• Korean Journal of Environmental Biology
• /
• v.33 no.4
• /
• pp.403-411
• /
• 2015

To understand differences of environmental factors and planktonic communities in closed (CS) versus open (OS) enclosed experimental systems, we performed a study on a 100-L indoor-type artificial marine microcosm. For environmental factors, including water temperature, dissolved inorganic phosphorus, and dissolved silica, there were no significant differences between CS and OS; however, salinity was higher in CS than that of OS due to the evaporation effect. The concentration of dissolved oxygen and dissolved inorganic nitrogen was lower in CS than in OS. The abundance of phytoplankton was lower in CS than in OS. However, abundance of autotrophic nanoflagellates and heterotrophic bacteria varied inversely with that of phytoplankton abundances. In particular, the abundance of heterotrophic nanoflagellates and ciliates increased with bacterial growth after a time lag. Therefore, environmental factors and planktonic communities in CS gradually changed over time and characterized a different artificial ecosystem than in OS.

• BMB Reports
• /
• v.48 no.1
• /
• pp.42-47
• /
• 2015

Streptococcus mutans is frequently associated with dental caries. Bacterial fermentation of food debris generates an acidic environment on the tooth surface, ultimately resulting in tooth deterioration. Therefore, various mouthwashes have been used to reduce and prevent Streptococcus mutans. The aim of this study was to evaluate the antimicrobial activities of 4 commercial mouthwashes and those of 10% and 20% ethanol solutions (formula A, B, C, D, E and F) against Streptococcus mutans using biofilm and planktonic methods. The range of reduction in the viable cell count of Streptococcus mutans as estimated by the biofilm and planktonic methods was 0.05-5.51 log ($P{\leq}0.01$) and 1.23-7.51 log ($P{\leq}0.001$) compared with the negative control, respectively, indicating that the planktonic method had a stronger antibacterial effect against S. mutans. Among the tested formulations, formula A (Garglin $regular^{(R)}$ mouthwash) was the most effective against Streptococcus mutans ($P{\leq}0.001$).

• Ocean and Polar Research
• /
• v.27 no.3
• /
• pp.341-349
• /
• 2005

Temporal variation of the natural planktonic community in the Southern Sea of Korea was investigated by using low floating enclosed bags (3.2m deep and 2,500 liter) in order to understand the effect of enriched nitrate on the planktonic community in the spring (March-April) of 2002. Prior to beginning the incubation, the bags were placed in two different concentrations of nitrate, which consisted of control (ambient water) and experimental mesocosms (final concentration of $12{\mu}M$). The nitrate concentration in the experimental mesocosms remained significantly higher than those in control mesocosms throughout the study period (ANOYA, p<0.001). Following the addition of nitrate, abundance and chi-a concentration of phytoplankton peaked on Day 1, when diatoms established the peak in the experimental mesocosms. Diatoms consisted mainly of Thalasxiosira decipiens, Pseudo-nitzschia pungem, Leptocylindrus danicu, Thalassionema nitzschioides, Chaetoceros pseudocrinitus and Actinoptychus senariu. However, the peak did not lead to the difference in abundance and composition of phytoplankton between control and experimental mesocosms during the study period. The dinoflagellates began to increase soon after the diatoms decreased in all mesocosms. Copepods, as a dominant group in the rnosozooplankton community, showed no immediate peak in relation to the nitrate addition, but only their own developmental process from the eggs to adult stage during the study period. The bottom-up control from enriched nitrate via phytoplankton to adult copepods was not distinguished in terms of the abundance of the planktonic community. This might stem from the relatively low nitrate availability of phytoplankton at no N-limited seawater and the weak coupling between rapidly sunken diatoms and copepods through the water column.

• International Journal of Oral Biology
• /
• v.37 no.4
• /
• pp.197-201
• /
• 2012

LIVE/DEAD$^{(R)}$ BacLight$^{TM}$ and alamarBlue$^{(R)}$ are fluorescent materials used for the enumeration of live and dead bacteria. LIVE/DEAD$^{(R)}$ BacLight$^{TM}$ is generally used for confocal microscopy applications to differentiate live from dead bacteria in a biofilm or planktonic state. AlamarBlue$^{(R)}$ has also been used widely to assay live and dead bacteria in a planktonic state. Whilst these materials are successfully utilized in experiments to discriminate live from dead bacteria for several species of bacteria, the application of these techniques to oral bacteria is limited to the use of LIVE/DEAD$^{(R)}$ BacLight$^{TM}$ in biofilm studies. In our present study, we assessed whether these two methods could enumerate live and dead oral bacterial species in a planktonic state. We tested the reagents on Streptococcus mutans, Streptococcus sobrinus, Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans and Enterococcus faecalis and found that only LIVE/DEAD$^{(R)}$ BacLight$^{TM}$ could differentiate live from dead cells for all five of these oral strains. AlamarBlue$^{(R)}$ was not effective in this regard for P. gingivalis or A. actinomycetemcomitans. In addition, the differentiation of live and dead bacterial cells by alamarBlue$^{(R)}$ could not be performed for concentrations lower than $2{\times}10^6$ cells/ml. Our data thus indicate that LIVE/DEAD$^{(R)}$ BacLight$^{TM}$ is a more effective reagent for this analysis.

• Journal of Microbiology and Biotechnology
• /
• v.30 no.11
• /
• pp.1729-1738
• /
• 2020

Salmonellosis is a form of gastroenteritis caused by Salmonella infection. The main transmission route of salmonellosis has been identified as poorly cooked meat and poultry products contaminated with Salmonella. However, in recent years, the number of outbreaks attributed to contaminated raw produce has increased dramatically. To understand how Salmonella adapts to produce, transcriptomic analysis was conducted on Salmonella enterica serovar Virchow exposed to fresh-cut radish greens. Considering the different Salmonella lifestyles in contact with fresh produce, such as motile and sessile lifestyles, total RNA was extracted from planktonic and epiphytic cells separately. Transcriptomic analysis of S. Virchow cells revealed different transcription profiles between lifestyles. During bacterial adaptation to fresh-cut radish greens, planktonic cells were likely to shift toward anaerobic metabolism, exploiting nitrate as an electron acceptor of anaerobic respiration, and utilizing cobalamin as a cofactor for coupled metabolic pathways. Meanwhile, Salmonella cells adhering to plant surfaces showed coordinated upregulation in genes associated with translation and ribosomal biogenesis, indicating dramatic cellular reprogramming in response to environmental changes. In accordance with the extensive translational response, epiphytic cells showed an increase in the transcription of genes that are important for bacterial motility, nucleotide transporter/metabolism, cell envelope biogenesis, and defense mechanisms. Intriguingly, Salmonella pathogenicity island (SPI)-1 and SPI-2 displayed up- and downregulation, respectively, regardless of lifestyles in contact with the radish greens, suggesting altered Salmonella virulence during adaptation to plant environments. This study provides molecular insights into Salmonella adaptation to plants as an alternative environmental reservoir.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.38 no.1
• /
• pp.55-64
• /
• 2005

Spatio-temporal variations of phytoplankton abundance and nutrient concentrations were investigated in the Namdaechon estuary, Yangyang, from April to December, 2003. A total of 51 phytoplankton species were identified with 32 diatom species in the study area. Phytoplankton abundance ranged from 14 cells/mL to 3,798 cells/mL. Small sized benthic and pennate-type diatoms like Cymbella spp., Fragilaria spp., Navicula spp., Synedra spp. were dominant at throughout the whole study area. Various planktonic species like Chlamydomonas sp., Peridinium spp., Euglena spp., Cryptomonas spp. etc. were abundant especially at the estuary of the Namdaechon, from May to August. Phytoplankton bloom (>3,000 \;cells/mL) occurred from the late May to mid June. After September when the sandbank of estuary was broken by the typhoon 'Maemi', planktonic species disappeared. These planktonic species were followed by oceanic diatoms, Skeletonema costatum and Chaetoceros spp.. Concentrations of dissolved inorganic nitrogen (DIN) and silicate were relatively high at the upstream in summer. In May, before phytoplankton bloom, high concentrations of phosphate $(>3.5\;{\mu}mol/L)$ were observed at all the study area. These results suggested that spatio-temporal variation of phytoplankton in the Namdaechon estuary was related to formation of sandbank at the mouth of the estuary, fluid speed affected by sandbank and nutrients supplied in spring. High correlation $(r^2=0.928)$ between chlorophyll a and biological oxygen demand (BOD) implies that BOD was related to phytoplankton abundance in the Namdaechon estuary.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.26 no.3
• /
• pp.248-262
• /
• 2021

Marine planktonic ciliates include two major groups, loricated tintinnids and naked oligotrichs. The study of marine ciliate plankton in Korea began with taxonomic efforts on tintinnids based on the morphology of lorica, a vase-shaped shell. Despite polymorphism in the lorica, it is utilized as a key characteristic in identification of tintinnid species. However, oligotrichs have been studied only recently in Korea due to challenges associated with the observation of ciliary arrangements and the technical development for cell staining. Species diversity and phylogenetic classification of the ciliates have been informed by recent advances in morphological and molecular analyses. Illustrations of the planktonic ciliate in Korea have been published on the basis of taxonomic data of tintinnids and oligotrichs. Planktonic ciliates acting as the major consumers of pico- and nanoplankton as well as the prey of mesozooplankton, has been monitored by spatial and temporal investigations in Korean coastal waters. A practical approach addressing the limitations and potential of marine ciliate studies in Korea is proposed here to improve the data quality of planktonic ciliates, providing an enhanced basis for quality control of ciliate monitoring.

• Journal of Microbiology and Biotechnology
• /
• v.24 no.8
• /
• pp.1059-1064
• /
• 2014

Staphylococcus aureus is a major human pathogen, implicated in both community and hospital acquired infections. The therapy for methicillin-resistant Staphylococcus aureus (MRSA) infections is becoming more difficult because of multidrug resistance and strong biofilm-forming properties. Schiff bases have attracted attention as promising antibacterial agents. In this study, we investigated the in vitro activity of taurine-5-bromosalicylaldehyde Schiff base (TBSSB) against MRSA. The minimum inhibitory concentrations (MIC) and minimum bactericidal concentration (MBC) were determined using a microtiter broth dilution method. TBSSB effectively inhibited planktonic MRSA, with an MIC of $32{\mu}g/ml$. The time-kill curve confirmed that TBSSB exhibited bactericidal activity against MRSA. TBSSB was also found to significantly inhibit MRSA biofilm formation at 24 h, especially at $1{\times}MIC$ and sub-MIC levels. Furthermore, scanning electron microscopy and transmission electron microscopy showed remarkable morphological and ultrastructural changes on the MRSA cell surface, due to exposure to TBSSB. This study indicated that TBSSB may be an effective bactericidal agent against MRSA.

• Journal of Microbiology and Biotechnology
• /
• v.27 no.3
• /
• pp.542-551
• /
• 2017

Small phytochemicals have been successfully adopted as antibacterial chemotherapies and are being increasingly viewed as potential antibiofilm agents. Some of these molecules are known to repress biofilm and toxin production by certain bacterial and yeast pathogens, but information is lacking with regard to the genes allied with biofilm formation. The present study was performed to investigate the inhibitory effect of burdock root extract (BRE) and of chlorogenic acid (CGA; a component of BRE) on clinical isolates of Klebsiella pneumoniae. BRE and CGA exhibited significant antibiofilm activity against K. pneumoniae without inflicting any harm to its planktonic counterparts. In vitro assays supported the ${\beta}$-lactamase inhibitory effect of CGA and BRE while in silico docking showed that CGA bound strongly with the active sites of sulfhydryl-variable-1 ${\beta}$-lactamase. Furthermore, the mRNA transcript levels of two biofilm-associated genes (type 3 fimbriae mrkD and trehalose-6-phosphate hydrolase treC) were significantly downregulated in CGA- and BRE-treated samples. In addition, CGA inhibited biofilm formation by Escherichia coli and Candida albicans without affecting their planktonic cell growth. These findings show that BRE and its component CGA have potential use in antibiofilm strategies against persistent K. pneumoniae infections.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.47 no.5
• /
• pp.562-566
• /
• 2014

Larvae of pandalid shrimp Pandalopsis japonica are benthic, and may prefer bottom to planktonic food items. Three diets, enriched Artemia meta-nauplii (AR), clam meat (CM), and crumbled shrimp (CD), were evaluated as food for early larvae in terms of biometric growth R:D ratios. Larvae fed AR and CM had significantly greater total length and dry weight than did larvae fed CD (P<0.05). Survival was significantly greater in larvae fed CM than in those fed AR and CD (P<0.05). R:D ratios were also significantly higher in larvae fed AR and CM than in those fed CD (P<0.05). Planktonic Artemia meta-nauplii containing high levels of fatty acids and amino acids were not suitable for either normal somatic growth or survival at early benthic larval stages. Furthermore, it is necessary to determine the optimal feeding duration to increase digestibility of AD. Thus, we propose that clam meat is the best diet for pandalid shrimp larvae.