• Journal of Microbiology and Biotechnology
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• v.30 no.7
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• pp.1108-1108
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• 2020

• 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.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.

• 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.

• Journal of Dairy Science and Biotechnology
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• v.31 no.2
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• pp.179-186
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• 2013

Pseudomonas spp. are Gram-negative psychrophilic bacteria, which can proliferate at refrigeration temperature. The bacteria produce heat-stable enzymes that can degrade fat and protein in foods. Hence, Pseudomonas spp. are related to the spoilage of milk, dairy products, and meat products under cold storage, causing economic loss. In the food industry, various methods have been used to remove bacteria including Pseudomonas spp. in food-related conditions, but they can be resistant to antimicrobials and sanitizers because they form biofilms regulated by quorum sensing (cell density-dependent cell-to-cell signaling). Since Pseudomonas cells in biofilms can cross-contaminate foods resulting in food spoilage and the survival of food-borne pathogens in food-related conditions, efficient decontamination technology and microbiological criteria should be established to reduce the occurrence of food spoilage by Pseudomonas spp.

• BMB Reports
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• v.44 no.1
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• pp.1-10
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• 2011

Inter-cellular communication via diffusible small molecules is a defining character not only of multicellular forms of life but also of single-celled organisms. A large number of bacterial genes are regulated by the change of chemical milieu mediated by the local population density of its own species or others. The cell density-dependent "autoinducer" molecules regulate the expression of those genes involved in genetic competence, biofilm formation and persistence, virulence, sporulation, bioluminescence, antibiotic production, and many others. Recent innovations in recombinant DNA technology and micro-/nano-fluidics systems render the genetic circuitry responsible for cell-to-cell communication feasible to and malleable via synthetic biological approaches. Here we review the current understanding of the molecular biology of bacterial intercellular communication and the novel experimental protocols and platforms used to investigate this phenomenon. A particular emphasis is given to the genetic regulatory circuits that provide the standard building blocks which constitute the syntax of the biochemical communication network. Thus, this review gives focus to the engineering principles necessary for rewiring bacterial chemo-communication for various applications, ranging from population-level gene expression control to the study of host-pathogen interactions.