Electron Microscopic Study of the Nuclei in a Sorangium species

Abstract

SUMMARY: Electron microscopy of ultrathin sections enabled the fine structural peculiarities of a myxobacterium (Sorangium sp.) to be studied. The myxobacteria did not show the dense membrane characteristic of eubacterial cells. A very thin membrane in the myxobacteria cells was not distinguishable from the cytoplasm. In ultrathin sections of the myxobacteria there was observed a broad dark coloured cytoplasmic layer, a light mesh-like nuclear vacuole located in the centre of the cell and a rather large nucleus situated in the vacuole; the nucleus displayed density, dark colour and roundness. The elongated myxobacteria cells may include two to three nuclei. Phase-contrast microscopy of living unstained organisms of the Sorangium sp. studied revealed large rounded nuclei. The observations of living cells permitted the amitotic division of nuclei which precedes cell division in myxobacteria to be studied. The studies of the ultrathin sections with the aid of electron microscopy and the microscopy of the living cells supply similar data about the fine structure of the myxobacterial cells. The structure of the myxobacterial cells is more complicated than in the Eubacteria. The peculiar life cycle and the existence of a large nucleus easily detectable (by various methods) enables one to place the myxobacteria among the relatively highly organized micro-organisms.