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Transcriptomic and phenotypic analyses of the Sigma B-dependent characteristics and the synergism between Sigma B and Sigma L in Listeria monocytogenes EGD-e


Mattila, Mirjami; Somervuo, Panu; Korkeala, Hannu; Stephan, Roger; Tasara, Taurai (2020). Transcriptomic and phenotypic analyses of the Sigma B-dependent characteristics and the synergism between Sigma B and Sigma L in Listeria monocytogenes EGD-e. Microorganisms, 8(11):1644.

Abstract

Numerous gene expression and stress adaptation responses in L. monocytogenes are regulated through alternative sigma factors σB and σL. Stress response phenotypes and transcriptomes were compared between L. monocytogenes EGD-e and its ΔsigB and ΔsigBL mutants. Targeted growth phenotypic analysis revealed that the ΔsigB and ΔsigBL mutants are impaired during growth under cold and organic-acid stress conditions. Phenotypic microarrays revealed increased sensitivity in both mutants to various antimicrobial compounds. Genes de-regulated in these two mutants were identified by genome-wide transcriptome analysis during exponential growth in BHI. The ΔsigB and ΔsigBL strains repressed 198 and 254 genes, respectively, compared to the parent EGD-e strain at 3 °C, whereas 86 and 139 genes, respectively, were repressed in these mutants during growth at 37 °C. Genes repressed in these mutants are involved in various cellular functions including transcription regulation, energy metabolism and nutrient transport functions, and viral-associated processes. Exposure to cold stress induced a significant increase in σB and σL co-dependent genes of L. monocytogenes EGD-e since most (62%) of the down-regulated genes uncovered at 3 °C were detected in the ΔsigBL double-deletion mutant but not in ΔsigB or ΔsigL single-deletion mutants. Overall, the current study provides an expanded insight into σB and σL phenotypic roles and functional interactions in L. monocytogenes. Besides previously known σB- and σL-dependent genes, the transcriptomes defined in ΔsigB and ΔsigBL mutants reveal several new genes that are positively regulated by σB alone, as well as those co-regulated through σB- and σL-dependent mechanisms during L. monocytogenes growth under optimal and cold-stress temperature conditions.

Abstract

Numerous gene expression and stress adaptation responses in L. monocytogenes are regulated through alternative sigma factors σB and σL. Stress response phenotypes and transcriptomes were compared between L. monocytogenes EGD-e and its ΔsigB and ΔsigBL mutants. Targeted growth phenotypic analysis revealed that the ΔsigB and ΔsigBL mutants are impaired during growth under cold and organic-acid stress conditions. Phenotypic microarrays revealed increased sensitivity in both mutants to various antimicrobial compounds. Genes de-regulated in these two mutants were identified by genome-wide transcriptome analysis during exponential growth in BHI. The ΔsigB and ΔsigBL strains repressed 198 and 254 genes, respectively, compared to the parent EGD-e strain at 3 °C, whereas 86 and 139 genes, respectively, were repressed in these mutants during growth at 37 °C. Genes repressed in these mutants are involved in various cellular functions including transcription regulation, energy metabolism and nutrient transport functions, and viral-associated processes. Exposure to cold stress induced a significant increase in σB and σL co-dependent genes of L. monocytogenes EGD-e since most (62%) of the down-regulated genes uncovered at 3 °C were detected in the ΔsigBL double-deletion mutant but not in ΔsigB or ΔsigL single-deletion mutants. Overall, the current study provides an expanded insight into σB and σL phenotypic roles and functional interactions in L. monocytogenes. Besides previously known σB- and σL-dependent genes, the transcriptomes defined in ΔsigB and ΔsigBL mutants reveal several new genes that are positively regulated by σB alone, as well as those co-regulated through σB- and σL-dependent mechanisms during L. monocytogenes growth under optimal and cold-stress temperature conditions.

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Item Type:Journal Article, refereed, original work
Communities & Collections:05 Vetsuisse Faculty > Institute of Food Safety and Hygiene
Dewey Decimal Classification:570 Life sciences; biology
610 Medicine & health
Scopus Subject Areas:Life Sciences > Microbiology
Life Sciences > Virology
Health Sciences > Microbiology (medical)
Language:English
Date:23 October 2020
Deposited On:15 Feb 2021 17:23
Last Modified:18 Feb 2021 11:50
Publisher:MDPI Publishing
ISSN:2076-2607
OA Status:Gold
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.3390/microorganisms8111644

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