The Alternative Sigma Factors Of Listeria Monocytogenes: Stress Response Regulation At The Level Of Non-Coding Rnas And Proteins
The foodborne pathogen Listeria monocytogenes is ubiquitous in the environment and can cause a life-threatening invasive infection in humans. L. monocytogenes has the ability to survive a wide range of environmental and physiological stress conditions through complex stress response and virulence mechanisms. Among the key mechanisms L. monocytogenes employs to respond to changing conditions, including those encountered during growth on food and in the infection process, is the regulation of gene, protein, and non-coding RNA (ncRNA) expression through the regulatory network of the alternative sigma factors, [sigma]B , [sigma]C, [sigma]H, and [sigma]L. In these studies we (i) explored [sigma]B-dependent regulation of the ncRNA SbrE, and (ii) determined [sigma]B , [sigma]C, [sigma]H, and [sigma]L regulons at the protein level using a quantitative proteomics approach. We demonstrated [sigma]B-dependent transcription of SbrE and identified putative targets of SbrE at the transcriptomic and proteomic level. We also found increased transcript levels of SbrE in stationary phase and after exposure of L. monocytogenes to oxidative stress. Our proteomic analysis of L. monocytogenes parent strain 10403S and a [DELTA]sigB mutant combined with a meta-analysis of published transcriptomic studies identified 149 genes and proteins as positively regulated by [sigma]B at either or both the transcript and protein level, and suggested contributions of [sigma]B to gene expression through direct regulation of gene transcription and through indirect mechanisms, including regulation of ncRNA. Finally, our comparison of the protein expression profiles of parent strain 10403S and a quadruple mutant [DELTA]sigBCHL, and comparisons of [DELTA]sigBCHL with triple mutants, [DELTA]sigBCH, [DELTA]sigBCL, and [DELTA]sigBHL, characterized the independent regulons of [sigma]L, [sigma]H, and [sigma]C at the protein level, as well as co-regulation and protein expression in the absence of all four alternative [sigma] factors. Co-regulated proteins identified included MptA, which has a potential role in regulation of PrfA, a transcriptional activator of L. monocytogenes virulence genes. These studies identify and characterize components of the complex regulatory network of L. monocytogenes alternative [sigma] factors and illustrate co-regulation of gene expression by multiple alternative [sigma] factors, which contributes to our understanding of the alternative [sigma] factor dependent stress response and virulence abilities of L. monocytogenes.
Listeria monocytogenes; Alternative sigma factors
Pell, Alice N; Miller, Dennis D.
Food Science & Technology
Ph.D. of Food Science & Technology
Doctor of Philosophy
dissertation or thesis