Comparison of dispersed Pseudomonas aeruginosa biofilm cells and the remaining biofilms
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ABSTRACT: Pseudomonas aeruginosa biofilms were dispersed spontaneously, with 18 mM glutamate, 500 uM SNP, by stopping the flow for 1 hour and restarting it or via vapor nanobubbles.
Project description:A hallmark of the biofilm architecture is the presence of microcolonies. However, little is known about the underlying mechanisms governing microcolony formation. In the human pathogen Pseudomonas aeruginosa, microcolony formation is dependent on the two-component regulator MifR, with mifR mutant biofilms exhibiting an overall thin structure lacking microcolonies, and overexpression of mifR resulting in hyper-microcolony formation. Here, we made use of the distinct MifR-dependent phenotypes to elucidate mechanisms associated with microcolony formation. Using global transcriptomic and proteomic approaches, we demonstrate that cells located within microcolonies experience stressful, oxygen limited, and energy starving conditions, as indicated by the activation of stress response mechanisms and anaerobic and fermentative processes, in particular pyruvate fermentation. Inactivation of genes involved in pyruvate utilization including uspK, acnA and ldhA abrogated microcolony formation in a manner similar to mifR inactivation. Moreover, depletion of pyruvate from the growth medium impaired biofilm and microcolony formation, while addition of pyruvate significantly increased microcolony formation. Addition of pyruvate partly restored microcolony formation in M-bM-^HM-^FmifR biofilms. Moreover, addition of pyruvate to or expression of mifR in lactate dehydrogenase (ldhA) mutant biofilms did not restore microcolony formation. Consistent with the finding of denitrification genes not demonstrating distinct expression patterns in biofilms forming or lacking microcolonies, addition of nitrate did not alter microcolony formation. Our findings indicate the fermentative utilization of pyruvate to be a microcolony-specific adaptation to the oxygen limitation and energy starvation of the P. aeruginosa biofilm environment. For biofilm growth experiments, three independent replicates of P. aeruginosa strains PAO1 and M-NM-^TmifR were grown as biofilms in a flow-through system using a once-through continuous flow tube reactor system for biofilm sample collection and in flow cells (BioSurface Technologies) for the analysis of biofilm architecture as previously described (Sauer et al., 2002, Sauer et al., 2004, Petrova & Sauer, 2009). Cells were treated with RNAprotect (Qiagen) and total RNA was extracted using an RNeasy mini purification kit (Qiagen) per the manufacturerM-bM-^@M-^Ys instructions. RNA quality and the presence of residual DNA were checked on an Agilent Bioanalyzer 2100 electrophoretic system pre- and post-DNase treatment. Ten micrograms of total RNA was used for cDNA synthesis, fragmentation, and labeling according to the Affymetrix GeneChip P. aeruginosa genome array expression analysis protocol. Sauer, K., A. K. Camper, G. D. Ehrlich, J. W. Costerton & D. G. Davies, (2002) Pseudomonas aeruginosa displays multiple phenotypes during development as a biofilm. J. Bacteriol. 184: 1140-1154. Sauer, K., M. C. Cullen, A. H. Rickard, L. A. H. Zeef, D. G. Davies & P. Gilbert, (2004) Characterization of nutrient-induced dispersion in Pseudomonas aeruginosa PAO1 biofilm. J. Bacteriol. 186: 7312-7326. Petrova, O. E. & K. Sauer, (2009) A novel signaling network essential for regulating Pseudomonas aeruginosa biofilm development. PLoS Pathogens 5: e1000668.
Project description:Abstract: Transcriptome analysis was applied to characterize the physiological activities of Pseudomonas aeruginosa grown for three days in drip-flow biofilm reactors. Conventional applications of transcriptional profiling often compare two paired data sets that differ in a single experimentally controlled variable. In contrast this study obtained the transcriptome of a single biofilm state, ranked transcript signals to make the priorities of the population manifest, and compared rankings for a priori identified physiological marker genes between the biofilm and published data sets. Two drip flow biofilm conditions with three replicates each: (1) baseline control at 72hrs, (2) no treatment for 12 hours past baseline. Data from these two conditions were pooled
Project description:In the present in vitro study, interactions between P. aeruginosa (sessile biofilms as well as planktonic cells) and PMNs were analyzed by means of DNA microarray based transcriptomics. We found that the P. aeruginosa wild type biofilms, in contrast to planktonic cultures and quorum sensing (QS) deficient strains, respond to PMN exposure in a rather aggressive manner. The response does not involve protective mechanisms such as those involved in oxidative stress. Rather it is dominated by QS controlled virulence determinants such as those encoded by pqs, phz, rhlAB, all of which are designed to cripple Eukaryotic cells including PMNs and macrophages. Our comparative analysis supports the view that QS plays a major role in mechanisms by which P. aeruginosa evades host defense systems. Keywords: Stress response The biofilms were allowed to grow and develop in the biofilm flow chambers for 3 days before challenge with PMNs. Fresh PMNs from human volunteers were isolated and resuspended in RPMI-1640 medium (BIOCHROM AG) as previously described by Bjarnsholt et al. 2005 (Bjarnsholt et al., 2005). Prior to PMN injection the flow was halted. Ten million PMNs were resuspended in 6 ml of RPMI media and injected into the flow chamber. The concentration of PMNs was found by microscopy to be approximately 1 PMN per 1000 bacterial cells. PMNs and biofilm were incubated for 2 hours. The flow chambers were rolled every 15 minutes to ensure that the entire biofilm was exposed to the PMNs. After incubation the fluid inside the chamber was discarded and the attached biofilm cells were loosened by rolling. The cells were then mechanically removed and collected in 6 ml of RNAlater®
Project description:Three E.coli affymetrix antisense arrays were used to examine the global gene expression of pNCF carrying E.coli biofilm. The pNCF is the derivative of only 65 kb non-conjugative factor of F plasmid. It was introduced to E.coli MG1655 strains before prepare the biofilm samples. The biofilms were cultured under the continuous flow cell system using MOP minimal medium supplemented with 0.02% glucose at 37C. The total RNA was extracted directly from the chamber after 48h of incubation for further array procedures according to the manufacture manual.
Project description:we examined the three different mature biofilms and searched the genes which promoted the rapid biofilm formation when their population hosing the plasmids. We investigate the global transcriptional differences between the non-conjugative or conjugative plasmid-carrying and plasmid-free strains.
Project description:We investigate the global transcriptional differences between the generated E.coli F- phenocopies cells and planktonic cultures using DNA microarray technology. We validated and compared our expression profiling approach with the most E.coli K-12 global expression biofilm-induced genes, in association with the observation of bacterial characteristics using the electron microscope. This functional patterning led us to assign the F- phenocopies/biofilm-related function to 84 genes which involved in the role of F factor during the initial of biofilm formation.
Project description:LD13 mutant was considered for this analysis since it generated mushroom-type mature biofilm. This strain looses 17.6% of parental chromosome and lacks of several bacterial surface structures/genes but still has some novel autoaggregation genes. The global gene-expression profiles of LD13 flow-cell biofilm were compared after 24, 48, 72, 96, and 144 hr, respectively, as well as with those of LD13 planktonic cultures.
Project description:Transcriptome analysis was applied to characterize the physiological activities of Psuedomonas aeruginosa cells grown for three days in drip flow biofilm reactors when compared to the activities of P. aeruginosa grown planktonically to exponential phase in the same media. Here, rather than examining the effect of an individual gene on biofilm antibiotic tolerance, we used a transcriptomics approach to identify regulons and groups of related genes that are induced during biofilm growth of Pseudomonas aeruginosa. We then tested for statistically significant overlap between the biofilm-induced genes and independently compiled gene lists corresponding to stress responses and other putative antibiotic protective mechanisms. This data was evaluated and used to select strains that carry transposon mutations in genes that might play a role in antibiotic tolerance of biofilms. The strains were evaluated for defects in biofilm tolerance. One planktonic condition with four biological replicates; One drip flow biofilm condition grown for 72 hours with three biological replicates; One drip flow biofilm condition grown for 84 hours with three biological replicates.