Effect of rifampicin (3-(4-methylpiperazinyl-iminomethyl)rifamycin) on heterocyst differentiation in the blue-green algae Anabaena and Calothrix.

Chains of multiple heterocysts form in Anabaena und Calothrix filaments on treatment with rifampicin. The multiple heterocysts form irrespective of whether the rifampicin treatment is given in combined nitrogen-free or supplemented medium. This suggests the possibility of involvement of a species of RNA or of protein as intracellular heterocyst inhibitor and indicates that some latent pattern-determining mechanism may operate in the combined nitrogen medium.