Phage‐mediated transfer of virulence genes

Bacteriophages as accessory genetic elements play a crucial role in the dissemination of genes and the promotion of genetic diversity within bacterial populations. Such horizontal transfer of DNA is critical in the emergence of new pathogenic organisms, through the dissemination of genes encoding virulence factors such as toxins, adhesins and agressins. Phages can transfer genes that are not necessary for bacteriophage persistence and are generally recognised by their ability to convert their host bacteria to new phenotypes. This phenomenon is known as phage conversion. If such converting genes encode for virulence factors, the consequences of phage infection may include increased virulence of the host bacteria, and the conversion of a non‐pathogenic strain to a potentially dangerous pathogen. A number of virulence factors in bacteria causing diseases in plants, animals and humans are encoded by converting phages, the vast majority of which are temperate as opposed to lytic in nature. © 2001 Society of Chemical Industry     

脲酶抑制剂的研究综述

在土壤脲酶的作用下,尿素能迅速水解生成氨和碳酸氢铵,易挥发损失,致使氮利用率低。脲酶抑制剂能有效抑制脲酶活性,延缓尿素分解,提高氮素利用率。本文简单介绍了土壤脲酶概况、脲酶抑制剂的作用机理和种类,综述了脲酶抑制剂的研究进展,并提出存在问题及发展方向。     

Environmental Stimuli Shape Biofilm Formation and the Virulence of Periodontal Pathogens

Periodontitis is a common inflammatory disease affecting the tooth-supporting structures. It is initiated by bacteria growing as a biofilm at the gingival margin, and communication of the biofilms differs in health and disease. The bacterial composition of periodontitis-associated biofilms has been well documented and is under continual investigation. However, the roles of several host response and inflammation driven environmental stimuli on biofilm formation is not well understood. This review article addresses the effects of environmental factors such as pH, temperature, cytokines, hormones, and oxidative stress on periodontal biofilm formation and bacterial virulence.     

Inhibition of activity of urease in native form and immobilized on chitosan membrane by sodium fluoride

The influence of sodium fluoride inhibitor on the activity of urease in native form and immobilized covalently on glutaraldehyde-pretreated chitosan membrane was studied. Initially, in the presence of fluoride ions (I), a complex EI is formed which undergoes slow isomerization into a secondary form EI*. Both stages are represented on the progress curves. The dissociation constant of EI, K_i, for native and bonded urease were determined. The apparent rate constant as a function of the initial urea concentration for a given fluoride ion concentration was calculated, k = k ([I], [S]). It was found that sodium fluoride is a competitive slow-binding inhibitor of urease. Hydrolysis of urea in the standard conditions, at pH = 7.0, at 25° and a constant ionic strength and variable concentrations of substrate and of inhibitor has been studied. The reaction was initiated by addition of enzyme and was observed over a period of 10 min. The rate of hydrolysis at any point of time for both forms of urease, free and bound, may be calculated from the inhibition constants K_i, K*_i and apparent rate constant, k. It was found that immobilized urease is more resistant to the action of the inhibitor than the native one. This property offers potential for practical application.     

May Staphylococcus lugdunensis Be an Etiological Factor of Chronic Maxillary Sinuses Infection?

Staphylococcus lugdunensis is an opportunistic pathogen found in the healthy human skin microbiome bacterial community that is able to cause infections of diverse localization, manifestation, and course, including laryngological infections, such as necrotizing sinusitis. Chronic maxillary sinusitis is a disease present in up to one third of European and American populations, and its etiology is not fully described. Within this study, we aimed to characterize 18 S. lugdunensis strains recovered from maxillary sinuses and evaluate them as etiological agents of chronic disease. We performed MLST analysis, the complex analysis of both phenotypic and genetic virulence factors, antibiotic susceptibility profiles, and biofilm formation assay for the detection of biofilm-associated genes. Altogether, S. lugdunensis strains were clustered into eight different STs, and we demonstrated several virulence factors associated with the chronic disease. All tested strains were able to produce biofilm in vitro with numerous strains with a very strong ability, and overall, they were mostly susceptible to antibiotics, although we found resistance to fosfomycin, erythromycin, and clindamycin in several strains. We believe that further in-depth analysis of S. lugdunensis strains from different niches, including the nasal one, should be performed in the future in order to reduce infection rate and broaden the knowledge about this opportunistic pathogen that is gaining attention.     

单片机课程教学中工程项目案例的虚拟仿真

本文提出单片机课程改革的一条新思路--3＋1模式的教学（理论、实验、仿真＋案例）,即在Proteus虚拟仿真软件的基础上,讲述完单片机一些基本部件的理论和实验后,从一些实用的工程项目出发,利用虚拟串口,VB、VC及Labview等虚拟及应用软件,在课堂上详述一些实用工程项目的开发,帮助学生更好的理解单片机各部件的原理及应用。     

基于ARM7TDMI的μcLinux内核移植的Proteus仿真

将μcLinux内核移植到ARM7TDMI嵌入式处理器上,不仅可以合理地对软硬件资源进行调度,而且为用户提供方便的应用接口。在Proteus平台下设计了基于ARM7TDMI嵌入式处理器的硬件电路,成功地仿真了μcLinux的芯片级移植。利用Proteus在嵌入式系统开发初期就对硬件电路设计和内核移植部分进行尽可能的仿真,不仅节约了成本,还大大缩短了研发周期。