• Microbiology and Biotechnology Letters
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• v.50 no.4
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• pp.548-556
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• 2022

Acylases can have a significant effect on biofilm formation owing to their quorum quenching activity. In this study, we investigated the effects of acylase treatment episodes on multispecies biofilm development. A consortium composed of 9 species belonging to different genera was allowed to form biofilms for 5 days under various treatment episodes (different treatment periods, 1, 2, 3, or 4 days; and two application timings, beginning or later) at 1, 5, 10, 20 and 50 mg·l^-1 acylase concentrations. The acylase treatment for 5 days showed that acylase concentration was negative with biofilm development (linear regression, Y = -0.05·x + 2.37, p < 0.05, R² = 0.88). Acylase was more effective in reducing biofilm formation when it was applied in the beginning (vs. in later development stage) at all acylase concentrations (p < 0.05). ANOVA indicated that treatment period was significant on biofilm formation in both application timings at ≥ 10 mg·l^-1 (p < 0.05). Linearity test results showed that all slope values between period and biofilm were negative in both timings at ≥ 10 mg·l^-1 (p < 0.05, except for the later application at 20 mg·l^-1). When temporal biofilm dynamics were monitored at 20 mg·l^-1, biofilms gradually increased with time at all treatment episodes (p < 0.05), and slope values in linear regression between biofilm and time were lower when acylase was applied in the beginning (p < 0.05). Our findings suggest the importance of the acylase treatment period and application timing on biofilm control.

• Journal of Microbiology and Biotechnology
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• v.23 no.5
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• pp.644-651
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• 2013

The fermented manure derivative known as Preparation 500 is traditionally used as a field spray in biodynamic agriculture for maintaining and increasing soil fertility. This work aimed at characterizing the product from a microbiological standpoint and at assaying its bioactive properties. The approach involved molecular taxonomical characterization of the culturable microbial community; ARISA fingerprints of the total bacteria and fungal communities; chemical elemental macronutrient analysis via a combustion analyzer; activity assays for six key enzymes; bioassays for bacterial quorum sensing and chitolipooligosaccharide production; and plant hormone-like activity. The material was found to harbor a bacterial community of $2.38{\times}10^8$ CFU/g dw dominated by Gram-positives with minor instances of Actinobacteria and Gammaproteobacteria. ARISA showed a coherence of bacterial assemblages in different preparation lots of the same year in spite of geographic origin. Enzymatic activities showed elevated values of ${\beta}$-glucosidase, alkaline phosphatase, chitinase, and esterase. The preparation had no quorum sensing-detectable signal, and no rhizobial nod gene-inducing properties, but displayed a strong auxin-like effect on plants. Enzymatic analyses indicated a bioactive potential in the fertility and nutrient cycling contexts. The IAA activity and microbial degradation products qualify for a possible activity as soil biostimulants. Quantitative details and possible modes of action are discussed.

• Journal of Life Science
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• v.27 no.10
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• pp.1161-1167
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• 2017

In order to find a new antimicrobial bacterium, we performed screening for antimicrobial activity of bacteria isolated from the eggs of a sea hare. The newly identified strain was designated as Phaeobacter inhibens KJ-2, based on the biochemical characterization and 16S rRNA gene sequence analysis. A colony of P. inhibens KJ-2 showed a circular and ruler-like smooth form at the edge, and a brown color. However, when maintained with a longer incubation time, its coloring was transformed into dark brown. From the result of SEM, P. inhibens KJ-2 is a bacillus which has a length of $0.8{\sim}1.0{\mu}m$ and a width of $0.4{\sim}0.6{\mu}m$. The optimal growth and antimicrobial activity were observed by shaking the culture for 24 hr at $20^{\circ}C$, which showed potent activity against pathogenic bacteria including Vibrio logei, Vibrio campbellii, Vibrio mimicus, Vibrio vulnificus, and Vibrio salmonicida. The antimicrobial activity was proportional to the amount of produced acylated homoserine lactones (AHLs). Therefore, we suggest that production of antimicrobial materials from P. inhibens KJ-2 is regulated by Quorum sensing (QS).

• Journal of Life Science
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• v.25 no.2
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• pp.136-150
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• 2015

Pseudomonas syringae pathovar tabaci is a plant pathogenic bacterium that causes wildfire disease in tobacco plants. In P. syringae pv. tabaci, PsyI, a LuxI-type protein, acts as an AHL synthase, while primary and secondary sequence analysis of PsyR has revealed that it is a homolog of the LuxR-type transcriptional regulator that responds to AHL molecules. In this study, using phenotypic and genetic analyses in P. syringae pv. tabaci, we show the effect of PsyR protein as a quorum-sensing (QS) transcriptional regulator. Regulatory effects of PsyR on swarming motility and production of siderophores, tabtoxin, and N-acyl homoserine lactones were examined via phenotypic assays, and confirmed by quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR). Further qRT-PCR showed that PsyR regulates expression of these virulence genes in response to environmental signals. However, an upstream region of the gene was not bound with purified MBP-PsyR protein; rather, PsyR was only able to shift the upstream region of psyI. These results suggested that PsyR may be indirectly controlled via intermediate-regulatory systems and that auto-regulation by PsyR does not occur.

• Korean Journal of Microbiology
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• v.44 no.4
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• pp.352-357
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• 2008

We evaluated cultivation methods to obtain pure cultures of previously uncultivated bacteria from soil. Soil bacteria (suspensions) were inoculated onto various oligotrophic media with one of the following additives: 1) soil extract; 2) anthraquinone disulfonate (humic acid analogue); 3) acyl homoserine lactones (quorum-signaling compounds); 4) catalase (for the protection of bacteria from exogenous peroxides). After the relatively long period (60 days) of incubation with elevated concentrations of $CO_2$ (5%, v/v), the media containing catalase showed the highest colony count. We purified 147 randomly selected colonies from the media and the isolates were subjected to the phylogenetic analyses of their 16S rRNA gene sequences. Phylogenetic analysis revealed that approximately 30% of the isolates might belong to novel species or novel family, suggesting that the media and incubation conditions used could be useful for the cultivation of as-yet-uncultured bacteria. Especially, bacteria belonging to the phylum Acidobacteria, ubiquitous bacterial taxon known as an uncultured bacterial group (at least difficult to culture from environmental samples), were successfully cultured in this study.

• Journal of Dairy Science and Biotechnology
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• v.32 no.2
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• pp.141-145
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• 2014

There is a burgeoning number of products on the market that contain probiotics, but do they do you any good? What exactly are probiotics? They have been defined as living organisms that, when ingested in sufficient quantities, provide health benefits beyond basic nutrition. They are often referred to as "friendly bacteria" or "good bacteria." Probiotics have been claimed, amongst other things, to (i) reduce the incidence of colon cancer and other diseases of the colon, such as IBS, (ii) stimulate the immune system, (iii) have anti-hypertensive and anti-cholesterolemic properties, (iv) mitigate against the effect of antibiotics on the intestinal microbiota, and (v) protect against gastrointestinal infections. However, the scientific basis for many of these claims is not well-established. Indeed, the European Food Safety Authority has denied the use of several health claims associated with probiotics, particularly those related to mitigation of diarrhea following consumption of antibiotics. Thus, there is a need for research on the mechanisms of action of probiotics. We have been mainly interested in the use of probiotics to control enteric infections. There are several possible modes of action to explain how probiotics may protect the host from enteric pathogens, including competitive exclusion and immunomodulation. We have shown that probiotics produce bioactive molecules that interfere with bacterial cell-cell communication (also called quorum sensing), and this results in a down-regulation of virulence genes that are responsible for attachment of the pathogen to the gastrointestinal epithelium. These bioactive molecules act on a variety of bacteria, including enterohemorrhagic and enterotoxigenic Escherichia coli, Salmonella, Clostridium difficile and Clostridium perfringens, and there is evidence that they can inhibit the formation of biofilms by Listeria monocytogenes. These bioactive molecules, which are peptidic in nature, can exert their effects not only in vitro but also in vivo, and we have shown that they mitigate against E. coli O157:H7 and Salmonella in mice and Salmonella and E. coli K88 infections in pigs. They can be delivered in foods such as yoghurt and maintain their activity.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.46 no.1
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• pp.23-29
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• 2020

The skin is colonized by a large number of microorganisms with a stable composition of species. However, disease states of skin such as acne vulgaris, psoriasis, and atopic dermatitis have specific microbiome compositions that are different from those of healthy skin. The target modulation of the skin microbiome can be a potential treatment for these skin diseases. Quorum sensing (QS), a bacterial cell-cell communication system, can control the survival of bacteria and increase cell density. Also, QS affects the pathogenicity of bacteria such as biofilm formation and protease production. In this study, we confirmed anti-QS activity of Amorepacific patented ingredients, which are Lactobacillus ferment lysate (using Lactobacillus plantarum APsulloc 331261, KCCM 11179P) through bio-reporter bacterial strain Chromobacterium violaceum. The purple pigment production of C. violaceum controlled by QS was reduced 27.3% by adding 10 ㎍/mL of Lactobacillus ferment lysate (freeze dried). In addition, the Lactobacillus ferment lysate increased growth of Staphylococcus epidermidis 12% and decreased growth of Pseudomonas aeruginosa 38.5% and its biofilm formation 17.7% at a concentration of 10 ㎍/mL compared to the untreated control group. Moreover, S. epidermidis was co-cultured with the representative dermatological bacterium Staphylococcus aureus in the same genus, the growth of S. epidermidis was increased 134 % and the growth of S. aureus was decreased 13%. These results suggest that fermented lysate using Lactobacillus plantarum APsulloc 331261 may be useful as a cosmetic ingredient that can control the balance of skin microbiome.

• Journal of Life Science
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• v.33 no.11
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• pp.936-943
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• 2023

This study was conducted to investigate the potential of Stewartia koreana as anti-microbial materials. The branches, stems and leaves of S. koreana were extracted into 70% ethanol and their antibacterial activity against P. aeruginosa was confirmed. The leaf, branch and stems extracts (1 mg/disc) showed the antibacterial activity against P. aeruginosa and leaf extracts showed higher antibacterial activities than those from branch extracts. The MIC against P. aeruginosa was 0.8 mg/ml and showed bacteriostatic action. The inhibitory effects of extract on biofilm formation and gene expression related to biofilm formation of P. aeruginosa was determined by biofilm biomass staining, SEM and qRT-PCR analysis. The biofilm biomass and cell growth of P. aeruginosa in the cultures treated with 0.2~2.0 mg/ml of S. koreana leaf extracts were significantly decreased in a concentration-dependent manner. We observed that the extract had an inhibitory effect on the formation of P. aeruginosa biofilms at concentrations of 0.8 mg/ml by SEM. qRT-PCR analysis showed that the lasI and rh1I gene expression associated to quorum sensing (QS) in the cultures treated with 0.2~2.0 mg/ml of S. koreana leaf extracts were suppressed in a concentration-dependent manner. Based on the above results, it can be concluded that S. koreana leaf extracts can be used as anti-microbial material derived from natural materials, as demonstrated by the antibacterial action and inhibition of biofilm formation of P. aeruginosa by QS inhibition.

• Journal of Microbiology and Biotechnology
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• v.26 no.1
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• pp.139-144
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• 2016

Synthetic oscillators are gene circuits in which the protein expression will change over time. The delay of transcription, translation, and protein folding is used to form this kind of behavior. Here, we tried to design a synthetic oscillator by a negative feedback combined with a positive feedback. With the mutant promoter P_LacC repressed by LacIq and P_Lux activated by AHL-bound LuxR, two gene circuits, Os-LAA and Os-ASV, were constructed and introduced into LacI-deleted E. coli DH5α cells. When glucose was used as the carbon source, a low level of fluorescence was detected in the culture, and the bacteria with Os-ASV showed no oscillation, whereas a small portion of those carrying Os-LAA demonstrated oscillation behavior with a period of about 68.3 ± 20 min. When glycerol was used as the carbon source, bacteria with Os-ASV demonstrated high fluorescence value and oscillation behavior with the period of about 121 ± 21 min.

• Microbiology and Biotechnology Letters
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• v.47 no.4
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• pp.473-486
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• 2019

In the aquatic environment, microorganisms are predominantly organized as biofilms. Biofilms are formed by the aggregation of microbial cells and are surrounded by a matrix of extracellular polymeric substances (EPS) secreted by the microbial cells. Biofilms are attached to various surfaces, such as the living tissues, indwelling medical devices, and piping of the industrial potable water system. Biofilms formed from a single species has been extensively studied. However, there is an increased research focus on multispecies biofilms in recent years. It is important to assess the microbial mechanisms underlying the regulation of multispecies biofilm formation to determine the drinking water microbial composition. These mechanisms contribute to the predominance of the best-adapted species in an aquatic environment. This review focuses on the interactions in the multispecies biofilms, such as coaggregation, co-metabolism, cross-species protection, jamming of quorum sensing, lateral gene transfer, synergism, and antagonism. Further, this review explores the dynamics and the factors favoring biofilm formation and pathogen transmission within the drinking water distribution systems. The understanding of the physiology and biodiversity of microbial species in the biofilm may aid in the development of novel biofilm control and drinking water disinfection processes.