Sequential Modifications of DNA‐Dependent RNA Polymerase during Sporogenesis in Bacillus thuringiensis

A purification procedure of DNA‐dependent RNA polymerase from vegetative and sporulating cells of Bacillus thuringiensis is described. The subunit composition of the vegetative enzyme has been established as β′βσαa2. It has been shown that two active forms of the enzyme are present in sporulating cells; for one of them the modification of a β subunit has been observed. The relative amounts of the two polymerases vary throughout the sporulation process. Changes in template specificity and results from chromatography on phosphocellulose of purified enzymes suggest an early modification of σ factor for the two forms. Subunit composition of spore polymerase is also given: the disappearance of α subunits is reported, while two new subunits of lower molecular weights are present. Results are summarized in a scheme giving the kinetics of these modifications.