'Chlorobium-type' Vesicles of Photosynthetically-grown Chloroflexus aurantiacus Observed Using Negative Staining Techniques

Abstract

Electron microscopic studies of several strains of Chloroflexus aurantiacus, a new genus of filamentous photosynthetic bacteria containing bacteriochlorophylls a and c, demonstrated that all strains contained vesicular structures very similar to the ‘chlorobium vesicles’ of the green bacteria when grown under anaerobic conditions in the light. The dimensions of these structures varied from strain to strain; they were 90 to 150 nm long and 25 to 70 nm wide. Photoautotrophically-grown C. aurantiacus as well as photoheterotrophically-grown organisms contained photosynthetic vesicles, while heterotrophically, dark-grown organisms contained no bacteriochlorophyll and no distinguishable ‘chlorobium vesicles’. Filament diameter and length varied from strain to strain, although all strains examined were regularly septate.