Methods for Characterizing the Co-development of Biofilm and Habitat Heterogeneity

Li, Xiaobao; Song, Jisun L.; Culotti, Alessandro; Zhang, Wei; Chopp, David L.; Lu, Nanxi; Packman, Aaron I.

doi:10.3791/52602

Cited by 3 publications

(3 citation statements)

References 24 publications

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“…Customizable chips allow full control of environmental conditions, such as hydrodynamic variables, establishment of chemical gradients and differing properties of substratum [38,57]. Some microfluidic chips are also being adapted into high-throughput commercialized platforms [58].…”

Section: Microfluidic Platformsmentioning

confidence: 99%

Biofilm Models of Polymicrobial Infection

2015

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Interactions between microbes are complex and play an important role in the pathogenesis of infections. These interactions can range from fierce competition for nutrients and niches to highly evolved cooperative mechanisms between different species that support their mutual growth. An increasing appreciation for these interactions, and desire to uncover the mechanisms that govern them, has resulted in a shift from monomicrobial to polymicrobial biofilm studies in different disease models. Here we provide an overview of biofilm models used to study select polymicrobial infections and highlight the impact that the interactions between microbes within these biofilms have on disease progression. Notable recent advances in the development of polymicrobial biofilm-associated infection models and challenges facing the study of polymicrobial biofilms are addressed. Polymicrobial interactions in biofilmsOver the past 2 decades there has been a revolutionary paradigm shift in the field of microbiology with the appreciation that bacteria present in most biological systems exist in biofilms, rather than in a free-living state. This understanding has dramatically changed the way we study bacteria in the laboratory and resulted in the development of many new experimental systems that replicate biofilm environments [1][2][3][4][5]. Studies utilizing these systems have demonstrated time and time again that bacteria behave very differently when in a biofilm than during planktonic growth. In many ways, we now have to relearn everything we thought we knew about bacterial behavior through the view of the biofilm lens.Similarly, the recent explosion of metagenomic studies has significantly increased our appreciation of the complexity of the microbial populations present in biofilms [6,7]. This is also true for infections, most of which are thought to be biofilm related and inherently polymicrobial, including various species of bacteria, fungi and viruses [8]. It is thought that microbes act in concert to establish biofilms, which in turn can increase tolerance to antimicrobials, exacerbate of the host's immune response and increase persistence at the infection site [7,[9][10][11].Genetic diversity of microbes within biofilm communities is thought to increase the fitness of the residing community, making them more equipped to survive environmental stresses. In large part, this is due to an expanded gene pool, which can be more easily shared within the confines of a biofilm community [12]. Community composition and interactions within the community can have huge influences on bacterial behavior. Thus, just as the behavior of planktonic versus biofilm-associated bacteria is dramatically different, so is that of bacteria in single species versus multispecies systems.Interactions between microbes are complex and highly dependent on context. They can range from fierce competition for nutrients and niches, manifested by antagonistic behavior, to highly evolved cooperative mechanisms between different species that support their mutual grow...

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Section: Microfluidic Platformsmentioning

confidence: 99%

Biofilm Models of Polymicrobial Infection

2015

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“…We observed changes in solute transport and chlorine killing in P. aeruginosa PAO1-gfp biofilms before and after biomineralization and particle deposition. PAO1 biofilms were grown in flow cells following a protocol described previously (32). Prior to inoculation, the flow cell system was sterilized by autoclaving.…”

Section: Methodsmentioning

confidence: 99%

In Situ Biomineralization and Particle Deposition Distinctively Mediate Biofilm Susceptibility to Chlorine

Chopp

Russin

et al. 2016

Appl Environ Microbiol

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Microbial biofilms and mineral precipitation commonly co-occur in engineered water systems, such as cooling towers and water purification systems, and both decrease process performance. Microbial biofilms are extremely challenging to control and eradicate. We previously showed that in situ biomineralization and the precipitation and deposition of abiotic particles occur simultaneously in biofilms under oversaturated conditions. Both processes could potentially alter the essential properties of biofilms, including susceptibility to biocides. However, the specific interactions between mineral formation and biofilm processes remain poorly understood. Here we show that the susceptibility of biofilms to chlorination depends specifically on internal transport processes mediated by biomineralization and the accumulation of abiotic mineral deposits. Using injections of the fluorescent tracer Cy5, we show that Pseudomonas aeruginosa biofilms are more permeable to solutes after in situ calcite biomineralization and are less permeable after the deposition of abiotically precipitated calcite particles. We further show that biofilms are more susceptible to chlorine killing after biomineralization and less susceptible after particle deposition. Based on these observations, we found a strong correlation between enhanced solute transport and chlorine killing in biofilms, indicating that biomineralization and particle deposition regulate biofilm susceptibility by altering biocide penetration into the biofilm. The distinct effects of in situ biomineralization and particle deposition on biocide killing highlight the importance of understanding the mechanisms and patterns of biomineralization and scale formation to achieve successful biofilm control.T he development of biofilms in engineered water systems is usually detrimental. Excessive biofilm growth decreases process performance; for example, it reduces the heat exchange efficiency in cooling towers and hinders the flow through high-pressure water treatment membranes (1, 2). Biofilms in water systems are also potential reservoirs of human pathogens (2-6). Biofilms are difficult to eradicate because they are much less susceptible to antimicrobials and biocides than suspended microbial cells (7,8). The decreased susceptibility of biofilms to biocides results from a combination of the decreased penetration of solutes into the biofilm structure, the protection provided by extracellular polymers, reduced cellular metabolism within biofilms, and the development of resistant cellular phenotypes (persisters) (9-11). Chlorine is one of the most commonly used biocides for biofilm control in engineered water systems (12, 13). Prior studies have found that the limited transport of chlorine to the interior of biofilms reduces the overall killing efficacy of chlorination (12,14).Biofilm biofouling is often associated with the formation of scale, which is an inorganic mineral precipitate that commonly includes calcium carbonate, sulfate, and phosphate (1, 15, 16). The co-occurrence of a biofi...

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“…The artificial urine composition can be found in the supplemental material. The flow cell system was described previously (27); it contains a peristaltic pump to deliver growth medium to the flow cell. Flow cells were sterilized with 1% bleach for 24 h and then thoroughly rinsed with autoclaved deionized water before inoculation.…”

Section: Methodsmentioning

confidence: 99%

Ureolytic Biomineralization Reduces Proteus mirabilis Biofilm Susceptibility to Ciprofloxacin

Brady

et al. 2016

Antimicrob Agents Chemother

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Ureolytic biomineralization induced by urease-producing bacteria, particularly Proteus mirabilis, is responsible for the formation of urinary tract calculi and the encrustation of indwelling urinary catheters. Such microbial biofilms are challenging to eradicate and contribute to the persistence of catheter-associated urinary tract infections, but the mechanisms responsible for this recalcitrance remain obscure. In this study, we characterized the susceptibility of wild-type (ure؉) and urease-negative (ure؊) P. mirabilis biofilms to killing by ciprofloxacin. Ure؉ biofilms produced fine biomineral precipitates that were homogeneously distributed within the biofilm biomass in artificial urine, while ure؊ biofilms did not produce biomineral deposits under identical growth conditions. Following exposure to ciprofloxacin, ure؉ biofilms showed greater survival (less killing) than ure؊ biofilms, indicating that biomineralization protected biofilm-resident cells against the antimicrobial. To evaluate the mechanism responsible for this recalcitrance, we observed and quantified the transport of Cy5-conjugated ciprofloxacin into the biofilm by video confocal microscopy. These observations revealed that the reduced susceptibility of ure؉ biofilms resulted from hindered delivery of ciprofloxacin into biomineralized regions of the biofilm. Further, biomineralization enhanced retention of viable cells on the surface following antimicrobial exposure. These findings together show that ureolytic biomineralization induced by P. mirabilis metabolism strongly regulates antimicrobial susceptibility by reducing internal solute transport and increasing biofilm stability. Proteus mirabilis is one of the most common human pathogens found in catheter-associated urinary tract infections (CAUTIs) (1, 2). Although long-term CAUTIs are usually polymicrobial, P. mirabilis is considered to play a unique and important role in both CAUTI establishment and catheter blockage, due to its strong ability to induce mineral precipitation (3, 4). P. mirabilis produces extensive urease, which hydrolyzes urea to ammonia, increasing pH and inducing mineral precipitation. This process is commonly referred to as ureolytic biomineralization (5). In CAUTIs, P. mirabilis forms distinctive crystalline biofilms through ureolytic biomineralization (6). Typical minerals produced by P. mirabilis in CAUTIs are struvite (magnesium ammonium phosphate), apatite (calcium phosphate), and calcite (calcium carbonate) (7-9).The treatment of CAUTIs is challenging. Although antimicrobials such as ciprofloxacin and ampicillin are still the most commonly recommended therapeutic agents for urinary tract infections (UTIs) (10), crystalline biofilms are generally recalcitrant to antimicrobials (11). As a result, many patients suffer recurrent biofilm-based infections and catheter encrustation and blockage (12). Alternative therapies, including irrigation with antibioticcontaining solutions and the use of antibiotic-impregnated catheters, also show limited efficacy in preventing biof...

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Methods for Characterizing the Co-development of Biofilm and Habitat Heterogeneity

Cited by 3 publications

References 24 publications

Biofilm Models of Polymicrobial Infection

Biofilm Models of Polymicrobial Infection

In Situ Biomineralization and Particle Deposition Distinctively Mediate Biofilm Susceptibility to Chlorine

Ureolytic Biomineralization Reduces Proteus mirabilis Biofilm Susceptibility to Ciprofloxacin

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