Puech Virginie, Chami Mohamed, Lemassu Anne, Lanéelle Marie-Antoinette, Schiffler Bettina, Gounon Pierre, Bayan Nicolas, Benz Roland, Daffé Mamadou
Institut de Pharmacologie et Biologie Structurale, Centre National de la Recherche Scientifique/Université Paul Sabatier (UMR 5089), 205 route de Narbonne, 31077, Toulouse Cedex 04, France1.
Centre de Génétique Moléculaire, CNRS, 91190 Gif-sur-Yvette, France5.
Microbiology (Reading). 2001 May;147(Pt 5):1365-1382. doi: 10.1099/00221287-147-5-1365.
With the recent success of the heterologous expression of mycobacterial antigens in corynebacteria, in addition to the importance of these bacteria in biotechnology and medicine, a better understanding of the structure of their cell envelopes was needed. A combination of molecular compositional analysis, ultrastructural appearance and freeze-etch electron microscopy study was used to arrive at a chemical model, unique to corynebacteria but consistent with their phylogenetic relatedness to mycobacteria and other members of the distinctive suprageneric actinomycete taxon. Transmission electron microscopy and chemical analyses showed that the cell envelopes of the representative strains of corynebacteria examined consisted of (i) an outer layer composed of polysaccharides (primarily a high-molecular-mass glucan and arabinomannans), proteins, which include the mycoloyltransferase PS1, and lipids; (ii) a cell wall glycan core of peptidoglycan-arabinogalactan which may contain other sugar residues and was usually esterified by corynomycolic acids; and (iii) a typical plasma membrane bilayer. Freeze-etch electron microscopy showed that most corynomycolate-containing strains exhibited a main fracture plane in their cell wall and contained low-molecular-mass porins, while the fracture occurred within the plasma membrane of strains devoid of both corynomycolate and pore-forming proteins. Importantly, in most strains, the amount of cell wall-linked corynomycolates was not sufficient to cover the bacterial surface; interestingly, the occurrence of a cell wall fracture plane correlated with the amount of non-covalently bound lipids of the strains. Furthermore, these lipids were shown to spontaneously form liposomes, indicating that they may participate in a bilayer structure. Altogether, the data suggested that the cell wall permeability barrier in corynebacteria involved both covalently linked corynomycolates and non-covalently bound lipids of their cell envelopes.
随着分枝杆菌抗原在棒状杆菌中的异源表达最近取得成功，除了这些细菌在生物技术和医学中的重要性外，还需要更好地了解它们的细胞壁结构。结合分子组成分析、超微结构外观和冷冻蚀刻电子显微镜研究，得出了一个化学模型，该模型是棒状杆菌特有的，但与其与分枝杆菌及独特的超属放线菌分类群其他成员的系统发育相关性一致。透射电子显微镜和化学分析表明，所检测的棒状杆菌代表性菌株的细胞壁由以下部分组成：(i) 外层，由多糖（主要是高分子量葡聚糖和阿拉伯甘露聚糖）、蛋白质（包括分枝酰基转移酶PS1）和脂质组成；(ii) 肽聚糖 - 阿拉伯半乳聚糖的细胞壁聚糖核心，可能含有其他糖残基，通常被棒状菌酸酯化；(iii) 典型的质膜双层。冷冻蚀刻电子显微镜显示，大多数含棒状菌酸的菌株在其细胞壁上呈现主要断裂面，并含有低分子量孔蛋白，而在既不含棒状菌酸也不含成孔蛋白的菌株中，断裂发生在质膜内。重要的是，在大多数菌株中，细胞壁连接的棒状菌酸的量不足以覆盖细菌表面；有趣的是，细胞壁断裂面的出现与菌株中非共价结合脂质的量相关。此外，这些脂质被证明能自发形成脂质体，表明它们可能参与双层结构。总之，数据表明棒状杆菌的细胞壁渗透屏障涉及细胞壁中与共价连接的棒状菌酸和非共价结合的脂质。
