Systematic Review of the Listeria Monocytogenes σ ^B Regulon Supports a Role in Stress Response, Virulence and Metabolism

Abstract

Among the alternative sigma factors of Listeria monocytogenes, σ B controls the largest regulon. The aim of this study was to perform a comprehensive review of σ B -regulated genes, and the functions they confer. Materials & methods: A systematic search of PubMed and Web of Knowledge was carried out to identify members of the σ B regulon based on experimental evidence of σ B -dependent transcription and presence of a consensus σ B -dependent promoter. Results: The literature review identified σ B -dependent transcription units encompassing 304 genes encoding different functions including stress response and virulence. Conclusion: Our review supports the well-known roles of σ B in virulence and stress response and provides new insight into novel roles for σ B in metabolism and overall resilience of L. monocytogenes.

Transcriptome Sequencing of Listeria monocytogenes Reveals Major Gene Expression Changes in Response to Lactic Acid Stress Exposure but a Less Pronounced Response to Oxidative Stress

“…The sigma factor σ B is an important regulator of stress and virulence genes in L. monocytogenes. Using data from three studies (Raengpradub et al, 2008;Oliver et al, 2009;Liu et al, 2019), we created a panel of 387 genes representing the σ B regulon ( Supplementary Table S9); of these genes, 6179 and R479a possessed homologs to 380 and 369, respectively (Figure 3). Following the exposure to lactic acid, each strain exhibited differential expression of 311 of the σ B genes found in that strain.…”

The σB-Mediated General Stress Response of Listeria monocytogenes: Life and Death Decision Making in a Pathogen

“…To establish an infection L. monocytogenes needs to survive under the harsh conditions of the gastrointestinal (GI) tract, including the acidic conditions of the stomach, osmotic stress in the small intestine, and the presence of bile salts in the duodenum (Sleator et al, 2009;Gaballa et al, 2019;Tiensuu et al, 2019). Survival in the presence of these stresses is partially dependent on σ B , as an intragastrically inoculated sigB strain exhibits attenuated virulence (Garner et al, 2006;Oliver et al, 2010).…”

“…A growing body of evidence points toward a complex twoway regulatory network between σ B and the master regulator of virulence, PrfA (Gaballa et al, 2019;Tiensuu et al, 2019). σ B is also responsible for the regulation of the RNA chaperone Hfq which also plays a role in virulence and osmotic stress resistance (Christiansen et al, 2004).…”

“…Finally the role of the GSR in modulating the virulence of L. monocytogenes is still an open question. There are multiple lines of evidence suggesting regulatory crosstalk between σ B and PrfA and these need to be explored further (Gaballa et al, 2019;Tiensuu et al, 2019). While σ B plays an essential role during the GI stage of the infectious cycle, it is less important during the systemic stages, where PrfA appears to be the dominant regulator.…”

Homburgvirus LP-018 Has a Unique Ability to Infect Phage-Resistant Listeria monocytogenes

“…Three of these mutations were found in LMRG_00278, which was annotated as an HdeD family acid-resistance protein, and six of these mutations were found in LMRG_01613, which was annotated as a precursor to the foldase protein PrsA2 ( Figure 5). Expression of LMRG_00278, which encodes the putative HdeD family acid-resistance protein, an uncharacterized membrane protein, is known to be regulated by the general stress response alternative sigma factor B [42,43]. If LP-018 infection depends on the expression of LMRG_00278, further work should be conducted to determine if LP-018 shows improved lytic activity against L. monocytogenes under σB active conditions [44].…”