Crucial roles of MicA and RybB as vital factors for σ-dependent cell lysis in Escherichia coli long-term stationary phase.

σ(E)-dependent cell lysis has been proposed to eliminate damaged cells in the stationary phase in Escherichia coli. In order to explore the relationship of this process to long-term stationary phase existence, we considered that micA and rybB could be important small regulatory RNA (sRNA) genes for σ(E)-dependent cell lysis. A long-term stationary phase was observed at temperatures of <37°C, but not >38°C, and was found even in an rpoS knock-out background.

Novel pathway directed by σ E to cause cell lysis in Escherichia coli.

A large number of Escherichia coli cells become viable but nonculturable at early stationary phase, most of which are directed to lysis in cells with an enhanced active σ(E) level. In this study, we examined the effect of small noncoding RNAs, MicA and RybB, as σ(E) regulon as well as regulators of outer membrane protein (Omp) genes, on the lysis process. micA- and rybB-disrupted mutations almost completely suppressed the cell lysis.

Molecular strategy for survival at a critical high temperature in Eschierichia coli.

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.

Dissection of sigma(E)-dependent cell lysis in Escherichia coli: roles of RpoE regulators RseA, RseB and periplasmic folding catalyst PpiD.

To understand the mechanism of sigma(E)-dependent cell lysis, we examined the consequences of deletion derivatives of rpoE regulators rseA, rseB and rseC on sigma(E) transcription, on levels of free versus membrane-bound sigma(E) and on OMP-biogenesis limiting factor(s) that could impact cell lysis. RT-PCR showed that individual nonpolar DeltarseA and DeltarseB increased the rpoE expression to varying extents, with pronounced induction in DeltarseA. Significantly the ratio of soluble (free) versus membrane-bound form of RpoE increased in DeltarseA, however without increase of its total amount, unraveling furthermore complexity in RpoE regulation.

Characterization of endoplasmic reticulum-associated degradation of a protein S mutant identified in a family of quantitative protein S deficiency.

Introduction: Misfolded and unassembled glycoproteins are eliminated from the endoplasmic reticulum (ER) lumen by the ER-associated degradation (ERAD). We previously identified a Tyr595Cys (Y595C) mutation of protein S (PS) in a family of a quantitative PS deficiency. The mutation causes intracellular degradation and decreased secretion of the Y595C mutant PS.

Characterization of the ves gene, which is expressed at a low temperature in Escherichia coli.

A gene, designated ves, that is expressionally responsive to temperature was found in Escherichia coli. Experiments with a single-copy lacZ operon fusion and primer extension analysis revealed that ves was expressed at a low temperature with a peak around 25 degrees C but was hardly expressed at 42 degrees C. After a temperature downshift, the mRNA level increased until 6 to 12 h and then decreased.