Mariscal Vicente, Herrero Antonia, Flores Enrique
Instituto de Bioquímica Vegetal y Fotosíntesis, C.S.I.C. and Universidad de Sevilla, Américo Vespucio 49, E-41092 Seville, Spain.
Mol Microbiol. 2007 Aug;65(4):1139-45. doi: 10.1111/j.1365-2958.2007.05856.x. Epub 2007 Jul 21.
The cyanobacteria bear a Gram-negative type of cell wall that includes a peptidoglycan layer and an outer membrane outside of the cytoplasmic membrane. In filamentous cyanobacteria, the outer membrane appears to be continuous along the filament of cells. In the heterocyst-forming cyanobacteria, two cell types contribute specialized functions for growth: vegetative cells provide reduced carbon to heterocysts, which provide N2-derived fixed nitrogen to vegetative cells. The promoter of the patS gene, which is active specifically in developing proheterocysts and heterocysts of Anabaena sp. PCC 7120, was used to direct the expression of altered versions of the gfp gene. An engineered green fluorescent protein (GFP) that was exported to the periplasm of the proheterocysts through the twin-arginine translocation system was observed also in the periphery of neighbouring vegetative cells. However, if the GFP was anchored to the cytoplasmic membrane, it was observed in the periphery of the producing proheterocysts or heterocysts but not in adjacent vegetative cells. These results show that there is no cytoplasmic membrane continuity between heterocysts and vegetative cells and that the GFP protein can move along the filament in the periplasm, which is functionally continuous and so provides a conduit that can be used for chemical communication between cells.
蓝细菌具有革兰氏阴性类型的细胞壁，包括肽聚糖层和位于细胞质膜外侧的外膜。在丝状蓝细菌中，外膜似乎沿着细胞丝是连续的。在形成异形胞的蓝细菌中，两种细胞类型为生长发挥专门功能：营养细胞为异形胞提供还原态碳，而异形胞为营养细胞提供源自N2的固定氮。patS基因的启动子在鱼腥藻PCC 7120的前异形胞和异形胞发育过程中特异性激活，被用于指导gfp基因改变版本的表达。一种通过双精氨酸转运系统输出到前异形胞周质的工程化绿色荧光蛋白（GFP），在相邻营养细胞的周边也被观察到。然而，如果GFP锚定在细胞质膜上，则在产生前异形胞或异形胞的周边观察到它，而在相邻营养细胞中未观察到。这些结果表明，异形胞与营养细胞之间不存在细胞质膜连续性，并且GFP蛋白可以在功能上连续的周质中沿着丝移动，从而提供了一个可用于细胞间化学通讯的通道。
