Dataset Information

Novel DNA Binding and Regulatory Activities for ?54 (RpoN) in Salmonella enterica Serovar Typhimurium 14028s.

ABSTRACT: The variable sigma (?) subunit of the bacterial RNA polymerase (RNAP) holoenzyme, which is responsible for promoter specificity and open complex formation, plays a strategic role in the response to environmental changes. Salmonella enterica serovar Typhimurium utilizes the housekeeping ?70 and five alternative sigma factors, including ?54 The ?54-RNAP differs from other ?-RNAP holoenzymes in that it forms a stable closed complex with the promoter and requires ATP hydrolysis by an activated cognate bacterial enhancer binding protein (bEBP) to transition to an open complex and initiate transcription. In S. Typhimurium, ?54-dependent promoters normally respond to one of 13 different bEBPs, each of which is activated under a specific growth condition. Here, we utilized a constitutively active, promiscuous bEBP to perform a genome-wide identification of ?54-RNAP DNA binding sites and the transcriptome of the ?54 regulon of S. Typhimurium. The position and context of many of the identified ?54 RNAP DNA binding sites suggest regulatory roles for ?54-RNAP that connect the ?54 regulon to regulons of other ? factors to provide a dynamic response to rapidly changing environmental conditions.IMPORTANCE The alternative sigma factor ?54 (RpoN) is required for expression of genes involved in processes with significance in agriculture, bioenergy production, bioremediation, and host-microbe interactions. The characterization of the ?54 regulon of the versatile pathogen S. Typhimurium has expanded our understanding of the scope of the ?54 regulon and how it links to other ? regulons within the complex regulatory network for gene expression in bacteria.

SUBMITTER: Bono AC

PROVIDER: S-EPMC5446619 | biostudies-literature | 2017 Jun

REPOSITORIES: biostudies-literature

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Publications

Novel DNA Binding and Regulatory Activities for σ54 (RpoN) in Salmonella enterica Serovar Typhimurium 14028s.

Bono Ashley C AC Hartman Christine E CE Solaimanpour Sina S Tong Hao H Porwollik Steffen S McClelland Michael M Frye Jonathan G JG Mrázek Jan J Karls Anna C AC

Journal of bacteriology 20170525 12

The variable sigma (σ) subunit of the bacterial RNA polymerase (RNAP) holoenzyme, which is responsible for promoter specificity and open complex formation, plays a strategic role in the response to environmental changes. Salmonella enterica serovar Typhimurium utilizes the housekeeping σ70 and five alternative sigma factors, including σ54 The σ54-RNAP differs from other σ-RNAP holoenzymes in that it forms a stable closed complex with the promoter and requi ...[more]

PMID: 28373272

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Project description:Contamination of edible produce leaves with human bacterial pathogens has been associated with serious disease outbreaks and has become a major public health concern affecting all aspects of the market, from farmers to consumers. While pathogen populations residing on the surface of ready-to-eat produce can be potentially removed through thorough washing, there is no disinfection technology available that effectively eliminates internal bacterial populations. By screening 303 multi-gene deletion (MGD) mutants of Salmonella enterica serovar Typhimurium (STm) 14028s, we were able to identify ten genomic regions that play a role in opening the stomatal pore of lettuce leaves. The major metabolic functions of the deleted regions are associated with sensing the environment, bacterium movement, transport through the bacterial membrane, and biosynthesis of surface appendages. Interestingly, at 21 days post inoculation, seven of these mutants showed increased population titers inside the leaf, two mutants showed similar titers as the wild type bacterium, whereas one mutant with a large deletion that includes the Salmonella pathogenicity island 2 (SPI-2) showed significantly impaired persistence in the leaf apoplast. These findings suggest that not all the genomic regions required for initiation of leaf colonization (i.e., epiphytic behavior and tissue penetration) are essential for continuing bacterial survival as an endophyte. We also observed that mutants lacking either SPI-1 (Mut3) or SPI-2 (Mut9) induce callose deposition levels comparable to those of the wild type STm 14028s; therefore, these islands do not seem to affect this lettuce defense mechanism. However, the growth of Mut9, but not Mut3, was significantly impaired in the leaf apoplastic wash fluid (AWF) suggesting that the STm persistence in the apoplast may be linked to nutrient acquisition capabilities or overall bacterial fitness in this niche, which are dependent on the gene(s) deleted in the Mut9 strain. The genetic basis of STm colonization of leaves investigated in this study provides a foundation from which to develop mitigation tactics to enhance food safety.

Dataset Information

Novel DNA Binding and Regulatory Activities for ?54 (RpoN) in Salmonella enterica Serovar Typhimurium 14028s.

Publications

Novel DNA Binding and Regulatory Activities for σ<sup>54</sup> (RpoN) in Salmonella enterica Serovar Typhimurium 14028s.

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