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Shear stress increases the residence time of adhesion of Pseudomonas aeruginosa.

ABSTRACT: Although ubiquitous, the processes by which bacteria colonize surfaces remain poorly understood. Here we report results for the influence of the wall shear stress on the early-stage adhesion of Pseudomonas aeruginosa PA14 on glass and polydimethylsiloxane surfaces. We use image analysis to measure the residence time of each adhering bacterium under flow. Our main finding is that, on either surface, the characteristic residence time of bacteria increases approximately linearly as the shear stress increases (?0-3.5 Pa). To investigate this phenomenon, we used mutant strains defective in surface organelles (type I pili, type IV pili, or the flagellum) or extracellular matrix production. Our results show that, although these bacterial surface features influence the frequency of adhesion events and the early-stage detachment probability, none of them is responsible for the trend in the shear-enhanced adhesion time. These observations bring what we believe are new insights into the mechanism of bacterial attachment in shear flows, and suggest a role for other intrinsic features of the cell surface, or a dynamic cell response to shear stress.

SUBMITTER: Lecuyer S

PROVIDER: S-EPMC3021681 | biostudies-literature | 2011 Jan

REPOSITORIES: biostudies-literature

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Shear stress increases the residence time of adhesion of Pseudomonas aeruginosa.

Lecuyer Sigolene S Rusconi Roberto R Shen Yi Y Forsyth Alison A Vlamakis Hera H Kolter Roberto R Stone Howard A HA

Biophysical journal 20110101 2

Although ubiquitous, the processes by which bacteria colonize surfaces remain poorly understood. Here we report results for the influence of the wall shear stress on the early-stage adhesion of Pseudomonas aeruginosa PA14 on glass and polydimethylsiloxane surfaces. We use image analysis to measure the residence time of each adhering bacterium under flow. Our main finding is that, on either surface, the characteristic residence time of bacteria increases approximately linearly as the shear stress ...[more]

PMID: 21244830

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Project description:Chronic colonization of the lungs by Pseudomonas aeruginosa is one of the major causes of morbidity and mortality in cystic fibrosis (CF) patients. To gain insights into the characteristic biofilm phenotype of P. aeruginosa in the CF lungs, mimicking the CF lung environment is critical. We previously showed that growth of the non-CF-adapted P. aeruginosa PAO1 strain in a rotating wall vessel, a device that simulates the low fluid shear (LS) conditions present in the CF lung, leads to the formation of in-suspension, self-aggregating biofilms. In the present study, we determined the phenotypic and transcriptomic changes associated with the growth of a highly adapted, transmissible P. aeruginosa CF strain in artificial sputum medium under LS conditions. Robust self-aggregating biofilms were observed only under LS conditions. Growth under LS conditions resulted in the upregulation of genes involved in stress response, alginate biosynthesis, denitrification, glycine betaine biosynthesis, glycerol metabolism, and cell shape maintenance, while genes involved in phenazine biosynthesis, type VI secretion, and multidrug efflux were downregulated. In addition, a number of small RNAs appeared to be involved in the response to shear stress. Finally, quorum sensing was found to be slightly but significantly affected by shear stress, resulting in higher production of autoinducer molecules during growth under high fluid shear (HS) conditions. In summary, our study revealed a way to modulate the behavior of a highly adapted P. aeruginosa CF strain by means of introducing shear stress, driving it from a biofilm lifestyle to a more planktonic lifestyle. Biofilm formation by Pseudomonas aeruginosa is one of the hallmarks of chronic cystic fibrosis (CF) lung infections. The biofilm matrix protects this bacterium from antibiotics as well as from the immune system. Hence, the prevention or reversion of biofilm formation is believed to have a great impact on treatment of chronic P. aeruginosa CF lung infections. In the present study, we showed that it is possible to modulate the behavior of a highly adapted transmissible P. aeruginosa CF isolate at both the transcriptomic and phenotypic levels by introducing shear stress in a CF-like environment, driving it from a biofilm to a planktonic lifestyle. Consequently, the results obtained in this study are of great importance with regard to therapeutic applications that introduce shear stress in the lungs of CF patients.

Project description:Anticipating the risk for infectious disease during space exploration and habitation is a critical factor to ensure safety, health and performance of the crewmembers. As a ubiquitous environmental organism that is occasionally part of the human flora, Pseudomonas aeruginosa could pose a health hazard for the immuno-compromised astronauts. In order to gain insights in the behavior of P. aeruginosa in spaceflight conditions, two spaceflight-analogue culture systems, i.e. the rotating wall vessel (RWV) and the random position machine (RPM), were used. Microarray analysis of P. aeruginosa PAO1 grown in the low shear modeled microgravity (LSMMG) environment of the RWV compared to the normal gravity control (NG), revealed a regulatory role for AlgU (RpoE). Specifically, P. aeruginosa cultured in LSMMG exhibited increased alginate production and up-regulation of AlgU-controlled transcripts, including those encoding stress-related proteins. This study also shows the involvement of Hfq in the LSMMG response, consistent with its previously identified role in the Salmonella LSMMG- and spaceflight response. Furthermore, cultivation in LSMMG increased heat- and oxidative stress resistance and caused a decrease in the culture oxygen transfer rate. Interestingly, the global transcriptional response of P. aeruginosa grown in the RPM was similar to that in NG. The possible role of differences in fluid mixing between the RWV and RPM is discussed, with the overall collective data favoring the RWV as the optimal model to study the LSMMG-response of suspended cells. This study represents a first step towards the identification of specific virulence mechanisms of P. aeruginosa activated in response to spaceflight-analogue conditions, and could direct future research regarding the risk assessment and prevention of Pseudomonas infections for the crew in flight and the general public. The wild type P. aeruginosa PAO1 strain (ATCC 15692) was used in this study and all cultures were grown in Lennox L Broth Base (LB) (Life Technologies) at 28 Â°C. An overnight shaking culture (125 r.p.m.) of P. aeruginosa in LB was washed and diluted in 0.85% NaCl solution to an OD600 of 1. This bacterial suspension was used to inoculate fresh LB medium at a final concentration of 10-4 CFU/ml. Synthecon Rotating Wall Vessel bioreactors (RWV) (50 ml or 10 ml) were filled with inoculated medium so that no headspace (i.e. no bubbles) was present. Other than for stress resistance assays, for which 10 ml capacity bioreactors were used, RWV bioreactors with a capacity of 50 ml were adopted for all experiments. Identical bioreactors were mounted in triplicate on (i) a RWV device in vertical position (LSMMG) (Cellon), (ii) a RWV device in horizontal position (NG) and (iii) the center of the inner Random Positioning Machine (RPM) frame (RG) (Fokker Space), and placed in a large humidified (70%-80% relative humidity) culture chamber, to avoid evaporation of culture medium through the gas-permeable membrane at the back of each vessel (Figure 1). A 25 r.p.m. rotation speed was adopted for the RWV cultures, while RPM-cultures were randomly rotated at 10 r.p.m. (60Â°/s). Bacteria were grown in the three described test conditions for 24 hours. After 24 hours of cultivation, the contents of every bioreactor was gently mixed by pipetting and divided into several aliquots. Ten millilitres of culture from each growth condition was immediately fixed with RNA Protect Reagent (Qiagen), following the manufacturer's instructions, and fixed cell pellets were frozen at -20 Â°C until RNA extraction. Samples were immediately exposed to different stresses.

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Shear stress increases the residence time of adhesion of Pseudomonas aeruginosa.

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Shear stress increases the residence time of adhesion of Pseudomonas aeruginosa.

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