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粘质沙雷氏菌AS-1中SpnR功能及卤化呋喃对其群体感应的抑制(英文) 被引量:3
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作者 陶寅璐 诸星知宏 +2 位作者 加藤纪弘 池田宰 庄惠生 《微生物学报》 CAS CSCD 北大核心 2008年第3期391-397,共7页
通过分泌和感知一系列信号分子,细菌能够根据自身菌体密度的变化调控基因的表达,从而控制一系列重要的表现型,包括毒力因子的产生,生物膜的形成以及菌体发光等。这种广泛存在的信号机制被称为群体感应。在沙雷氏菌种中已经发现了多套群... 通过分泌和感知一系列信号分子,细菌能够根据自身菌体密度的变化调控基因的表达,从而控制一系列重要的表现型,包括毒力因子的产生,生物膜的形成以及菌体发光等。这种广泛存在的信号机制被称为群体感应。在沙雷氏菌种中已经发现了多套群体感应机制。粘质沙雷氏菌AS-1从土壤中分离,其中含有LuxI/LuxR的同类蛋白,被称为SpnI/SpnR。粘质沙雷氏菌AS-1合成AHLs分子N-hexanoyl-L-homoserine lactone(C6-HSL)和N-(3-oxohexanoyl)-L-homoserine lactone(3-oxo-C6-HSL)作为其信号分子,通过群体感应感知菌体密度来控制基因的表达。通过基因替代的方法制得了spnR基因破坏的变异株,命名为粘质沙雷氏菌AS-1R。对粘质沙雷氏菌AS-1R的研究表明SpnR蛋白消极的调控沙雷氏菌红色色素的产生,运动性以及生物膜的形成等一系列由群体感应控制的性状;另一方面,作为一种天然的群体感应抑制剂,卤化呋喃能够有效的抑制粘质沙雷氏菌AS-1的群体感应,但并不干扰AHL-SpnR的相互作用。为运用粘质沙雷氏菌群体感应调节抑制其致病性提供了方法和依据,同时也为卤化呋喃对群体感应抑制机理的研究提供了新的思路。 展开更多
关键词 群体感应 spnr 抑制型 卤化呋喃
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Comparisons of the H.264 and H.263 Video Compression Standards 被引量:1
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作者 SALAHELDIN Ali Aboulkhsam 《Computer Aided Drafting,Design and Manufacturing》 2007年第1期86-94,共9页
The International Telecommunications Union (ITU-T) and the International Standardization Organization/International Electrotechnical Commission (ISO/IEC) are the only two formal organizations that developed video ... The International Telecommunications Union (ITU-T) and the International Standardization Organization/International Electrotechnical Commission (ISO/IEC) are the only two formal organizations that developed video coding standards. The ITU-T video coding standards called recommendations and are usually optimized for real-time video communication such as videoconference and video telephony while the ISO/IEC standards are mainly designed for storage (DVD) and broadcast (satellite and digital TV). ITU-T and the ISO/IEC JTC1 have agreed to join their efforts in the development of H.264 standard, which was initiated by ITU-T committee. The ITU-T H.264 video coding standard has been developed to achieve significant improvements over the existing standards in compression performance, although the basic coding framework of the standard is similar to that of the existing standards. H.264 standard is compared with H.263 and test results showed the coding gains obtained by the H.264 encoder is over the H.263 encoder for Common Intermediate Format (CIF) and Quarter Common Intermediate Format (QCIF)sequences, respectively. H.264 achieves an average of 4 dB PSNR(peak signal-to-noise rate) gain for the selected ten CIF sequences at 30 frames per second, and 4.57 dB Peak Signal-to-Noise Rate (PSNR) gain for the selected ten QCIF sequences at 30 frames per second. 展开更多
关键词 H.264 H.263 ITU-T ISO/IEC spnr CIF QCIF PSNR
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