How Many Initiator tRNA Genes Does Escherichia coli Need?

Samhita, Laasya and Nanjundiah, Vidyanand and Varshney, Umesh (2014) How Many Initiator tRNA Genes Does Escherichia coli Need? In: JOURNAL OF BACTERIOLOGY, 196 (14). pp. 2607-2615.

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Abstract

Multiple copies of a gene require enhanced investment on the part of the cell and, as such, call for an explanation. The observation that Escherichia coli has four copies of initiator tRNA (tRNA(i)) genes, encoding a special tRNA (tRNA(fMet)) required to start protein synthesis, is puzzling particularly because the cell appears to be unaffected by the removal of one copy. However, the fitness of an organism has both absolute and relative connotations. Thus, we carried out growth competition experiments between E. coli strains that differ in the number of tRNA(i) genes they contain. This has enabled us to uncover an unexpected link between the number of tRNA(i) genes and protein synthesis, nutritional status, and fitness. Wild-type strains with the canonical four tRNA(i) genes are favored in nutrient-rich environments, and those carrying fewer are favored in nutrient-poor environments. Auxotrophs behave as if they have a nutritionally poor internal environment. A heuristic model that links tRNA(i) gene copy number, genetic stress, and growth rate accounts for the findings. Our observations provide strong evidence that natural selection can work through seemingly minor quantitative variations in gene copy number and thereby impact organismal fitness.

Item Type:	Journal Article
Publication:	JOURNAL OF BACTERIOLOGY
Publisher:	AMER SOC MICROBIOLOGY
Additional Information:	Copy right for this article belongs to the AMER SOC MICROBIOLOGY, 1752 N ST NW, WASHINGTON, DC 20036-2904 USA
Department/Centre:	Division of Biological Sciences > Microbiology & Cell Biology Division of Biological Sciences > Molecular Reproduction, Development & Genetics
Date Deposited:	21 Aug 2014 10:27
Last Modified:	21 Aug 2014 10:27
URI:	http://eprints.iisc.ac.in/id/eprint/49629

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