Project description:We studied SOS mutator effect mediated by recA730 and changes in the dNTP pool. We found that established dNTP pool changes resulting from deficiencies in the ndk or dcd genes, had a strongly suppressive effect on the recA730 mutator effect. To investigate whether the observed reduction in SOS mutator effect is due to lowered expression of the entire SOS regulon, we performed microarray analysis of gene expression profiles in each of the single ndk, dcd, and recA730 strains, as well as the double recA730 ndk and recA730 dcd strains.
Project description:We studied SOS mutator effect mediated by recA730 and changes in the dNTP pool. We found that established dNTP pool changes resulting from deficiencies in the ndk or dcd genes, had a strongly suppressive effect on the recA730 mutator effect. To investigate whether the observed reduction in SOS mutator effect is due to lowered expression of the entire SOS regulon, we performed microarray analysis of gene expression profiles in each of the single ndk, dcd, and recA730 strains, as well as the double recA730 ndk and recA730 dcd strains. Comparison of transcriptomes of the bacterium Escherichia coli six strains: wt, dcd, ndk, recA730, recA730 dcd and recA730 ndk. All strains were derivatives of the MC4100 strain, carrying a sulA366 allele (?(argF-lac)169 sulA366). dcd and ndk alleles used were dcd::kan and ndk::cam, respectively. Strains were compared in pairs: wt vs dcd, wt vs ndk, wt vs recA730, recA730 vs recA730 dcd and recA730 vs recA730 ndk. Two or three biological replicates for each strain were used. Each biological replicate had two technical replicates with dye swapping.
Project description:The transcriptional changes in Escherichia coli upon induction of the SOS response are investigated by utilizing custom designed oligonucleotide microarrays. Keywords: Gene expression during the SOS response in Escherichia coli
Project description:The transcriptional changes in Escherichia coli upon induction of the SOS response are investigated by utilizing custom designed oligonucleotide microarrays. Keywords: Gene expression during the SOS response in Escherichia coli Escherichia coli K-12 MG1655 single colony in five parallells was grown to mid-log phase and exposed to UV to induce the SOS response. Total RNA was extracted from induced and uninduced cells and cDNA was prepared, fragmented and labelled prior to hybridizing to arrays. The arrays was designed to maximize the genomic coverage whilst simultaneous including only probes estimated to give an approximately uniform binding affinity. Regions coding for non-hypothetical proteins or RNAs where covered less densely than the intergenic parts.
Project description:Despite the characterization of many aetiologic genetic changes. The specific causative factors in the development of sporadic colorectal cancer remain unclear. This study was performed to detect the possible role of Enteropathogenic Escherichia coli (EPEC) in developing colorectal carcinoma.
Project description:We have previously reported that phosphoenolpyruvate carboxykinase(Pck) overexpression under glycolytic conditions enables Escherichia coli to harbor a high intracellular ATP pool resulting in enhanced recombinant protein synthesis and biohydrogen production. To understand possible reasons of the high ATP haboring cell, we carried out transcriptome and metabolic flux analysis.
Project description:YbjN, an enterobacteria-specific protein, is a multicopy suppressor of ts9 temperature sensitivity in Escherichia coli. Microarray study revealed that the expression level of ybjN was inversely correlated with the expression of flagellar, fimbrial and acid resistance genes. Over-expression of ybjN significantly down-regulated genes involved in the citric acid cycle, glycolysis, the glyoxylate shunt, oxidative phosphorylation, and amino acid and nucleotide metabolism. On the other hand, over-expression of ybjN up-regulated toxin-antitoxin modules, the SOS responsive pathway, cold shock proteins and starvation-induced transporter genes. Our results collectively suggest that YbjN may play important roles in regulating bacterial multicellular behaviors, metabolism and survival under various stress conditions in Es. coli.
Project description:YbjN, an enterobacteria-specific protein, is a multicopy suppressor of ts9 temperature sensitivity in Escherichia coli. Microarray study revealed that the expression level of ybjN was inversely correlated with the expression of flagellar, fimbrial and acid resistance genes. Over-expression of ybjN significantly down-regulated genes involved in the citric acid cycle, glycolysis, the glyoxylate shunt, oxidative phosphorylation, and amino acid and nucleotide metabolism. On the other hand, over-expression of ybjN up-regulated toxin-antitoxin modules, the SOS responsive pathway, cold shock proteins and starvation-induced transporter genes. Our results collectively suggest that YbjN may play important roles in regulating bacterial multicellular behaviors, metabolism and survival under various stress conditions in Es. coli. A total of 8 samples were analyzed: E. coli wild type strain (2 replicates); E. coli ybjN mutant strain (3 replicates); E. coli ybjN over-expression strain (3 replicates).
Project description:The dpiA and dpiB genes of Escherichia coli, which are orthologs of genes that regulate citrate uptake and utilization in Klebsiella pneumoniae, comprise a two-component signal transduction system that can modulate the replication of and destabilize the inheritance of pSC101 and certain other plasmids. Here we show that perturbed replication and inheritance result from binding of the effector protein DpiA to A+T-rich replication origin sequences that resemble those in the K. pneumoniae promoter region targeted by the DpiA ortholog, CitB. Consistent with its ability to bind to A+T-rich origin sequences, overproduction of DpiA induced the SOS response in E. coli, suggesting that chromosomal DNA replication is affected. Bacteria that overexpressed DpiA showed an increased amount of DNA per cell and increased cell size-both also characteristic of the SOS response. Concurrent overexpression of the DNA replication initiation protein, DnaA, or the DNA helicase, DnaB-both of which act at A+T-rich replication origin sequences in the E. coli chromosome and DpiA-targeted plasmids-reversed SOS induction as well as plasmid destabilization by DpiA. Our finding that physical and functional interactions between DpiA and sites of replication initiation modulate DNA replication and plasmid inheritance suggests a mechanism by which environmental stimuli transmitted by these gene products can regulate chromosomal and plasmid dynamics.
Project description:Our laboratory has recently discovered that E. coli cells starved for the DNA precursor dGTP are killed efficiently (dGTP starvation) in a manner similar to that described for Thymineless Death (TLD). Conditions for specific dGTP starvation can be achieved by depriving an E. coli optA1 gpt strain of the purine nucleotide precursor hypoxanthine (Hx). To gain insight into the mechanisms underlying dGTP starvation, we conducted genome-wide gene expression analyses on actively growing optA1 gpt strains subjected to hypoxanthine deprivation for increasing periods of time. The data show that, upon Hx withdrawal, the optA1 gpt strain displays a diminished ability to de-repress the de novo purine biosynthesis genes, and this is likely due to internal guanine accumulation. The impairment to fully induce the purR regulon may be a contributing factor to the lethality of dGTP starvation. At later time points, and coinciding with cell lethality, strong induction of the SOS is observed, supporting the concept of replication stress as a final cause of death. No evidence was observed for the participation of other stress responses, including the rpoS-mediated global stress response in the starved cells, and reinforcing the lack of feedback of replication stress into the global metabolism of the cell. The genome-wide expression data also provide direct evidence for increased genome complexity during dGTP starvation, as a markedly increased gradient is observed for expression of genes located nearby the replication origin relative to those located towards the replication terminus.