Heavy metal ion-induced changes of ribosomal RNA synthesis in Synechococcus sp. strain PCC 6301, a cyanobacterium.

Abstract

We examined the effect of cadmium, zinc, copper and mercury ions on the rate of total RNA synthesis and on the accumulation of ribosomal RNAs in Synechococcus sp. PCC 6301, an obligate photoautotrophic cyanobacterium. It was found that treatment of cells with growth-inhibitory concentrations of cadmium and zinc ions severely decreased the rate of total RNA synthesis both under light (growing) and dark (non-growing) conditions, while copper and mercury ions had different inhibitory effects under these conditions. Moreover, cadmium and zinc ions substantially inhibited the "normal" processing of high-molecular-mass rRNAs and the in vivo postmaturational cleavage of 23S rRNA in the light and interfered with the accumulation of dark-specific RNAs of 0.33 x 10(6), 0.24 x 10(6) and 0.16 x 10(6) daltons in the dark. On the other hand, copper and mercury ions had a similar effect in the light, but did not abolish the accumulation of dark-specific, rRNA-derived, RNAs in the dark.