Unknown,Transcriptomics,Genomics,Proteomics

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Regulatory network underlying the adaptive physiology of Pseudomonas aeruginosa under urinary tract-like conditions

ABSTRACT: Pseudomonas aeruginosa is one of the most frequent pathogen dominant in complicated urinary tract infections (UTI). To unravel the adaptation strategies of P. aeruginosa to the conditions in the urinary tract and to define the underlying regulatory network an artificial growth system mimicking the conditions in the urinary tract was established. Transcriptome analyses were used to investigate the physiological status of P. aeruginosa under this conditions. We performed comparisons to identify genes induced under artificial urinary tract conditions to unravel the adaptive strategies and the underlying regulatory network used by Pseudomonas aeruginosa during urinary tract infections using Affimetrix GeneChips. Pseudomonas aeruginosa wild type strain PAO1 was grown in an artificial in vitro growth system mimicking the conditions in the urinary tract. Therefore, biofilms were grown on the surface of membrane filters placed on agar plates at 37 Â°C up to the late logarithmic state under aerobic and anaerobic conditions (incubated in an anaerobic beanch). An artificial urine medium (AUM) simulating the averaged urine of an human adult was used as nutrient souce. 10-fold diluted Luria Bertani (LB)-medium was used as reference medium. For growth under oxygen depletion the media were supplemented with 50 mM KNO3 to sustain anaerobic respiration. The biofilms were harveted at this time points and resuspsended in 0.9% (w/v) NaCl. The OD578 of biofilm suspension was 0.8 for all tested conditions. First comparison: Identification of genes induced or repressed under aerobic conditions in the P. aeruginosa wild type PAO1. Here we compared the transcriptome profile of P. aeruginosa PAO1 grown aerobically for 18 h to the late logarithmic phase in biofilms on AUM with the transcriptome profile of the PAO1 strain, which was grown aerobically for 18 h to the late logarithmic phase in biofilms on 10-fold diluted LB. Second comparison: Identification of genes induced or repressed under anaerobic conditions in the P. aeruginosa wild type PAO1. Here we compared the transcriptome profile of P. aeruginosa PAO1 grown anaerobically for 2 days up to the late logarithmic phase in biofilms on AUM supplemented with 50 mM nitrate with the transcriptome profile of the PAO1 strain, which was grown anaerobically for 2 days up to the late logarithmic phase in biofilms on 10-fold diluted LB supplemented with 50 mM nitrate.

ORGANISM(S): Pseudomonas aeruginosa PAO1

SUBMITTER: Petra Tielen

PROVIDER: E-GEOD-33160 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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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:The anaerobic metabolism of the opportunistic pathogen Pseudomonas aeruginosa is important for growth and survival during persistent infections. The two Fnr-type transcription factors Anr and Dnr regulate different parts of the underlying network. Both are proposed to bind to a non-distinguishable DNA sequence named Anr box. The aim of this study was the identification of genes induced under anaerobic conditions in the P. aeruginosa wild type and identification of genes under control of the Anr or Dnr regulators. We performed three comparisons to identify genes induced under anaerobic denitrifying conditions in the P. aeruginosa wild type strain and genes which are under control of the Anr or Dnr regulators under these anaerobic conditions. Since the anr and dnr mutant strains do not grow under anaerobic denitrifying conditions, we applied anaerobic shift experiments. Pseudomonas aeruginosa was grown in a modified AB minimal medium, containing 25 ÂµM FeSO4, 20 mM glucose and 50 mM NaNO3. The 200 ml aerobic cultures were grown in 1 l Erlenmeyer flasks at 37 oC and 300 rpm. The aerobic culture was grown to an OD578 of 0.3. For the aerobic culture, cells were harvested at this point. For the anaerobic shift experiments 130 ml of the respective aerobic culture were transferred to a 135 ml sealed serum flask. Control experiments verified that oxygen tension decreased within 3 - 5 min below the detection limit of an oxygen electrode. The cells were harvested after incubation for additional 2h under anaerobic conditions. Within these 2h incubation period no growth of the wild type, the anr mutant or the dnr mutant strain was observed. First comparison: Identification of genes induced or repressed under anaerobic conditions in the P. aeruginosa wild type PAO1. Here we compared the transcriptome profile of P. aeruginosa PAO1 grown under aerobic conditions up to an OD578 of 0.3 with the transcriptome profile of the PAO1 strain, which was first grown under aerobic conditions up to an OD578 of 0.3 and than shifted to anaerobic conditions by transfer to a sealed serum flask and further incubated for two hours under anaerobic conditions. Second comparison: Identification of genes regulated differently in the anr mutant strain PAO6261. Here we compared the transcriptome profile of the P. aeruginosa wild type PAO1 with the transcriptome profile of the P. aeruginosa anr mutant strain PAO6261. Both strains were harvested after 2h incubation under anaerobic conditions. Third comparison: Identification of genes regulated differently in the dnr mutant strain RM536. Here we compared the transcriptome profile of the P. aeruginosa wild type PAO1 with the transcriptome profile of the P. aeruginosa dnr mutant strain RM536. Both strains were harvested after 2h incubation under anaerobic conditions.

Project description:Bacteria growing in biofilms are physiologically heterogeneous, due in part to their adaptation to local environmental conditions. Here, we characterized the local transcriptional responses of Pseudomonas aeruginosa growing in biofilms by using microarray analysis of isolated biofilm subpopulations. The results demonstrated that cells at the top of the biofilms had high mRNA abundances for genes involved in general metabolic functions, while mRNAs for these housekeeping genes were low in cells at the bottom of the biofilms. Selective GFP labeling showed that cells at the top of the biofilm were actively dividing. However, the dividing cells had high mRNAs levels for genes regulated by the hypoxia induced regulator, Anr. Slow-growing cells deep in the biofilms had little expression of Anr-regulated genes and may have experienced long-termanoxia. Transcripts for ribosomal proteins were primarily associated with the metabolically active cell fraction, while ribosomal RNAs were abundant throughout the biofilms, indicating that ribosomes are stably maintained even in slowly growing cells. Consistent with these results was the identification of mRNAs for ribosome hibernation factors (rmf and PA4463) at the bottom of the biofilms. A P. aeruginosa M-bM-^HM-^Frmf strain had increased uptake of the membrane integrity stain, propidium iodide. Using selective GFP labeling and cell sorting, we showed that the dividing cells were more susceptible to tobramycin and ciprofloxacin than the dormant subpopulation. The results demonstrate that in thick P. aeruginosa biofilms, cells are physiologically distinct spatially, with cells deep in the biofilm in a viable but antibiotic-tolerant slow-growth state. 52-hour Pseudomonas aeruginosa TSA colony biofilms were cryoembedded, thin sectioned, and laser dissected (LCM) to obtain samples from the top and bottom 50 M-BM-5m of the biofilms. 9 sections per biofilm were pooled. RNA was extracted with the RNeasy Micro kit, Turbo DNase treated, poly(A) tailed, and amplified using the Quantitect WTA kit. After clean up, the resulting product was fragmented and end labeled before hybridization.

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Regulatory network underlying the adaptive physiology of Pseudomonas aeruginosa under urinary tract-like conditions

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