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Aims: The antibiofilm activity of endophytic fungus Nigrospora sphaerica CL-OP30 isolated from Swietenia macrophylla King was investigated. Methodology and results: The ability of the fungal endophytic crude extract to impede Streptococcus mutans biofilm formation was preliminarily screened with Congo red agar test. It was proven that S. mutans biofilm formation was hindered on the agar supplemented with the fungal endophytic crude extract. The antibiofilm activity of the fungal endophytic crude extract was evaluated using a microtiter plate method on both initially formed and preformed biofilm. Antibiofilm activity was recorded in a concentration-dependent pattern whereby higher concentrations reduced biofilm formation better than the lower concentrations of extract for both initially formed and preformed biofilm. The architecture of biofilm tested with fungal endophytic crude extract was also observed. Visualization under a light microscope and SEM revealed that the adherence of S. mutans biofilm treated with fungal endophytic crude extract was significantly reduced in both initially formed and preformed biofilm. In addition, observation under SEM showed that the matrices surrounding the bacterial cells were disintegrated and bacterial cells in biofilm completely lost their original shape. The overall data demonstrated that the ethyl acetate N. spaherica CL-OP30 crude extract showed good antibiofilm activity. Conclusion, significance and impact of study: The antibiofilm study suggested the potential of N. sphaerica CL-OP30 crude extract against S. mutans biofilm by disrupting the biofilm formation, the disintegration of matrices surrounding the biofilm and responsible for the formation of irregular cell shape. This extract may have a promising potential to be developed as an antibiofilm agent. [ABSTRACT FROM AUTHOR]

Aim: To assess in a cross‐sectional clinical study the effect of antibiotics on the diversity, structure and metabolic pathways of bacterial communities in various oral environments in patients with acute primary infections. Methodology: Samples of saliva (SA), supragingival biofilm (SB) and from the pulp cavity (PC) were collected from teeth with acute primary infections and then grouped according to previous use of antibiotics (NoAtb = no antibiotics [n = 6]; Atb = antibiotics [n = 6]). DNA sequencing was conducted using MiSeq (Illumina, San Diego, CA, USA). The V1–V3 hyper‐variable region of the 16S rRNA gene was amplified. A custom Mothur pipeline was used for 16S rRNA processing. Subsequent analyses of the sequence dataset were performed in R (using vegan, phyloseq and ggplot2 packages) or QIIME. Results: Twelve patients aged from 22 to 56 years were recruited. Participants in the Atb group had taken the beta‐lactamics amoxicillin (5/6) or cephalexin (1/6) for 2–3 days. A total of 332 bacterial taxa (OTUs) were identified, belonging to 120 genera, 60 families and nine phyla. Firmicutes (41%) and Bacteroidetes (38%) were the most abundant phyla in all samples. Taxa clustered significantly by oral site (PCoA analysis; P < 0.05, ANOSIM). Use of antibiotics had little effect on this clustering. However, SA, SB and PC had different degrees of richness, diversity and evenness. The greatest diversity was observed in SB samples and the least diversity was observed in PC samples. Metabolic prediction identified 163 pathways and previous use of antibiotics had a major effect on the estimated functional clustering in SA and PC samples. Conclusion: The ecological niche had a strong influence on the bacterial content of samples from various oral sites. Previous exposure to antibiotics may exert an effect on the phylogenetic composition of SA. Metabolic pathways appear to be modulated by antimicrobial agents in SA and PC samples. The dynamics of host/microbial interactions in the apical region and the functional ecology of the infected pulp cavity should be revisited. [ABSTRACT FROM AUTHOR]

Two ruthenium polypyridyl complexes: [Ru(dmb)2(ETPIP)](ClO4)2 (Ru(II)-1) and [Ru(phen)2(ETPIP)](ClO4)2 (Ru(II)-2) (dmb = 4,4′-dimethyl-2,2′-bipyridine, phen = 1,10-phenanthroline, ETPIP = 2-(4-(thiophen-2-ylethynyl)phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline), have been synthesized and characterized. Their antimicrobial activities against S. aureus were assessed. Both the complexes Ru(II)-1, and Ru(II)-2 show meaningful activity against Staphylococcus aureus and the lead complex of this set, Ru(II)-2 (MIC = 0.025 mg mL−1), was further tested against biofilms. Given the fact that S. aureus could easily develop resistance to common antimicrobials, we also investigated whether bacteria can easily develop resistance to Ru(II)-2. The result demonstrated that S. aureus did not easily develop resistance to the ruthenium complexes. In addition, the synergism between Ru(II)-2 and common antibiotics against S. aureus was also investigated using the checkerboard method. Interestingly, Ru(II)-2 could increase the susceptibility of S. aureus to the aminoglycoside antibiotic (kanamycin). Finally, a possible mechanism of the observed synergetic effects was investigated by real-time PCR. All in all, these results confirmed that ruthenium complexes have good antimicrobial activity against Staphylococcus aureus. [ABSTRACT FROM AUTHOR]

Background: The appearance of MDR strains and the development of biofilms make Pseudomonas aeruginosa infections a therapeutic challenge. To overcome this scenario, bacteriocins have been proposed as a potential adjuvant or alternative to antibiotic treatment.Objectives: To study the activity of R-pyocins on biofilms and in a murine model of pneumonia using a high-risk clone of P. aeruginosa.Methods: The activity of R-pyocins on P. aeruginosa biofilms was tested on bacteria attached to a silicone surface, before and after biofilm formation. The effectiveness of R1-pyocin was studied in a murine model of pneumonia using ST175, a high-risk clone of P. aeruginosa.Results: R-pyocins attacked adherent bacteria, preventing biofilm formation, and penetrated into the biofilm, killing P. aeruginosa within it, resulting in a dramatic reduction in bacterial load. R1-pyocin was active in a murine model of P. aeruginosa lung infection, administered before infection as a preventive treatment, and in acute pneumonia, with efficiency higher than standard colistin treatment. In addition, this work is the first to describe histopathological lung changes after administration of R-pyocins, contributing to the resolution of P. aeruginosa pneumonia in a murine model.Conclusions: This work highlights the potential use of the R-pyocins as therapeutic agents, alone or as adjuvants, due to its effectiveness on biofilms and in a murine model of pneumonia using ST175, a high-risk clone of P. aeruginosa. It may thus be feasible to consider R-pyocins as a possible therapeutic alternative in XDR infections, where treatment alternatives are limited. [ABSTRACT FROM AUTHOR]

Four new Schiff bases have been synthesized. The effectiveness of ferrocene systems in inhibiting formation of Staphylococcus aureus biofilms is tested. One of studied ferrocene Schiff bases efficiently inhibits formation of methicillin-sensitive Staphylococcus aureus (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA) biofilms. [ABSTRACT FROM AUTHOR]

Streptococci from the mitis group (represented mainly by Streptococcus mitis, Streptococcus oralis, Streptococcus sanguinis and Streptococcus gordonii) form robust biofilms with Candida albicans in different experimental models. These microorganisms have been found in polymicrobial biofilms forming on titanium biomaterial surfaces in humans with peri-implant disease. The purpose of this work was to study mutualistic interactions in biofilms forming on titanium and their effect on the adjacent mucosa, using a relevant infection model. Single and mixed biofilms of C. albicans and each Streptococcus species were grown on titanium disks. Bacterial and fungal biovolume and biomass were quantified in these biofilms. Organotypic mucosal constructs were exposed to preformed titanium surface biofilms to test their effect on secretion of proinflammatory cytokines and cell damage. C. albicans promoted bacterial biofilms of all mitis Streptococcus species on titanium surfaces. This relationship was mutualistic since all bacterial species up-regulated the efg1 hypha-associated gene in C. albicans. Mixed biofilms caused increased tissue damage, but did not increase proinflammatory cytokine responses compared to Candida alone. Interestingly, spent culture media from tissues exposed to titanium biofilms suppressed Candida growth on titanium surfaces. [ABSTRACT FROM AUTHOR]

Aim: To investigate the null hypothesis that neither the surface conditioning (collagen, serum, saliva) of hydroxyapatite (HA) discs, nor the biofilm age (3 days vs. 21 days) has a significant effect on the cellular and matrix composition of biofilms, using Enterococcus faecalis as the model organism. Methodology: Sterile HA discs were conditioned with collagen, saliva or serum, and inoculated with E. faecalis to form 3‐day and 21‐day‐old biofilms. Unconditioned discs served as controls. The biofilms were analysed using culture‐dependent and independent (confocal microscopy and biochemical analysis) methods, to determine the colony‐forming units and the biofilm matrix composition (polysaccharides and proteins), respectively. Statistical analyses were performed using appropriate parametric and nonparametric tests (P = 0.05). Results: Collagen conditioning significantly increased the number of CFUs in the 21‐day biofilms, compared to the 3‐day biofilms (P < 0.05). Although the biochemical analysis revealed that surface conditioning had no significant effect on the total carbohydrate content in the 21‐day biofilms, confocal microscopic analysis revealed that collagen and saliva conditioning selectively increased the polysaccharide content of 21‐day biofilms, compared to the 3‐day biofilms (P < 0.05). Conclusions: The results of this study raise an important methodological concern that the substrate conditioning substances and biofilm age differentially influence the cellular and extracellular matrix components of E. faecalis biofilms. [ABSTRACT FROM AUTHOR]

Summary: Settlement of many benthic marine invertebrates is stimulated by bacterial biofilms, although it is not known if patterns of settlement reflect microbial communities that are specific to discrete habitats. Here, we characterized the taxonomic and functional gene diversity (16S rRNA gene amplicon and metagenomic sequencing analyses), as well as the specific bacterial abundances, in biofilms from diverse nearby and distant locations, both inshore and offshore, and tested them for their ability to induce settlement of the biofouling tubeworm Hydroides elegans, an inhabitant of bays and harbours around the world. We found that compositions of the bacterial biofilms were site specific, with the greatest differences between inshore and offshore sites. Further, biofilms were highly diverse in their taxonomic and functional compositions across inshore sites, while relatively low diversity was found at offshore sites. Hydroides elegans settled on all biofilms tested, with settlement strongly correlated with bacterial abundance. Bacterial density in biofilms was positively correlated with biofilm age. Our results suggest that the localized distribution of H. elegans is not determined by 'selection' to locations by specific bacteria, but it is more likely linked to the prevailing local ecology and oceanographic features that affect the development of dense biofilms and the occurrence of larvae. [ABSTRACT FROM AUTHOR]

Introduction Dental unit waterlines (DUWLs) are notorious for being contaminated with different bacterial species including the opportunistic pathogen Pseudomonas aeruginosa which poses a risk to patients and professionals. This work aimed at studying the occurrence and biofilm-forming ability (BFA) of P. aeruginosa in the output of DUWLs in a dental center in Egypt. Methods Water samples were collected from the outlets of the high-speed hand piece, the air/water syringe and the cup filler waterlines. Bacteriological analysis included heterotrophic plate count (HPC), isolation and identification of P. aeruginosa and determination of the antimicrobial susceptibility and the BFA of the isolates by tissue culture plate (TCP) method and tube method (TM). Results The average concentration of HPC bacteria in the output of the 3 DUWLs was 2.9×104 CFU/mL where 88.3% of the samples exceeded the Egyptian standards for drinking water (<50 CFU/mL). P. aeruginosa was isolated from nine cup filler samples (which had a water source different from the other waterlines). The isolates were sensitive to all tested antimicrobials. Of these nine isolates, 6, 5 and 4 were positive for BFA by TCP, modified TCP and TM, respectively. Conclusions More stringent measures are required to ensure safer dental water; as the majority of studied samples exceeded the required HPC bacterial limit and P. aeruginosa isolates were detected. P. aeruginosa isolates from DUWLs may not be as resistant to antibiotics as what is reported in the literature about clinical isolates. Some P. aeruginosa isolates can colonize DUWLs despite their inability to form biofilms in experimental testing. [ABSTRACT FROM AUTHOR]

We evaluated the antifungal and antibiofilm potential of the hydroalcoholic extract of bark from Anadenanthera colubrina (vel l.) Brenan, known as Angico, against Candida spp. Antifungal activity was evaluated using the microdilution technique through the Minimum Inhibitory and Fungicide Concentrations (MIC and MFC). The antibiofilm potential was tested in mature biofilms formed by Candida species and analyzed through the counting of CFU/mL and scanning electron micrograph (SEM). In vivo toxicity and therapeutic action was evaluated in the Galleria mellonella model. The treatment with the extract, in low doses, was able to reduce the growth of planktonic cells of Candida species. MIC values range between 19.5 and 39 µg/mL and MFC values range between 79 and 625 µg/mL. In addition was able to reduce the number of CFU/mL in biofilms and to cause structural alteration and cellular destruction, observed via SEM. A. colubrina showed low toxicity in the in vivo assay, having not affected the viability of the larvae at doses below 100mg/kg and high potential in the treatment of C. albicans infection. Considering its high antifungal potential, its low toxicity and potential to treatment of infections in in vivo model, A. colubrina extract is a strong candidate for development of a new agent for the treatment of oral candidiasis. [ABSTRACT FROM AUTHOR]

Mycobacterium abscessus complex can cause severe lung infections and has proven to be a serious threat to patients with cystic fibrosis and a challenge for clinicians due to difficulties in timely diagnosis and complex multidrug treatment regimes. Mycobacterial culture is the gold standard for diagnosis, but in most cystic fibrosis centers it is performed less frequently than culture for other pathogens. Consensus today recommends just one annual mycobacterial culture for asymptomatic patients with cystic fibrosis, a strategy likely to lead to diagnostic delays. Postponement of diagnosis might be the deciding factor in whether an early colonization turns into chronic infection. This review highlights the latest developments in knowledge about the pathogenicity and clinical consequences of M. abscessus complex pulmonary disease, addressing the central theme of why pulmonary infection requires early identification and aggressive antibiotic treatment. The window of opportunity, before M. abscessus complex transforms from a mucosal colonizer to a chronic biofilm infection, is where microbial eradication is most likely to be successful, making early diagnosis essential for improved outcomes. [ABSTRACT FROM AUTHOR]

Biofilms are communities of bacteria that exhibit a multitude of multiscale biomechanical behaviours. Recent experimental advances have led to characterisations of these behaviours in terms of measurements of the viscoelastic moduli of biofilms grown in bioreactors and the fracture and fragmentation properties of biofilms. These properties are macroscale features of biofilms; however, a previous work by our group has shown that heterogeneous microscale features are critical in predicting biofilm rheology. In this paper, we use tools from statistical physics to develop a generative statistical model of the positions of bacteria in biofilms. Specifically, the model is a type of pairwise interaction model (PIM). We show through simulation that the macroscopic mechanical properties of biofilms depend on the choice of microscale spatial model. A key finding is that uniform and non-uniform sets of points lead to differing mechanical properties. This distinction appears not to have been previously considered in mathematical biofilm literature. We also found that realisations of a biologically informed PIM have realistic in silico mechanical properties, and have statistical properties that closely match experimental data. We also note that a Poisson spatial point process of suitable number density also yields realistic mechanical properties, but that the spatial distribution of points does not reflect those occurring in our experimentally observed biofilm. [ABSTRACT FROM AUTHOR]

The work presents the analysis of the free boundary value problem related to the one-dimensional invasion model of new species in biofilm reactors. In the framework of continuum approach to mathematical modelling of biofilm growth, the problem consists of a system of non-linear hyperbolic partial differential equations governing the microbial species growth and a system of semi-linear elliptic partial differential equations describing the substrate trends. The model is completed with a system of elliptic partial differential equations governing the diffusion and reaction of planktonic cells, which are able to switch their mode of growth from planktonic to sessile when specific environmental conditions are found. Two systems of non-linear differential equations for the substrate and planktonic cells mass balance within the bulk liquid are also considered. The free boundary evolution is governed by a differential equation that accounts for detachment. The qualitative analysis is performed and a uniqueness and existence result is presented. Furthermore, two special models of biological and engineering interest are discussed numerically. The invasion of Anammox bacteria in a constituted biofilm inhabiting the deammonification units of the wastewater treatment plants is simulated. Numerical simulations are run to evaluate the influence of the colonization process on biofilm structure and activity. [ABSTRACT FROM AUTHOR]

Highlights • Sludge cake acts as key actor of filtration in SFD-MBR for wastewater treatment. • IFAS integration decreased the excess sludge and enhanced denitrification. • The presence of carriers increased the frequency of mesh clogging. • Both SFD-MBRs showed performance comparable to MBR in same operating conditions. Abstract Two lab-scale Self Forming Dynamic Membrane BioReactors (SFD-MBR), equipped with 50 µm nylon meshes were set up and operated for the treatment of real municipal wastewater. Plastic carriers were added in one of the two bioreactors to generate a combination of the Integrated Fixed-film Activated Sludge (IFAS) and the SFD-MBR technologies. Overall, the two systems performed very well, achieving excellent effluent quality under steady state conditions and showing good resilience to extreme organic loading conditions. Continuous air scouring and periodical mesh cleaning by jet rinsing with tap water were effective in maintaining stable and high productivity (membrane flux around 67 L m2 h−1) over a period of 140 days. The application of the IFAS process resulted in lower production of excess sludge and improved denitrification. On the other hand, under the tested conditions the combined IFAS-SFD-MBR showed a higher tendency to mesh clogging with respect to the SFD-MBR. [ABSTRACT FROM AUTHOR]

Abstract Biofilm formation is initiated by adhesion of individual bacteria to a surface. However, surface adhesion alone is not sufficient to form the complex community architecture of a biofilm. Surface-sensing creates bacterial awareness of their adhering state on the surface and is essential to initiate the phenotypic and genotypic changes that characterize the transition from initial bacterial adhesion to a biofilm. Physico-chemistry has been frequently applied to explain initial bacterial adhesion phenomena, including bacterial mass transport, role of substratum surface properties in initial adhesion and the transition from reversible to irreversible adhesion. However, also emergent biofilm properties, such as production of extracellular-polymeric-substances (EPS), can be surface-programmed. This review presents a four-step, comprehensive description of the role of physico-chemistry from initial bacterial adhesion to surface-programmed biofilm growth: (1) bacterial mass transport towards a surface, (2) reversible bacterial adhesion and (3) transition to irreversible adhesion and (4) cell wall deformation and associated emergent properties. Bacterial transport mostly occurs from sedimentation or convective-diffusion, while initial bacterial adhesion can be described by surface thermodynamic and Derjaguin−Landau−Verwey−Overbeek (DLVO)-analyses, considering bacteria as smooth, inert colloidal particles. DLVO-analyses however, require precise indication of the bacterial cell surface, which is impossible due to the presence of bacterial surface tethers, creating a multi-scale roughness that impedes proper definition of the interaction distance in DLVO-analyses. Application of surface thermodynamics is also difficult, because initial bacterial adhesion is only an equilibrium phenomenon for a short period of time, when bacteria are attached to a substratum surface through few surface tethers. Physico-chemical bond-strengthening occurs in several minutes leading to irreversible adhesion due to progressive removal of interfacial water, conformational changes in cell surface proteins, re-orientation of bacteria on a surface and the progressive involvement of more tethers in adhesion. After initial bond-strengthening, adhesion forces arising from a substratum surface cause nanoscopic deformation of the bacterial cell wall against the elasticity of the rigid peptidoglycan layer positioned in the cell wall and the intracellular pressure of the cytoplasm. Cell wall deformation not only increases the contact area with a substratum surface, presenting another physico-chemical bond-strengthening mechanism, but is also accompanied by membrane surface tension changes. Membrane-located sensor molecules subsequently react to control emergent phenotypic and genotypic properties in biofilms, most notably adhesion-associated ones like EPS production. Moreover, also bacterial efflux pump systems may be activated or mechano-sensitive channels may be opened upon adhesion-induced cell wall deformation. The physico-chemical properties of the substratum surface thus control the response of initially adhering bacteria and through excretion of autoinducer molecules extend the awareness of their adhering state to other biofilm inhabitants who subsequently respond with similar emergent properties. Herewith, physico-chemistry is not only involved in initial bacterial adhesion to surfaces but also in what we here propose to call "surface-programmed" biofilm growth. This conclusion is pivotal for the development of new strategies to control biofilm formation on substratum surfaces, that have hitherto been largely confined to the initial bacterial adhesion phenomena. Graphical abstract Unlabelled Image Highlights • Physico-chemistry dictates initial bacterial adhesion to substratum surfaces • Bond-strengthening leads to irreversible adhesion of bacteria (and inert colloids) • Through quorum-sensing, bacteria share information on substratum surface properties • Substratum surface properties program emergent biofilm properties • Regarding bacteria as inert colloids, does not yield a generalized biofilm model [ABSTRACT FROM AUTHOR]

Aim: To determine the presence of Prevotella species, the cfxA/cfxA2, blaZ and blaTEM genes associated with resistance to lactamic agents in different oral niches of children with pulp necrosis. Methodology: Children with pulp necrosis in primary teeth had samples of saliva, supragingival, pulp chamber and root canal biofilms collected and tested for Prevotella species (P. intermedia, P. nigrescens, P. tannerae) and for beta‐lactam resistance genes (cfxA/cfxA2, blaZ and blaTEM). The presence of bacterial DNA was examined through PCR, with a specific primer directed to the 16S rRNA gene. Specific primers were used to detect the Prevotella species and beta‐lactam resistance genes. The chi‐square test was used to analyse associations between the presence of bacteria and clinical variables. The Cochran's Q test was used to assess whether the proportion of gene detection is the same between different sites. Results: Thirty‐two teeth were sampled from 27 patients with a mean age of 5.5 years (±1.76). The total detection rate of Prevotella strains was 29.1%, 25%, 21.8% and 32.29% in saliva, supragingival, pulp chamber and root canal samples, respectively. P. nigrescens was the most commonly detected species in all oral niches. The previous use of antibiotics was associated with detection of P. nigrescens in saliva (P = 0.03). Pain was associated with the presence of P. nigrescens (P = 0.04) and P. tannerae (P = 0.01) in pulp chamber biofilm. blaTEM was detected in the four oral niches, being more frequent (23.8%) in supragingival biofilm (Cochran's Q test, P = 0.04). The presence of P. intermedia in SB and PC was associated with the detection of blaTEM in saliva (P = 0.04). The cfxA/cfxA2 and blaZ genes were not detected in any of the four oral niches. Conclusions: The oral cavity of children with pulp necrosis had a variable distribution of Prevotella strains in different niches. Saliva, supragingival biofilm, pulp chamber and root canals of primary teeth with necrotic pulps can harbour resistance genes to beta‐lactams agents. [ABSTRACT FROM AUTHOR]

Abstract Background Pseudomonas aeruginosa is an opportunistic pathogen and utilizes several virulence factors for pathogenesis. One of the most important factors is alginate, found in the biofilm which enables P. aeruginosa to establish chronic lung infections. Materials and methods In this study, 25 clinical alginate-degrading isolates were selected. Biochemical and molecular approach were carried out to identify the isolates by 16S rDNA gene amplification. Growth conditions and enzyme production were the criteria for selection. Since the main objective of the project was the production and characterization of alginate lyase and its effect on biofilm elimination, the P. aeruginosa sp.TAG48 alginate lyase-encoding gene was isolated, cloned, sequenced and expressed in E.coli DH5α. The resultant enzyme was purified by affinity chromatography. Ciprofloxacin, tobramycin and cefixime were also used to test the effectiveness of these antibiotics on P. aeruginosa biofilm by minimum biofilm inhibitory concentration (MBIC) and minimum biofilm eradication concentration (MBEC). The synergistic effects of these antibiotics and the recombinant alginate lyase on biofilm were evaluated. Results Results indicate that the addition of alginate (0.2%–0.8%) and NaCl (0.2–0.5 M) to the medium significantly increases cell growth followed by higher enzyme production (p ≤ 0.05). Moreover, substrate specificity of alginate lyase produced by P. aeruginosa sp.TAG48 shows the enzyme is capable of degrading both polyM and polyG alginate and acts bifunctionally. Results from the antimicrobial characteristics of the antibiotics and the enzyme have shown MBIC for ciprofloxacin, tobramycin, cefixime and enzyme in the following concentrations 4, 32, 256 and 18.75 μg/ml, and MBEC: 32, 128, ≥ 512 and 37.5 μg/ml, respectively. The study of synergism between the antibiotics and the enzyme to prevent growth and eradication of P. aeruginosa sp.TAG48 biofilm shows that alginate lyase exhibits synergy with tobramycin and cefixime but not with ciprofloxacin. Conclusion The results indicate that the use of purified novel alginate lyase with antibiotics could be a beneficial alternative for the treatment of P. aeruginosa infections. Elucidation of mechanisms involved in antibiotic resistance and the role of biofilm structure could assist physicians select optimum treatment regimen. Highlights • Isolation of alginate lyase producing clinical P. aeruginosa. • Cloning and expression of lyase-encoding gene, algL , in a heterologous host. • Positive effect of alginate as sole carbon source for bacterial growth. • FBEC and FBIC show synergistic effect of recombinant alginate lyase with tobramycin and with cefixime. • Recombinant alginate lyase was, in general, effective in biofilm inhibition and eradication. [ABSTRACT FROM AUTHOR]

Growing demand for efficient wastewater treatment systems is spurring on the development of new technologies. Biofilm‐based reactors can be used for the treatment of a variety of wastewaters and these reactors are resistant to toxic environments. Bioreactors, such as sequencing batch biofilm and moving bed biofilm are advanced techniques to treat various types of wastewaters with diverse operating conditions. Ammonium oxidizing bacteria, nitrite oxidizing bacteria and Anammox (anaerobic ammonium oxidation) bacteria are reported to be responsible for nutrient removal. In recent decades, the performance of these systems has been studied widely and compared for a number of wastewater treatment applications. In general, they are particularly suitable for high‐rate nitrification and nitrogen removal. The efficiency of these reactors has been confirmed in the laboratory and large‐scale plants. Their efficiency depends on the surface area of the biocarrier, the filling percentage volume of biofilm carriers, organic loading and diffused aeration supply. Chemical oxygen demand removal of 50–98% was reported for <12 h hydraulic retention time, 0.2 to 6.5 mg L−1 dissolved oxygen concentration and temperature range 15–35 °C. Also, the ratio of nitrate to ammonium conversion was from 0.2 to 90 and N2 conversion was from 0 to 8.5 mg. This review studied each of these bioreactors in the removal of nutrients (nitrogen, phosphorus and oxygen) from different wastewaters and compared them to conventional treatment. The review also includes the relevant studies on laboratory and pilot‐scale bioreactors to enhance their performance and reduce their costs. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

BACKGROUND This research is focused on the effect of temperature on the growth of active biofilms on polypropylene (PP) filter media in aerobic fixed biofilm reactors (FBR) for wastewater treatment. RESULTS: High‐throughput sequencing was used to explore the composition and diversity of the microbial community of 14‐days‐old (starting phase) biofilms grown at 10, 20 and 30°C. Members of the classes Proteobacteria, Bacteroidetes, and Firmicutes were predominant in all the biofilm samples retrieved from PP‐FBRs. A total of 108 genera of bacteria were identified, with some of them present in all three reactors, including Trichococcus, Zoogloea, Aeromonas, Acidovorax, and Malikias, among others. Besides these shared populations, certain genera were abundantly found in individual biofilm samples, like Brevundimonas (17.1%), Chitinimonas (10.3%) and Roseateles (39.3%), at 10, 20, and 30°C, respectively. The metabolic capabilities of active microbial communities in PP‐FBRs were estimated by assessing the changes in different variables (BOD, DO, and pH) in the influent and effluent during operation. A noteworthy BOD removal (66.6%) was shown by PP‐FBRs operating at 30°C, compared with 20°C (28.3%) and 10°C (28.8%),consistent with the DO levels recorded in the effluents, highest at 30°C (70.5%), and decreasing with declining temperatures. Substantial wastewater treatment efficiencies were observed in the reactors at 30°C, attributable to the higher relative abundance and diversity of microbial biofilms. CONCLUSIONS: The development of physiologically active biofilms in PP at all prevailing temperatures strongly suggests that the material is suitable to be employed in FBRs for wastewater treatment at different operational temperatures. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Purpose To detect co-infections in the culture-proven acanthamoebic keratitis (AK) cases, and to test the capability of biofilm formation in the isolated microbiota. The clinical findings, habit of wearing contact lens and in-vitro antibiotic resistance were analyzed further according to the biofilm formation capability. Methods After clinical examination, corneal scraps and swabs were taken from 240 clinically suspected AK cases, for Acanthamoeba and microbiological cultures. In cases of keratoplasty, trimmed corneal tissue was collected and sent for histopathological examination. Scanning electron microscopy was done for some samples. Biofilm formation capability was investigated using a tissue culture plate method. Antibiotic resistance pattern was determined using a modified-Kirby-Bauer disc diffusion method. Results In 102 AK culture proven cases, 11 had no co-infection, 74 had a single co-infection and 17 had double co-infections. Enterobactericae and Aspergillus were the commonest bacterial and fungal isolates, respectively. Regarding the biofilm formation, 64.7% of Enterobactericae , 50% of Pseudomonas aeuroginosa , 43.75% of Staph aureus , 76.92% of Streptococcus pneumoniae , 28.57% of Corynebacterium , 60% of α-haemolytic streptococci , 40% of Acinetobacter , 100% of Candida and 77.8% Aspergillus isolates were biofilm producers. Severe manifestations were more frequently reported in cases co-infected with biofilm producers than with non-biofilm producers. Generally, high percentages of the biofilm forming bacterial isolates were sensitive to antibiotics in-vitro . Conclusions Routine investigations for co-infection and biofilm formation in addition to Acanthamoeba culture are strongly recommended in suspected AK cases. Co-infection with biofilm producers may precipitate extrinsic in-vivo drug resistance despite of the in-vitro sensitivity. Designing a biofilm-dissolving topical drug is highly recommended to enhance the response to the standard therapeutic regimen especially in the resistant AK cases. [ABSTRACT FROM AUTHOR]

The article discusses a study on the efficacy of chlorine to kill acute hepatopancreatic necrosis disease (AHPND)‐causing Vibrio parahaemolyticus which reportedly is dependent on the organic load. It emphasizes on the need to decrease the organic load as much as possible prior to disinfection in order to obtain an effective disinfection, and suggests further studies using advanced biofilm analysis methods.

The increasing use of silver nanoparticles (AgNPs) in consumer products, and their resulting influx into wastewater, may pose a threat to biological nutrient removal in wastewater treatment plants. Planktonic ammonia-oxidizing bacteria (AOB), which convert ammonia to nitrite in the first step of nitrification, are highly sensitive to AgNPs and their released silver ions (Ag + ), but the sensitivity of AOB biofilms to AgNPs and Ag + is less clear. This study demonstrated that biofilms of Nitrosomonas europaea , a model AOB, were more resistant to both short-term and long-term exposure to AgNP and Ag + than planktonic cells. The increased resistance of N. europaea biofilms was attributed primarily to the increased biomass and slower growth rates present in the biofilm. Similar inhibition mechanisms were observed for AgNPs and Ag + in both planktonic cells and biofilms with enzymatic inhibition observed at lower concentrations and cell lysis observed at higher concentrations. Long-term continuous exposure to AgNPs lowered the inhibitory concentration by 1–2 orders of magnitude below that required by short-term exposures. Although the total AgNP load was similar between the short and long-term exposure scenarios, the long-term exposure resulted in an order of magnitude more silver being associated in the biofilms and is the primary reason for the increased sensitivity observed. This suggests that short-term batch toxicity assays may greatly underestimate the sensitivity of biofilm treatment systems to long-term exposures of low concentrations of AgNPs and Ag + . [ABSTRACT FROM AUTHOR]

This study reports the influence of Mg ions on the development and architecture of biofilms by a chromium resistant and reducing bacterium Arthrobacter sp. SUK 1201 and their utilization in the removal of toxic hexavalent chromium. Among the different metal ions tested, Mg(II) greatly influenced the biofilm growth in peptone yeast extract glucose medium. Both Scanning and Confocal Laser Scanning Microscopy revealed that biofilms formed under the induction of Mg(II) had characteristic higher cell densities. The cells remain embedded in thick porous layers of extracellular polymeric substances as evident from the fluorescein isothiocyanate labeled lectin concanavalin A and 4, 6-diamino-2-phenylindole staining. COMSTAT analysis also indicated maximum thickness and roughness coefficient of the biofilm grown in presence of Mg(II). Biofilms of Arthrobacter sp. SUK 1201 developed under such Mg (II) influenced condition showed complete removal of 0.5 mM Cr (VI) in mineral salts medium. The biofilm of this isolate grown in presence of Mg(II) was also able to remove 60mM Cr(VI) from mine seepage water suggesting its possible implication in effective bioremediation of chromium polluted environments. [ABSTRACT FROM AUTHOR]

Two lab-scale nitrifying sequencing batch biofilm reactors, with (SBBR_CN) or without the addition of organics (SBBR_N), were operated to investigate potential roles of acyl homoserine lactone (AHL) based quorum sensing. AHLs of N-[(RS)-3-Hydroxybutyryl]-L-homoserine lactone, N-hexanoyl-L-homoserine lactone (C 6 -HSL) and N-octanoyl-L-homoserine lactone (C 8 -HSL) were detected in both reactors. C 6 -HSL and C 8 -HSL were also detected in batch experiments, especially with stimulated nitrite oxidizing bacteria activities. Quorum sensing affected biofilm formation mainly through the regulation of extracellular protein production. By the metagenomics analysis, many identified genera and species could participate in quorum sensing, quorum quenching and extracellular polymeric substances (EPS) production. A high quorum quenching activity was obtained in SBBR_CN, whereas a high quorum sensing activity in SBBR_N. Nitrosomonas -like ammonia oxidizing bacteria, Nitrospira -like nitrite oxidizing bacteria and Comammox harbored genes for AHL synthesis and EPS production. Possible relationships among AHLs synthesis, biofilm formation and nitrifiers activity were proposed. [ABSTRACT FROM AUTHOR]

Using multigenerational, single-cell tracking we explore the earliest events of biofilm formation by Pseudomonas aeruginosa. During initial stages of surface engagement (≤20 h), the surface cell population of this microbe comprises overwhelmingly cells that attach poorly (~95% stay <30 s, well below the ~1-h division time) with little increase in surface population. If we harvest cells previously exposed to a surface and direct them to a virgin surface, we find that these surface-exposed cells and their descendants attach strongly and then rapidly increase the surface cell population. This "adaptive," time-delayed adhesion requires determinants we showed previously are critical for surface sensing: type IV pili (TFP) and cAMP signaling via the Pil-Chp-TFP system. We show that these surface-adapted cells exhibit damped, coupled out-of-phase oscillations of intracellular cAMP levels and associated TFP activity that persist for multiple generations, whereas surface-naïve cells show uncorrelated cAMP and TFP activity. These correlated cAMP-TFP oscillations, which effectively impart intergenerational memory to cells in a lineage, can be understood in terms of a Turing stochastic model based on the Pil-Chp-TFP framework. Importantly, these cAMP-TFP oscillations create a state characterized by a suppression of TFP motility coordinated across entire lineages and lead to a drastic increase in the number of surface-associated cells with near-zero translational motion. The appearance of this surface-adapted state, which can serve to define the historical classification of "irreversibly attached" cells, correlates with family tree architectures that facilitate exponential increases in surface cell populations necessary for biofilm formation. [ABSTRACT FROM AUTHOR]

Having worked with biofilms since the 1970s, I know that they are ubiquitous in nature, of great value in water technology, and scientifically fascinating. Biofilms are naturally able to remove BOD, transform N, generate methane, and biodegrade micropollutants. What I also discovered is that biofilms can do a lot more for us in terms of providing environmental services if we give them a bit of help. Here, I explore how we can use active substrata to enable our biofilm partners to provide particularly challenging environmental services. In particular, I delve into three examples in which an active substratum makes it possible for a biofilm to accomplish a task that otherwise seems impossible. The first example is the delivery of hydrogen gas (H 2 ) as an electron donor to drive the reduction and detoxification of the rising number of oxidized contaminant: e.g., perchlorate, selenate, chromate, chlorinated solvents, and more. The active substratum is a gas-transfer membrane that delivers H 2 directly to the biofilm in a membrane biofilm reactor (MBfR), which makes it possible to deliver a low-solubility gaseous substrate with 100% efficiency. The second example is the biofilm anode of a microbial electrochemical cell (MxC). Here, the anode is the electron acceptor for anode-respiring bacteria, which “liberate” electrons from organic compounds and send them ultimately to a cathode, where we can harvest valuable products or services. The anode's potential is a sensitive tool for managing the microbial ecology and reaction kinetics of the biofilm anode. The third example is intimately coupled photobiocatalysis (ICPB), in which we use photocatalysis to enable the biodegradation of intrinsically recalcitrant organic pollutants. Photocatalysis transforms the recalcitrant organics just enough so that the products are rapidly biodegradable substrates for bacteria in a nearby biofilm. The macroporous substratum, which houses the photocatalyst on its exterior, actively provides donor substrate and protects the biofilm from UV light and free radicals in its interior. These three well-developed topics illustrate how and why an active substratum expands the scope of what biofilms can do to enhance water sustainability. [ABSTRACT FROM AUTHOR]

Salmonella enteritidis is a common food-borne pathogen associated with consumption of contaminated poultry meat and eggs, which frequently causes gastroenteritis in humans. Salmonella secreted effector K1 (SseK1), as a translocated and secreted protein has been identified to be essential for the virulence of Salmonella typhimurium in host cells. However, the role of the sseK1 gene in the pathogenicity of S. enteritidis remain unclear. In this study, a sseK1 deletion mutant of S. enteritidis was constructed and its biological characteristics were examined. It was found that the sseK1 deletion mutant did not affect the growth, adherence and invasion of Salmonella enteritidis when compared to the wild-type S. enteritidis. However, the mutant showed decreased formation of biofilm and significantly reduced intracellular survival of bacteria in activated mouse peritoneal macrophages, as well as showed reduced pathogenicity to a murine model by increasing the lethal dose 50% (LD 50 ) value and decreasing the proliferation ratio of bacteria in vivo . Taken together, this study determined an important role for SseK1 in the pathogenicity of S. enteritidis in vitro and in vivo . [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the ability of Pseudomonas spp. strains isolated from milk, dairy products and dairy plants, to produce blue pigment in situ , to form biofilm onto polystyrene surfaces and to perform different types of motility. Molecular identification revealed that, out of 72 Pseudomonas spp. isolates, P . fluorescens was the most common species (50 isolates) followed by P . putida (9), P . koreensis (4), P . brenneri (4), P . aeruginosa (2), P . granadensis (2) and P . veronii (1). The evaluation of blue colour production showed that the pigment was produced at 10 °C but not at 30 °C; in addition this character was strain- and species-dependent, with only 16 P. fluorescens strains showing blue pigment production. Most of the studied strains produced biofilm although with some differences related to the strains and the incubation temperatures. Within the most abundant isolated species ( P . fluorescens ), about 46%, 34% and 26% of the strains were able to swim, swarm and twitch, respectively. The observed relationship between biofilm formation and blue pigment production in P . fluorescens strains was statistically significant. Since these characteristics may contribute to the persistence of microorganisms in food processing environments and therefore to the contamination of food products, our results may help to focus on the control of the strains involved in the blue discolouration of dairy products. [ABSTRACT FROM AUTHOR]

A systems biology approach was used to study all the biofilm related genes of P. aeruginosa PAO1, and the interaction of titanium dioxide (TiO 2 ) anatase with biofilm related proteins. Among the 71 genes, the interactions of all the nodal pairs were extracted by STRING 10.5 database. The inter-relationship among these genes was predicted by constructing complete PPI network and visualized in Cytoscape v 3.4.0. Total number of nodes of the network was found to be 335 and edges were 795. The network was further investigated for its clusters and the best cluster was further analyzed for the hub proteins which significantly contribute in cross-regulation of the biofilm related process. The hub proteins were identified based on four topological parameters of degree, closeness, betweeness and radiality. Four major hub proteins of P. aeruginosa PAO1 were identified to be algD, gacS, rpoS and rpoN which were common in all the hubs. Further, we have also elucidated the probable mechanism of TiO 2 interaction with P. aeruginosa PAO1 at molecular level. Using STITCH server, the major target gene of TiO 2 was identified as kat A which also appeared commonly in our main dataset and this gene has been focused for the further study because of its unique common appearance in gene–gene network as well as gene-anatase network. The direct interacting partners of katA were found to be dnaK, hfq, rpoS and rpoA . Based on these findings and available gene regulatory information, probable TiO 2 interacting cascade has been represented. This in silico study of P. aeruginosa PAO1 biofilm genes and the interaction of protein products with TiO 2 might be significant to understand the perspective pathogenic resistance as well as the toxicity research pertaining to nanoparticles. [ABSTRACT FROM AUTHOR]

Silver nanoparticles were synthesized using Olive oil (O-AgNPs) as reducing as well as capping agent and extensively characterized by UV–vis spectroscopy, fourier transform infrared, energy disperse spectroscopy, dynamic light scattering and atomic force microscopy. The chrome yellow color solution of O-AgNPs show the typical absorption maximum at 430 nm. FTIR analysis revealed that the carbonyl (C O) groups of Olive oil plays the most vital role in reduction of Ag + and the nanoparticles synthesis. The morphology of O-AgNPs were found spherical in nature, while the size of O-AgNPs ranges between 35 to 65 nm as established by AFM and DLS studies, respectively. Stability of O-AgNPs studied by varying storage period, temperature, salt and pH of the medium were found quite stable probably because of oil suspension nature. Despite potent antimicrobial, anti-biofilm and biofilm eradicating activities, O-AgNPs were found to be non-toxic on cell lines. Moreover, chemosensing properties of the O-AgNPs were also tested against different drugs. The O-AgNPs showed high selectivity towards nitrofurazone (NFZ) with the lowest detection limit of 1.88 μM as was monitored by UV–vis spectroscopy. The mechanism of O-AgNPs interaction with drug was followed by DLS suggest that NFZ induces a time dependent nanoparticles aggregation. [ABSTRACT FROM AUTHOR]

Concentrations of viable microbial cells were monitored using culture-based and culture-independent methods across multichamber ozone contactors in a full-scale drinking water treatment plant. Membrane-intact and culturable cell concentrations in ozone contactor effluents ranged from 1200 to 3750 cells/mL and from 200 to 3850 colony forming units/mL, respectively. Viable cell concentrations decreased significantly in the first ozone contact chamber, but rose, even as ozone exposure increased, in subsequent chambers. Our results implicate microbial detachment from biofilms on contactor surfaces, and from biomass present within lime softening sediments in a hydraulic dead zone, as a possible reason for increasing cell concentrations in water samples from sequential ozone chambers. Biofilm community structures on baffle walls upstream and downstream from the dead zone were significantly different from each other (p = 0.017). The biofilms downstream of the dead zone contained a significantly (p = 0.036) higher relative abundance of bacteria of the genera Mycobacterium and Legionella than the upstream biofilms. These results have important implications as the effluent from ozone contactors is often treated further in biologically active filters and bacteria in ozonated water continuously seed filter microbial communities. [ABSTRACT FROM AUTHOR]

Among 13 serotypes of Listeria monocytogenes , serotypes 4b and 1/2a account for most of the sporadic listeriosis cases and environmental isolations. To understand the mechanism of stress response in these serotypes, six strains of each serotype were selected in this study to differentiate the physiological and genetic response of these L. monocytogenes under oxidative stress. Oxidative stress tolerance was examined by plate count after hydrogen peroxide exposure during exponential phase, long-term-survival phase and biofilm state. The biofilm forming capability of the two serotypes was also compared using crystal violet assay. Three oxidation resistance genes ( kat, sod and fri ), two stress-regulator encoding genes ( sigB and perR ), and one DNA repair gene ( recA ) were selected for transcription analysis by quantitative RT-PCR. Most serotype 4b strains exhibited a stronger resistance to 0.6% H 2 O 2 than serotype 1/2a during exponential phase and long-term-survival phase, while the latter demonstrated stronger biofilm forming capacity in BHI broth at 37 °C. At the genetic level, there were significant differences in the expression of three genes ( sod , fri and perR ) under oxidative stress between two serotypes, which suggests a role in the observed variation towards stress resistance. In addition, the expression of recA was induced under oxidative stress in L. monocytogenes strains of both serotypes. [ABSTRACT FROM AUTHOR]

Listeria monocytogenes ( L. monocytogenes ) is a well-known food-borne pathogen that causes systemic listeriosis. Its biofilm-forming ability is known to be important for its antimicrobial resistance and persistence. Epigallocatechin-gallate (EGCG) is the highest component of tea polyphenols in tea extracts and has broad-spectrum antimicrobial activities. In this study, the efficacys of EGCG to inhibit biofilm formation and hemolytic activity of L. monocytogenes were determined. EGCG at 20 μg/mL, 40 μg/mL (less than compound's minimum inhibitory concentration, MIC) and 200 μg/mL (1 MIC) were tested. Crystal violet staining showed that sub-MIC and MIC of EGCG could significantly reduce the biofilm formation by L. monocytogenes on polystyrene microtiter plates at three temperatures (15 °C, 30 °C and 37 °C). EGCG reduced the sessile cell numbers present in biofilm at those temperatures. EGCG also significantly inhibited hemolytic activity of L. monocytogenes as measured by sheep red blood cells. Real time PCR assay was used to investigate the relative gene expression of L. monocytogenes grown at 37 °C and revealed that EGCG down-regulated virulence genes ( inlA and hly ), SOS response genes ( recA and yneA ) and quorum sensing gene ( agrA ). These results suggested the feasibility of using EGCG in food industry to control L. monocytogenes biofilm formation. [ABSTRACT FROM AUTHOR]

Microbial probiotic supplements are used to improve the health and wellness of people. For checking this ability (resistance to gastrointestinal conditions, auto-aggregation, cell surface hydrophobicity or biofilm formation abilities), it is crucial to evaluate some kinetics parameters. The objective of the present study was to establish an adequate method for studying the probiotic potential of Saccharomyces and non- Saccharomyces strains isolated from food ecosystems. A new protocol was designed based on kinetics parameters: lag phase (λ), generation time (G) and maximum OD (ODmax). The design was done using a step-by-step approach (up to 10 protocols), focusing on the choice of controls and the conditions to simulate the stomach and intestine. Each decision was made based on multifactorial statistical assay results. A preliminary screening indicates that protocol is adequate, quick and reproducible and that S. cerevisiae strains are more resistant than non- Saccharomyces ones. S. boulardii , (commercial control), was not one of the best yeasts evaluated. Thus, the most relevant results of the work are the setup of a new method for studying the survival/resistance of yeasts to the transit into the gut based on a complex statistical analysis of results and to mark the probiotic character in Saccharomyces yeasts versus non- Saccharomyces. [ABSTRACT FROM AUTHOR]

Novel antifungal agents are required against pathogenic fungi such as Candida albicans . We report the anticandidal activity of battacin lipopeptide antibiotics with previously unexplored antifungal activity. From amongst sixteen battacin lipopeptides tested against C. alibicans (SC5314) the 4-methyl hexanoyl conjugated trimeric lipopeptide 13 emerged as the lead candidate with a MIC of 6.25 μM and negligible haemolysis of mouse red blood cells. The potency of this lipopeptide was maintained under acidic conditions. Additionally, antifungal activity was further enhanced with amphotericin B at its non-haemolytic concentrations. Herein we have demonstrated for the first time that battacin lipopeptides prevent C. albicans biofilm colonisation as well as inhibit pre-formed biofilms of this fungal pathogen. XTT biofilm assays revealed that 13 prevented colonisation of C. albicans biofilms at its MIC (6.25 μM) and, at a higher concentration, eradicated 24 h (25 μM) and 48 h (62.5 μM) old preformed biofilms. In comparison, we found that amphotericin at much lower concentrations prevented biofilm colonisation (0.78 μM) and inhibited 24 h old preformed biofilms (6.25 μM), however was completely inactive against 48 h old preformed biofilms. Thus, lipopeptide 13 is more effective than amphotericin at eradicating more mature C. albicans biofilms. The membrane lytic mechanism of action of compound 13 was validated by a colorimetric assay using lipid vesicles mimicking fungal membranes in which compound 13 effected an immediate dark purple to red colour transition of suspended vesicles upon peptide interaction. In addition, TEM images of C. albicans cells exposed to 13 showed clearly disrupted cellular membranes. Interestingly, compound 13 increased the endogenous generation of reactive oxygen species (ROS) in a concentration dependent manner. In the presence of an antioxidant, ascorbic acid, ROS production was diminished yet antifungal activity persisted, possibly indicating that ROS production is a secondary effect from membrane lysis caused by lipopeptide 13 . The lipopeptide was non-haemolytic against mouse red blood cells at the highest tested concentration (1 mM). [ABSTRACT FROM AUTHOR]

Klebsiella pneumoniae is an important human pathogen that is considered in recent years due to nosocomial infections resistant to treatment as well as the ability to form biofilms particularly in patients with urinary tract infection in ICU or hospital. The aim of this study was to evaluate the prevalence of VIM1, IMP1 genes and their ability to form biofilm in K. pneumoniae strains isolated from patients with urinary tract infection. In the study, using culture and biochemical methods, 1807 K. pneumoniae samples were isolated from patients with urinary tract infection hospitalized or referred to hospitals in Qom in 2013–2014. For isolation of MBL producing isolates, Double Disk Synergy Test (DDST) was used. Then MBL positive isolates were examined for the presence of VIM1, IMP1 genes using PCR method. Furthermore, all strains were investigated for biofilm formation by phenotypic microplate method. From 3165 urine samples cultured, 1807 isolates of K. pneumoniae were isolated and 109 strains (93.2%) were positive for MBL enzymes production. PCR results showed that the prevalence of VIM1 and IMP1 genes are 15.6 and 6.4%, respectively. The Phenotypic method indicated that 91.2% of isolates formed biofilm. Biofilm formation in K. pneumoniae isolates is high and there is a significant relationship between strong biofilm formation and prevalence of VIM1 and IMP1 genes. Also due to the presence of MBL genes in K. pneumoniae and horizontal transfer of genes to other bacteria, and to control the indiscriminate use of antibiotics, the hospital infection control methods must be considered. [ABSTRACT FROM AUTHOR]

Static magnetic field (SMF) has been shown to biologically affect various microorganisms, but its effects on Enterococcus faecalis, which is associated with multiple dental infections, have not been reported yet. Besides, Enterococcus faecalis was found to be resistant to the alkaline environment provided by a major dental antimicrobial, calcium hydroxide. Therefore, the antibacterial activity of prolonged exposure to moderate SMF (170 mT) and its possible synergistic activity with alkaline pH (pH = 9) were evaluated in the study. The ability to form a biofilm under these conditions was examined by crystal violet assay. Real-time quantitative PCR was performed to evaluate the relative expression of stress (dnaK and groEL) and virulence (efaA, ace, gelE and fsrC) related genes. As the results indicated, cell proliferation was inhibited after 120 h of SMF exposure. What's more, the combined treatment of SMF and alkaline pH showed significantly improved antimicrobial action when compared to single SMF and alkaline pH treatment for more than 24 h and 72 h respectively. However, the ability to form a biofilm was also enhanced under SMF and alkaline pH treatments. SMF can induce stress response by up-regulating the expression of dnaK and elevate virulence gene expression (efaA and ace). These responses were more significant and more genes were up-regulated including groEL, gelE and fsrC when exposed to SMF and alkaline pH simultaneously. Hence, combination of SMF and alkaline pH could be a promising disinfection strategy in dental area and other areas associated with Enterococcus faecalis infections. [ABSTRACT FROM AUTHOR]

This study aims to evaluate the antibacterial activity of clove oil-loaded chitosan nanoparticles (CO@CNPs) and gelatin electrospun nanofibers against Escherichia coli O157:H7 ( E . coli O157:H7) biofilms on cucumbers. The optimal CO@CNPs were prepared when the initial concentration of clove oil (CO) was 2.5 mg/mL according to the ionic crosslinking method. CO@CNPs showed high antibacterial activity against E . coli O157:H7 biofilms. After 8 h treatment, almost 99.98% reduction in E . coli O157:H7 population was achie v ed when CO@CNPs were applied at 30% (w/v). Subsequently, the prepared CO@CNPs were incorporated successfully within gelatin nanofibers by electrospinning. After 9 mg/mL gelatin/CO@CNPs treatment for 24 h, the population of E . coli O157:H7 biofilm reduced by about 99.99% in vitro . Further, the application of gelatin/CO@CNPs nanofibers on cucumber against E . coli O157:H7 biofilm was evaluated as well. After 6 mg/mL and 9 mg/mL gelatin/CO@CNPs nanofibers treatment at 12 °C for 4 days, 4.28 and 4.97 log 10 reductions of E . coli O157:H7 biofilm in population were observed, respectively. Finally, the sensory evaluation results implied that the gelatin/CO@CNPs nanofibers treatment could maintain the color and flavor of cucumber well for > 4 days. [ABSTRACT FROM AUTHOR]

A mesocosm case study was conducted to gain understanding and practical knowledge on biofilm emerging contaminants biodegradation capacity under stressor and multiple stressor conditions. Two real life scenarios: I) biodegradation in a pristine intermittent stream experiencing acute pollution and II) biodegradation in a chronically polluted intermittent stream, were examined via a multifactorial experiment using an artificial stream facility. Stream biofilms were exposed to different water flow conditions i.e. permanent and intermittent water flow. Venlafaxine, a readily biodegradable pharmaceutical was used as a measure of biodegradation capacity while pollution was simulated by a mixture of four emerging contaminants (erythromycin, sulfisoxazole, diclofenac and imidacloprid in addition to venlafaxine) in environmentally relevant concentrations. Biodegradation kinetics monitored via LC-MS/MS was established, statistically evaluated, and used to link biodegradation with stress events. The results suggest that the effects of intermittent flow do not hinder and may even stimulate pristine biofilm biodegradation capacity. Chronic pollution completely reduced biodegradation in permanent water flow experimental treatments while no change in intermittent streams was observed. A combined effect of water flow conditions and emerging contaminants exposure on biodegradation was found. The decrease in biodegradation due to exposure to emerging contaminants is significantly greater in streams with permanent water flow suggesting that the short and medium term biodegradation capacity in intermittent systems may be preserved or even greater than in perennial streams. [ABSTRACT FROM AUTHOR]

Factors governing the photoelectrochemical output of photosynthetic microorganisms are poorly understood, and energy loss may occur due to inefficient electron transfer (ET) processes. Here, we systematically compare the photoelectrochemistry of photosystem II (PSII) protein-films to cyanobacteria biofilms to derive: (i) the losses in light-to-charge conversion efficiencies, (ii) gains in photocatalytic longevity, and (iii) insights into the ET mechanism at the biofilm interface. This study was enabled by the use of hierarchically structured electrodes, which could be tailored for high/stable loadings of PSII core complexes and Synechocystis sp. PCC 6803 cells. The mediated photocurrent densities generated by the biofilm were 2 orders of magnitude lower than those of the protein-film. This was partly attributed to a lower photocatalyst loading as the rate of mediated electron extraction from PSII in vitro is only double that of PSII in vivo. On the other hand, the biofilm exhibited much greater longevity (>5 days) than the protein-film (<6 h), with turnover numbers surpassing those of the protein-film after 2 days. The mechanism of biofilm electrogenesis is suggested to involve an intracellular redox mediator, which is released during light irradiation. [ABSTRACT FROM AUTHOR]

Presence of Cronobacter malonaticus in powdered infant formula (PIF) poses a high risk to infant and public health. Cronobacter malonaticus has been widely distributed in food and food processing environments, and the true origin of C. malonaticus in PIF is poorly understood. Control and prevention of C. malonaticus is necessary for achieving microbial safety of PIF. However, little information about decontamination of C. malonaticus is available. In this study, effects of hydrogen peroxide on inactivation and morphological changes of C. malonaticus cells were determined. Furthermore, inhibitory effects of H2O2 on biofilm formation in C. malonaticus were also performed. Results indicated that H2O2 could completely inactivate C. malonaticus in sterile water with 0.06% H2O2 for 25 min, 0.08% H2O2 for 15 min, and 0.10% for 10 min, respectively, whereas the survival rates of C. malonaticus in tryptic soy broth medium significantly increased with the same treatment time and concentration of H2O2. In addition, morphological changes of C. malonaticus cells, including cell shrinkage, disruption of cells, cell intercession, and leakage of intercellular material in sterile water after H2O2 treatment, were more predominant than those in tryptic soy broth. Finally, significant reduction in biofilm formation by H2O2 was found using crystal violet staining, scanning electron microscopy, and confocal laser scanning microscopy detection compared with control samples. This is the first report to determine the effects of H2O2 on C. malonaticus cells and biofilm formation. The findings provided valuable information for practical application of H2O2 for decontamination of C. malonaticus in dairy processing [ABSTRACT FROM AUTHOR]

Nanoparticles (NP) used as remediation agents for groundwater treatment may interact with biofilms naturally present, altering NP mobility and/or reactivity and thereby NP effectiveness. The influence of the presence of a multi species biofilm on the mobility of two types of zero-valent iron NP (nZVI; NANOFER 25S and optimized NANOFER STAR, NanoIron s.r.o. (Czech Republic)) was tested in laboratory experiments with columns mimicking aquifer conditions. Biofilms were grown in columns filled with sand in nitrate reducing conditions using groundwater from an industrial site as inoculum. After two months growth, they were composed of several bacterial species, dominated by Pseudomonas stutzeri . Biofilm strongly affected the physical characteristics of the sand, decreasing total porosity from ~ 30% to ~ 15%, and creating preferential pathways with high flow velocities. nZVI suspensions were injected into the columns at a seepage velocity of 10 m day − 1 . Presence of biofilm did not impact the concentrations of Fe at the column outlet nor the amount of total Fe retained in the sand, as attested by the measurement of magnetic susceptibility. However, it had a significant impact on NP size sorting as well as on total Fe distribution along the column. This suggests nZVI-biofilm interactions that were confirmed by microscopic observations using SEM/STEM coupled with energy-dispersive X-ray spectroscopy. Our study shows that biofilm modifies the water flow velocity in the porous media, favoring the transport of large aggregates and decreased NP mobility due to physical and chemical interactions. [ABSTRACT FROM AUTHOR]

In Gram-negative bacteria, quorum sensing systems are based on the N -acyl-homoserine lactone (AHL) molecule. The objective of this study was to investigate the role of quorum sensing systems during biofilm formation by a microbial community while degrading the pollutant. Our model system included 1,2,4-trichlorobenzene (1,2,4-TCB) and its mineralizing Gram-negative bacterial community to investigate the relationships between AHL dynamics, cell growth and pollutant degradation. Biomineralization of 1,2,4-TCB was monitored for both the planktonic bacterial community with and without sterile clay particles in liquid cultures. The bacterial growth and production of AHLs were quantified by fluorescent in situ hybridization and immunoassay analysis, respectively. A rapid production of AHLs which occurred coincided with the biofilm formation and the increase of mineralization rate of 1,2,4-TCB in liquid cultures. There is a positive correlation between the cell density of Bodertella on the clay particles and mineralization rate of 1,2,4-TCB. 3-oxo-C 12:1 -HSL appears to be the dominant AHL with the highest intensity and rapidly degraded by the bacterial community via two main consecutive reactions (lactone hydrolysis and decarboxylic reaction). These findings suggest that the integrated AHLs and their degraded products play a crucial role in biofilm formation and biomineralization of 1,2,4-TCB in culture. [ABSTRACT FROM AUTHOR]

Biofilms on the surface of dairy manufacturing plants are potential reservoirs of microbial contamination. These microbial aggregates may harbour pathogenic and spoilage organisms which contaminate dairy products. The biofilm forming capacity of many spore forming isolates of dairy origin has not been given much attention. The present study explored the biofilm forming potential of 148 isolates, comprising mesophilic and thermophilic bacteria, with particular emphasis on Bacillus licheniformis on polystyrene and stainless steel (SS) surfaces. We concluded that only four species are of significance for biofilm development on the surface of SS in the presence of skimmed milk, namely, B. licheniformis , Geobacillus stearothermophilus , Geobacillus thermoleovorans group and Anoxybacillus flavithermus . The maximum number of cells recovered from the biofilms developed on SS coupons in the presence of skimmed milk for these four species was as follows: 4.8, 5.2, 4.5 and 5.3 log CFU/cm 2 , respectively. Number of cells recovered from biofilms on 1 cm 2 SS coupons increased in the presence of tryptic soy broth (TSB) for all mesophiles including B. licheniformis , while decreased for G. stearothermophilus , G. thermoleovorans group and A. flavithermus . The crystal violet staining assay on polystyrene proved to be inadequate to predict cell counts on SS for the bacteria tested in our trial in the presence of either TSB or skimmed milk. The results support the idea that biofilm formation is an important part of bacterial survival strategy as only the most prevalent isolates from milk powders formed good biofilms on SS in the presence of skimmed milk. Biofilm formation also proved to be a strain-dependent characteristic and interestingly significant variation in biofilm formation was observed within the same RAPD groups of B. licheniformis which supports the previously reported genetic and phenotypic heterogeneity within the same RAPD based groups. The work reported in this manuscript will broaden our knowledge on biofilm formation of a large number of dairy isolates and emphasize strain and substrate dependence. [ABSTRACT FROM AUTHOR]

Biofilm formation and dipeptidyl peptidase IV (DPPIV) enzyme activity contribute to the virulence of oral bacteria, and these virulence factors are partly regulated by quorum sensing signaling system. We recently demonstrated that estradiol regulates growth properties and DPPIV activity of Prevotella intermedia , Prevotella nigrescens , and Prevotella pallens . Here, we examined the DPPIV dependency of biofilm formation of Prevotella aurantiaca. Three strains (two clinical strains AHN 37505 and 37552 and the type strain CCUG 57723) were incubated in three estradiol concentrations (30, 90, and 120 nmol/L). Regulation of DPPIV activity, biofilm and fimbria formation, and coaggregation of bacterial strains were analyzed after incubation with four concentrations (10 nM, 100 nM, 1 μM, 10 μM) of dihydroxy-2,3-pentaedione (DPD), the universal precursor of autoinducer -2 (AI-2), and analogs (ethyl-DPD, butyl-DPD, and isobutyl-DPD) for 24 h. Estradiol enhanced the planktonic growth, coaggregation, and biofilm formation of P. aurantiaca strains. The whole cell extract of AHN 37505 had the highest DPPIV activity, followed by CCUG 57723 and AHN 37552. Inhibition of DPPIV activity with di-isopropylfluorophosphate suppressed the effect of estradiol on biofilm formation. At 100 nM and 10 μM concentrations of DPD, butyl DPD, and isobutyl DPD, biofilm formation of P. aurantiaca was significantly inhibited. Fimbriae formation was enhanced up to concentrations of 100 nM and 1 μM followed by a significant inhibition at higher concentrations of DPD and all analogs. A slight but significant inhibitory effect of DPD and analogs on DPPIV activity was observed. Our results indicate that DPPIV plays a key role in the estradiol-regulated biofilm formation of P. aurantiaca. Quorum sensing autoinducer DPD and C1-alkyl analogs could inhibit biofilm-related virulence of P. aurantiaca . [ABSTRACT FROM AUTHOR]

Bacterial contamination of blood products poses a major risk in transfusion medicine, including transfusions involving platelet products. Although testing systems are in place for routine screening of platelet units, the formation of bacterial biofilms in such units may decrease the likelihood that bacteria will be detected. This work determined the surface properties of p-PVC platelet concentrate bags and investigated how these characteristics influenced biofilm formation. Serratia marcescens and Staphylococcus epidermidis , two species commonly implicated in platelet contamination, were used to study biofilm growth. The platelet concentrate bags were physically flattened to determine if reducing the surface roughness altered biofilm formation. The results demonstrated that the flattening process of the platelet bags affected the chemistry of the surface and reduced the surface hydrophobicity. Flattening of the surfaces resulted in a reduction in biofilm formation for both species after 5 days, with S. marcescens demonstrating a greater reduction. However, there was no significant difference between the smooth and flat surfaces following 7 days’ incubation for S. marcescens and no significant differences between any of the surfaces following 7 days’ incubation for S. epidermidis . The results suggest that flattening the p-PVC surfaces may limit potential biofilm formation for the current duration of platelet storage time of 5 days. It is hoped that this work will enhance the understanding of how surface properties influence the development of microbial biofilms in platelet concentrate bags in order to devise a solution to discourage biofilm formation. [ABSTRACT FROM AUTHOR]

Microbial catalysed electrochemical systems are intensively used in basic and applied research as a sustainable platform for harnessing energy and generating value added bio-products. Recently more emphasis is being laid on enhancement of AD (Anaerobic Digestion) by integrating ME (Microbial Electrolysis) with it to convert CO 2 (Carbon dioxide) directly to CH 4 (Methane). This research attempts to shed light on the effects of electrode positioning and arrangement along with hydraulic retention time (HRT), on CH 4 generation, and organic removal in novel microbial electrolysis coupled anaerobic digestion (ME-AD) reactors. However, the positioning and placement of electrodes in a ME-AD reactor have not yet been evaluated. Four reactors (S1, S2, S3 and S4) are designed with different electrode arrangements and run in four different HRTs (12, 18, 24 and 36 h) with beer brewery wastewater as the substrate for treatment. The reactors with electrodes arranged at the bottom are better in performance than the reactors with electrodes placed at the top. They have maximum COD, TOC and Carbohydrate removal efficiencies of 92.1%, 64.2% and 98.9% respectively, high methane production rate (MPR) and methane yield (MY) with 304.5 mLCH 4 /Lreactor/day and 275.8 mL/gCOD respectively and a maximum current generation of 10 mA, all at 36 h HRT. Electrode placement also has crucial roles to play in microbial community prevalence on the electrode biofilm of the reactors. Methanogens and electrogens are well enriched on the electrode biofilms of the reactors with bottom positioned electrodes, revealing the basis behind their maximum organic removal, methane production efficiencies and current generation. This study demonstrates that the optimization of appropriate electrode position and placement in ME-AD reactors is crucial for their performance and development. [ABSTRACT FROM AUTHOR]

The impacts of exogenous or endogenous quorum sensing (QS) signaling molecules on mixed-culture electroactive biofilms (EABs), especially extracellular polymeric substances (EPS) and exoelectrogens using direct electron transfer mechanism inside EABs are poorly understood. This research focuses on the influence of acylhomoserine lactones (AHLs), the most common QS signaling molecules for gram negative bacteria, on mixed-culture EABs. Results indicated that both exogenous and endogenous AHLs played the role as regulators to improve the electrochemical activities of EABs. The energy recovery of MFCs increased from 20.5% ± 3.9% to 28.3% ± 4.1% with endogenous AHLs and further rose to 36.2% ± 5.1% with exogenous AHLs, and the start-up period of MFCs shortened from 13 days to 10 days with endogenous AHLs and further reduced to 4 days in the presence of exogenous AHLs. The influences of exogenous and endogenous AHLs were non-instantaneous. They improved some intrinsic properties, i.e. the electrode-associated biomass, the biofilm compactness and the ratio of live/dead cells to obtain superior EABs. Meanwhile, both endogenous and exogenous AHLs increased the concentration and redox activities of EPS. Besides, endogenous AHLs enhanced the diversity of EPS components. Noteworthily, the relative abundance of Geoboacter sp. which is the typical microbe using direct electron transfer mechanism is raised by exogenous AHLs, though so far neither known chemical QS-related gene nor protein has been reported in this genus. These findings will increase the current understanding of QS in EABs and open up an opportunity for regulating mixed-culture MFCs via QS. [ABSTRACT FROM AUTHOR]

This paper represents the first study to simulate the biodegradation rates (BDRs) of several components in the sewer using the sewer biodegradation model (SBDM). In order to verify the fitness between the experimental values and model values, experiments were conducted in a 21 m long sewer pilot plant and the results showed high fitness (All correlational coefficient values were greater than 0.91). Since the SBDM was validated, the biodegradation rate (BDR) was simulated. The production of hydrogen sulfide was also simulated. The results revealed that aerobic growth of heterotrophs in biofilm predominated the biodegradation. The growth rate of heterotrophs in biofilm was greater than the decay rate from initial time to the 3rd hour, but it changed after the 4th hour because of low substrate concentration. During the experimental period, the BDRs were greater than the supply rate for five components. For two components, the supply rates were greater than the BDRs. The BDR of dissolved oxygen was greater than the supply rate before the 3rd hour but that reversed after the 3rd hour. According to the results, the sewer biodeterioration could be simulated using SBDM. [ABSTRACT FROM AUTHOR]

A novel method to investigate penetration, distribution and metabolic effects of biocides in microbial biofilms is described. LASCA (laser ablation solvent capture by air flow) mass spectrometry imaging (MSI) allowed for the visualization of distributions of specific ion masses, including the signature of a quaternary ammonium salt biocide, benzyl dimethyl dodecyl ammonium chloride (BDDAC), throughout the biofilm. The biocide penetrated the upper layers of a Marinobacter sp. biofilm on a carbon steel coupon in seawater after 30 min. The concentration initially decreased with depth; however, it again increased close to the metal surface. Penetration of the biocide primarily occurred close to the center of the circular coupon, where ions with negative mass defects were preferentially detected, indicating that this is the anodic region of the corroding coupon. Future work using high performance liquid chromatography/mass spectrometry (HPLC/MS) will allow the identification within the biofilm of bacterial metabolites directly affected by biocide action. [ABSTRACT FROM AUTHOR]