and restriction site polymorphisms were analyzed. AluI was the most useful of the restriction enzymes analyzed and produced reproducible digestion profiles in the L. helveticus, L. plantarum, and L. casei groups, as well as in L. acidophilus. This restriction fragment length polymorphism method may be useful for the identification of L. acidophilus strains in dairy products.

3' Flanking Region↗
PubMed2004

Modified immunoliposome sandwich assay for the detection of Escherichia coli O157:H7 in apple cider.

Detection of Escherichia coli O157:H7 in fruit juices such as apple cider is necessary for diagnosis of infection and epidemiological investigations. However, inhibitors in the apple cider, such as endogenous polyphenols and acids, often decrease the sensitivity of PCR assays and immunoassays, thus routinely requiring laborious cell separation steps to increase the sensitivity. In the current study, polyethylene glycol (PEG)-derivatized liposomes encapsulating sulforhodamine B were tagged with anti-E. coli O157:H7 antibodies and used in an immunoliposome sandwich assay for the detection of E. coli O157:H7 in apple cider. Even without prior separation, this assay can detect E. coli O157:H7 in apple cider samples inoculated with as few as 1 CFU/ml after an 8-h enrichment period. The lower limit of detection in pure cultures without enrichment was 7 x 10(3) CFU/ml (280 CFU/40-microl sample). PEGylated immunoliposomes are suitable as an analytical reagent for the detection of E. coli O157:H7 in fruit juices containing polyphenols.

Antibodies, Bacterial↗
PubMed2003

Influence of topology on bacterial social interaction.

The environmental topology of complex structures is used by Escherichia coli to create traveling waves of high cell density, a prelude to quorum sensing. When cells are grown to a moderate density within a confining microenvironment, these traveling waves of cell density allow the cells to find and collapse into confining topologies, which are unstable to population fluctuations above a critical threshold. This was first observed in mazes designed to mimic complex environments, then more clearly in a simpler geometry consisting of a large open area surrounding a square (250 x 250 microm) with a narrow opening of 10-30 microm. Our results thus show that under nutrient-deprived conditions bacteria search out each other in a collective manner and that the bacteria can dynamically confine themselves to highly enclosed spaces.

Biophysical Phenomena↗