蛋白分泌系统与细菌许多重要生理过程密切相关。革兰氏阴性细菌的蛋白分泌主要围绕变形杆菌门进行，而拟杆菌门则缺乏研究。最近，在拟杆菌门的牙龈卟啉单胞菌中发现一类新型蛋白分泌系统 (PorSS)，已发现有12个蛋白参与该系统但其蛋白转运机理尚不清楚。哈氏噬纤维菌是拟杆菌门中一种具有极强的纤维素降解能力的滑动细菌。其独特的纤维素降解和滑动机制都需要多种细胞表面蛋白的参与。我们通过序列比对和初步实验证明哈氏噬纤维菌具有类似PorSS的蛋白运输系统。本课题拟对序列比对获得的PorSS相似基因逐一进行基因敲除，以确定SSpor系统的主要组分。并根据突变株蛋白分泌情况和主要组分的亚细胞定位以及聚合体形成，初步确定SSpor的基本结构。通过突变株和野生株的差异分泌蛋白谱，确定SSpor的主要效应蛋白。通过对效应蛋白的逐段敲除突变和亚细胞定位，确定效应蛋白的穿膜识别序列，尤其是无信号肽效应蛋白的穿膜识别序列。

Protein secretion system is closely related to bacterial physiological processes. The study of the protein secretion system of Gram-negative bacteria was mainly focused on phylum Proteobacteria while phylum Bacteroidetes was lack of study. Recently, a novel protein secretion system named the Por secretion system (PorSS) has been found in Porphyromonas gingivalis which belongs to phylum Bacteroidetes. 12 proteins was identified in PorSS but transport mechanism of the system is still unkonwn. Cytophaga hutchinsonii is a cellulolytic gliding bacterium in phylum Bacteroidetes. Its unique cellulose degradation mechanism and gliding mechanism required the participation of a variety of cell surface proteins. Genome sequence analysis and our preliminary experiments proved that it also has similar PorSS system. This project intends to knockout the predicted PorSS genes in order to identify the major component of the PorSS of C. hutchinsonii. The basic structure of the PorSS will be determined by the study of the protein secretion property of the knockout mutant, subcellular localization of the major components and formation of protein polymers. The effector proteins secreted by the SSpor of C. hutchinsonii will be identified by comparing the proteomes of the secretoty proteins of knockout mutant and the wild type strain. The recognition sequence of the secretory proteins of SSpor C. hutchinsonii will be determined by gradual knocking out of the two ends of the protein sequence and the subcellular localization of the mutant protein, especially recognition sequence of the secretory proteins without signal peptide.