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Yoon, J.-H.

Publications and source records attributed to Yoon, J.-H..

2 recordsLinked to original sources
bioRxiv2018

Physiological Characteristics of Viable-but-nonculturable Vibrio parahaemolyticus upon Prolonged Exposure to the Refrigerator Temperature

Although it has been reported that viable-but-nonculturable (VBNC) cells of Vibrio parahaemolyticus can be developed by a prolonged duration of cold-starvation there are restricted cellular characteristics available on understanding the exact mechanisms governing the entry of pathogens into the VBNC state. Therefore, this research was aimed at determining the cellular profile of VBNC cells of V. parahaemolyticus upon exposure to the refrigerator temperature. Strains of V. parahaemolyticus were incubated in artificial sea water (ASW) microcosms (pH 6) added with different amounts of NaCl at 4{degrees}C until these pathogens entered into such a dormant state. At a regular time-interval, both culturability and viability of these bacteria were enumerated, and then cellular profiling were carried out in terms of cellular membrane permeability, enzymatic activity, hydrophobicity, fatty acid composition, and morphological changes after cells of V. parahaemolyticus became the VBNC state. Three strains of V. parahaemolyticus used in this study showed that VBNC cells retained the strong virulent properties to Vero and CACO-2 cell lines, re-gained the cytotoxicity even after resuscitation, became permeabilized in terms of the outer membrane, showed lower levels of enzymatic (catalase and glutathione-S-transferase) activities, exerted the increasing hydrophobicity, and then exhibited increasing amounts of saturated fatty acids.\n\nIMPORTANCETo the current best knowledge, there are restricted information available on understanding the physiological characterization of viable-but-nonculturable cells. Most previous studies are still making a degree of efforts in discovering the causative effector causing microorganisms to be induced into the VBNC state. Herein, the present study showed that pathogenic V. parahaemolyticus can enter into the VBNC state when challenged by a certain environmental stress where higher amounts of NaCl combined with acidic pHs was artificially controlled. Importantly, it was indicated that VBNC V. parahaemolyticus maintained peculiarly different physiological characteristics. Furthermore, this study proposed a novel approach on the transient/stepwise conversion of the bacteria into the VBNC state. Specific alternative tools for measuring and controlling the incidence of VBNC pathogens on food are not established until now. In this aspect, results obtained from this study will used to provide an effective insight in determining physiological properties of viable-but-nonculturable V. parahaemolyticus.

microbiology↗
bioRxiv2018

Analysis of the Resuscitation-Availability of Viable-But-Nonculturable Cells of Vibrio parahaemolyticus upon Exposure to the Refrigerator Temperature

Major pathogenic strains of Vibrio parahaemolyticus can enter into the viable-but-nonculturable (VBNC) state when subjected to environmental conditions commonly encountered during food processing. Especially, VBNC cells can be recovered to the culturable state reversibly by removing the causative stress, expressing higher levels of virulence factors. Therefore, the aim of this study was to determine if VBNC V. parahaemolyticus strains retain the resuscitation-availability upon eliminating the adverse condition, followed by the enrichment in developed resuscitation-facilitating buffers. Bacterial cells were shown to enter into the VBNC state in artificial sea water (ASW, pH 6) microcosms at 4{degrees}C within 70 days. VBNC cells were harvested, inoculated in formulated resuscitation-buffers, and then incubated at 25{degrees}C for several days. TSB (pH 8) supplemented with 3% NaCl (TSBA) exhibited the higher resuscitation-availability of VBNC cells. It was also shown that TSBA containing 10,000 U/mg/protein catalase, 2% sodium pyruvate, 20 mM MgSO4, 5 mM ethylenediaminetetraacetic acid (EDTA), and cell free supernatants extracted from the pure cultures of V. parahaemolyticus was more effective in resuscitating VBNC cells of V. parahaemolyticus, showing by 7.69-8.91 log10 CFU/ml.\n\nIMPORTANCEGenerally, higher concentrations ([≤]40%) of NaCl are used for preserving different sorts of food products from bacterial contaminations. However, it was shown from the present study that strains of V. parahaemolyticus were able to persist in maintaining the cellular viability, thereby entering into the VBNC state upon exposure to the refrigerator temperature for 80 days. Hence, the ability of VBNC V. parahaemolyticus to re-enter into the culturable state was examined, using various resuscitation buffers that were formulated in this study. VBNC cells re-gained the culturability successfully when transferred onto the resuscitation-buffer D, and then incubated at 25{degrees}C for several days. Resuscitation-facilitating agent D is consisting of antioxidizing agents, mineral, an emulsifier, and cell free supernatants from the actively growing cells of V. parahaemolyticus. It appeared that such a reversible conversion of VBNC cells to the culturable state would depend on multiple resuscitation-related channels.

microbiology↗