Dataset Information

Biofilm disruption by an air bubble reveals heterogeneous age-dependent detachment patterns dictated by initial extracellular matrix distribution.

ABSTRACT: Bacteria often adhere to surfaces, where they form communities known as biofilms. Recently, it has been shown that biofilm formation initiates with the microscopically heterogeneous deposition of a skeleton of extracellular polymeric substances (EPS) by individual cells crawling on the surface, followed by growth of the biofilm into a surface-covering continuum. Here we report microfluidic experiments with Pseudomonas aeruginosa biofilms showing that their "hidden" heterogeneity can affect the later dynamics of their disruption. Using controlled air bubbles as a model for mechanical insult, we demonstrate that biofilm disruption is strongly dependent on biofilm age, and that disruption to early-stage biofilms can take the shape of a semi-regular pattern of ~15?µm diameter holes from which bacteria have been removed. We explain hole formation in terms of the rupture and retreat of the thin liquid layer created by the long bubble, which scrapes bacteria off the surface and rearranges their distribution. We find that the resulting pattern correlates with the spatial distribution of EPS: holes form where there is less EPS, whereas regions with more EPS act as strongholds against the scraping liquid front. These results show that heterogeneity in the microscale EPS skeleton of biofilms has profound consequences for later dynamics, including disruption. Because few attached cells suffice to regrow a biofilm, these results point to the importance of considering microscale heterogeneity when designing and assessing the effectiveness of biofilm removal strategies by mechanical forces.

SUBMITTER: Jang H

PROVIDER: S-EPMC5460265 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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Biofilm disruption by an air bubble reveals heterogeneous age-dependent detachment patterns dictated by initial extracellular matrix distribution.

Jang Hongchul H Rusconi Roberto R Stocker Roman R

NPJ biofilms and microbiomes 20170303

Bacteria often adhere to surfaces, where they form communities known as biofilms. Recently, it has been shown that biofilm formation initiates with the microscopically heterogeneous deposition of a skeleton of extracellular polymeric substances (EPS) by individual cells crawling on the surface, followed by growth of the biofilm into a surface-covering continuum. Here we report microfluidic experiments with <i>Pseudomonas aeruginosa</i> biofilms showing that their "hidden" heterogeneity can affec ...[more]

PMID: 28649407

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Project description:PurposeTo compare the efficacy of air bubble tamponade alone versus air bubble tamponade with internal fluid aspiration for nonplanar Descemet's membrane detachment after clear corneal incision phacoemulsification.MethodsThis study is a prospective, intervention, comparative randomised clinical trial, conducted at a private eye centre, Ismailia, Egypt, from March 2019 to March 2020. It contained 30 eyes of 24 patients who had postphacoemulsification nonplanar Descemet's membrane detachment involving the periphery and the central area of the cornea (>50% of the cornea) with corneal oedema. The patients were divided into two groups: group A: patients with nonplanar DMD affecting the central cornea treated by air bubble tamponade only and group B: patients with nonplanar DMD affecting the central cornea treated by air bubble tamponade augmented by internal fluid aspiration. Trial Registration: This trial was registered at www.pactr.org and the identification number for the registry is PACTR202006612296119.ResultsDuring the 12-month study period, this study included 30 eyes (24 patients) out of 1356 phaco surgeries with postphacoemulsification nonplanar Descemet's membrane detachment. Six patients had DMD in both eyes, eight patients had DMD in the right eye, and ten patients had DMD in the left eye. All patients have successful surgeries without complications. The calculated incidence rate for visually significant DMD was 2.2% per year. The mean ± SD time interval from cataract surgery to the primary intervention was 4.2 ± 1.1 days. Descemet's membrane was attached in 56.25% of patients in group A (9 out of 16 eyes) and 92.6% of patients in group B (13 out of 14 eyes) with a minimum of one-month follow-up.ConclusionAir descemetopexy combined with the internal fluid aspiration demonstrated to be more efficient than air descemetopexy only to treat Descemet's membrane detachment following phacoemulsification. It should be tried before planning other major surgeries in patients with severe Descemet's membrane detachment.

Project description:The self-produced biofilm provides beneficial protection for the enclosed cells, but the costly production of matrix components makes producer cells susceptible to cheating by nonproducing individuals. Despite detrimental effects of nonproducers, biofilms can be heterogeneous, with isogenic nonproducers being a natural consequence of phenotypic differentiation processes. For instance, in Bacillus subtilis biofilm cells differ in production of the two major matrix components, the amyloid fiber protein TasA and exopolysaccharides (EPS), demonstrating different expression levels of corresponding matrix genes. This raises questions regarding matrix gene expression dynamics during biofilm development and the impact of phenotypic nonproducers on biofilm robustness. Here, we show that biofilms are structurally heterogeneous and can be separated into strongly and weakly associated clusters. We reveal that spatiotemporal changes in structural heterogeneity correlate with matrix gene expression, with TasA playing a key role in biofilm integrity and timing of development. We show that the matrix remains partially privatized by the producer subpopulation, where cells tightly stick together even when exposed to shear stress. Our results support previous findings on the existence of "weak points" in seemingly robust biofilms as well as on the key role of linkage proteins in biofilm formation. Furthermore, we provide a starting point for investigating the privatization of common goods within isogenic populations.IMPORTANCE Biofilms are communities of bacteria protected by a self-produced extracellular matrix. The detrimental effects of nonproducing individuals on biofilm development raise questions about the dynamics between community members, especially when isogenic nonproducers exist within wild-type populations. We asked ourselves whether phenotypic nonproducers impact biofilm robustness, and where and when this heterogeneity of matrix gene expression occurs. Based on our results, we propose that the matrix remains partly privatized by the producing subpopulation, since producing cells stick together when exposed to shear stress. The important role of linkage proteins in robustness and development of the structurally heterogeneous biofilm provides an entry into studying the privatization of common goods within isogenic populations.

Project description:Biofilms are commonly recalcitrant to antibiotics, through incompletely elucidated mechanisms such as tolerance and persistence. We aimed at investigating how a Pseudomonas aeruginosa biofilm escapes ciprofloxacin treatment. P. aeruginosa PA14 in vitro mature biofilms were challenged with supra-MIC ciprofloxacin concentrations. Cell viability was quantified by fluorescein diacetate assay. Population dynamics were determined by counts of surviving culturable cells. Biofilms were analyzed using confocal laser scanning microscopy (CLSM), and the expression of genes involved in stringent response, toxin-antitoxin HigB/HigA, and type 3 secretion system (T3SS) was quantified by RT-qPCR in untreated and treated biofilms. Ciprofloxacin exposure resulted in an initial reduction of bacterial counts following a biphasic time-kill curve. After 24 h of treatment, the overall cell activity and the density of culturable cells significantly decreased as compared to untreated biofilm. No resistant mutant was isolated among the <1% surviving cells. Phenotypic adaptation toward persistence appeared to start after only 1 h of antibiotic exposure, by an overexpression of the genes involved in stringent response and in the toxin-antitoxin system, whereas the expression of genes encoding for the T3SS remained unchanged. After 4 h of ciprofloxacin exposure, stringent response genes returned to their basal level of expression. After a prolonged ciprofloxacin exposure, a deep alteration in the matrix structure that became thinner and lost mushroom-like aggregates was observed, in relation with reduced biovolumes of exopolysaccharides and extracellular DNA. These results support that ciprofloxacin might first induce the bacterial killing of most bacterial cells, but simultaneously activate stringent response mechanisms contributing to the switch of a subpopulation toward a persister phenotype. Once the persister phenotype is expressed, and despite an unexpected alteration of the biofilm matrix, ciprofloxacin fails to eradicate biofilm.

Dataset Information

Biofilm disruption by an air bubble reveals heterogeneous age-dependent detachment patterns dictated by initial extracellular matrix distribution.

Publications

Biofilm disruption by an air bubble reveals heterogeneous age-dependent detachment patterns dictated by initial extracellular matrix distribution.

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