Physical evidence for plasmids in autotrophic, especially hydrogen-oxidizing bacteria

Abstract

Agarose gel electrophoresis of crude lysates from 23 species of autotrophic bacteria revealed plasmids of various sizes in 12 species. The plasmid pattern varied considerably. While the majority of the plasmid-bearing species harbored one or two plasmids, one species, Alcaligenes latus, exhibited more than six ccc-DNA bands. With one exception the molecular masses of the plasmids were 50×106 or higher. In Achromobacter carboxydus, Alcaligenes latus, Derxia gummosa and three strains of Paracoccus denitrificans large plasmids of molecular masses higher than 300×106 were resolved. The examination of Thiobacillus A2 resulted in the discovery of two plasmids while Pseudomonas oxalaticus was apparently free of resident plasmid DNA. So far these plasmids can only be characterized as cryptic. Future studies may allow to correlate them with specific metabolic activities of their hosts such as the ability to grow on carbon monoxide or thiosulfate, to fix molecular nitrogen and to form soluble NAD-reducing and/or membrane-bound hydrogenases.