Transcriptional activity at supraoptimal temperature of growth in the Antarctic psychrotrophic bacterium Pseudomonas syringae

Transcriptional activity was monitored in cells of the Antarctic psychrotro phic bacterium Pseudomonas syringae (Lz4W), which does not grow above 30 de grees C. It was observed that the bacterium was capable of synthesising RNA at a temperature range of 0-37 degrees C, both in vitro and in vivo. The n et incorporation of the radioactive precursor, [H-3]uridine, into RNA was f ound to be affected at 37 degrees C. A pulse-chase experiment following a P -32 labeling of RNA in vivo indicated that the ribosomal RNAs (rRNAs) degra de faster at and above 30 degrees C. It was also found that the increased r ibonuclease (RNase) activity at high temperature might be responsible for t his degradation. The attack on ribosomal RNAs by RNase took place after the ir assembly into ribosomal particles. It is suggested that the degradation of rRNAs at supraoptimal temperatures might be a detrimental factor for gro wth above 30 degrees C.