细菌表面多糖抗原是细菌的主要表面成分和重要致病因子，其在宿主免疫系统的长期选择压力下形成了生物界最丰富的多样性之一，该多样性是细菌血清学分型的基础。负责多糖抗原合成的基因簇是细菌染色体上最具多变性的区域，也是研究致病菌进化规律的良好材料。鲍曼不动杆菌是重要的院内感染致病菌，但尚缺乏对该菌表面多糖抗原多样性的系统研究，也无相应的成熟血清学分型体系。本项目将首次定位鲍曼不动杆菌的表面多糖抗原基因簇位点；破译并分析该菌中存在的所有表面多糖抗原基因簇（50种以上）；功能鉴定新发现的糖合成基因，以认识该菌表面多糖抗原的合成机制。将整体性解析鲍曼不动杆菌表面多糖抗原的多样性进化机制，重点研究其中与致病性密切相关的多糖抗原的形成机理，并以此为基础认识该菌的变异机制。将首次建立鲍曼不动杆菌分子血清学分型系统和快速检测方法，可为鲍曼不动杆菌的检测、流行病学调查、溯源等提供技术保障。

Surface polysaccharide antigen (an important virulence factor), presents as a major part of the outer membrane of bacteria and exhibits one of the richest diversities in nature due to long-term selection pressures from host immune systems. It is also the basis for bacterial serotyping. The gene cluster responsible for the synthesis of surface polysaccharide antigen is one of the most variable regions in bacterial chromosome, and is one of the most suitable materials for studying the laws of evolutionary routes that are relevant in pathogenic bacteria.Bacteria belonging to the species Acinetobacter baumannii are among the most problematic nosocomial pathogens. However, there is no systematic study on the A. baumannii surface polysaccharide antigen diversity. There is also no reliable serotyping system for A. baumannii. In this project, we will localize the surface polysaccharide antigen gene cluster on the genome of A. baumannii for the first time, and sequence and analyze all surface polysaccharide antigen gene clusters (>50). We will also identify the function of several sugar synthesis genes in biochemical level, and the result will be useful to understand the synthesis process of A. baumannii surface polysaccharide antigen. We will comprehensively analyze the evolutionary mechanism of all surface polysaccharide antigens in A. baumannii, especially which are closely related with pathogenic strains. The data obtained in this project will provide a basis for understanding the evolution and variation of bacterial pathogens. We will also develop a molecular serotyping system for A. baumannii, which will be very useful for rapid detection of the clinical pathogenic bacteria and epidemiological survey.