Project description:Quorum sensing is a communication strategy that bacteria use to collectively alter gene expression in response to cell density. Pathogens use quorum sensing systems to control activities vital to infection, such as the production of virulence factors and biofilm formation. The Pseudomonas virulence factor (pvf) gene cluster encodes a quorum sensing system (Pvf) that is present in over 500 strains of proteobacteria, including strains that infect a variety of plant and human hosts. We have shown that the Pvf quorum sensing system regulates the production of secreted proteins and small molecules in the insect pathogen Pseudomonas entomophila L48. Here, we identified genes that are likely regulated by Pvf using the model strain P. entomophila L48 which does not contain other known quorum sensing systems. Pvf regulated genes were identified through comparing the transcriptomes of wildtype P. entomophila and a pvf deletion mutant (ΔpvfA-D). We found that deletion of pvfA-D affected the expression of approximately 300 genes involved in virulence, the type VI secretion system, siderophore transport, and branched chain amino acid biosynthesis. Additionally, we identified seven putative biosynthetic gene clusters whose expression are reduced in ΔpvfA-D. Our results indicate that Pvf controls multiple virulence mechanisms in P. entomophila L48. Characterizing genes regulated by Pvf will aid understanding of host-pathogen interactions and development of anti-virulence strategies against P. entomophila and other pvf-containing strains.
Project description:We sought to compare and contrast plant host and bacterial transcriptional changes during compatible infections that cause disease (albeit within different symptoms). We investigated the infection by the two Pseudomonas syringae sensu lato strains P. syringae pv. syringae B728a (Psy) and P. amygdali pv. tabaci 11528 (Pta) of Nicotiana benthamiana at an early time point post inoculation to understand how a plant host responds to two related bacteria with different infection strategies. Plant and bacterial transcriptomes were analyzed prior to and five hours post inoculation.
Project description:Methylrhodomelol (1) is a bromophenol from the red alga Vertebrata lanosa (L.) T.A.Christensen that has been associated with antimicrobial properties. Aim of the current study was therefore, to assess the antimicrobial potential of this compound in more detail against the gram-negative pathogen Pseudomonas aeruginosa. 1 exerted weak bacteriostatic activity against different strains when grown in minimal medium, whereas other phenolics were inactive. In addition, 1 (35 and 10 µg/mL) markedly enhanced the susceptibility of multidrug resistant P. aeruginosa towards the aminoglycoside gentamicin, while it did not affect the viability of Vero kidney cells up to 100 µM. Finally, pyoverdine release was reduced in bacteria treated at sub-inhibitory concentration, but no effect on other virulence factors was observed. Transcriptome analysis of treated versus untreated P. aeruginosa indicated an interference of 1 with bacterial carbon and energy metabolism, which was corroborated by RT-qPCR and decreased ATP-levels in treated bacteria.
Project description:P. aeruginosa was cultured in a MultiScreen-Mesh plate, which has a filter at the bottom of the wells. The plate was immersed in either in medium alone (control) or in medium inoculated with a mixture of five bacterial strains commonly found in cystic fibrosis sputum (\"microbiome\"). The filter prevented physical contact between P. aeruginosa and the other bacteria, yet soluble products could migrate through the filter into the P. aeruginosa biofilm. P. aeruginosa was then allowed to form biofilms in the wells for 72h, then the biofilm was harvested and a fraction of the harvested cells were used for re-inoculations. This was repeated for 18 cycles for a total of 54 days.
Project description:Some soil bacteria promote plant growth, including Pseudomonas species. With this approach we detected significant changes in Arabidopsis genes related to primary metabolism that were induced by the bacteria.