• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.11 no.8
• /
• pp.3862-3888
• /
• 2017

In high diversity node situation, single-channel MAC protocols suffer from many collisions. To solve this problem, the research of multichannel MAC protocol has become a hotspot. And the cyclic quorum-based multichannel (CQM) MAC protocol outperformed others owing to its high frequency utilization. In addition, it can avoid the bottleneck that others suffered from and can be easily realized with only one transceiver. To obtain the accurate performance of CQM MAC protocol, a Markov chain model, which combines the channel hopping strategy of CQM protocol and IEEE 802.11 distributed coordination function (DCF), is proposed. The metrics (throughput and average packet transmission delay) are calculated in performance analysis, with respect to node number, packet rate, channel slot length and channel number. The results of numerical analysis show that the optimal performance of CQM protocol can be obtained in saturation bound situation. And then we obtain the saturation bound of CQM system by bird swarm algorithm (BSA). Finally, the Markov chain model and saturation bound are verified by Qualnet platform. And the simulation results show that the analytic and simulation results match very well.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.17 no.4
• /
• pp.21-35
• /
• 2007

In ad hoc networks, position-based routing schemes, that use geographical positions of nodes, have been proposed to efficiently route messages. In these routing schemes, the location service is one of the key elements that determines and effects security and efficiency of the protocol. In this paper, we define security threats of location service and propose a new quorum based location service protocol. In our proposed protocol, nodes register their public keys in other nodes during the initialization phase and these registered keys are used to verify locations of other nodes and the messages exchanged. In this paper, we prove that our protocol is robust against traditional attacks and new attacks that may occur due to the use of position-based routing. We also analyze the efficiency of our protocol using various simulations.

• 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.

• Journal of Microbiology and Biotechnology
• /
• v.34 no.8
• /
• pp.1642-1652
• /
• 2024

Arctium lappa (Burdock) root is used in various culinary applications especially in Asian Cuisine. Arctigenin (ARC) is a polyphenolic compound abundant in the roots of the burdock plant from which it derives its name. The emergence of bacterial resistance is a growing global worry, specifically due to the declining availability of new antibiotics. Screening for the antibacterial candidates among the safe natural products is a promising approach. The present study was aimed to assess the antibacterial activity of ARC against Pseudomonas aeruginosa exploring its effect on the bacterial cell membrane. Furthermore, the anti-virulence activities and anti-quorum sensing (QS) activities of ARC were in vitro, in vivo and in silico assessed against P. aeruginosa. The current results showed the ARC antibacterial activity was owed to its disruption effect of the cell membrane. ARC at sub-MIC significantly decreased the formation of biofilm, motility, production of extracellular enzymes and in vivo protected mice against P. aeruginosa. These anti-virulence activities of ARC are owed to its interference with bacterial QS and its expression. Furthermore, ARC showed mild effect on mammalian erythrocytes, low probability to induce resistance and synergistically combined with antibiotics. In summary, the promising anti-virulence properties of ARC indicate its potential as an effective supplement to conventional antibiotics for treating severe P. aeruginosa infections.

• Microbiology and Biotechnology Letters
• /
• v.37 no.3
• /
• pp.248-257
• /
• 2009

The inhibitors against Vibrio harveyi quorum sensing (QS) signaling were developed by modifying the molecular structure of the major signal, N-3-hydroxybutanoyl-L-homoserine lactone (3-OH-$C_4$-HSL). A series of structural derivatives, N-(3-hydroxysulfonyl)-L-homoserine lactones (HSHLs) were synthesized by the solid-phase organic synthesis method. The in vivo QS inhibition by these compounds was measured by a bioassay system using the V. harveyi bioluminescence, and all showed significant inhibitory effects. To analyze the interaction between these compounds and LuxN, a 3-OH-$C_4$-HSL receptor protein of V. harveyi, we tentatively determined the putative signal binding domain of LuxN based on the sequence homology with other acyl-HSL binding proteins, and predicted the partial 3-D structure of the putative signal binding domain of LuxN by using ORCHESTRA program, and further estimated the binding poses and energies (docking scores) of 3-OH-$C_4$-HSL and HSHLs within the domain. In comparison of the result from this modeling study with that of in vivo bioassay, we suggest that the in silica interpretation of the interaction between ligands and their receptor proteins can be a valuable way to develop better competitive inhibitors, especially in the case that the structural information of the protein is limited.

• 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.

• 한국생물공학회:학술대회논문집
• /
• 2005.10a
• /
• pp.848-848
• /
• 2005

• Proceedings of the IEEK Conference
• /
• 2009.05a
• /
• pp.281-283
• /
• 2009

Forming Community is important to manage and provide the service in Ubiquitous Environments including embedded tiny computers. Community Computing is that members constitute the community and cooperate. A mutual exclusion problem occurs when many processors try to use one resource and race condition happens. In the expanded concept, a group mutual exclusion problem is that processors in the same group can share the resource but processors in different groups cannot share. As mutual exclusion problems might be in community computing environments, we propose algorithm which improves the execution speed using RMS (resource management service). In this paper describes proposed algorithm and proves its performance by experiments, comparing proposed algorithm with previous method using quorum-based algorithm.

• Journal of the Korean Institute of Telematics and Electronics B
• /
• v.31B no.2
• /
• pp.1-9
• /
• 1994

In distributed environments, data replication increases availability and decreases communication cost. However, it is difficult to maintain consistency and availability of data if site failure occurs. When we use the conventional hierarchical quorum consensus(HQC) method in order to maintain the consistency of data, occurrence of site failures makes it harder to perform the operation on replicated data because of insufficient votes. The objective of this paper is to improve the possibility of retaining necessary votes by reconstructing the HQC structure, when the site failure occurs. Furthermore, we compare the modified HQC method with the conventional HQC and QC methods in terms of improvement of availability.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
• /
• 2003.07a
• /
• pp.283-288
• /
• 2003

이 논문에서는 Manabe［2］에 의해 제안된 그룹상호배제를 위한 쿼럼(Quorum)기반의 알고리즘을 바탕으로 암호 기법을 이용한 보다 안전한 분산 알고리즘에 대하여 논한다. 그룹 상호배제는 하나의 리소스를 같은 그룹 내의 모든 프로세스에 의해서 공유되도록 할 수 있는 상호배제의 일반화이다［1］［4］. 하지만, 다른 그룹의 프로세스들은 상호 배타적인 방법으로 하나의 리소스를 사용하도록 요청된다. 즉, 다른 그룹의 프로세스들은 이미 임계영역에 있는 프로세스가 그 리소스에 대한 사용이 끝난 후 임계영역에 들어갈 수 있다. 분산 컴퓨팅 분야에서 계속적으로 제안된 알고리즘은 실제 개방된 인터넷상에서 각 프로세스들 간의 안전한 통신이 이루어져야 함에도 불구하고 프로세스들 간의 상호배제에만 초점을 맞춤으로서 안전성을 전혀 고려하지 않고 있다. 이 논문에서는 분산알고리즘에 암호학적 기법을 적용한 안전한 분산 알고리즘을 제시한다.