Electron microscopic investigation of the hydrogen-oxidizing acetate-forming anaerobic bacterium Acetobacterium woodii

Acetobacterium woodii is a Gram-positive anaerobic nonsporeforming bacterium able to grow on H₂ and CO₂ as sole sources of energy. The product of fermentation is acetic acid. Fine structural analysis showed rod-shaped flagellated cells, and coccoid cells without flagella arranged predominantly in pairs and chains. The cell wall was found to be composed of three layers. The cell surface exhibited a periodic array of particles consisting of subunits. The cytoplasmic membrane showed particles either either in random distribution or in a hexagonal pattern. Intracytoplasmic membranes were rarely observed, whereas inclusion bodies of varying shapes, predominantly in an uncommon disc-shape, could frequently be observed. Their content was dissolved in ultrathin sections indicating hydrophobic nature.