Bacterial Biofilm Growth Research Articles

Bacterial nanotubes mediate bacterial growth on periodic nano-pillars.

Surface topography designed to achieve spatial segregation has shown promise in delaying bacterial attachment and biofilm growth. However, the underlying mechanisms linking surface topography to the inhibition of microbial attachment and growth still remain unclear. Here, we investigated bacterial attachment, cell alignment and biofilm formation of Pseudomonas aeruginosa on periodic nano-pillar surfaces with different pillar spacing. Using fluorescence and scanning electron microscopy, bacteria were shown to align between the nanopillars. Threadlike structures ("bacterial nanotubes") protruded from the majority of bacterial cells and appeared to link cells directly with the nanopillars. Using ΔfliM and ΔpilA mutants lacking flagella or pili, respectively, we further demonstrated that cell alignment behavior within nano-pillars is independent of the flagella or pili. The presence of bacteria nanotubes was found in all cases, and is not linked to the expression of flagella or pili. We propose that bacterial nanotubes are produced to aid in cell-surface or cell-cell connections. Nano-pillars with smaller spacing appeared to enhance the extension and elongation of bacterial nanotube networks. Therefore, nano-pillars with narrow spacing can be easily overcome by nanotubes that connect isolated bacterial aggregates. Such nanotube networks may aid cell-cell communication, thereby promoting biofilm development.

The Effects of Subcellular Nanograting Geometry on the Formation and Growth of Bacterial Biofilms.

Biofilm formation by bacteria protects them against environmental stresses such as desiccation, shear forces and antimicrobial agents, making them much harder to remove and increasing their virulence and persistence in industrial water systems and biomedical equipment. One promising method of disrupting biofilm formation and growth is to employ passive surface structures to inhibit bacterial adhesion and aggregation. However, most studies thus far have mainly focused on the early stages of biofilm formation and it is unclear if the influence of surface topography in the early phase will propagate to later stages. Here, we attempt to address this with an investigation into the biofilm formation of Pseudomonas aeruginosa on 25 different nanograting geometries, with dimensions that were systematically varied from subcellular to cellular sizes. The biofilms were characterized from the exponential growth phase to the decline phase, in intervals of 24 H over 4 days, using confocal scanning laser microscopy. Comparing the maximum volume of biofilm formed on each surface over 96 H, it was found that approximately 1/3 of the nanograting geometries exhibited 72 ± 16 % lower biovolume density than a flat surface. Bacteria on these nanogratings were also observed to form 40 ± 11 % smaller microcolonies that were 17 ± 6 % less compact than that found on the control surface. The majority of these nanogratings had deep trenches (i.e. depth ≥ 70% of the cell diameter). Furthermore, P. aeruginosa cells were observed to multiply at approximately twice the rate on almost all the nanogratings compared to flat surfaces, but these cell populations also began to decline 24 H earlier than those on a flat surface. Using available literature on P. aeruginosa, a qualitative model was put forth, attributing the results to increased cell motility, decreased exopolysaccharide formation and disrupted psl adhesin/signal trails on nanogratings. These factors, together, led to the net effects of reduced attachment, increased scattering of cells and rapid decline of the biofilms on nanogratings. The insights derived from this study suggest that passive surface geometries can be designed and optimized to successfully control/inhibit biofilm formation and growth.

Pulsed 450 nm blue light suppresses MRSA and Propionibacterium acnes in planktonic cultures and bacterial biofilms

In our recent study, we showed that pulsed blue light (PBL) suppresses the growth of Propionibacterium acnes more than continuous wave (CW) blue light in vitro, but it is not known that other bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA), respond similarly to PBL. The high potency of PBL relative to CW blue light makes it a suitable antimicrobial for suppressing bacterial growth in biofilms as well. Therefore, we determined if MRSA—a deadly bacterium of global concern—is susceptible to 450 nm PBL irradiation in vitro, and ascertained whether the bactericidal effect of PBL on planktonic P. acnes culture can be replicated in biofilms of P. acnes and MRSA. In three series of experiments, we irradiated P. acnes and MRSA respectively, either in planktonic cultures, forming biofilms or formed biofilms. Compared to controls, the results showed 100% bacterial suppression in planktonic cultures of MRSA irradiated with 3 mW/cm2 irradiance and 7.6 J/cm2 radiant exposure three times at 30-minute intervals, and also in P. acnes cultures irradiated with 2 mW/cm2 irradiance 5 J/cm2 radiant exposure thrice daily during each of 3 days. Irradiation of biofilms with the same irradiances and radiant exposures that gave 100% bacterial suppression in planktonic cultures resulted in disruption and disassembly of the architecture of MRSA and P. acnes biofilms, more so in forming biofilms than formed biofilms. The antimicrobial effect on each bacterium was minimal in forming biofilms, and even less in formed biofilms. Increasing radiant exposure slightly from 7.6 J/cm2 to 10.8 J/cm2 without changing any other parameter, yielded more disruption of the biofilm and fewer live MRSA and P. acnes, suggesting that 100% bacterial suppression is possible with further refinement of the protocol. In both planktonic cultures and biofilms, PBL suppressed MRSA more than P. acnes.

The Therapeutic Effect of 1,8-Cineol on Pathogenic Bacteria Species Present in Chronic Rhinosinusitis.

Chronic rhinosinusitis (CRS) is marked by an inflamed mucosa of sinuses and is accompanied by a significantly reduced quality of live. Since no guidelines for the treatment of CRS are available, long lasting clinical histories with health care costs adding up to dozens of billion $ annually are caused by CRS. The progression of CRS is often induced by bacterial infections and/or a shift in microbiome as well as biofilm formation. The exact microbiome alterations are still unclear and the impenetrable biofilm renders the treatment with common antibiotics ineffective. This study focuses on characterizing the microbiome changes in CRS and investigating the inhibition of biofilm growth by 1,8-Cineol, a small, non-polar and hence biofilm penetrating molecule with known antimicrobial potential. We performed MALDI-TOF MS based characterization of the microbiomes of healthy individuals and CRS patients (n = 50). The microbiome in our test group was shifted to pathogens (Staphylococcus aureus, Escherichia coli, and Moraxella catarrhalis). In contrast to published studies, solely based on cell culture techniques, we could not verify the abundance of Pseudomonas aeruginosa in CRS. The inhibition of bacterial proliferation and biofilm growth by 1,8-Cineol was measured for these three pathogens. Interestingly, S. aureus, the most prominent germ in CRS, showed a biofilm inhibition not simply correlated to its inhibition of proliferation. RT-qPCR confirmed that this was due to the downregulations of major key players in biofilm generation (agrA, SarA and σB) by 1,8-Cineol. Furthermore we verified this high biofilm inhibition potential in a model host system consisting out of S. aureus biofilm grown on mature respiratory epithelium. A second host model, comprising organotypic slices, was utilized to investigate the reaction of the innate immune system present in the nasal mucosa upon biofilm formation and treatment with 1,8-Cineol. Interestingly Staphylococcus epidermidis, the cause of very common catheter infections, possesses a biofilm generation pathway very similar to S. aureus and might be treatable in a similar fashion. The two presented in vitro model systems might be transferred to combinations of every biofilm forming bacterial with most kind of epithelium and mucosa.

Universal stress proteins contribute Edwardsiella piscicida adversity resistance and pathogenicity and promote blocking host immune response

Universal stress proteins (Usps) exist ubiquitously in bacteria and other organisms. Usps play an important role in adaptation of bacteria to a variety of environmental stresses. There is increasing evidence that Usps facilitate pathogens to adapt host environment and are involved in pathogenicity. Edwardsiella piscicida (formerly included in E. tarda) is a severe fish pathogen and infects various important economic fish including tilapia (Oreochromis niloticus). In E. piscicida, a number of systems and factors that are involved in stress resistance and pathogenesis were identified. However, the function of Usps in E. piscicida is totally unknown. In this study, we examined the expressions of 13 usp genes in E. piscicida and found that most of these usp genes were up-regulated expression under high temperature, oxidative stress, acid stress, and host serum stress. Particularly, among these usp genes, usp13, exhibited dramatically high expression level upon several stress conditions. To investigate the biological role of usp13, a markerless usp13 in-frame mutant strain, TX01Δusp13, was constructed. Compared to the wild type TX01, TX01Δusp13 exhibited markedly compromised tolerance to high temperature, hydrogen peroxide, and low pH. Deletion of usp13 significantly retarded bacterial biofilm growth and decreased resistance against serum killing. Pathogenicity analysis showed that the inactivation of usp13 significantly impaired the ability of E. piscicida to invade into host cell and infect host tissue. Introduction of a trans-expressed usp13 gene restored the lost virulence of TX01Δusp13. In support of these results, host immune response induced by TX01 and TX01Δusp13 was examined, and the results showed reactive oxygen species (ROS) levels in TX01Δusp13-infected macrophages were significantly higher than those in TX01-infected cells. The expression level of several cytokines (IL-6, IL-8, IL-10, TNF-α, and CC2) in TX01Δusp13-infected fish was significantly higher than that in TX01-infected fish. These results suggested that the deletion of usp13 attenuated the ability of bacteria to overcome the host immune response to pathogen infection. Taken together, our study indicated Usp13 of E. piscicida was not only important participant in adversity resistance, but also was essential for E. piscicida pathogenicity and contributed to block host immune response to pathogen infection.

HutZ is required for biofilm formation and contributes to the pathogenicity of Edwardsiella piscicida

Edwardsiella piscicida is a severe fish pathogen. Haem utilization systems play an important role in bacterial adversity adaptation and pathogenicity. In this study, a speculative haem utilization protein, HutZEp, was characterized in E. piscicida. hutZEp is encoded with two other genes, hutW and hutX, in an operon that is similar to the haem utilization operon hutWXZ identified in V. cholerae. However, protein activity analysis showed that HutZEp is probably not related to hemin utilization. To explore the biological role of HutZEp, a markerless hutZEp in-frame mutant strain, TX01ΔhutZ, was constructed. Deletion of hutZEp did not significantly affect bacterial growth in normal medium, in iron-deficient conditions, or in the presence of haem but significantly retarded bacterial biofilm growth. The expression of known genes related to biofilm growth was not affected by hutZEp deletion, which indicated that HutZEp was probably a novel factor promoting biofilm formation in E. piscicida. Compared to the wild-type TX01, TX01ΔhutZ exhibited markedly compromised tolerance to acid stress and host serum stress. Pathogenicity analysis showed that inactivation of hutZEp significantly impaired the ability of E. piscicida to invade and reproduce in host cells and to infect host tissue. In contrast to TX01, TX01ΔhutZ was defective in blocking host macrophage activation. The expression of hutZEp was directly regulated by the ferric uptake regulator Fur. This study is the first functional characterization of HutZ in a fish pathogen, and these findings suggested that HutZEp is essential for E. piscicida biofilm formation and contributes to host infection.

Synthesis of Novel 2-(Het)arylpyrrolidine Derivatives and Evaluation of Their Anticancer and Anti-Biofilm Activity.

A library of novel 2-(het)arylpyrrolidine-1-carboxamides were obtained via a modular approach based on the intramolecular cyclization/Mannich-type reaction of N-(4,4-diethoxybutyl)ureas. Their anti-cancer activities both in vitro and in vivo were tested. The in vitro activity of some compounds towards M-Hela tumor cell lines was twice that of the reference drug tamoxifen, whereas cytotoxicity towards normal Chang liver cell did not exceed the tamoxifen toxicity. In vivo studies showed that the number of surviving animals on day 60 of observation was up to 83% and increased life span (ILS) was up to 447%. Additionally, some pyrrolidine-1-carboxamides possessing a benzofuroxan moiety obtained were found to effectively suppress bacterial biofilm growth. Thus, these compounds are promising candidates for further development both as anti-cancer and anti-bacterial agents.

Acid‐Catalyzed Intramolecular Imination / Nucleophilic Trapping of 4‐Aminobutanal Derivatives: One‐Pot Access to 2‐(Pyrazolyl)pyrrolidines

A first successful synthesis of 2‐(pyrazolyl)pyrrolidines is reported starting from readily available reagents. A wide variety of N‐substituted 2‐(pyrazolyl)pyrrolidines are obtained with up to 96 % yield. The influence of the obtained compounds on biofilm formation by V. aquamarinus DSM 26054 and A. calcoaceticus VKPM B–10353 have been studied. Some of the tested compounds were found to suppress the growth of bacterial biofilms at nanomolar concentrations and thus are promising candidates for further studies.

The Use of Microbial Coatings, Nutrients and Chemical Defense Systems in Oyster Restoration

AbstractMany oyster species are keystone species that help mitigate shoreline erosion, provide habitats for juvenile fishes, and improve water quality. A number of human-driven factors have led to a decline in their populations worldwide. This article focuses on the chemistry of a novel substrate (nutrient-enriched concrete, or NEC) used to induce settlement and colonization of wild diploid oyster spat and is divided into four sections: (1) composition of the bulk material used for oyster restoration, (2) nutrients added to stimulate growth of bacterial and or algal biofilms, (3) nutrients included for the recently settled oyster spat, and (4) the potential use of natural chemical defense systems to control predators and competing marine life. The goal is to develop a material that can be manufactured and used on a large scale.

Self‐Stratifying Silicone Coating with Nonleaching Antifoulant for Marine Anti‐Biofouling

AbstractChemical immobilization of antifoulant groups to polymers is a promising approach to develop ecofriendly antifouling materials with static antifouling ability and a durable efficacy. In this work, telomer of dodecafluoroheptyl methacrylate (DFMA), triclosan acrylate (TA), and 3‐mercaptopropyl trimethoxysilane (KH590) is grafted to bis‐silanol terminated poly(dimethylsiloxane) (PDMS), yielding a novel self‐stratifying silicone coating containing nonleaching antifoulants. X‐ray photoelectron spectroscopy (XPS) analysis reveals that the antifoulant groups are enriched on the coating surface due to DFMA migration. Such a modified PDMS coating can significantly inhibit the growth of marine bacterial biofilm and the adhesion of diatoms owing to the nonleaching antifoulant groups. On the other hand, the coating exhibits a good fouling release performance since it inherits the low surface energy (≈20 mJ m−2) and low elastic modulus (<2 MPa) from PDMS forming a physically dynamic surface. Marine field tests demonstrate that the coating has excellent antifouling ability after immersion in natural seawater for more than 6 months.

Facile and Cost-Effective Ag Nanoparticles Fabricated by Lilium lancifolium Leaf Extract: Antibacterial and Antibiofilm Potential

In the present study one-pot green fabrication of silver nanoparticles (Ag NPs) with aqueous leaf extract of Lilium lancifolium. Synthesized Ag NPs were illustrated by UV–Vis, FT-IR, XRD, AFM and TEM analysis. A surface plasmon resonance peak was noticed at 411 nm in UV–Vis analysis. XRD patterns of Ag NPs showed high crystalline nature with face centered cubic structure. AFM and TEM analysis of Ag NPs exhibit special and anisotropic morphology with accurate particle size about 10–70 nm and average mean value of 45 nm. Ag NPs were tested for antibacterial and anti-biofilm activity against Gram positive and Gram-negative bacterial strains. The exposure to 25 µL exhibited better antibacterial activity and 50 µL significantly control the bacterial biofilm growth. Overall, the proposed green synthesis method of Ag NPs is facile, convenient, less time consuming and environmentally safe.

Thioredoxin H (TrxH) contributes to adversity adaptation and pathogenicity of Edwardsiella piscicida

Thioredoxins (Trxs) play an important role in defending against oxidative stress and keeping disulfide bonding correct to maintain protein function. Edwardsiella piscicida, a severe fish pathogen, has been shown to encode several thioredoxins including TrxA, TrxC, and TrxH, but their biological roles remain unknown. In this study, we characterized TrxH of E. piscicida (named TrxHEp) and examined its expression and function. TrxHEp is composed of 125 residues and possesses typical thioredoxin H motifs. Expression of trxHEp was upregulated under conditions of oxidative stress, iron starvation, low pH, and during infection of host cells. trxHEp expression was also regulated by ferric uptake regulator (Fur), an important global regulatory of E. piscicida. Compared to the wild type TX01, a markerless trxHEp in-frame mutant strain TX01∆trxH exhibited markedly compromised tolerance of the pathogen to hydrogen peroxide, acid stress, and iron deficiency. Deletion of trxHEp significantly retarded bacterial biofilm growth and decreased resistance against serum killing. Pathogenicity analysis shows that the inactivation of trxHEp significantly impaired the ability of E. piscicida to invade host cells, reproduce in macrophages, and infect host tissues. Introduction of a trans-expressed trxH gene restored the lost virulence of TX01∆trxH. There is likely to be a complex relationship of functional complementation or expression regulation between TrxH and another two thioredoxins, TrxA and TrxC, of E. piscicida. This is the first functional report of TrxH in fish pathogens, and the findings suggest that TrxHEp is essential for coping with adverse circumstances and contributes to host infection of E. piscicida.

Toward the Development of an Innovative Implant: NiTi Alloy Functionalized by Multifunctional β-TCP+Ag/SiO2 Coatings.

In recent years, one of the more important and costly problems of modern medicine is the need to replace or supplement organs in order to improve the quality of human life. In this field, promising solutions seem to have been implants which are based on NiTi alloys with shape memory effects. Unfortunately, this material is susceptible to the corrosion and release of toxic nickel to the human organism. Hence, its application as a long-term material is strongly limited. Therefore, this paper presents a new solution which should help to improve the functionality of the NiTi alloy and elongate its medical stability to use. The idea was focused on functionalization of the implant surface by a biocompatible, multifunctional coating without any impact on the features of the substrate, i.e., the martensitic transformation responsible for shape memory effects. For this purpose, we prepared a colloidal suspension, composed of β-TCP (particle size ∼450 nm) and the Ag/SiO2 nanocomposite which due to the electrophoretic deposition (EPD) led to the formation of structurally atypical calcium phosphosilicate coating. Those biomaterials formed a crack-free coating, adhering well to the NiTi surface when distributed over the entire surface, with low concentration of metallic and oxide silver (<3 at. %). At the same time, the coat-forming materials had resulted in the growth of a Gram-negative bacterial biofilm. Additionally, the additive of the silver-silica composite enhances cell proliferation, effectively a few times higher than commonly used coat-forming materials (e.g., pure β-TCP).

Live Cell Analysis of Shear Stress on Pseudomonas aeruginosa Using an Automated Higher-Throughput Microfluidic System.

A higher-throughput microfluidic in vitro bioreactor coupled with fluorescence microscopy has been used to study bacterial biofilm growth and morphology, including Pseudomonas aeruginosa (P. aeruginosa). Here, we will describe how the system can be used to study the growth kinetics and the morphological properties such as the surface roughness and textural entropy of P. aeruginosa strain PA01 that expresses an enhanced green fluorescent protein (PA01-EGFP). A detailed protocol will describe how to grow and seed PA01-EGFP cultures, how to set up the microscope and autorun, and conduct the image analysis to determine growth rate and morphological properties using a variety of shear forces that are controlled by the microfluidic device. This article will provide a detailed description of a technique to improve the study of PA01-EGFP biofilms which eventually can be applied towards other strains of bacteria, fungi, or algae biofilms using the microfluidic platform.

Microfluidic-based Growth and Imaging of Bacterial Biofilms

Biofilms are a ubiquitous form of growth for bacteria on surfaces in most environments, natural or manmade. Here we present a protocol using the Bioflux microfluidic system to investigate the organized structure and development of these multicellular communities. Microfluidic systems present an opportunity to grow biofilms in a stable, physiologically maintained environment that is readily observable via time-lapse microscopy.

Fabrication and in vitro behavior of dual-function chitosan/silver nanocomposites for potential wound dressing applications

We report the synthesis and in vitro evaluation of dual-function chitosan-silver nanoparticles (CTS-AgNPs) films with potential applications as wound dressings. We attempted to formulate nanocomposite films with appropriate AgNPs concentrations to simultaneously display antibacterial activity and suitability for cell culture. Nanocomposites were obtained by CTS-mediated in situ chemical reduction of AgNO3. Circular-shape AgNPs (sizes ca. 7–50 nm) well distributed within the CTS matrices were obtained in concentrations from 0.018 to 0.573 wt%. Efficacy (bacteriostatic and bactericidal properties) of CTS-AgNPs films to decrease planktonic and biofilm bacterial growth was AgNPs concentration- and bacteria strain-dependent. Films showed significant antibacterial activity against Gram-negative E. coli and P. aeruginosa and Gram-positive S. aureus. Antibacterial activity against S. epidermidis was moderated. Films suitability for cell culture was characterized using primary human fibroblasts (HF). HF displayed cell viability higher than 90% and the characteristic fusiform morphology of adhered fibroblast upon culture on films with AgNPs concentration ≤ 0.036 wt%. HF cultured on these films also showed positive expression of tropoelastin, procollagen type I and Ki-67, characteristic proteins of extracellular matrix and proliferative cells, respectively. In vitro assays demonstrated that cytocompatibility/antibacterial properties decreased/increased as silver concentration increased, suggesting that CTS-AgNPS nanocomposite films with ≈0.04–0.20 wt% might be considered as potential temporary dual-function wound dressings.

Antimicrobial Features of Organic Functionalized Graphene-Oxide with Selected Amines.

(1) Background: Graphene oxide is a new carbon-based material that contains functional groups (carboxyl, hydroxyl, carbonyl, epoxy) and therefore can be easily functionalized with organic compounds of interest, yielding hybrid materials with important properties and applications. (2) Methods: Graphene oxide has been obtained by a modified Hummers method and activated by thionyl chloride in order to be covalently functionalized with amines. Thus obtained hybrid materials were characterized by infrared and Raman spectroscopy, elemental analysis and scanning electron microscopy and then tested for their antimicrobial and anti-biofilm activity. (3) Results: Eight amines of interest were used to functionalize grapheme oxide and the materials thus obtained were tested against Gram-negative (Escherichia coli, Pseudomonas aeruginosa) and Gram-positive (Staphylococcus aureus) bacterial strainsin plankonic and biofilm growth state. Both amines, as well as the functionalized materials, exhibited anti-microbial features. Three to five functionalized graphene oxide materials exhibited improved inhibitory activity against planktonic strains as compared with the respective amines. In exchange, the amines alone proved generally more efficient against biofilm-embedded cells. (4) Conclusions: Such hybrid materials may have a wide range of potential use in biomedical applications.

Functional Enzyme Mimics for Oxidative Halogenation Reactions that Combat Biofilm Formation.

Transition-metal oxide nanoparticles and molecular coordination compounds are highlighted as functional mimics of halogenating enzymes. These enzymes are involved in halometabolite biosynthesis. Their activity is based upon the formation of hypohalous acids from halides and hydrogen peroxide or oxygen, which form bioactive secondary metabolites of microbial origin with strong antibacterial and antifungal activities in follow-up reactions. Therefore, enzyme mimics and halogenating enzymes may be valuable tools to combat biofilm formation. Here, halogenating enzyme models are briefly described, enzyme mimics are classified according to their catalytic functions, and current knowledge about the settlement chemistry and adhesion of fouling organisms is summarized. Enzyme mimics with the highest potential are showcased. They may find application in antifouling coatings, indoor and outdoor paints, polymer membranes for water desalination, or in aquacultures, but also on surfaces for food packaging, door handles, hand rails, push buttons, keyboards, and other elements made of plastic where biofilms are present. The use of natural compounds, formed in situ with nontoxic and abundant metal oxide enzyme mimics, represents a novel and efficient "green" strategy to emulate and utilize a natural defense system for preventing bacterial colonization and biofilm growth.

Enhanced antibacterial nanocomposite mats by coaxial electrospinning of polycaprolactone fibers loaded with Zn-based nanoparticles

ZnO and Zn acetate nanoparticles were embedded in polycaprolactone coaxial-fibers and uniaxial-fibers matrices to develop potential antibacterial nanocomposite wound dressings (mats). Morphology, composition, wettability, crystallinity and fiber structure of mats were characterized. Antibacterial properties of mats were tested against E. coli and S. aureus by turbidity and MTT assays. The effect of UVA illumination (prior to bacteria inoculation) on mats’ antibacterial activity was also studied. Results showed that a coaxial-fibers design maintained nanoparticles distributed in the outer-shell of fibers and, in general, enhanced the antibacterial effect of the mats, in comparison to conventional uniaxial-fibers mats. Results indicated that mats simultaneously inhibited planktonic and biofilm bacterial growth by, probably, two main antibacterial mechanisms; 1) release of Zn2+ ions (mainly from Zn acetate nanoparticles) and 2) photocatalytic oxidative processes exerted by ZnO nanoparticles. Antibacterial properties of mats were significantly improved by coaxial-fibers design and exposure to UVA-light prior to bacteria inoculation.

Microbial Corrosion Assessment of Ag-Doped Hybrid Coatings in a Microbial Fuel Cells System

Biofilms are able to change the electrochemical characteristics of passivable metals, creating anodic and cathodic areas and inducing electroactive effects that can directly influence the corrosion rate of the material in a specific environment. This kind of process is referred to as Microbial Influenced Corrosion (MIC), and, even if its mechanisms have been widely studied in literature, it remains a problem largely underestimated and difficult to prevent. A huge number of bacteria are generally involved in MIC process and one of the difficulties of carrying out laboratory tests is to reproduce this great variety. The technique employed in this study aims at overcoming these issues using a Microbial Fuel Cell (MFC) as environment to test the microbial corrosion behavior of metallic samples. In a MFC, fuel is typically composed of the organic substance dissolved in the solution that fills the anodic half-cell. Bacterial populations, inoculated in the anodic solution, build up an electroactive biofilm on the anode that catalyzes the fuel oxidation. In traditional fuel cells the anodic half-cell is separated from the cathodic one by an electrolytic membrane. In more simple MFC air-breathing systems, the biofilm growing on the cathode both consumes the oxygen diffusing through the pores, thereby guaranteeing anaerobic conditions to the anode, and catalyzes the oxygen reduction. The redox mechanisms of electroactive bacterial occurring on the anode and cathode in a MFC are similar to those involved in microbial corrosion. Therefore laboratory studies on electrophilic bacteria acting on microbial fuel cell electrodes, offer the possibility to study in well-defined anodic and cathodic regions, the mechanisms responsible for microbiological corrosion. This study, in particular, has been carried out in order to characterize the electrochemical behavior of Ag-doped hybrid coatings deposited on stainless steel. The hybrid coatings are based on epoxy resin formulations where the silver nanoparticles are produced in-situ with a bottom-up approach: the silver precursor undergoes a photoreduction reaction during the UV-curing process and leads to a microstructure with nanoparticles dispersed inside the polymeric matrix. The sample under study is inserted in the chamber of the fuel cell and connected to the two electrodes in order to be able to monitor and analyze the variation in time of the current flowing between each one of the three system nodes affected by the same bacteria pool. Both coated and uncoated stainless steel samples have been immersed in the MFC anodic chamber containing wastewater inoculated with swine manure and acetate (as fuel). The performance and growth of bacterial biofilm on the coated samples, in anaerobic conditions, have been investigated by means of anodic and cathodic polarization and electrochemical impedance spectroscopy (EIS). Eventually, the coatings and the biofilms have been morphologically characterized by means of field emission scanning electron microscopy.