Stewart M, Beveridge T J, Trust T J
J Bacteriol. 1986 Apr;166(1):120-7. doi: 10.1128/jb.166.1.120-127.1986.
Electron micrographs of negatively stained regular surface layers (A-layers) of Aeromonas salmonicida showed two square patterns having p4 symmetry. Computer image processing demonstrated that, at a resolution of 2.3 nm, both square arrays were composed of two different morphological units arranged alternatively to give a face-centered lattice in which the four nearest neighbors of each unit were the other type of unit. The lattice constant was slightly but significantly different in the two patterns, and the orientation of one of the two morphological units changed by about 20 degrees between patterns. These patterns were probably not derived from different strains present in the preparation, since both were seen in material that appeared to come from a single layer. This and the difference in lattice constant made it unlikely that they represented different sides of the A-layer. However, it is possible that the two patterns may reflect a structural transformation of the layer. In this respect, it is interesting that the rotation of one morphological subunit changed the size of the gaps between units in the layer. This raised the possibility that the transformation could be related to a change in permeability of the A-layer, possibly analogous to that proposed for gap junctions in eucaryotic cells.
杀鲑气单胞菌负染色规则表面层（A层）的电子显微照片显示出两种具有p4对称性的方形图案。计算机图像处理表明，在2.3纳米的分辨率下，两种方形阵列均由两种不同的形态学单元交替排列组成，形成面心晶格，其中每个单元的四个最近邻是另一种类型的单元。两种图案的晶格常数略有但显著不同，并且两种形态学单元之一的取向在图案之间变化约20度。这些图案可能并非源自制备物中存在的不同菌株，因为在似乎来自单层的材料中都观察到了这两种图案。这一点以及晶格常数的差异使得它们不太可能代表A层的不同面。然而，这两种图案有可能反映了该层的结构转变。在这方面，有趣的是一个形态学亚基的旋转改变了层中单元之间间隙的大小。这增加了这种转变可能与A层通透性变化有关的可能性，这可能类似于真核细胞中缝隙连接所提出的情况。
