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Journal of Bacteriology, March 2007, p. 2359-2368, Vol. 189, No. 6
0021-9193/07/$08.00+0 doi:10.1128/JB.01562-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.
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Graduate School of Pharmaceutical Sciences, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8675,1 Faculty of Pharmacy, Chiba Institute of Science, 15-8 Shiomi-cho, Choshi, Chiba 288-0025,2 Graduate School of Agriculture of Kinki University, 3327-204 Nakamachi, Nara 631-8505,3 Department of Frontier Bioscience and Micro-Nano Technology Research Center, Hosei University, Koganei, Tokyo 184-8584, Japan4
Received 10 October 2006/ Accepted 5 January 2007
Proteins whose synthesis is enhanced by polyamines at the level of translation were identified in a polyamine-requiring mutant cultured in the presence of 0.1% glucose and 0.02% glutamate instead of 0.4% glucose as an energy source. Under these conditions, enhancement of cell growth by polyamines was almost the same as that in the presence of 0.4% glucose. It was found that synthesis of RpoN, Cra, and H-NS was enhanced by polyamines at the level of translation at the early logarithmic phase of growth (A540 of 0.15). The effects of polyamines on synthesis of RpoN, H-NS, and Cra were due to the existence of unusual Shine-Dalgarno sequences (RpoN and H-NS) and an inefficient GUG initiation codon (Cra) in their mRNAs. Thus, rpoN, cra, and hns genes were identified as new members of the polyamine modulon. Because most of the polyamine modulon genes thus far identified encode transcription factors (RpoS [
38], Cya, FecI [
18], Fis, RpoN [
54], Cra, and H-NS), DNA microarray analysis of mRNA expressed in cells was performed. At the early logarithmic phase of growth, a total of 97 species of mRNAs that were up-regulated by polyamines more than twofold were under the control of seven polyamine modulon genes mentioned above.
Published ahead of print on 12 January 2007.
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