Loss of sigb in listeria monocytogenes strains egd-e and 10403s confers hyperresistance to hydrogen peroxide in stationary phase under aerobic conditions

Marcia Boura, Ciara Keating, Kevin Royet, Ranju Paudyal, Beth O'Donoghue, Conor P. O'Byrne, Kimon A.G. Karatzas

Research output: Contribution to a Journal (Peer & Non Peer)Articlepeer-review

21 Citations (Scopus)

Abstract

SigB is the main stress gene regulator in Listeria monocytogenes affecting the expression of more than 150 genes and thus contributing to multiple-stress resistance. Despite its clear role in most stresses, its role in oxidative stress is uncertain, as results accompanying the loss of sigB range from hyperresistance to hypersensitivity. Previously, these differences have been attributed to strain variation. In this study, we show conclusively that unlike for all other stresses, loss of sigB results in hyperresistance to H2O2 (more than 8 log CFU ml-1 compared to the wild type) in aerobically grown stationary-phase cultures of L. monocytogenes strains 10403S and EGD-e. Furthermore, growth at 30°C resulted in higher resistance to oxidative stress than that at 37°C. Oxidative stress resistance seemed to be higher with higher levels of oxygen. Under anaerobic conditions, the loss of SigB in 10403S did not affect survival against H2O2, while in EGD-e, it resulted in a sensitive phenotype. During exponential phase, minor differences occurred, and this result was expected due to the absence of sigB transcription. Catalase tests were performed under all conditions, and stronger catalase results corresponded well with a higher survival rate, underpinning the important role of catalase in this phenotype. Furthermore, we assessed the catalase activity in protein lysates, which corresponded with the catalase tests and survival. In addition, reverse transcription-PCR (RT-PCR) showed no differences in transcription between the wild type and the sigB mutant in various oxidative stress genes. Further investigation of the molecular mechanism behind this phenotype and its possible consequences for the overall phenotype of L. monocytogenes are under way.

Original languageEnglish
Pages (from-to)4584-4591
Number of pages8
JournalApplied and Environmental Microbiology
Volume82
Issue number15
DOIs
Publication statusPublished - 2016

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