Ultrastructure of the Obligately Anaerobic Bacteria Clostridium Kluyveri and Cl. Acetobutylicum

Abstract

The morphology of Cl. kluyveri is compared with that of CI. acetobutylicum. The multilayered cell wall of both organisms differ in the number of layers and total thickness. The plasma membrane of Cl. acetobutylicum is asymmetric in electron density and can be separated from the rest of the cell by plasmolysis. Tubular or vesicular structures are observed between the wall and the plasma membrane. In contrast, the plasma membrane of Cl. kluyveri is more symmetrical, with no structures between the cell wall and the plasma membrane. Intracytoplasmic membrane systems present in Cl. acetobutylicum are morphologically similar to the mesosomes of Gram-positive aerobes. The intracytoplasmic membrane systems' of ct. kluyveri are characteristically rough in appearance, and differ in general morphology from systems usually described as mesosomes. Roughness is attributed to membrane-bound ribosomes, these being smaller than those of Escherichia coli. Polygonal structures containing moderately electron-dense material (possibly DNA) were observed in C/. kluyveri. Cl. acetobutylicum possesses membrane-bounded inclusions containing electron-dense particles similar in dimensions to E. coli ribosomes. Rows of electron-dense bands were also observed. It is suggested that the polygonal structures and rough membranes of Cl. kluyveri are components of a system for the functional expression of genetic information. © 1973 ASEG.