RETARDED RNA TURNOVER IN ESCHERICHIA-COLI - A MEANS OF MAINTAINING GENE-EXPRESSION DURING ANAEROBIOSIS

In this study, we extend earlier observations on the influence of grow th rate on mRNA stability and rRNA processing in Escherichia coli duri ng continuous culture, to the effect of anaerobiosis. During slow anae robic growth (generation time 700 min) both ompA and bla mRNA had a pr olonged half-life compared to that during slow aerobic growth and the processing of 9S RNA was even more profoundly retarded, which indicate d a general slowing of mRNA turnover. The latter was confirmed by a ne arly fourfold increase in the functional half-life of bulk mRNA. In sp ite of this difference in stability, steady state levels of RNA, as ju dged by those of the ompA and 9S transcripts, were the same in aerobic and anaerobic cells at a given growth rate. Furthermore, we found tha t RNA synthesis during anaerobiosis was a fraction of that observed du ring slow aerobic growth and it is proposed that this offsets the gene ral increase in mRNA stability. Our data therefore suggest that a cons tant level of RNA is maintained by matching the rate of decay to the l evel of RNA synthesis.