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Journal of Bacteriology, May 2000, p. 2893-2899, Vol. 182, No. 10
Department of Physics, Osaka Medical College,
Takatsuki, Osaka 569-0084,1 and
Department of Molecular Genetics, National Institute of
Genetics, Mishima, Shizuoka 411-8540,2
Japan, and Department of Molecular Biology, Uppsala
University, S-751 24 Uppsala, Sweden3
Received 25 October 1999/Accepted 22 February 2000
The growth phase-dependent change in sucrose density gradient
centrifugation patterns of ribosomes was analyzed for both laboratory strains of Escherichia coli and natural isolates from the
ECOR collection. All of the natural isolates examined formed 100S
ribosome dimers in the stationary phase, and ribosome modulation factor (RMF) was associated with the ribosome dimers in the ECOR strains as in
the laboratory strain W3110. The ribosome profile (70S monomers versus
100S dimers) follows a defined pattern over time during lengthy culture
in both the laboratory strains and natural isolates. There are four
discrete stages: (i) formation of 100S dimers in the early stationary
phase; (ii) transient decrease in the dimer level; (iii) return of
dimers to the maximum level; and (iv) dissociation of 100S dimers into
70S ribosomes, which are quickly degraded into subassemblies. The total
time for this cycle of ribosome profile change, however, varied from
strain to strain, resulting in apparent differences in the ribosome
profiles when observed at a fixed time point. A correlation was noted
in all strains between the decay of 100S ribosomes and the subsequent
loss of cell viability. Two types of E. coli mutants
defective in ribosome dimerization were identified, both of which were
unable to survive for a prolonged period in stationary phase. The W3110
mutant, with a disrupted rmf gene, has a defect in ribosome
dimerization because of lack of RMF, while strain Q13 is unable to form
ribosome dimers due to a ribosomal defect in binding RMF.
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Growth Phase-Coupled Changes of the Ribosome Profile in Natural
Isolates and Laboratory Strains of Escherichia
coli
*
Corresponding author. Mailing address: Department of
Molecular Genetics, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan. Phone: 81-559-81-6741. Fax: 81-559-81-6746. E-mail: aishiham{at}lab.nig.ac.jp.
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