噬菌体裂解酶应用研究进展

近年来,随着抗生素的滥用,导致多重耐药性菌株出现的频率加快。因细菌感染导致死亡的人数逐年增多,人类健康面临巨大挑战,因此研制新型抗菌药物刻不容缓。噬菌体裂解酶因其高效的杀菌能力及高度的宿主专一性而成为新一代抗菌制剂的候选之一。其是一种细胞壁水解酶,在双链DNA噬菌体复制后期被合成,通过水解细胞壁肽聚糖上的化学键,从而裂解细菌细胞壁,释放出子代噬菌体。本文系统地介绍了噬菌体裂解酶的研究进展,为相关裂解酶抗菌药物的研发做出有益探索。     

提高噬菌体裂解酶抗菌活性的研究进展

随着细菌耐药性问题的日益严重,人们开始寻求新型抗菌制剂。噬菌体裂解酶是一种由ds DNA噬菌体编码的水解酶,能高效特异性地裂解细菌细胞壁且不易使细菌产生耐药性。由于天然裂解酶具有宿主谱窄,不能裂解革兰阴性菌等缺点,研究者对裂解酶进行了大量的设计改造。本研究主要对提高噬菌体裂解酶抗菌活性的研究进展进行综述。     

噬菌体裂解酶的抗菌特性

摘要：噬菌体裂解酶是一类细胞壁水解酶,可水解肽聚糖,造成细菌的破裂。裂解酶一般具有两到三个结构域,参与对底物的催化和结合。作为一种新型的杀菌制剂,裂解酶已被越来越多地应用于化脓链球菌、肺炎链球菌、金黄色葡萄球菌等革兰氏阳性细菌病的治疗。与抗生素治疗相比,裂解酶不易使细菌产生抗性且作用相对专一,这可能是解决现在日趋严重的细菌耐药性的一种可行方法。另外,裂解酶还具有高效性,作用协同性,且自身抗体不削弱其作用等优势,使之成为未来预防、控制致病菌一种可能的新途径。     

噬菌体裂解酶研究进展

噬菌体裂解酶是双链DNA噬菌体所特有的细胞壁水解酶。研究表明,所有噬菌体裂解酶在结构上具有相似性,即含有2个结构域：比较保守的N端催化区和差异较大的C端特异性结合区。裂解酶的高亲和性与种属特异的细胞壁糖基有关,而后常常是细菌存活的必要成分。所以,细菌难以产生对裂解酶的抗性。本简要综述噬茵体裂解酶的研究进展。     

噬菌体及其裂解酶控制金黄色葡萄球菌的研究进展

近70年来,由于抗生素的广泛使用,耐药金黄色葡萄球菌不断出现。美国1999～2005年因感染耐甲氧西林金黄色葡萄球菌（MRSA）而入院的患者增加1倍多,其中诊断为败血症的患者增加81．2％。因此,寻找控制耐药菌的新对策十分迫切。目前有望替代抗生素的控菌手段有抗菌肽、噬菌体等。其中,噬菌体的发现早于抗生素,后因抗生素的普及而被忽视。如今,耐药菌株的流行使噬菌体治疗再次受到关注。本文就应用噬菌体及其裂解酶控制金黄色葡萄球菌的研究进展进行综述。     

裂解酶治疗的研究进展与应用前景

多耐药病原细菌的不断出现和传播给公共医疗造成了严峻的威胁和挑战,开发新的抗菌分子迫在眉睫。噬菌体裂解酶来源于噬菌体,具有独特的进化和选择优势,不仅能高效快速的杀灭多耐药细菌,而且不易诱导细菌产生新的耐药性。本文对噬菌体裂解酶的结构和功能进行了简要的介绍,重点综述了裂解酶在抗细菌感染中近年的研究进展和应用前景。     

炭疽杆菌噬菌体裂解酶基因在大肠杆菌中的表达及鉴定

利用PCR方法扩增炭疽杆菌噬菌体裂解酶 (γlysin)基因 ,克隆至大肠杆菌表达载体pET2 2b中 ,经菌落PCR筛选、序列测定和酶切鉴定证实表达载体pET22b-γlysin构建成功 ,并在EscherichiacoliBL21(DE3)中获得了高表达。目的蛋白约占菌体总蛋白的40% ,5L发酵罐中的产酶水平高达 15g L。菌体经超声破碎 ,制备无细胞抽提液 ,StreamlineSP和SPHP柱层析以及SephacrylS-100凝胶过滤三步纯化 ,得到分子量为 2 7kD单一条带的目的蛋白 ,薄层扫描分析显示其纯度大于 95 %。目的蛋白的收率为19.1% ,纯化倍数为350。生物活性鉴定重组的γ噬菌体裂解酶具有特异性 :可快速裂解炭疽杆菌 ,比活为 1400u mg左右 ;而对大肠杆菌、枯草杆菌及蜡样芽孢杆菌没有裂解活性。     

噬菌体及其裂解酶对细菌生物被膜作用的研究进展

细菌形成的生物被膜,可保护细菌不易被抗生素杀死,这给临床上相应疾病的治疗及医疗器械的消毒带来极大困难。研究表明,噬菌体及其裂解酶对生物被膜有降解作用。噬菌体能清除细菌在有生物活性或无生物活性的介质表面形成的生物被膜。此外,噬菌体裂解酶比如LySMP、肽酶CHAPk、细胞壁溶解酶CWHs等能清除特定的生物被膜,这可能与裂解酶直接溶菌和裂解细菌细胞外基质有关。同时,与抗生素、钴离子、氯等物质联合使用时,噬菌体对生物被膜的清除作用会更强。本文从噬菌体、噬菌体编码的裂解酶、以及它们联合其他物质对细菌生物被膜的作用进行综述,并对其实际应用做了展望。     

鱼源副乳房链球菌前噬菌体裂解酶Sply828的抗菌活性

【背景】副乳房链球菌（Streptococcus parauberis）是重要的水产病原菌,该病原菌已逐渐出现新的血清型及多重耐药性状,因此亟须开发出一种新的抗菌药物用于该病害的防治。研究发现,前噬菌体编码的裂解酶能够有效地杀死其宿主,具有良好的抗菌应用前景。【目的】以副乳房链球菌前噬菌体裂解酶为对象,研究其杀菌宿主谱并优化其裂解活性的条件。【方法】利用PHASTER工具对副乳房链球菌菌株KRS02083全基因组序列分析发现,其前噬菌体包含一种裂解酶的基因Sply828;通过基因克隆、表达和纯化等技术得到裂解酶Sply828蛋白;通过浊度递减实验探究裂解酶Sply828对不同细菌的杀菌活性及其最适的裂解条件。【结果】裂解酶Sply828对鱼源副乳房链球菌具有最佳的杀菌活性,并发现该酶对处于指数生长期的细菌杀菌效果最好;其最适裂解温度为28°C,最适pH为6.2;Ca²⁺和Mg²⁺对该酶的杀菌活性有促进作用,但是Zn²⁺、Cu²⁺、Fe²⁺、Ni²⁺明显抑制...     

噬菌体及其裂解酶在食源性致病菌检测和控制中的应用

微生物致病菌引起的食源性疾病在全世界频频发生,对人类健康造成严重危害,尤其是致病菌耐药性的出现使常规治疗陷入困境。噬菌体及其编码的裂解酶的发现及应用,为食源性致病菌的检测及生物防治开辟了新的途径。综述噬菌体及其裂解酶在构建食源性致病菌的快速检测方法和生物防治方面的应用。     

噬菌体溶壁酶研究进展

溶壁酶是噬菌体在感染末期表达的蛋白质,可水解细菌的细胞壁,使子代噬菌体释放出来。研究表明,溶壁酶在体外能高效地杀死细菌,同样对感染细菌的模型动物有很好的治疗作用。因此,溶壁酶是一种新型的抗菌物质,具有广阔的应用前景。溶壁酶通过水解细菌细胞壁肽聚糖上糖与肽间的酰胺键或肽内氨基酸残基间的连键,从而使细菌裂解。溶壁酶分子由结合功能域和催化功能域两部分组成,其晶体结构使之具有对细胞壁肽聚糖水解的高效性和特异性。对噬菌体溶壁酶的体内外抗菌作用、抗菌机理、晶体结构等最新研究成果及其应用前景进行了综述。     

噬菌体治疗研究进展

噬菌体发现之初, 便被前苏联和东欧医学界用来治疗细菌感染。但是, 随着抗生素时代的到来, 人们慢慢忽略了对噬菌体的深入研究。近来, 由于全球耐药菌感染率不断攀升, 用抗生素治疗细菌感染面临了前所未有的挑战, 一些科学家和临床工作者开始重新把注意力集中到噬菌体研究上来, 并在这个领域取得了极大的进展, 尤其是通过大量的实验证明: 噬菌体可以有效地提高细菌感染的实验动物的存活率。本文就近几年国内外的科研工作者在噬菌体治疗领域所取得的进展做一综述。     

噬菌体治疗——旧概念, 新阶段

噬菌体治疗技术由来已久.噬菌体治疗的研究始于上世纪初,之后由于抗生素的出现及其他原因在美国和西欧等国家中断.近年来,全球范围的细菌耐药性使得科学家们重新审视和评估噬菌体治疗技术,显示出巨大潜力.论述噬菌体发现历程及早期研究、人类及动物细菌感染的应用、噬菌体治疗与抗生素的不同之处、存在的问题等,并探讨噬菌体技术可能的发展...     

Bacteriophage evolution given spatial constraint

Spatial structure can impede mixing, diffusion, and motility. In microbiology laboratories, spatial structure is commonly achieved via formation of agar gels, within which bacteriophage (phage) replication results in localized clearings called plaques. Developing a better understanding of phage plaque formation is relevant because of the ubiquity of phage plaquing in the laboratory; because plaque size has been employed as a measure of phage fitness; because many bacteria exist within environments that display significant spatial structure (e.g., biofilms, soils, sediments, and in or on plant or animal tissues); and because spatial structure could impede phage exploitation of bacterial communities. There is, however, a relative dearth of experimentation and analysis considering phage plaque formation from the perspective of selection acting on individual phage growth parameters-latent period, burst size, and adsorption rate. Here we consider the impact of these parameters on rates of plaque wavefront velocity (rates of radial plaque enlargement), especially as functions of existing phage and environmental properties. We do so based on analyses of published equations which predict plaque enlargement rates. These indicate that greater wavefront velocities should be associated with (i) latent period reductions, (ii) larger burst sizes, or (iii) faster virion binding to bacteria. We suggest, however, that deviations could occur, respectively, (i) if virion adsorption is "slow" or if burst sizes are large, (ii) if burst sizes are already large, or (iii) if virion binding rates are already fast, bacterial densities are especially high, or burst sizes are large. Higher initial lawn bacterial densities could also contribute to faster plaque expansion, but only if adsorption is otherwise slow or burst sizes are large. By contrast, faster virion diffusion is always expected to result in greater plaque wavefront velocities. Overall, we provide a snapshot of how phage populations may respond evolutionarily to selection for more-rapid propagation during spatially constrained growth.     

Bacteriophage HK97 head assembly

Abstract: The head assembly pathway of bacteriophage HK97 shares many features with head assembly pathways determined for other dsDNA phages, and it also provides examples of novel variations on the basic theme. We describe aspects of two specific steps in the assembly pathway, the covalent cross-linking among the assembled head protein subunits and the cleavage of those subunits that takes place earlier in the pathway. Comparisons of head assembly pathways among different phages, as well as comparisons of the organization of the genes that specify those pathways, suggest the range of different solutions phages have found to common assembly problems and give insight into the evolutionary histories of these assembly processes.     

Bacteriophage burst size during multiple infections

A significant positive correlation was observed between multiplicity of infection and burst size of mycobacteriophage 13. During multiple infections, the average contribution of each infecting phage to the burst size was inversely correlated with multiplicity of infection even when bacterial resources were not limiting. We conclude that the efficiency of phage-coded functions rather than the extent of bacterial resources determines the burst size.     

A Novel Type of Peptidoglycan-binding Domain Highly Specific for Amidated d-Asp Cross-bridge,Identified in Lactobacillus casei Bacteriophage Endolysins

Peptidoglycan hydrolases (PGHs) are responsible for bacterial cell lysis. Most PGHs have a modular structure comprising a catalytic domain and a cell wall-binding domain (CWBD). PGHs of bacteriophage origin, called endolysins, are involved in bacterial lysis at the end of the infection cycle. We have characterized two endolysins, Lc-Lys and Lc-Lys-2, identified in prophages present in the genome of Lactobacillus casei BL23. These two enzymes have different catalytic domains but similar putative C-terminal CWBDs. By analyzing purified peptidoglycan (PG) degradation products, we showed that Lc-Lys is an N-acetylmuramoyl-l-alanine amidase, whereas Lc-Lys-2 is a γ-d-glutamyl-l-lysyl endopeptidase. Remarkably, both lysins were able to lyse only Gram-positive bacterial strains that possess PG with d-Ala⁴→d-Asx-l-Lys³ in their cross-bridge, such as Lactococcus casei, Lactococcus lactis, and Enterococcus faecium. By testing a panel of L. lactis cell wall mutants, we observed that Lc-Lys and Lc-Lys-2 were not able to lyse mutants with a modified PG cross-bridge, constituting d-Ala⁴→l-Ala-(l-Ala/l-Ser)-l-Lys³; moreover, they do not lyse the L. lactis mutant containing only the nonamidated d-Asp cross-bridge, i.e. d-Ala⁴→d-Asp-l-Lys³. In contrast, Lc-Lys could lyse the ampicillin-resistant E. faecium mutant with 3→3 l-Lys³-d-Asn-l-Lys³ bridges replacing the wild-type 4→3 d-Ala⁴-d-Asn-l-Lys³ bridges. We showed that the C-terminal CWBD of Lc-Lys binds PG containing mainly d-Asn but not PG with only the nonamidated d-Asp-containing cross-bridge, indicating that the CWBD confers to Lc-Lys its narrow specificity. In conclusion, the CWBD characterized in this study is a novel type of PG-binding domain targeting specifically the d-Asn interpeptide bridge of PG.