• Animal Bioscience
• /
• v.37 no.2_spc
• /
• pp.337-345
• /
• 2024

Ruminants possess a specialized four-compartment forestomach, consisting of the reticulum, rumen, omasum, and abomasum. The rumen, the primary fermentative chamber, harbours a dynamic ecosystem comprising bacteria, protozoa, fungi, archaea, and bacteriophages. These microorganisms engage in diverse ecological interactions within the rumen microbiome, primarily benefiting the host animal by deriving energy from plant material breakdown. These interactions encompass symbiosis, such as mutualism and commensalism, as well as parasitism, predation, and competition. These ecological interactions are dependent on many factors, including the production of diverse molecules, such as those involved in quorum sensing (QS). QS is a density-dependent signalling mechanism involving the release of autoinducer (AIs) compounds, when cell density increases AIs bind to receptors causing the altered expression of certain genes. These AIs are classified as mainly being N-acyl-homoserine lactones (AHL; commonly used by Gram-negative bacteria) or autoinducer-2 based systems (AI-2; used by Gram-positive and Gram-negative bacteria); although other less common AI systems exist. Most of our understanding of QS at a gene-level comes from pure culture in vitro studies using bacterial pathogens, with much being unknown on a commensal bacterial and ecosystem level, especially in the context of the rumen microbiome. A small number of studies have explored QS in the rumen using 'omic' technologies, revealing a prevalence of AI-2 QS systems among rumen bacteria. Nevertheless, the implications of these signalling systems on gene regulation, rumen ecology, and ruminant characteristics are largely uncharted territory. Metatranscriptome data tracking the colonization of perennial ryegrass by rumen microbes suggest that these chemicals may influence transitions in bacterial diversity during colonization. The likelihood of undiscovered chemicals within the rumen microbial arsenal is high, with the identified chemicals representing only the tip of the iceberg. A comprehensive grasp of rumen microbial chemical signalling is crucial for addressing the challenges of food security and climate targets.

• Microbiology and Biotechnology Letters
• /
• v.39 no.1
• /
• pp.29-36
• /
• 2011

Pseudomonas aeruginosa is an opportunistic pathogen that causes various infections on urinary track, cornea, respiratory track, and burn wound site, and mainly relies on quorum sensing (QS) for its virulence. To control the infectivity of P. aeruginosa, we previously synthesized the structural analogues of a major QS signal, N-3-oxododecanoyl homoserine lactone (3OC12-HSL) to use as a QS inhibitor. Two of them (5b and 5f) had been confirmed to have an inhibitory effect on LasR, a major QS signal receptor of P. aeruginosa in the screening by the recombinant Escherichia coli reporter. To further evaluate these compounds, we tested their efficacy to control the QS and virulence of P. aeruginosa. Unlike the result from E. coli reporter, both 5b and 5f failed to affect the LasR activity in P. aeruginosa, but instead they selectively affected the activity of QscR, another 3OC12-HSL receptor of P. aeruginosa. Interestingly, their effect on QscR was complex and opposite to what we obtained with E. coli system. Both 5b and 5f enhanced the QscR activity at the low concentration range (< 10 ${\mu}m$), but high concentration of 5f (${\approx}$1 mM) strongly inhibited QscR. While 5b and 5f didn't affect the production of proteases, the key virulence factor, they significantly reduced the biofilm formation that is important in mediating chronic infections. Especially, 5f inhibited the initial attachment of P. aeruginosa, rather than the biofilm maturation. Based on our results, we suggest that 5f can be applied for an anti-biofilm agent without increasing virulence of P. aeruginosa.

• Applied Biological Chemistry
• /
• v.48 no.1
• /
• pp.1-15
• /
• 2005

Pathogens, insects and weeds have significantly reduced agricultural productivity. Thus, to increase the productivity, synthetic agricultural chemicals have been overused. However, these synthetic compounds that are different from natural products cannot be broken down easily in natural systems, causing the destruction of soil quality and agricultural environments and the gradually difficulty in continuous agriculture. Now agriculture is faced with the various problems of minimizing the damage in agricultural environments, securing the safety of human health, while simultaneously increasing agricultural productivity. Meanwhile, plants produce secondary metabolites to protect themselves from external invaders and to secure their region for survival. Plants infected with pathogens produce antibiotics phytoalexin; monocotyledonous plants produce flavonoids and diterpenoids phytoalexins, and dicotylodoneous plant, despite of infected pathogens, produce family-specific phytoalexin such as flavonoids in Leguminosae, indole derivatives in Cruciferae, sesquitepenoids in Solanaceae, coumarins in Umbelliferae, making the plant resistant to specific pathogen. Growth inhibitor or antifeedant substances to insects are terpenoids pyrethrin, azadirachtin, limonin, cedrelanoid, toosendanin and fraxinellone/dictamnine, and terpenoid-alkaloid mixed compounds sesquiterpene pyridine and norditerpenoids, and azepine-, amide-, loline-, stemofoline-, pyrrolizidine-alkaloids and so on. Also plants produces the substances to inhibit other plant growths to secure the regions for plant itself, which is including terpenoids essential oil and sesquiterpene lactone, and additionally, benzoxazinoids, glucosinolate, quassinoid, cyanogenic glycoside, saponin, sorgolennone, juglone and lots of other different of secondary metabolites. Hence, phytoalexin, an antibiotic compound produced by plants infected with pathogens, can be employed for pathogen control. Terpenoids and alkaloids inhibiting insect growth can be utilized for insect control. Allelochemicals, a compound released from a certain plant to hinder the growth of other plants for their survival, can be also used directly as a herbicides for weed control as well. Therefore, the use of the natural secondary metabolites for pest control might be one of the alternatives for environmentally friendly agriculture. However, the natural substances are destroyed easily causing low the pest-control efficacy, and also there is the limitation to producing the substances using plant cell. In the future, effects should be made to try to find the secondary metabolites with good pest-control effect and no harmful to human health. Also the biosynthetic pathways of secondary metabolites have to be elucidated continuously, and the metabolic engineering should be applied to improve transgenics having the resistance to specific pest.

• Korean Journal of Microbiology
• /
• v.48 no.3
• /
• pp.180-186
• /
• 2012

Pseudomonas aeruginosa, a Gram-negative bacterium, is an ubiquitous and opportunistic human pathogen, which expresses many virulence factors through quorum sensing (QS) regulation. QscR, one of the QS signal receptors of P. aeruginosa, has unique features that make it possible to distinguish QscR from other QS receptors. In the present study, we focused on amino acid residues responsible for such a broad signal specificity of QscR. Thus we constructed mutant QscRs: $QscR_{T72I}$, $QscR_{R132M}$, and $QscR_{T140I}$ by substituting $72^{nd}$ threonine, $132^{nd}$ arginine, and $140^{th}$ threonine residues with isoleucine, methionine, and isoleucine, respectively by site-directed mutagenesis. When we examined the activity of these mutant QscRs, $QscR_{R132M}$ failed to respond to N-3-oxododecanoyl homoserine lactone (3OC12-HSL), but $QscR_{T72I}$ and $QscR_{T140I}$ remained the ability to respond to 3OC12-HSL despite much reduction of the sensitivity. When we treated a variety of acyl-HSLs with different structure, $QscR_{T72I}$ and $QscR_{T140I}$ showed better responsiveness to N-decanoyl HSL (C10-HSL) or N-dodecanoyl HSL (C12-HSL) that has no oxo-moiety at $3^{rd}$ carbon of acyl group than to 3OC12-HSL, and $QscR_{R132M}$ showed no responsiveness to any acyl-HSLs tested here. In addition, $QscR_{T72I}$ and $QscR_{T140I}$ were inhibited by 5f, a QscR inhibitor as similarly as wild type QscR was. These results suggest that while the $130^{th}$ arginine is crucial in both activity and acyl-HSL binding of QscR, the $72^{nd}$ and $140^{th}$ threonines are important in the activity, but they are little responsible for the discrimination of acyl-HSLs or competitive inhibitor.

• Clinical and Experimental Reproductive Medicine
• /
• v.10 no.2
• /
• pp.1-11
• /
• 1983

${\beta}$-Glucuronidase from bull seminal plasma was partially purified by $(NH_4)_2SO_4$fractionation, two successive DEAE-cellulose columns, isoelectric focusing (pH 4 to 6) and Gel filtration on Sephadex G-200. Only one form of ${\beta}$-glucuronidase was obtained by isoelectric focusing at pH 5.13. Highly purified ${\beta}$-glucuronidase had specific activity of 34 units/mg protein and showed one major and some minor contaminants by disc gelk electrophoresis. The enzyme showed maximum activity at pH 5.2 and at $48^{\circ}C$. The enzyme was completely inhibited by 1,4 saccharo-${\alpha}$-lactone (5 mM). Albumin and 0.15 M NaCl increased the ${\beta}$-glucuronidase activity. Km of ${\beta}$-glucuronidase using phenolphthalein mono-${\beta}$-glucuronic acid as substrate was 2.9 mM and Vmax was $0.8{\mu}$mole/min. The enzyme appeared to be a glycoprotein by its binding to concanvalin·A. Rabbit and human sperm-acrosomal extracts and seminal plasma showed high ${\beta}$-glucuronidase activity.

• Applied Biological Chemistry
• /
• v.40 no.1
• /
• pp.85-88
• /
• 1997

In orther to isolate antibacterial substances from the flower of Chrysanthemum zawadskii Herbich var. latilobum Kitam., the chloroform fraction was fractionated according to the activity against B. subtilis, S. aureus and V. parahaemolyticus. Two antibacterial substances were isolated and purified by preparative TLC and recrystallization. Compound I showed activity against all the tested bacteria and compound II exhibited the activity against B. subtilis and v. parahaemolyticus except S. aureus. Compared to benzoic acid and sorbic acid which are being used as food preservatives, compounds I and II showed about five-fold stronger antibacterial activity against B. subtilis and V. parahaemolyticus. On the basis of spectrometric studies including $^1H-NMR,\;^{13}C-NMR,\;DEPT,\;^1H-^1H\;COSY,\;^{13}C-^1H\;COSY$ and Mass, compounds I and II were identified as angeloylcumambrin B and cumambrin A, respectively. This is the first report of the isolation of angeloylcumambrin B and cumambrin A from this plant.

• Food Science of Animal Resources
• /
• v.33 no.5
• /
• pp.664-671
• /
• 2013

The objective of this study was to investigate the effect of high pressure treatment and type of binding agents on the quality characteristics of restructured pork. For binding agents, 2% (w/w) isolated soy protein (SP), 0.5% (w/w) wheat flour (WF) and 0.5% (w/w) ${\kappa}$-carrageenan (KC) were incorporated into meat batter with or without 0.5% (w/w) glucono-${\delta}$-lactone (GdL). The restructured pork was pressurized at varying pressure levels (0.1-450 MPa) for 3 min under ambient temperature and thermal treated at $75^{\circ}C$ for 30 min. As quality parameters of restructured pork, pH, water binding properties, instrumental color and texture profile analysis were determined and compared with control (C, no binder). For type of binders, SP exhibited the best water binding properties, however, the impact on textural properties were lesser than KC and WF. The addition of GdL decreased the pH of restructured pork down to 0.4 unit, while high pressure processing prevented the moisture loss caused from pH decrease by GdL. In particular, meat restructuring efficiency of SP as a binder improved under the presence of GdL. Therefore, the present study demonstrated the potential advantages of low amount of GdL (0.5%, w/w) combined with protein based binder (SP) and high pressure processing in restructuring meat particles.

• Tuberculosis and Respiratory Diseases
• /
• v.45 no.3
• /
• pp.546-552
• /
• 1998

Background: Up to 90% of a theophylline dose is biotransformed, by interaction with one or more the variants of the cytochrome P-450 drug metabolism system. Macrolides affect the elimination of theophylline by influencing on the microsomal enzyme systems. We evaluate the effect of erythromycin and new macrolides on the serum theophylline level and clearance. Method : Subjects consisted of moderate asthmatic patients with normal renal and hepatic functions. All subjects were non-smokers and treated with oral theophylline 400 mg per day. We randomly assigned 53 patients into four groups. Each group was treated with one macrolides, the first group erythromycin(n:19, 500 mg bid), second roxithromycin (n:14. 150 mg bid), third clarithromycin (n:10, 250 mg bid) and fourth azithromycin(n:10, 250 mg bid). We measured the serum theophylline level and clearance at three intervals, at pretreatment, after the first and fourth week after receiving the following macrolides, erythromycin, roxithromycin and clarithromycin. When azithromycin was administered, the serum theophylline level was measured at pretreatment and after one week of treatment They were measured by a computerized program of Bayesian method. Results : When compared with control, erythromycin and roxithromycin-treated groups had a significantly elevated serum theophylline level and decreased clearance. However, there were no significant changes of the serum theophylline level and clearance in clarithromycin and azithromycin-treated groups. Conclusion : These results suggest that theophylline dose may need to be readjusted and have periodic drug monitoring when erythromycin or roxithromycin is administered concurrently.

• Journal of Microbiology and Biotechnology
• /
• v.30 no.6
• /
• pp.937-945
• /
• 2020

N-acyl-homoserine lactone (AHL)-mediated quorum sensing (QS) plays a major role in development of biofilms, which contribute to rise in infections and biofouling in water-related industries. Interference in QS, called quorum quenching (QQ), has recieved a lot of attention in recent years. Rhodococcus spp. are known to have prominent quorum quenching activity and in previous reports it was suggested that this genus possesses multiple QQ enzymes, but only one gene, qsdA, which encodes an AHL-lactonase belonging to phosphotriesterase family, has been identified. Therefore, we conducted a whole genome sequencing and analysis of Rhodococcus sp. BH4 isolated from a wastewater treatment plant. The sequencing revealed another gene encoding a QQ enzyme (named jydB) that exhibited a high AHL degrading activity. This QQ enzyme had a 46% amino acid sequence similarity with the AHL-lactonase (AidH) of Ochrobactrum sp. T63. HPLC analysis and AHL restoration experiments by acidification revealed that the jydB gene encodes an AHL-lactonase which shares the known characteristics of the α/β hydrolase family. Purified recombinant JydB demonstrated a high hydrolytic activity against various AHLs. Kinetic analysis of JydB revealed a high catalytic efficiency (k_cat/K_M) against C4-HSL and 3-oxo-C6 HSL, ranging from 1.88 x 10⁶ to 1.45 x 10⁶ M^-1 s^-1, with distinctly low K_M values (0.16-0.24 mM). This study affirms that the AHL degrading activity and biofilm inhibition ability of Rhodococcus sp. BH4 may be due to the presence of multiple quorum quenching enzymes, including two types of AHL-lactonases, in addition to AHL-acylase and oxidoreductase, for which the genes have yet to be described.

• Microbiology and Biotechnology Letters
• /
• v.40 no.2
• /
• pp.83-91
• /
• 2012

Quorum sensing (QS) is a cell-to-cell communication system, which is used by many bacteria to regulate diverse gene expression in response to changes in population density. Bacteria recognize the differences in cell density by sensing the concentration of signal molecules such as N-acyl-homoserine lactones (AHL) and autoinducer-2 (AI-2). In particular, QS plays a key role in biofilm formation, which is a specific bacterial group behavior. Biofilms are dense aggregates of packed microbial communities that grow on surfaces, and are embedded in a self-produced matrix of extracellular polymeric substances (EPS). QS regulates biofilm dispersal as well as the production of EPS. In some bacteria, biofilm formations are regulated by c-di-GMP-mediated signaling as well as QS, thus the two signaling systems are mutually connected. Biofilms are one of the major virulence factors in pathogenic bacteria. In addition, they cause numerous problems in industrial fields, such as the biofouling of pipes, tanks and membrane bioreactors (MBR). Therefore, the interference of QS, referred to as quorum quenching (QQ) has received a great deal of attention. To inhibit biofilm formation, several strategies to disrupt bacterial QS have been reported, and many enzymes which can degrade or modify the signal molecule AHL have been studied. QQ enzymes, such as AHL-lactonase, AHL-acylase, and oxidoreductases may offer great potential for the effective control of biofilm formation and membrane biofouling in the future. This review describes the process of bacterial QS, biofilm formation, and the close relationship between them. Finally, QQ enzymes and their applications for the reduction of biofouling are also discussed.