Project description:Listeria monocytogenes (Lm) cells can attach to both cantaloupe surface and food contact surfaces and promote biofilm growth. This study was to understand the impact of cantaloupe juice on the physiology and transcriptome of Lm planktonic cells and biofilm cells grown on stainless steel coupons using confocal laser scanning microscopy (CLSM), Cryo-Scanning Electron Microscopy (Cryo-SEM) and RNA Seq technology. Lm showed a strong autoaggregation phenotype when grown in cantaloupe juice at room temperature. It is interesting to note that Lm formed significantly more biofilms on stainless steel (SS) coupons when grown in cantaloupe juice than in TSB. SEM images revealed a different attachment profile of Lm on SS coupons. In TSB, Lm cells were mainly found in scratches/groves of the metal surface, whereas, in cantaloupe juice they attached to the smooth surface as well. Interestingly, Lm planktonic and biofilm cells in cantaloupe juice showed an elongated cell shape which might be a stress-induced phenotype in cantaloupe juice. Cantaloupe juice induced a distinct transcriptional profile of biofilm and planktonic cells of Lm from TSB. Functional annotation indicated that the significantly differentially expressed genes (DEGs, Padj < 0.05, log2foldchange ≥ 1) from the comparison mainly participated in metabolism, signaling and stress response. Notably, certain pathways downregulated for planktonic cells were significantly upregulated for biofilm cells in cantaloupe juice compared to TSB, including ABC transporters, two-component system, quorum sensing, chemotaxis, and flagellar assembly. These data highlighted the interaction of Lm with food matrix (i.e., cantaloupe) and the role of food matrix on Lm survival and adaptation. These results provided the basis for future functional characterization of genes with potential roles in biofilm formation and persistence of Lm in cantaloupe juice, as well as for development of mitigation practices for Lm biofilms on produce and food contact surfaces.
Project description:Transcriptional profiles of Salmonella Typhimurium str. ST4/74 air-dried onto stainless steel for 4 h was compared to an early stationary phase (ESP) culture control. Cells that had been air-dried for 4 h were then subsequently rehydrated with water for a 30 min period, after which the transcriptional profile was compared to an ESP control.
Project description:Transcriptional profiles of Salmonella Typhimurium str. ST4/74 air-dried onto stainless steel for 4 h was compared to an early stationary phase (ESP) culture control. Cells that had been air-dried for 4 h were then subsequently rehydrated with water for a 30 min period, after which the transcriptional profile was compared to an ESP control. Carried out using 2 biological replicates for each sample; hybridised in a two-channel hybridization against Salmonella genomic DNA as the comparator/reference.
Project description:Cronobacter sakazakii is well-known for its desiccation tolerance in the powdered infant formula (PIF) food production environment and the bacterium has been linked with high fatality rates in neonates who consume contaminated product. In this study, using deep-level RNA-sequencing, differentially expressed genes were studied in C. sakazakii ATCCTM29544 grown in simulated low-moisture environment designed to mimic the PIF production environment. Desiccation of bacteria was carried out on stainless steel coupons from which total RNA was subsequently recovered and sequenced. During 4 h of desiccation from the early stationary phase (ESP) grown culture, an approximately 3 log10 reduction was recorded for C. sakazakii viable cell count, with the largest change in viable cells occurring between desiccation hour 1 and 2 during which the culture medium was completely dried. Transcriptomic data obtained after 4 h of desiccation highlighted several highly-up regulated osmotolerance-related genes which were associated with the secondary response mechanism. These actively expressed genes mainly modulate pathways that synthetize glycine betaine and trehalose as well as the transport of these two and other compatible solutes. Understanding the activities of these genes and pathways will assist the development of technologies that mitigate the survival of C. sakazakii in the PIF production process.
Project description:Microscopic and transcriptomic characterization of Listeria monocytogenes aggregation and biofilm formation on stainless steel surfaces in the presence of cantaloupe juice extract
Project description:Antimicrobials have been shown to select for changes in biofilm formation and multidrug susceptibility in common human pathogens. We investigated whether common food preservatives selected for these changes in the food pathogen Salmonella enterica serovar Typhimurium. Bacteria were exposed to four food preservatives in either planktonic cultures or biofilms grown on stainless steel beads. Cultures were passaged into fresh media supplemented with the food preservative every 72 hours. Following approximately 1000 generations of continuous preservative exposure, populations were sequenced to determine the single nucleotide polymorphisms that were selected for over evolutionary time.