title: Ribosome degradation in growing bacteria.
abstract: Ribosomes are large ribozymes that synthesize all cellular proteins. As protein synthesis is rate-limiting for bacterial growth and ribosomes can comprise a large portion of the cellular mass, elucidation of ribosomal turnover is important to the understanding of cellular physiology. Although ribosomes are widely believed to be stable in growing cells, this has never been rigorously tested, owing to the lack of a suitable experimental system in commonly used bacterial model organisms. Here, we develop an experimental system to directly measure ribosomal stability in Escherichia coli. We show that (i) ribosomes are stable when cells are grown at a constant rate in the exponential phase; (ii) more than half of the ribosomes made during exponential growth are degraded during slowing of culture growth preceding the entry into stationary phase; and (iii) ribosomes are stable for many hours in the stationary phase. Ribosome degradation occurs in growing cultures that contain almost no dead cells and coincides with a reduction of comparable magnitude in the cellular RNA concentration.
authors: Institute of Molecular and Cell Biology, University of Tartu, Riia 23, Tartu 51010, Estonia.
authors: Kerli
authors: K
authors: Piir
authors: Anton
authors: A
authors: Paier
authors: Aivar
authors: A
authors: Liiv
authors: Tanel
authors: T
authors: Tenson
authors: Ulo
authors: U
authors: Maiväli
mesh_terms: D004926:Escherichia coli / Q000254:growth & development* / Q000378:metabolism*; D005434:Flow Cytometry; D031541:Fluorescence Resonance Energy Transfer; D009841:Oligonucleotides / Q000235:genetics; D010957:Plasmids / Q000235:genetics; D012335:RNA, Ribosomal / Q000378:metabolism; D012269:Ribosomal Proteins / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism*; D013997:Time Factors; D014316:Tritium
chemical_list: D009841:Oligonucleotides; D012335:RNA, Ribosomal; D012269:Ribosomal Proteins; D014316:Tritium