豌豆根瘤细菌周膜在发育中的变化

PERIBACTERIOD MEMBRANE CHANGES DURING THE DEVELOPMENT OF PEA ROOT NODULES

细菌周膜随发育不同而异。侵入线中的细菌没有细菌周膜,刚从侵入线释放到寄主细胞质中的细菌虽有这一特殊结构,但一般较小,表面光滑。然后随着发育而不断变大,有的表面甚至出现凹凸不平。在这些细菌周膜附近,常有一些高尔基体和内质网,有的还有一些纤维状物质和泡状结构位于它所包围的电子透明区域中。当细菌周膜继续向外扩展时,常与相邻细菌周膜相互嵌合,进而彼此融合。这种融合是一种不对称性融合,只出现在即将或已成熟的被侵染的细胞中。细菌周膜融合可能与共生体系的固氮和物质交换有关。

Ultrastructural changes of the peribacteriod membranes of the pea root nodules during development were observed by transmission electron microscopy. Observations show the peribacteriod membranes are various comparing developments. The bacteria in the infection threads are without peribacteroid membranes but the bacteroids liberated from the infection threads to the host cytoplasm possess the special structure which derive from the host plasma membrane. In general, the peribacteroid membranes are smaller in size, their surfaces are smoother, and there is one bacteroid enclosed by each peribacteroid membrane. As the time goes on, the peribacteroid membranes gradually become more extensive than before, some Golgi bodies and endoplasmic reticulum often locate near the peribacteroid membranes, some of which are excreting vesicles, at the same time, there are some fibrillar-shaped and vesiclar-shaped material in the electron-empty spaces of the bacteroids. When the peribacteroid membranes spread to the host cytoplasm, their surfaces often form some protrusions or hollows, and occure chimera phenomenon, then some of the chimera peribacteroid membranes fuse together, forming a new fusion body which possesses a common peribacteroid membrane and electronempty space. However, the peribacteroid membrane fusion is a kind of asymmetric fusion, it usually only appear in nearly mature or mature infected cells. The peribacteroid membrane fusion may be closely related to nitrogen fixation and material exchange in symbiotic system.