Novel molecular targets to combat antibiotic resistance: probing the assembly dynamics of a bacterial mitotic spindle

对多种抗生素具有耐药性的细菌对人类健康的危害日益严重。当第一种抗生素不能杀死细菌时，就必须改用第二种或第三种替代药物。有时没有替代药物可用。因此，抗生素耐药性的代价是生命和金钱，并给卫生保健资源带来沉重负担：据估计，NHS每年的费用约为10亿美元。细菌种群中超级细菌的出现是由细菌遗传遗产中自然发生的现象造成的，细菌遗传遗产由单个圆形（更罕见的是线性）DNA染色体和有时更小的DNA圈组成，称为质粒。由于染色体DNA的改变或突变，或从另一种细菌获得携带抗性基因的质粒，细菌可能产生耐药性。质粒是可移动的遗传元素，能够从一个细菌转移到另一个相同或不同物种。这种流动性是危险的，因为它助长了抗生素耐药基因的传播。多药耐药质粒隐藏着它们自己的生存工具箱，一个由两个基因和一段非编码DNA组成的分区盒。这种盒确保在细胞分裂时质粒从一代到下一代的准确分离。当这个系统出现故障时，质粒就不能稳定地遗传，并最终丢失。在我们的实验室里，我们一直在研究多药耐药质粒TP228的遗传和维持的分子机制，该质粒含有对六种不同抗生素耐药的基因。TP228的分割盒包含两个基因，分别命名为parF和parG，以及一个非编码DNA区域。parF基因指定的蛋白质非常特殊，因为它形成了可以通过电子显微镜看到的电缆状细丝。parG基因指定的蛋白是与质粒上的非编码DNA区域接触的DNA结合因子。该项目的目的是：探索细胞中ParF和ParG蛋白相互作用的动力学；研究ParG帮助ParF组装成索状结构的机制；并识别与ParF-ParG复合物相关的其他细菌蛋白质。这些研究将使我们更多地了解质粒在细菌细胞中维持的机制，并将为开发新的抗菌剂确定新的靶点。

Bacteria resistant to multiple antibiotics are a growing hazard to human health. When bacteria are not killed by a first antibiotic, the treatment has to be switched to a second or third alternative drug. Sometimes no alternative drug is available. Thus antibiotic resistance costs lives and money and puts a heavy burden on health care resources: it has been estimated that the costs for the NHS amount to around #1 billion a year. The emergence of superbugs among bacterial populations results from naturally occurring phenomena in the genetic patrimony of bacteria, which consists of a single circular (more rarely linear) chromosome of DNA and sometimes smaller circles of DNA, called plasmids. Resistance can develop in a bacterium as a consequence of a change or mutation in its chromosomal DNA or by acquisition of a plasmid carrying resistance genes from another bacterium. Plasmids are mobile genetic elements that are able to transfer from one bacterium to another of the same or different species. This mobility is dangerous as it foments the dissemination of antibiotic resistance genes. Multidrug resistance plasmids harbour their own survival kit, a partition cassette, consisting of two genes and a stretch of noncoding DNA. This cassette ensures accurate segregation of the plasmids from one generation to the next at cell division. When this system malfunctions, the plasmid is not stably inherited and is ultimately lost. In our laboratory, we have been investigating the molecular mechanisms involved in the inheritance and maintenance of the multidrug resistance plasmid TP228, which contains genes responsible for the resistance to six different antibiotics. The partition cassette of TP228 contains two genes, designated parF and parG, and a region of noncoding DNA. The protein specified by the parF gene is very peculiar as it forms cable-like filaments that can be seen by using an electron microscope. The protein specified by the parG gene is a DNA-binding factor contacting the noncoding DNA region on the plasmid. The aims of this project are: to explore the dynamics of the interaction of the ParF and ParG proteins in the cell; to investigate the mechanism whereby ParG helps the assembly of ParF into cable-like structures; and to identify other bacterial proteins that associate with the ParF-ParG complex. These studies will allow us to learn more about the mechanism whereby plasmids are maintained in bacterial cells and will identify novel targets for the development of new antimicrobial agents.