title: Molecular strategy for survival at a critical high temperature in Eschierichia coli.
abstract: The molecular mechanism supporting survival at a critical high temperature (CHT) in Escherichia coli was investigated. Genome-wide screening with a single-gene knockout library provided a list of genes indispensable for growth at 47°C, called thermotolerant genes. Genes for which expression was affected by exposure to CHT were identified by DNA chip analysis. Unexpectedly, the former contents did not overlap with the latter except for dnaJ and dnaK, indicating that a specific set of non-heat shock genes is required for the organism to survive under such a severe condition. More than half of the mutants of the thermotolerant genes were found to be sensitive to H(2)O(2) at 30°C, suggesting that the mechanism of thermotolerance partially overlaps with that of oxidative stress resistance. Their encoded enzymes or proteins are related to outer membrane organization, DNA double-strand break repair, tRNA modification, protein quality control, translation control or cell division. DNA chip analyses of essential genes suggest that many of the genes encoding ribosomal proteins are down-regulated at CHT. Bioinformatics analysis and comparison with the genomic information of other microbes suggest that E. coli possesses several systems for survival at CHT. This analysis allows us to speculate that a lipopolysaccharide biosynthesis system for outer membrane organization and a sulfur-relay system for tRNA modification have been acquired by horizontal gene transfer.
authors.affiliation: Applied Molecular Bioscience, Graduate School of Medicine, Yamaguchi University, Ube, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Murata
authors.forename: Hiroko
authors.initials: H
authors.lastname: Fujimoto
authors.forename: Kaori
authors.initials: K
authors.lastname: Nishimura
authors.forename: Kannikar
authors.initials: K
authors.lastname: Charoensuk
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nagamitsu
authors.forename: Satish
authors.initials: S
authors.lastname: Raina
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Kosaka
authors.forename: Taku
authors.initials: T
authors.lastname: Oshima
authors.forename: Naotake
authors.initials: N
authors.lastname: Ogasawara
authors.forename: Mamoru
authors.initials: M
authors.lastname: Yamada
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics; D019295:Computational Biology; D015536:Down-Regulation / Q000235:genetics; D048168:Escherichia coli K12 / Q000235:genetics* / Q000254:growth & development*; D015964:Gene Expression Regulation, Bacterial; D022761:Gene Transfer, Horizontal / Q000235:genetics; D005798:Genes, Bacterial / Q000235:genetics; D018869:Heat-Shock Response / Q000235:genetics; D006358:Hot Temperature; D050296:Microbial Viability / Q000235:genetics*; D018384:Oxidative Stress / Q000235:genetics; D015854:Up-Regulation / Q000235:genetics