Project description:Purpose: To elucidated key metabolic pathways important for S. Enteritidis survival in egg white. Methods: RNA sample of Mid-log phase bacteria cultures that grown in M9FeS medium were taken as 0h sample, and bacteria incubated with egg white for 6h 12h and 24h were taken as 6,12,24h RNA sample respectively. Three biological replicates were carried out per sample. RNA sample was sequenced with Illumina HiSeq 2000 System. DESeq2 method was used to calculate the differentially expressed genes. qRT–PCR and gene mutation were used to validate RNA-seq result. Results: A total of 12 samples were sequenced. The average output of each sample was 1.33 Gb, and the average comparison rate with the reference genome was 97.51%. M9FeS and egg whites cultivation resulted in 2400 to 2700 expressed genes accounting for 53 to 58% of the whole genome. In this group, 1240 to 1470 genes had significant levels of log2 fold changes ≥1, (Padj <0.05) compared with control. These accounted for 27.3 to 32.2% of the whole genome indicating a large shift in the transcriptional response to egg whites. qRT–PCR result of 21 selected genes highly consistent with the RNAseq results at all three timepoints. 8 out of 12 DEGs mutants showed decreased survival ability in egg white, suggested that the DEGs from the RNAseq results correlated significantly with the egg white resistance phenotype. Conclusions: Using strand-specific RNA sequencing, we found pathways significantly changed in egg white. Genes involved in SOS-dependent and independent DNA damage repair, alkaline pH adaption, osmotic stress adaption, envelope damage repair including maintaining periplasm homeostasis and reinforcing peptidoglycan layer, nitrogen assimilation, Salmonella pathogenicity island 2, iron absorption and biotin synthesis, were significantly up regulated in bacteria surviving in egg whites. Differentially expressed genes involved in energy metabolism, translation, and cell motility, Salmonella pathogenicity island 1 were significantly down-regulated in egg whites.
Project description:Even though the incidence of salmonellosis in humans has decreased over the last years, Salmonella spp. are still a leading cause of foodborne outbreaks in Europe (Anon., 2014). Of more than 2500 different serovars of Salmonella enterica, S. enterica serovar Enteritidis (S. Enteritidis) is the most frequently reported serovar in relation to food borne disease, and egg and egg products are the most important vehicles (Anon., 2014). It has recently been shown that S. Enteritidis is superior to other serovars tested regarding survival in egg white, which may explain why many egg borne outbreaks are caused by this serovar (De Vylder et al., 2013). The genetic background for this apparent better adaptation to survival in egg is only partially known. The aim of this work was to carry out gene expression analysis in order to understand how S. Enteritidis adapts to growth in the hostile environment of egg. This study analyzed gene expression of this bacterium during growth in whole egg, and whether highly expressed genes were essential for the growth. High quality RNA was extracted from S. Enteritidis using an improved modified RNA-extraction protocol. Global gene expression during growth in whole egg was compared to growth in LB-medium using DNA array method. Twenty-six genes were significantly upregulated during growth in egg; these belonged to amino acids biosynthesis, di/oligopeptide transport system, biotin synthesis, ferrous iron transport system, and type III secretion system. Significant downregulation of 15 genes related to formate hydrogenlyase (FHL) and trehalose metabolism was observed. The results suggested that S. Enteritidis is starved for amino-acids, biotin and iron when growing in egg.
Project description:White leghorn layers were infected with Salmonella Enteritidis. The cecum were collected at 7 days post infection for total RNA isolation. The significantly expressed microRNAs between infected and non-infected chickens were identified through Solexa sequencing technology.
Project description:Salmonella Entertidis (SE) causes persistent infections and egg contamination in laying ducks.Hcp roles as the core structural and effector proteins of T6SS. We generated an hcp deletion mutant MY1△hcp and detected its ability to invade duck granulosa cells (dGCs) and contaminate eggs. Then, Quantitative proteomics of Hcp-mediated Salmonella Enteritidis was performed.
Project description: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.
Project description:Screen for differences in gene expression between a parental Salmonella enterica serovar Enteritidis strain (ATCC4931) and an adapted strain with increased resistance to the widely used antimicrobial sanitizer dodecyltrimethylammonium chloride (DTAC) Time course of comparative gene expression changes between log phase parental and adapted Enteritidis strains after 0, 10, 30 and 150 min of exposure to 50% of the respective MIC of DTAC.
Project description:Purpose: To elucidate the survival strategies in egg white of Salmonella Pullorum, a host-restricted pathogen with vertical transmission capability. Methods: The logarithmic-phase wild-type and Δfim mutant strains were inoculated into LB medium and egg white (final concentration 80%) and statically cultured at 42°C for 6 hours. RNA samples were then extracted for sequencing. Three biological replicates were carried out per sample. RNA sample was sequenced with Illumina HiSeq 2000 System. EdgeR method was used to calculate the differentially expressed genes. qRT–PCR and gene mutation were used to validate RNA-seq result. Results: A total of 12 samples were sequenced. The average clean bases of each sample was 3.63 Gb, and the average comparison rate with the reference genome was more than 90%. Compared with LB broth, there were 1606 differentially expressed genes (FDR ≤0.05 and |Log2Fold change| ≥1) in egg white with 762 genes upregulated and 844 genes downregulated. These accounted for about 35% of the whole genome indicating a large shift in the transcriptional response to egg white. qRT–PCR result of 7 selected genes highly consistent with the RNA-seq results. Five mutants showed decreased survival ability in egg white, suggested that the DEGs from the RNAseq results correlated significantly with the egg white resistance phenotype.Moreover, a significant downregulation of all genes within the fim gene cluster was observed and the RNA-seq analysis of Δfim mutant in the egg white was further conducted. In comparison with wild-type in egg white, the fim mutant showed 36 differentially expressed genes, with most of them associated with energy metabolism pathways.