Project description:Genes were differentially expressed in wild-type Salmonella Typhimurium biofilms and an ΔaraE mutant when grown in the presence of 5mM or 40mM L-arabinose. Multiple biological pathways were impacted, including genes involved in arabinose metabolism, curli fimbriae, pentose phosphae pathway, TCA cycle. amino acid synthesis, pyrimidine and purine biosynthesis, and ATP synthesis.
Project description:Salmonella spp. biofilms have been implicated in persistence in the environment and plant surfaces. In addition, Salmonella is able to form biofilms on the surface on cholesterol gallstones. The ability of Salmonella spp. on these surfaces is superior to biofilm formation on surfaces on glass or plastic. Thus, we hypothesized that Salmonella gene expression is specific during biofilm development on cholesterol surfaces. Flow through assays were performed whereby S. Typhimurium was inoculated into chambers coated with glass or cholesterol. At 24h post-inoculation, planktonic (from the flow through), biofilms (from glass or cholesterol) were collected. Thus we had 4 samples: Planktonic (2) and Biofilms (2), each with 2 biological replicates
Project description:Salmonella spp. biofilms have been implicated in persistence in the environment and plant surfaces. In addition, Salmonella is able to form biofilms on the surface on cholesterol gallstones. The ability of Salmonella spp. on these surfaces is superior to biofilm formation on surfaces on glass or plastic. Thus, we hypothesized that Salmonella gene expression is specific during biofilm development on cholesterol surfaces.
Project description:Salmonella typhimurium 14028s Transposon library recovered after three consecutive rounds of growth to late log phase in M9 minimal medium (arabinose 0.4%) at 37°C with aeration, compared to an expansion of the initial library selected on Luria agar plates + kanamycin (50ug/ml), O/N at 37°C Keywords: Transposon tag analysis
Project description:Background: Biofilm formation by Salmonella species enhances the capacity of these pathogenic bacteria to survive stresses that are commonly encountered within food processing and during host infection. The persistence of Salmonella within the food chain has become a major health concern, as biofilms can serve as a reservoir to contaminate food products. While the molecular mechanisms required for the survival of bacteria on surfaces are not fully understood, transcriptional studies of other bacteria have demonstrated that biofilm growth triggers the expression of specific sets of genes, compared with planktonic cells. Until now, most transcriptomic studies of Salmonella have focused on the effect of infection-relevant stressors on virulence and on comparing mutant and wild-type (WT). However little is known about the physiological responses taking place inside a Salmonella biofilm. Results: We have determined the transcriptomic and proteomic profiles of biofilms of Salmonella enterica serovar Typhimurium. We discovered that 124 of detectable proteins were differentially expressed in the biofilm compared with planktonic cells, and that 10% (433 genes) of S. Typhimurium genes showed a biofilm-specific pattern of transcription (i.e. a 2-fold or more change in the biofilm compared with planktonic cells). The genes that were significantly up-regulated implicated specific cellular processes in biofilm development including amino acid metabolism, cell motility, global regulation and tolerance to stress. We found that the most highly down-regulated genes in the biofilm were located on Salmonella Pathogenicity Island 2 (SPI2), but that a functional SPI2 secretion system regulator (ssrA) was required for WT biofilm formation. We identified STM0341 as a gene of unknown function that was needed for WT biofilm growth. Genes involved in tryptophan (trp) biosynthesis and transport were up-regulated in the biofilm. Deletion of trpE led to a decrease in bacterial attachment and we show that this biofilm defect is restored by exogenous tryptophan or indole. Conclusion: Biofilm growth of S. Typhimurium causes distinct changes in gene and protein expression. Our results show that aromatic amino acids make an important contribution to biofilm formation, and reveal that SPI2 genes, required for virulence in host cells, show opposing patterns of expression to biofilm-specific genes in S. Typhimurium.
Project description:Comparisons of overexpression of PreA (in wt or preAB mutant Salmonella) to Salmonella lacking preA or preAB in late log phase growth in LB preA was externally supplied to wt or preAB mutant Salmonella typhimurium on a pBAD18 plasmid, which was then induced by 10mM arabinose and grown to late log phase (OD0.74). Transcription profiles were compared with those obtained from preA or preAB mutant Salmonella harboring pBAD18 only as vector control.
Project description:Background: Biofilm formation by Salmonella species enhances the capacity of these pathogenic bacteria to survive stresses that are commonly encountered within food processing and during host infection. The persistence of Salmonella within the food chain has become a major health concern, as biofilms can serve as a reservoir to contaminate food products. While the molecular mechanisms required for the survival of bacteria on surfaces are not fully understood, transcriptional studies of other bacteria have demonstrated that biofilm growth triggers the expression of specific sets of genes, compared with planktonic cells. Until now, most transcriptomic studies of Salmonella have focused on the effect of infection-relevant stressors on virulence and on comparing mutant and wild-type (WT). However little is known about the physiological responses taking place inside a Salmonella biofilm. Results: We have determined the transcriptomic and proteomic profiles of biofilms of Salmonella enterica serovar Typhimurium. We discovered that 124 of detectable proteins were differentially expressed in the biofilm compared with planktonic cells, and that 10% (433 genes) of S. Typhimurium genes showed a biofilm-specific pattern of transcription (i.e. a 2-fold or more change in the biofilm compared with planktonic cells). The genes that were significantly up-regulated implicated specific cellular processes in biofilm development including amino acid metabolism, cell motility, global regulation and tolerance to stress. We found that the most highly down-regulated genes in the biofilm were located on Salmonella Pathogenicity Island 2 (SPI2), but that a functional SPI2 secretion system regulator (ssrA) was required for WT biofilm formation. We identified STM0341 as a gene of unknown function that was needed for WT biofilm growth. Genes involved in tryptophan (trp) biosynthesis and transport were up-regulated in the biofilm. Deletion of trpE led to a decrease in bacterial attachment and we show that this biofilm defect is restored by exogenous tryptophan or indole. Conclusion: Biofilm growth of S. Typhimurium causes distinct changes in gene and protein expression. Our results show that aromatic amino acids make an important contribution to biofilm formation, and reveal that SPI2 genes, required for virulence in host cells, show opposing patterns of expression to biofilm-specific genes in S. Typhimurium. Overnight cultures of SL1344 grown in CFA broth were standardized to achieve an initial concentration of 10^6 CFU ml-1 and injected into a stirring influent flask containing 5 L of pre-warmed (25C) sterile CFA medium. The inoculated influent was then pumped through silicon tubing (5 mm internal diameter, Samco Silicon Products Ltd.) at 60 ml h-1 using a peristaltic pump (Minipulse 3, Gilson). The bacteria were allowed to flow through the closed system and either attach to a vertical piece of silicon tubing (1 meter length, 16 mm internal diameter, Samco Silicon Products Ltd.) or flow out into a waste reservoir. The tubing was positioned vertically to collect biofilm cells adherent to the tubing and minimise collecting bacteria that had simply sedimented. Possible backflow of media or bacteria into the influent from the silicon tubing was eliminated using media breaks. Samples taken to determine the pH of the medium or bacterial cell counts were removed via a media port located near the effluent and influent vessel, respectively. Planktonic cells were removed after 72 h of growth from the influent vessel to avoid any contamination with biofilm cells. The entire system was kept at a constant temperature of 25C and biofilm cells were isolated after 72 h of growth. All planktonic and biofilm samples were isolated from the same experimental system and used for both RNA and protein isolation. For this study, four biological replicates were performed at four different dates (Jun25, Jul5, Jul16, Oct11; as indicated in the sample title). For the dual-colour microarray hybridisations, we used Salmonella genomic DNA as the comparator which also acted as the control for spot quality. Individual labelled cDNA samples (RNA) were hybridised up to 4 times (technical replicates).
Project description:Infection with Salmonella enterica serovar Typhi in humans causes the systemic, life-threatening disease typhoid fever. In the laboratory, typhoid fever can be modeled through the inoculation of susceptible mice with Salmonella enterica serovar Typhimurium. The ensuing disease is characterized by systemic dissemination and colonization of many organs, including the liver, spleen and gallbladder. Using this murine model, we previously characterized the interactions between Salmonella Typhimurium and host cells in the gallbladder and showed that this pathogen can successfully invade gallbladder epithelial cells and proliferate. Additionally, we showed that Salmonella Typhimurium can use bile phospholipids to grow at high rates. These abilities are likely important for quick colonization of the gallbladder during typhoid fever and further pathogen dissemination through fecal shedding. To further characterize the interactions between Salmonella and the gallbladder environment we compared the transcriptome of Salmonella cultures grown in LB or physiological murine bile. Our data showed that many genes involved in bacterial central metabolism are affected by bile, with the citric acid cycle being repressed and alternative respiratory systems being activated. Additionally, our study revealed a new aspect of Salmonella interactions with bile through the identification of phoP as a bile-responsive gene. Repression of phoP expression does not involve PhoPQ sensing of a bile component. Due to its critical role in Salmonella virulence, further studies in this area will likely reveal aspects of the interaction between Salmonella and bile that are relevant to disease.
Project description:Salmonella typhimurium 14028s Transposon library grown in M9 minimal medium (arabinose 0.4%), O/N at 37°C with aeration, compared to the initial library selected on Luria agar plates + kanamycin (50ug/ml), O/N at 37°C Keywords: Transposon tag analysis