Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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Salmonella Enteritidis strains from poultry show differential responses to stress and survival in the egg albumen

ABSTRACT: Salmonella Enteritidis is the major food-borne pathogen primarily causing human infection through contaminated chicken meat and eggs. We recently demonstrated that S. Enteritidis strains from poultry differ in their ability to invade human intestinal cells and cause disease in orally challenged mice. Here we hypothesized that the differential pathogenicity of S. Enteritidis strains is due to the differential fitness in the adverse environments that may be encountered during infection in the host. The response of a panel of six S. Enteritidis strains to acid stress, oxidative stress, survival in egg albumen and the ability to cause infection in chickens were analyzed. This analysis allowed classification of strains into two categories: stress- sensitive and stress- resistant, with the former showing significantly (P<0.05) reduced survival in acidic (gastric phase of infection) and oxidative (intestinal and systemic phase of infection) stress. Stress-sensitive strains also showed impaired intestinal colonization and systemic dissemination in orally inoculated chickens and failed to survive/grow in egg albumen. Comparative genomic hybridization microarray analysis revealed no differences at the discriminatory level of the whole gene content between stress-sensitive and stress-resistant strains. However, sequencing of rpoS, a stress-regulatory gene, revealed that one of the three stress-sensitive strains carried an insertion mutation in the rpoS resulting in truncation of σS. Finding that one of the stress-sensitive strains carried an easily identifiable small polymorphism within a stress-response gene suggests that the other strains may also have small polymorphisms elsewhere in the genome, which likely impact regulation of stress or virulence associated genes in some manner. To determine if the differential stress response and virulence observed in this study could be due to the differences in the gene content between different strains, we compared the genomes of all the strains using CGH microarray designed based on the genomic information available for the sequenced strain. All strains (n=6) were hybridized in triplicate.

ORGANISM(S): Salmonella enterica subsp. enterica serovar Enteritidis

SUBMITTER: Devendra Shah

PROVIDER: E-GEOD-33102 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Intracellular small-molecule signaling has drawn increasing attention due to its importance in bacterial physiology and host-pathogen interactions. Here, we show that a new quinone-sensing transcriptional regulator, QsbR (quinone-stress sensing and bleomycin resistance regulator), is important for bacterial stress response and virulence in S. aureus. The mutant strain of qsbR exhibits dramatically reduced staphylococcal virulence in a murine abscess model of infection. Moreover, the qsbR mutant shows an accumulation of riboflavin and an increased resistance to quinone stress and bleomycin compared to the wild-type strain Newman. Microarray analysis confirmed that QsbR impacts the expression of genes that are involved in quinone stress response, bleomycin resistance, riboflavin biosynthesis, and pathogenesis. DNase-I footprinting and gel shift assays suggest that QsbR not only directly regulates transcription of genes involved in quinone detoxification and bleomycin resistance, but is also subject to autoregulation by binding to the palindromic consensus sequence GTATAN(5)TATAC in their promoter regions. This binding could be disrupted by quinone treatment in vitro. Mass spectrometric analysis showed that wild-type QsbR, but not QsbRC5S with Cys5 mutated to Ser, could be alkylated at Cys5 by quinone. Further mutagenesis studies revealed that Cys5 plays a key role in quinone sensing as substitution of Cys5 with Ser renders the bacterium more sensitive to quinone stress. Our results demonstrate that QsbR is a quinone-sensing regulator that dramatically impacts staphylococcal virulence and stress response. Sample preparation for transcriptional analysis. For each strain, 2 clones were inoculated in TSB and collected from mid-log or stationary phase. Appropriate volumes from each of the 2 cultures per strain were pooled and added to 2 volumes of RNAprotect reagent (Qiagen). Cultures were centrifuged and cell pellets were stored at 4 ÂºC until RNA extraction. During the experiment, OD600 and viable cfu per ml were monitored for each of the cultures. This procedure was repeated 2 independent times to generate 2 samples at each time point for each strain.

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Salmonella Enteritidis strains from poultry show differential responses to stress and survival in the egg albumen

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