THE FINE STRUCTURE OF THIOPLOCA INGRICA AND A COMPARISON WITH BEGGIATOA

Abstract

Electron micrographs of sections of Thioploca ingrica and of Beggiatoa showed that the wall of both consisted of multiple and similar layers, of which only the innermost took part in septum formation. Thioploca, however, contained an additional wall component. Invaginations of the cytoplasmic membrane produced extensive intracytoplasmic membranes in both organisms. Sulfur appeared to be deposited within this membrane system, which was accentuated in Thioploca by an enclosure of dense, vesicular material. The deposition of sulfur external (in effect) to the cytoplasmic membrane was also found when hydrogen sulfide and air were bubbled through cultures of a number of Gram-negative bacteria not considered to be sulfur bacteria. The cytoplasm of Beggiatoa was richer in ribosomes than the extraordinarily dense cytoplasm of Thioploca, and the lipid deposits of both left behind spaces that were not membrane-bounded. Metachromatic granules were observed only in Beggiatoa. A heterotrophic strain of Beggiatoa contained a diffuse nucleoplasm, but nucleoplasms could not be recognized either in the wild type or in Thioploca. Thioploca and Beggiatoa are sufficiently different in their infrastructure to be considered distinct organisms. The former consistently produce sheaths. Similarities in structure and in the arrangement of components are enough to support a family relationship.