Biofilms can cause severe problems to human health due to the high tolerance to antimicrobials; consequently, biofilm science and technology constitutes an important research field. Growing a ...relevant biofilm in the laboratory provides insights into the basic understanding of the biofilm life cycle including responses to antibiotic therapies. Therefore, the selection of an appropriate biofilm reactor is a critical decision, necessary to obtain reproducible and reliable in vitro results. A reactor should be chosen based upon the study goals and a balance between the pros and cons associated with its use and operational conditions that are as similar as possible to the clinical setting. However, standardization in biofilm studies is rare. This review will focus on the four reactors (Calgary biofilm device, Center for Disease Control biofilm reactor, drip flow biofilm reactor, and rotating disk reactor) approved by a standard setting organization (ASTM International) for biofilm experiments and how researchers have modified these standardized reactors and associated protocols to improve the study and understanding of medical biofilms.
Microorganisms attach to surfaces and develop biofilms. Biofilm-associated cells can be differentiated from their suspended counterparts by generation of an extracellular polymeric substance (EPS) ...matrix, reduced growth rates, and the up- and down- regulation of specific genes. Attachment is a complex process regulated by diverse characteristics of the growth medium, substratum, and cell surface. An established biofilm structure comprises microbial cells and EPS, has a defined architecture, and provides an optimal environment for the exchange of genetic material between cells. Cells may also communicate via quorum sensing, which may in turn affect biofilm processes such as detachment. Biofilms have great importance for public health because of their role in certain infectious diseases and importance in a variety of device-related infections. A greater understanding of biofilm processes should lead to novel, effective control strategies for biofilm control and a resulting improvement in patient management.
Over the last few decades, the study of microbial biofilms has been gaining interest among the scientific community. These microbial communities comprise cells adhered to surfaces that are surrounded ...by a self-produced exopolymeric matrix that protects biofilm cells against different external stresses. Biofilms can have a negative impact on different sectors within society, namely in agriculture, food industries, and veterinary and human health. As a consequence of their metabolic state and matrix protection, biofilm cells are very difficult to tackle with antibiotics or chemical disinfectants. Due to this problem, recent advances in the development of antibiotic alternatives or complementary strategies to prevent or control biofilms have been reported. This book includes different strategies to prevent biofilm formation or to control biofilm development and includes full research articles, reviews, a communication, and a perspective.
Bacteria often live in communities of mixed species embedded in a self-produced extracellular matrix of polysaccharides, proteins and DNA, termed biofilms. The BioFlux microfluidic flow system is ...useful for studying biofilm formation in different media under flow. However, analyzing the architecture and maturation of biofilms under flow requires a proper seeding, which can prove difficult when working with bacteria of different sizes, motile bacteria or aiming for a high number of replicates. Here we developed an efficient protocol that exploits viscosity tuning and seeding indicator dyes to improve seeding and allow for high-throughput examination and visualization of consistent mono- and mixed-species biofilm developments under flow.
An improved protocol for seeding bacteria in the BioFlux microfluidic flow system was developed using glycerol and Nigrosin to increase the viscosity and stain the media, respectively. This new protocol does not alter biofilm development and allows consistent mixed-species biofilm formation in a copious numbers of replicates.
Biofilm is difficult to thoroughly cure with conventional antibiotics due to the high mechanical stability and antimicrobial barrier resulting from extracellular polymeric substances. Encouraged by ...the great potential of magnetic micro-/nanorobots in various fields and their enhanced action in swarm form, we designed a magnetic microswarm consisting of porous Fe
O
mesoparticles (p-Fe
O
MPs) and explored its application in biofilm disruption. Here, the p-Fe
O
MPs microswarm (p-Fe
O
swarm) was generated and actuated by a simple rotating magnetic field, which exhibited the capability of remote actuation, high cargo capacity, and strong localized convections. Notably, the p-Fe
O
swarm could eliminate biofilms with high efficiency due to synergistic effects of chemical and physical processes: (i) generating bactericidal free radicals (•OH) for killing bacteria cells and degrading the biofilm by p-Fe
O
MPs; (ii) physically disrupting the biofilm and promoting •OH penetration deep into biofilms by the swarm motion. As a demonstration of targeted treatment, the p-Fe
O
swarm could be actuated to clear the biofilm along the geometrical route on a 2D surface and sweep away biofilm clogs in a 3D U-shaped tube. This designed microswarm platform holds great potential in treating biofilm occlusions particularly inside the tiny and tortuous cavities of medical and industrial settings.
This study assessed the conductivity of a Geobacter-enriched biofilm anode in a microbial electrochemical cell (MxC) equipped with two gold anodes (25 mM acetate medium), as different proton ...gradients were built throughout the biofilm. There was no pH gradient across the biofilm anode at 100 mM phosphate buffer (current density 2.38 A/m2) and biofilm conductivity (Kbio) was as high as 0.87 mS/cm. In comparison, an inner biofilm became acidic at 2.5 mM phosphate buffer in which dead cells were accumulated at ∼80 μm of the inner biofilm anode. At this low phosphate buffer, Kbio significantly decreased by 0.27 mS/cm, together with declined current density of 0.64 A/m2. This work demonstrates that biofilm conductivity depends on the composition of live and dead cells in the conductive biofilm anode.
Display omitted
•Relationship between proton accumulation and biofilm conductivity was studied.•Acidic pH at low buffer reduced microbial activity in Geobacter-enriched biofilm.•Electrical conductivity of biofilm anode significantly decreased at acidic pH.•Biofilm conductivity was associated with microbial activity.
Bacterial populations vary in their stress tolerance and population structure depending upon whether growth occurs in well-mixed or structured environments. We hypothesized that evolution in biofilms ...would generate greater genetic diversity than well-mixed environments and lead to different pathways of antibiotic resistance. We used experimental evolution and whole genome sequencing to test how the biofilm lifestyle influenced the rate, genetic mechanisms, and pleiotropic effects of resistance to ciprofloxacin in
populations. Both evolutionary dynamics and the identities of mutations differed between lifestyle. Planktonic populations experienced selective sweeps of mutations including the primary topoisomerase drug targets, whereas biofilm-adapted populations acquired mutations in regulators of efflux pumps. An overall trade-off between fitness and resistance level emerged, wherein biofilm-adapted clones were less resistant than planktonic but more fit in the absence of drug. However, biofilm populations developed collateral sensitivity to cephalosporins, demonstrating the clinical relevance of lifestyle on the evolution of resistance.
A hallmark of biofilms is their tolerance to killing by antimicrobial agents. In
, biofilm drug tolerance requires the c-di-GMP-responsive MerR transcriptional regulator BrlR. However, the mechanism ...by which BrlR mediates biofilm drug tolerance has not been elucidated. Here, we demonstrate that BrlR activates the expression of at least 7 ABC transport systems, including the PA1874-PA1875-PA1876-PA1877 (PA1874-77) operon, with chromatin immunoprecipitation and DNA binding assays confirming BrlR binding to the promoter region of PA1874-77. Insertional inactivation of the 7 ABC transport systems rendered
PAO1 biofilms susceptible to tobramycin or norfloxacin. Susceptibility was linked to drug accumulation, with BrlR contributing to norfloxacin accumulation in a manner dependent on multidrug efflux pumps and the PA1874-77 ABC transport system. Inactivation of the respective ABC transport system, furthermore, eliminated the recalcitrance of biofilms to killing by tobramycin but not norfloxacin, indicating that drug accumulation is not linked to biofilm drug tolerance. Our findings indicate for the first time that BrlR, a MerR-type transcriptional activator, activates genes encoding several ABC transport systems, in addition to multiple multidrug efflux pump genes. Moreover, our data confirm a BrlR target contributing to drug tolerance, likely countering the prevailing dogma that biofilm tolerance arises from a multiplicity of factors.
•Contaminant removal in the ABMFC was better than that in the MFC or AB alone.•62.93mW·m−2 power density and 6.26mg·L−1·d−1 lipid productivity were obtained.•Deltaproteobacteria grew well with algal ...biofilm but Betaproteobacteria did not.•Bioenergy of 0.094kWhperm3 of wastewater was obtained in continuous operation.
An algae biofilm microbial fuel cell (ABMFC) was established by integrating an algal biofilm (AB) with a microbial fuel cell (MFC) to facilitate the system’s operation for nutrient removal and bioenergy generation. In batch mode, the removal efficiencies of TN, TP and COD in the ABMFC reached 96.0%, 91.5% and 80.2%, respectively, which performed much better than MFC or AB alone. The highest power density of the ABMFC (62.93mW·m−2) was 18% higher than that of the MFC (52.33mW·m−2), and a lipid productivity of 6.26mg·L−1·d−1 could be obtained simultaneously. High-throughput sequencing revealed that Chlorobia and Deltaproteobacteria grew well in the symbiotic ABMFC system. Betaproteobacteria, versatile in organic pollutant degradation, was inhibited by algal biofilm; it may be due to the nutrients competitions between algae and Betaproteobacteria. It was proved that the ABMFC system was able to handle real, complex, variable wastewater in the continuous flow trials and a total energy of 0.094kWh·perm3 of wastewater was obtained in the process. This study not only developed a wastewater treatment and energy recovery method but also explored a better understanding of the mechanisms for the algae-bacteria system.
Biofilms are ubiquitous and their presence in industry can lead to production losses. However, nowhere do biofilms impact human health and welfare as much as those that are found contaminating the ...healthcare environment, surgical instruments, equipment, and medical implantable devices. Approximately 70% of healthcare-associated infections are due to biofilm formation, resulting in increased patient morbidity and mortality. Biofilms formed on medical implants are recalcitrant to antibiotic treatment, which leaves implant removal as the principal treatment option. In this book, we investigate the role of biofilms in breast and dental implant disease and cancer. We include in vitro models for investigating treatment of chronic wounds and disinfectant action against Candida sp. Also included are papers on the most recent strategies for treating biofilm infection ranging from antibiotics incorporated into bone void fillers to antimicrobial peptides and quorum sensing.
PDF
