First Stage Of Biofilm Formation Research Articles

Effect of pine oil on the adhesion and biofilm formation of Acidianus manzaensis on chalcopyrite

Pine oil, commonly used as a flotation frother, could affect the bioleaching process. The attachment and biofilm development of acidophiles on metal sulfides were essential for bioleaching. This study focused on the role of pine oil in the early adhesion and biofilm development by Acidianus manzaensis YN-25 on the chalcopyrite surface. It was revealed that pine oil had a negative effect on the adhesion amount of A. manzaensis on the chalcopyrite surface. After having reached adhesion equilibrium, the percentage of attached cells decreased as the concentration of pine oil increased. The addition of pine oil was found to decrease the negative charge of chalcopyrite and cells, resulting in a higher attraction of acid-base interaction energy and total interaction force. This ultimately led to a stronger adhesion force between chalcopyrite and A. manzaensis. While the addition of pine oil initially delayed the formation of cell microcolonies during the first stage of biofilm formation, which ultimately resulted in larger biofilm coverage compared with the control group. The microcolonies on the mineral surface were also larger and the corrosion pits were bigger with the addition of pine oil. Furthermore, the addition of pine oil weakened the passivation effect and promoted the biological dissolution of chalcopyrite. This study offers a better understanding of the effect of pine oil on the bioleaching of chalcopyrite.

Insights into the physical and chemical properties of struvite crystal surfaces in terms of the effectiveness of bacterial adhesion

In this paper, we present the results of research on the physicochemical properties of two selected faces of the struvite crystal, which is the main component of infectious urinary stones. Two main faces, (001) and (00overline{1}), ending the c-axis, were selected for the study. These faces are not related by symmetry relations, which means, among other things, that they should have a different atomic structure, which was confirmed experimentally. In addition, the studies show that the tested surfaces have hydrophilic properties, however, the (00overline{1}) face is more hydrophilic compared to the (001) face. The physicochemical properties of the crystal as a whole, as well as the physicochemical properties of these faces influence the magnitude of adhesion. The adhesive force in both water and artificial urine is greater for face (00overline{1}) compared to face (001). The assessment of the adhesion of Proteus mirabilis bacteria in artificial urine also shows that the adhesion is greater for face (00overline{1}) than for face (001). The adhesion of bacteria to the examined faces of the struvite crystal, and in particular the increased adhesion of bacteria to the face (00overline{1}), may be the first stage of biofilm formation, which may result in a high rate of recurrence of infectious urinary stones after treatment.

Antibiofilm Activity of 4-(Adamantyl-1)-1-(1-Aminobutyl) Benzol against Methicillin-Resistant Staphylococcus aureus

Staphylococcus aureus is a widespread opportunistic pathogen, causing community-acquired and nosocomial infections with both acute and chronic recurrent courses. The process of chronicity of the disease is provided by biofilms. Features of the structure and functioning of biofilms, in particular the presence of matrix, quorum sensing systems, persistent cells, and efflux pumps, provide microbial communities with resistance to antimicrobial drugs under their action in therapeutic concentrations. The insufficient eff ectiveness of modern antimicrobial chemotherapy against biofi lm microorganisms indicates the urgency of the problem to search for compounds with antibiofilm activity that can affect various stages of the biofilm formation and the formed biofilm. The aim of the study is to establish the antibiofilm activity of 4-(adamantyl-1)-1-(1-aminobutyl) benzol against methicillin-resistant S. aureus (MRSA) and to determine the mechanism of its action. Methods. The ability of adamantane-containing compound 4-(adamantyl-1)-1-(1-aminobutyl) benzol (AM-166) to prevent biofilm formation and destroy the formed biofilm of S. aureus was investigated on polystyrene plates by the sorption of gentian violet on its structures followed with desorption of the dye into the organic solvent. The viability of S. aureus cells at the first stage of biofilm formation and in the composition of mature biofilms was evaluated using specific dyes for living (acridine orange) and non-viable (propidium iodide) cells. Detection of genes responsible for antibiotic resistance and biofi lm formation was performed by the polymerase chain reaction (PCR) with detection of PCR products in agarose gel. Evaluation of the effect of AM-166 on the expression of genes regulating the biofilm formation (ica, agrA, sarA, and sigB) was investigated by the real-time PCR and semi-quantitative PCR. Results. It was found that the compound AM-166 shows activity against S. aureus biofilm formation. The most pronounced effect was registered at a concentration of 5.0 minimum inhibitory concentration (MIC) (92.3%.) Under the action of AM-166 on the formed 2-day biofilms, their destruction was marked: the biomass decreases by 30.9% at 5.0 MIC. According to the results of fluorescence microscopy, the adamantane derivative at 5.0 MIC helps to reduce the number of viable cells at different stages of formation of the S. aureus biofilm. The results of molecular genetic studies indicate that the ica gene expression is significantly inhibited by the action of subinhibitory concentrations of the compound AM-116. No significant changes in the expression of sarA, agrA, and sigB genes were registered. Conclusions. Experiments on the effect of adamantane derivative on S. aureus biofilms showed that the most pronounced activity of AM-116 was observed at the stage of biofilm formation, as evidenced by the inhibition of transcriptional activity of the ica gene responsible for early stages of the biofilm formation, in particular the adhesion of planktonic cells to the substrate.

Polysaccharide corona: The acetyl-rich envelope wraps the extracellular membrane vesicles and the cells of Shewanella vesiculosa providing adhesiveness

Bacterial extracellular membrane vesicles (EMVs) play an active role in many physiological and pathogenic processes. Here, we report the identification and the detailed structural characterization of the capsular polysaccharide from both cells and EMVs from Shewanella vesiculosa by NMR and chemical analysis. The polysaccharide consists of a pentasaccharide repeating unit containing neutral monosaccharides together with amino sugars, of which one has never been isolated from a natural source. The adhesion ability of the polymer both on synthetic surfaces, such as polystyrene nanoparticles and on vesicles with a bilayer mimicking the bacterial membrane in the presence and absence of lipopolysaccharide was investigated. In both cases, a “CPS-corona” that could be the first stage of biofilm formation was observed. The polymer also activates Caspases on colon cancer cells, making S. vesiculosa EMVs as natural nanocarriers for drug delivery.

Self-Sterilizing 3D-Printed Polylactic Acid Surfaces Coated with a BODIPY Photosensitizer.

Herein, we report the use of polylactic acid coated with a halogenated BODIPY photosensitizer (PS) as a novel self-sterilizing, low-cost, and eco-friendly material activated with visible light. In this article, polymeric surfaces were 3D-printed and treated with the PS using three simple methodologies: spin coating, aerosolization, and brush dispersion. Our studies showed that the polymeric matrix remains unaffected upon addition of the PS, as observed by dynamic mechanical analysis, Fourier transform infrared, scanning electron microscopy (SEM), and fluorescence microscopy. Furthermore, the photophysical and photodynamic properties of the dye remained intact after being adsorbed on the polymer. This photoactive material can be reused and was successfully inactivating methicillin-resistant Staphylococcus aureus and Escherichia coli in planktonic media for at least three inactivation cycles after short-time light exposure. A real-time experiment using a fluorescence microscope showed how bacteria anchored to the antimicrobial surface were inactivated within 30 min using visible light and low energy. Moreover, the material effectively eradicated these two bacterial strains on the first stage of biofilm formation, as elucidated by SEM. Unlike other antimicrobial approaches that implement a dissolved PS or non-sustainable materials, we offer an accessible green and economic alternative to acquire self-sterilizing surfaces with any desired shape.

Recent advances in anti-adhesion mechanism of natural antimicrobial agents on fresh produce

Bacterial adhesion is the first stage of biofilm formation. Adhesion and subsequent biofilm formation of foodborne pathogenic bacteria on food surface cause cross contamination, food spoilage and even diseases. Mature biofilm exhibits higher resistance to disinfectants or antimicrobials compared to initial biofilm. The initial adherent cells are very unstable, low resistant and can be easily eliminated from food surface. In recent years, plant extracts as green antimicrobials alternatives have drawn much attention of researchers in anti-adhesion. Furthermore, the combination of natural extracts with other agents (e.g. surfactant, nanoparticle, phage) at low concentration effectively restrain the adhesion of foodborne pathogenic bacteria. Understanding anti-adhesion mechanism is the key to increase the efficiency of natural antimicrobial agents and enhance their application in fresh produce industry. In this review, we summarized recent studies about the factors affecting bacterial adhesion, anti-adhesion mechanism and applications of natural antimicrobial agents to control adhesion and subsequent biofilm formation for enhancing food safety and food quality.

Investigations on biofilm forming bacteria involved in biocorrosion of carbon steel immerged in real wastewaters

Bacteria are able to construct biofilm adjacent to carbon steel surface and leading to the biocorrosion and metal deterioration. The impact of wasterwaters’ indigenious bacteria on biocorrosion of carbon steel was evaluated under different pH values (3,7 and 9), two chloride concentrations (0.5 g/L and 1.5 g/L), and for two wastewaters. In tannery wastewaters (TWW) and under pH 3, Pseudomonas aeruginosa sp. (MN788665) and Enterobacter aerogenes sp. (MN788688) were able to establish an irreversible adhesion on the first stage of biofilm formation on the carbon steel surface due to hydrophobic behaviour of the bacteria. However, under the same pH, bacteria from industrial wastewaters (IWW) such us Brevundimonas diminuta sp. (MN788672) and Enterobacter aerogenes sp. (MN788689) promote the reversible adhesion followed by a continuous attachment and consequently a limited biofilm. Subsequently, in TWW and 0.5 g/L of chlorides, indigenious bacteria like Enterobacter aerogenes sp. (MN790737) and Raoultella ornithinolytica sp. promote an irreversible attachment of biofilm enhanced by their hydrophobic property contrarily to the bacteria isolated in the medium at chloride concentration of 1.5 g/L. In IWW, 1.5 g/L of chlorides the biofilm attachment is reversible and therefore its inhibition role is of little influence.

Impact of Hydrodynamics on the First Stages of Biofilm Formation in Forward Osmosis with Spacers.

Initial deposition of bacteria is a critical stage during biofilm formation and biofouling development in membrane systems used in the water industry. However, the effects of hydrodynamic conditions on spatiotemporal deposition patterns of bacteria during the initial stages of biofilm formation remain unclear. Large field epifluorescence microscopy enabled in situ and real-time tracking of Bacillus subtilis in a forward osmosis system with spacers during the first 4 h of biofilm formation. This study quantitatively compares the spatiotemporal deposition patterns between different hydrodynamic conditions: high and low permeate water flux (6 or 30 L m-2 h-1) as well as high and low crossflow velocity (1 or 14 cm s-1). Low crossflow velocity and high permeate water flux maximized bacterial attachment to the membrane surface, which was 60 times greater (6 × 103 cells mm-2) than at high crossflow velocity and low permeate water flux (<100 cells mm-2). Imaging at 30 s intervals revealed three phases (i.e., lag, exponential, and linear) in the development of deposition over time. Quantification of spatial deposition patterns showed that an increase in the ratio of permeate water flux to crossflow velocity led to a homogeneous deposition, while a decrease had the opposite effect. The insights of this research indicate that an appropriate choice of hydrodynamic conditions can minimize bacteria accumulation prior to biofilm formation in new and cleaned FO membrane systems treating water of high fouling propensity.

Formation of microbial biofilms on stainless steel with different surface roughness

The physical essence of the formation and influence of bacteria on the surface of technological equipment in the dairy industry is considered as an essential factor leading to contamination of dairy products and is a major hygienic problem. The ability of microorganisms on the surfaces of technological equipment to form biofilm forms and requirements for steel grade, relief, and its roughness were analysed. The effect of surface roughness on promoting or preventing adhesion and reproduction of biofilm forms of bacteria, which reduce the efficiency of sanitary processing of dairy equipment and thereby increase the microbial contamination of dairy products with shortened shelf life, is substantiated. Research about the process of bacterial adhesion to the surface of metals with different roughness depending on the size and shape is presented. It is found that on the surface of stainless steel with roughness 2.687 ±0.014 micron film formation process in Escherichia coli and Staphylococcus aureus are similar from 3 to 24 hours and does not depend on the size of the bacteria, and accordingly allows us to argue that rod-shaped and coccid bacteria attach freely in the hollows of the roughness are the beginning of the process of the first stage of biofilm formation. It is found that on the surface of stainless steel with roughness 0.95 ±0.092 micron film formation process in S. aureus is more intense than in E. coli. Thus, within 3 hours of incubation, the density of biofilms formed S. aureus was 1.2 times bigger than biofilms E. coli, by the next 15 hours of incubation formed biofilms S. aureus were, on average, 1.3 times denser. It is established that S. aureus due to its spherical shape is able to fit in the hollows of the roughness 0.95 ±0.092 μm and faster to adhere to the surface at the same time. E. coli, due to its rod-like shape, with such surface roughness, can adhere to the cavities only over its entire length. It is proved that by surface roughness 0.63 ±0.087 μm film intensity S. aureus was, on average, 1.4 times faster than E. coli, for roughness 0.16 ±0.018 micron film formation process took place equally for S. aureus and E. coli, but biofilms were lower in density than those formed on roughness 0.63 ±0.087 micron. Studies suggest that the use of equipment in the dairy industry with a roughness of less than 0.5 microns will reduce the attachment of microorganisms to the surface and reduce the contamination of dairy products.

Evaluation of Biofilm Formation and Frequency of Genes Encoding Curli Fiber, Colanic Acid Capsule and F1c Fimberia Among Uropathogenic Escherichia coli Isolates With Strong Cell Surface Hydrophobicity

Background: The uropathogenic Escherichia coli (UPEC) is an important bacterium that colonizes the bladder mucous membrane as biofilm and causes urinary tract infection (UTI). In addition, UPEC favors long-term persistence and leads to relapses in untreatable UTI. Further, bacterial hydrophobic interactions play a role in bacterial adherence to the surface and facilitate biofilm formation due to adhesion. Similarly, cell surface hydrophobicity (CSH), fimbriae, curli fiber, and colanic capsule allow UPEC isolates to initiate infections. Considering the above-mentioned explanation, this study evaluated the association between genes encoding curli fimbriae, colanic acid (CA) capsule, and f1c fimbriae with biofilm formation and CSH among UPEC isolates. Methods: To this end, 100 Escherichia coli strains were isolated from the urine samples of the patients and were diagnosed by biochemical tests. Furthermore, a tissue culture plate method was used to determine the capacity of biofilm formation, followed by conducting microbial adhesion to hydrocarbons method for CSH determination. Finally, the presence of csgA, csgD, rcsA, rcsC, and foc genes was determined by applying polymerase chain reaction. Results: Totally, 40, 22, and 28 isolates had strong, moderate, and weak biofilm formation capacity, respectively. Moreover, 42 and 38 isolates had strong and moderate CSH. Similarly, among the isolates with strong CSH, 32, 13, and 5 isolates had strong, moderate and weak biofilm formation capacity and the prevalence of csgA, csgD, rcsA, and foc genes was 33, 35, 35, 16, and 29, respectively. Based on the findings, no significant difference was observed between the frequency of csgA, csgD, rcsA, rcsC, and foc genes among the strong, moderate, and weak biofilm producers. Conclusions: In general, there is an association between CSH and the biofilm formation of UPEC isolates. This result showed the role of CSH as an effective factor on bacterial adhesion for the first stage of biofilm formation. However, differentiating the strains is not confirmed regarding their ability to form biofilms and their CSH and the presence of all studied genes.

Control of primary adhesion of microorganisms and formation of biofilms on stomatological materials used for transdental implantation in dental stabilizing operations.

Transdental implantation is an effective way to restore the lost biomechanical properties of a resected or amputated tooth. The choice of structural materials for the implant is the most important stage of treatment, in relation to the adhesion of aggressive microbiota to them. To characterize the adhesion of microorganisms of periodontopathogenic and cariogenic groups in vitro to experimental samples of zirconium dioxide and titanium alloys using cultural and electronic microscopic methods of adhesion evaluation as the first stage of biofilm formation. Samples for the experiment were prepared in the form of a tablet of standard form, on which the test strains were applied in an amount of 106CFU/ml. After shaking the unattached cells with ultrasound, they were seeded into dense nutrient medium to determine their number. In total, 14 strains of perodontopathogenic and cariogenic groups (including 3 reference strains) were used in the experiment. Scanning electron microscopy was used to visualize the adhesion of microorganisms. The results of the adhesion test to titanium nickelide and zirconium dioxide showed a significant reduction in adhesion for all microorganism species. In all variants (with all strains) the adhesion values to titanium nickelide and zirconium dioxide were statistically significantly lower than when using samples from a traditional titanium alloy. In scanning electron microscopy, single cells of test strains of perodontopathogenic microorganisms were determined on zirconium dioxide samples, while a considerable number of cells and the initial phase of biofilm formation were observed on the compared structural materials. Zirconium dioxide can be considered as an optimal choice material for the manufacture of transdental implants, which, in terms of its technological characteristics and low adhesion characteristics of microbes, is superior to the traditionally used titanium alloys.

Molecular interactions and inhibition of the staphylococcal biofilm-forming protein SdrC

Staphylococcus aureus forms biofilms on indwelling medical devices using a variety of cell-surface proteins. There is growing evidence that specific homophilic interactions between these proteins represent an important mechanism of cell accumulation during biofilm formation, but the underlying molecular mechanisms are still not well-understood. Here we report the direct measurement of homophilic binding forces by the serine-aspartate repeat protein SdrC and their inhibition by a peptide. Using single-cell and single-molecule force measurements, we find that SdrC is engaged in low-affinity homophilic bonds that promote cell-cell adhesion. Low-affinity intercellular adhesion may play a role in favoring biofilm dynamics. We show that SdrC also mediates strong cellular interactions with hydrophobic surfaces, which are likely to be involved in the initial attachment to biomaterials, the first stage of biofilm formation. Furthermore, we demonstrate that a peptide derived from β-neurexin is a powerful competitive inhibitor capable of efficiently blocking surface attachment, homophilic adhesion, and biofilm accumulation. Molecular modeling suggests that this blocking activity may originate from binding of the peptide to a sequence of SdrC involved in homophilic interactions. Our study opens up avenues for understanding the role of homophilic interactions in staphylococcal adhesion, and for the design of new molecules to prevent biofilm formation during infection.

Forces guiding staphylococcal adhesion.

Staphylococcus epidermidis and Staphylococcus aureus are two important nosocomial pathogens that form biofilms on indwelling medical devices. Biofilm infections are difficult to fight as cells within the biofilm show increased resistance to antibiotics. Our understanding of the molecular interactions driving bacterial adhesion, the first stage of biofilm formation, has long been hampered by the paucity of appropriate force-measuring techniques. In this minireview, we discuss how atomic force microscopy techniques have enabled to shed light on the molecular forces at play during staphylococcal adhesion. Specific highlights include the study of the binding mechanisms of adhesion molecules by means of single-molecule force spectroscopy, the measurement of the forces involved in whole cell interactions using single-cell force spectroscopy, and the probing of the nanobiophysical properties of living bacteria via multiparametric imaging. Collectively, these findings emphasize the notion that force and function are tightly connected in staphylococcal adhesion.

Assessment of the antifouling effect of five different treatment strategies on a seawater cooling system

Biofouling is a complex and important problem in cooling systems using water from natural sources such as lakes, rivers and sea. The first stage of biofilm formation is the colonization and uncontrolled microbial growth on surfaces.The aim of this study was to evaluate and to compare the effectiveness of different antifouling treatments in a heat exchanger cooled by seawater. Two types of experiments were carried out. Firstly, by employing a pilot plant simulating an industrial heat exchanger, chlorination and its combination with other treatments (UV and copper ions) were tested and the formed fouling was monitored and quantified. Then, the disinfection effectiveness of biocides employed was checked on two marine bacteria in order to identify the antifouling action mechanism.The combination of chlorine and copper was the most effective strategy for mitigation of fouling growth. After 60 days of testing, the thermal resistance showed no significant increase and the total solids accumulated inside the test tube were reduced by 70% compared to control treatment. The effectiveness of chlorine–copper treatment against fouling is probably due to a combination of their synergic inactivation mechanisms under prolonged exposure times, such as those of fouling experiments (60 days).The effectiveness of antifouling treatment was not only affected by the concentration of chlorine in the cooling water, but also by the dosage pattern. A chlorine peak of 0.4 mg L−1 for 1 h a day over the concentration of control (0.12 mg L−1) was able to reduce the increment in Rf and the accumulation of solids by approximately 50%.The combined use of chlorine and copper as antifouling treatment can be recommended in specific cooling systems that use seawater.

Online monitoring of biofouling using coaxial stub resonator technique

Here we demonstrate the proof-of-principle that a coaxial stub resonator can be used to detect early stages of biofilm formation. After promising field tests using a stub resonator with a stainless steel inner conductor as sensitive element, the sensitivity of the system was improved by using a resonator of shorter physical length, implying higher resonance frequencies (and by that a higher frequency range of operation) and improved sensitivity towards dispersion. In addition, the space between inner and outer conductor was filled up with glass beads, thereby exploiting the larger surface area available for biofilm formation.Analysis of the biofilm and the stub resonator signal, both as function of time, indicates that the sensor allows detection of early stages of biofilm formation. In addition, the sensor signal clearly discriminates between the first stages of biofilm formation (characterized by separated, individual spots of bacterial growth on the glass beads) and the presence of a nearly homogeneous biofilm later on in time. Model simulations based on the transmission line theory predict a shift of the sensor response in the same direction and order of magnitude as observed in the biofouling experiments, thereby confirming the operating principle of the sensor.

Reprint of “Inhibition of biofilm formation by Camelid single-domain antibodies against the flagellum of Pseudomonas aeruginosa”

Pseudomonas aeruginosa is a leading cause of hospital-acquired infections in patients with compromised host defense mechanisms, including burn wound victims. In addition to its intrinsic resistance against most antibiotics, P. aeruginosa has the ability to form biofilms adhering to biotic or abiotic surfaces. These factors make treatment of P. aeruginosa infections complicated and demand new therapies and drugs. The flagellum of P. aeruginosa plays an important role in cell–cell and cell–surface interactions during the first stage of biofilm formation. In this study, we describe the selection of monoclonal anti-flagellin single-domain antibodies (VHHs) derived from the Camelid heavy-chain antibody repertoire of a llama immunized with P. aeruginosa antigens. The anti-flagellin VHHs could be produced efficiently in Saccharomyces cerevisiae, and surface plasmon resonance experiments demonstrated that they have apparent affinities in the nanomolar range. Functional screens showed that the anti-flagellin VHHs are capable of inhibiting P. aeruginosa from swimming and that they prevent biofilm formation in an in vitro assay. These data open doors for the development of novel methods for the prevention of P. aeruginosa-related infections.

Inhibition of biofilm formation by Camelid single-domain antibodies against the flagellum of Pseudomonas aeruginosa

Pseudomonas aeruginosa is a leading cause of hospital-acquired infections in patients with compromised host defense mechanisms, including burn wound victims. In addition to its intrinsic resistance against most antibiotics, P. aeruginosa has the ability to form biofilms adhering to biotic or abiotic surfaces. These factors make treatment of P. aeruginosa infections complicated and demand new therapies and drugs. The flagellum of P. aeruginosa plays an important role in cell–cell and cell–surface interactions during the first stage of biofilm formation. In this study, we describe the selection of monoclonal anti-flagellin single-domain antibodies (VHHs) derived from the Camelid heavy-chain antibody repertoire of a llama immunized with P. aeruginosa antigens. The anti-flagellin VHHs could be produced efficiently in Saccharomyces cerevisiae, and surface plasmon resonance experiments demonstrated that they have apparent affinities in the nanomolar range. Functional screens showed that the anti-flagellin VHHs are capable of inhibiting P. aeruginosa from swimming and that they prevent biofilm formation in an in vitro assay. These data open doors for the development of novel methods for the prevention of P. aeruginosa-related infections.

The Global Anaerobic Regulator Anr, Is Involved in Cell Attachment and Aggregation Influencing the First Stages of Biofilm Development in Pseudomonas extremaustralis

Pseudomonas extremaustralis is a versatile Antarctic bacterium, able to grow under microaerobic and anaerobic conditions and is related to several non-pathogenic Pseudomonads. Here we report on the role of the global anaerobic regulator Anr, in the early steps of P. extremaustralis biofilm development. We found that the anr mutant was reduced in its ability to attach, to form aggregates and to display twitching motility but presented higher swimming motility than the wild type. In addition, microscopy revealed that the wild type biofilm contained more biomass and was thicker, but were less rough than that of the anr mutant. In silico analysis of the P. extremaustralis genome for Anr-like binding sites led to the identification of two biofilm-related genes as potential targets of this regulator. When measured using Quantitative Real Time PCR, we found that the anr mutant expressed lower levels of pilG, which encodes a component of Type IV pili and has been previously implicated in cellular adhesion. Levels of morA, involved in signal transduction and flagella development, were also lower in the mutant. Our data suggest that under low oxygen conditions, such as those encountered in biofilms, Anr differentially regulates aggregation and motility thus affecting the first stages of biofilm formation.

Surface Cell Density Effects on Escherichia coli Gene Expression during Cell Attachment

Escherichia coli attachment to a surface initiates a complex series of interconnected signaling and regulation pathways that promote biofilm formation and maturation. The present work investigates the effect of deposited cell density on E. coli cell physiology, metabolic activity, and gene expression in the initial stages of biofilm development. Deposited cell density is controlled by exploiting the relationship between ionic strength and bacterial attachment efficiency in a packed bed column. Distinct differences in cell transcriptome are analyzed by comparing sessile cultures at two different cell surface densities and differentiating ionic strength effects by analyzing planktonic cultures in parallel. Our results indicate that operons regulating trypotophan production and the galactitol phosphotransferase system (including dihydroxyacetone phosphate synthesis) are strongly affected by cell density on the surface. Additional transcriptome and metabolomic impacts of cell density on succinate, proline, and pyroglutamic acid systems are also reported. These results are consistent with the hypothesis that surface cell density plays a major role in sessile cell physiology, commencing with the first stage of biofilm formation. These findings improve our understanding of biofilm formation in natural and engineered environmental systems and will contribute to future work ranging from pathogen migration in the environment to control of biofouling on engineered surfaces.

Antiadhesive activity of the biosurfactant pseudofactin II secreted by the Arctic bacterium Pseudomonas fluorescensBD5

BackgroundPseudofactin II is a recently identified biosurfactant secreted by Pseudomonas fluorescens BD5, the strain obtained from freshwater from the Arctic Archipelago of Svalbard. Pseudofactin II is a novel compound identified as cyclic lipopeptide with a palmitic acid connected to the terminal amino group of eighth amino acid in peptide moiety. The C-terminal carboxylic group of the last amino acid forms a lactone with the hydroxyl of Thr3.Adhesion is the first stage of biofilm formation and the best moment for the action of antiadhesive and anti-biofilm compounds. Adsorption of biosurfactants to a surface e.g. glass, polystyrene, silicone modifies its hydrophobicity, interfering with the microbial adhesion and desorption processes. In this study the role and applications of pseudofactin II as a antiadhesive compound has been investigated from medicinal and therapeutic perspectives.ResultsPseudofactin II lowered the adhesion to three types of surfaces (glass, polystyrene and silicone) of bacterial strains of five species: Escherichia coli, Enterococcus faecalis, Enterococcus hirae, Staphylococcus epidermidis, Proteus mirabilis and two Candida albicans strains. Pretreatment of a polystyrene surface with 0.5 mg/ml pseudofactin II inhibited bacterial adhesion by 36-90% and that of C. albicans by 92-99%. The same concentration of pseudofactin II dislodged 26-70% of preexisting biofilms grown on previously untreated surfaces. Pseudofactin II also caused a marked inhibition of the initial adhesion of E. faecalis, E. coli, E. hirae and C. albicans strains to silicone urethral catheters. The highest concentration tested (0.5 mg/ml) caused a total growth inhibition of S. epidermidis, partial (18-37%) inhibition of other bacteria and 8-9% inhibition of C. albicans growth.ConclusionPseudofactin II showed antiadhesive activity against several pathogenic microorganisms which are potential biofilm formers on catheters, implants and internal prostheses. Up to 99% prevention could be achieved by 0.5 mg/ml pseudofactin II. In addition, pseudofactin II dispersed preformed biofilms. Pseudofactin II can be used as a disinfectant or surface coating agent against microbial colonization of different surfaces, e.g. implants or urethral catheters.