[BK21 Plus Seminar]
              
                
             ▶Subject: Signaling, virulence, and biofilm formation of Pseudomonas aeruginosa and their control
                        
             ▶Speaker: Prof. Joon-Hee Lee
                       (Department of Pharmacy, College of Pharmacy, Pusan National University )
                                     
             ▶Date: 4:00PM/Aug. 28(Fri.)/2015
                     
             ▶Place: Life Science Bldg. #104
                      
                    *Abctract
              Pseudomonas aeruginosa is a ubiquitous and major opportunistic human pathogen that can cause cystic fibrosis, microbial keratitis, and burn wound infections. The virulence factors of P. aeruginosa were controlled by quorum-sensing (QS) which is a process that allows bacteria to communicate using secreted chemical signaling molecules called as acyl-homoserine lactones. QS of P. aeruginosa regulates several extracellular proteases that are important in its pathogenicity. To investigate whether the QS-dependent virulence against insect could be mediated by these extracellular proteases, we selected 8 candidate extracellular proteases that are expressed QS dependently and investigated their role in infection to insect. Of 8 candidates, Protease IV was very important for killing the Tenebrio moliter. T. molitor, an insect depends on innate immunity for defense against pathogenic bacteria. The defense includes both the expression of antibacterial peptides and the activation of prophenoloxidase cascades that leads to melanization of invading bacteria. In general, these systems are initiated from the recognition of bacterial peptidoglycan (PG) by the PG recognition proteins. While these pathways are specifically cascaded by host protease system, pathogenic bacteria also produce many proteases that are known as virulence factors during the infection process. To know how protease IV can interact with immune components in T. moliter, we purified protease IV and investigated their activity. Here we discuss the role of protease IV in Pseudomonas virulence against insect.
As well as the production of virulence factors like proteases, a life mode itself can enhance the infectivity of P. aeruginosa. The peculiar life mode is a biofilm. In nature, microbes exist in two distinct forms, nomadic (planktonic) or sedentary (sessile). Biofilms are a representative of the sessile form, in which microbial cells adhere to surfaces as microcolonies surrounded by a polysaccharide matrix. Because bacterial cells in biofilms are extremely resistant to the attack of immune cells, antibiotic medications, and disinfectant treatments, most persistent microbial infections are believed to be associated with biofilms. Moreover, in many civil architectures and facilities, such as water-supplying pipes, air ducts, catheters, fermentors in industries, etc., biofilms cause erosion, undesired biofouling, clogging, slippery coatings on the surface as well as harmful contamination of bacteria. Therefore, the control of biofilms has been a major interest in many fields including clinical microbiology, civil and environmental engineering, and industry. In many bacteria, the formation of biofilms is considered to be a bacterial group behavior, there is considerable evidence showing that biofilms are formed through cell-to-cell communication, the QS. P. aeruginosa also actively forms biofilms through QS, and its QS signal-deficient mutant has been known to be unable to form biofilms. In our efforts to establish an effective strategy for biofilm control, we have screened biofilm-deteriorating agents and developed a variety of biofilm model systems such as colony biofilms, microfluidic channel-based embedded biofilms, and flow cell biofilms. Using these various biofilm model systems, we have studied the regulation of gene expressions and physiology of bacterial cells in the spatial structure and environment of biofilms. Here, we introduce two recently developed biofilm model systems, colony and embedded biofilm systems, and a promising anti-biofilm agent, anthranilate.

            ▶Inquiry: Hwang, Cheol-Sang (279-2352)
                    
             * This seminar will be given in Korean.
     please refrain from taking photos during seminars. *