Regulated expression of the Methanococcus voltae hisA gene

Abstract

Summary The cloned DNA sequences of the hisA gene and surrounding open reading frames isolated from the methanogen, Methanococcus voltae have been used as probes for the determination of their respective methanogen mRNA levels. Addition of 3-amino-1,2,4-triazole (aminotriazole) to a growing culture of the methanogen leads to an inhibition of cell growth which is reversed by the addition of histidine to the medium. This is in keeping with the known ability of aminotriazole to inhibit histidine biosynthesis in several bacteria and yeast with the concomitant derepression of the histidine biosynthetic enzymes. The addition of aminotriazole to cultures of M. voltae leads to the enhanced production of methanogen mRNA which specifically hybridizes to hisA DNA and to DNA containing the surrounding open reading frames. Aminotriazole addition had no effect on the levels of RNA which hybridized to the cloned methanogen argG gene. Three hisA hybridizing RNA species were found in aminotriazole treated cultures having sizes of approximately 1.5, nine, and ten kilobases, whereas only the 1.5 kilobase species was detected from cultures grown on defined medium without aminotriazole. Our results suggest that the genes which determine the histidine biosynthetic pathway are regulated and subject to control at the level of transcription.