The stringent response to unacylated tRNA, energy-and temperature-downshift in Bacillus stearothermophilus

The response of the thermophile Bacillus stearothermophilus to inhibition of tRNA acylation, energy starvation and temperature downshift was characterized. We found that B. stearothermophilus, like other prokaryotic organisms, reacts with the so-called stringent response, which includes the accumulation of the unusual nucleotides guanosine 3',5' bis (diphosphate) [ppGpp] and guanosine 3'-diphosphate, 5'-tri-phosphate [pppGpp] and concomitantly the reduction of RNA synthesis and growth rate. The amount of (p)ppGpp formed depended on the cause of the stringent response: when tRNA acylation was inhibited (p)ppGpp synthesis was much higher than after energy starvation or temperature downshift whereas RNA synthesis was totally blocked in each case.