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Introduction

About Lab

Not many people can deny the fact that the importance of the food safety, especially in the microbial aspect, is continuously increasing. As a National Research Laboratory (NRL) appointed by the KOSEF( Korea Science and Education Foundation) in 2007, this lab is devoting all of its energy into elucidating the molecular basis of virulence in Vibrio vulnificus and Enterotoxigenic Escherichia coli (ETEC) and developing novel control practices in order to provide helpful information to various areas and promote public health.

To identify the virulence factors in V. vulnificus and ETEC and manifest their structural, functional and regulatory characteristics at a molecular level, the current experiments in this lab are being carried out using proteomics, DNA microarrays, and NGS (Next Generation Sequencing) technology. Specific research topics are described below.

I. The examination of the molecular mechanism of quorum sensing in V. vulnificus. Several bacteria can communicate with each other via quorum sensing. This process facilitates social networking in bacteria in response to environmental challenges that trigger alterations in gene expression. The SmcR protein has been proposed as a master quorum-sensing regulator in V. vulnificus, an opportunistic foodborne pathogen. In this lab, we have been trying to demonstrate the function, structure and other traits of SmcR.

II. The survival mechanism of the bacteria against ROS stress imposed by host defense systems. Pathogenic bacteria encounter a variety of stresses when they invade the host. Among stresses, reactive oxygen species (ROS) such as superoxide anion (O2-), hydrogen peroxide (H2O2), and hydroxyl radical (·OH) can lead to the damage of all cellular components including protein, DNA and membrane lipid of the bacteria. Pathogens have evolved sophisticated mechanisms to survive the oxidative stresses imposed by host defense systems, and the mechanisms are closely linked to their virulence. We have been engaged in understanding the protection mechanisms against oxidative stress in V. vulnificus and ETEC.

III. The regulation of the microbial biofilm generation. Bacteria can switch between planktonic (free-swimming) and biofilm (sessile) forms. Biofilms are the surface-attached bacterial communities marked by the excretion of a protective and adhesive matrix. Bacterial cells in a biofilm matrix acquire resistance to physical stresses, phagocytosis, and/or the penetration of toxic molecules, such as antibiotics. The ability of pathogens to form substancial biofilm structures is regarded as one of the virulence factors and also considered to be an important survival strategy in a wide range of environmental conditions. We are interested in the molecular mechanism involved in biofilm formation by V. vulnificus and ETEC.

IV. The examination of the molecular mechanism of the host-microbe interaction. When enteropathogenic bacteria invade into the host, they encounter quite big changes of environmental conditions such as temperature, pH, and nutrient availability. Especially, acquiring appropriate nutrients which are necessary for pathogen to survive and multiply in infection sites is no doubtfully important for successful pathogenesis. On the basis of this context, we have been studying to identify new transcriptional regulatory proteins related with nutrients acquisition / utilization, and to uncover its regulatory mechanisms. The mainly interested nutrient molecules are iron and sialic acid which are limited and prominently available, respectively, in host environment.

Aside from the projects mentioned above, we are interested in identifying new transcriptional regulatory proteins required specifically in the host for the expression of virulence factors of V. vulnificus and ETEC. We are confident that the food industry will be able to produce safer food products by gaining valuable information from our research results. Finally, we expect that understanding of the molecular mechanism for bacterial pathogenesis will be substantiated from our research on V. vulnificus and ETEC, and public health will be further assured.