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Series GSE6296

Query DataSets for GSE6296

Status

Public on Jan 30, 2007

Title

Analysis of the exression and regulation of NleA-E in Escherichia coli O157:H7

Organism

Escherichia coli

Experiment type

Expression profiling by array

Summary

Previous work has shown that locus of enterocyte effacement (LEE)-encoded effector proteins such as Tir and Map can be exported via the type III secretion system (T3SS) of E. coli O157:H7. Additionally, a family of non-LEE encoded (Nle) effector proteins has been shown to be secreted from Citrobacter rodentium, homologues of which are located on the E. coli O157 chromosome. While, NleA has been shown to be secreted from pathogenic E. coli, the secretion of other Nle effector proteins has only been detected under induced conditions or using a mutated type III secretion system. We aimed to determine if nle gene expression is regulated co-ordinately with other LEE-encoded effectors. Using data generated from a combination of transcriptome arrays, we demonstrate that only nleA is expressed co-ordinately with the LEE effector genes. Secretion and expression of NleA is regulated directly or indirectly by ler, a key activator of LEE expression.
Keywords: iMedia induction

Overall design

In order to assess if the nle genes were expressed co-ordinately with the LEE, whole transcript array analysis was performed. Strain TUV93-0 was cultured in 2 minimal media: DMEM and MEM-HEPES, total RNA extracted, and hybridisations performed as described in materials and methods. E. coli O157 strain TUV93-0 has been shown to secrete high levels of EspD and Tir effector proteins when cultured in MEM-HEPES, typically 5-10 fold higher than when the same strains are cultured in DMEM. Expression conditions were used that are highly selective for up-regulation of the LEE. The E. coli O157:H7 transcriptome was compared from bacteria cultured in MEM-HEPES with DMEM using triplicate cultures (independent biological replicates).

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