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Biofilm is central for biological water treatment processes in recirculating aquaculture systems (RAS). A lack of suitable methods for quantifying biofilm activity, however, makes it difficult to assess and compare the microbial status of biofilm. This type of information of the biofilm will be useful to assess the colonization status of nitrifying biocarriers or to evaluate the effect of disinfectants on the biofilm activity.Here we introduce a novel assay for rapid assessment of microbial activities in the biofilm attached on bioelements from a RAS biofilter. The assay consisted of an intermittent respirometer platform where biofilter elements were exposed to 10 mg/L hydrogen peroxide (H2O2) for 1 h, following concurrent measurements of oxygen release from the decomposition of H2O2 caused by biofilm-associated enzymes. A different number of colonized, mature bioelements from a moving bed biofilter in a freshwater RAS were tested with repeated H2O2 exposure, and compared against their autoclaved forms. A substantial increase in dissolved oxygen (DO) concentration (0.92–2.31 mg O2/L) occurred with mature bioelements during 1 h of H2O2 exposure, compared to small amounts of DO release (≤0.27 mg O2/L) with autoclaved bioelements. This substantiates that H2O2 decomposition by biofilm is mainly governed by microbial enzymatic activities. A monomolecular model fitted well with the observed oxygen release profiles of tested mature bioelements after H2O2 exposure (R2 > 0.98). The kinetic rate constant of net oxygen release (kor, h−1) was proportional (R2 for linear fit = 0.99) to the number of mature bioelements tested. Repeated exposure of H2O2 to the same bioelements did not change kor, which indicates that 10 mg/L H2O2 with an exposure time of 1 h does not suppress enzymatic activity in biofilm. Our study provides a new rapid method that allows simple quantification of microbial activity in biofilm samples from aquaculture systems, which could potentially be also applied to study biofilm from wastewater treatment plants and other industries.

Although residual tetracycline, NH4+-N, and P in aquaculture wastewater have been frequently detected, their simultaneous removal has received little attention. The simultaneous and efficient removal of tetracycline, NH4+-N, COD, and P in aquaculture wastewater was achieved with a laboratory-scale moving bed biofilm reactor (MBBR) under different influent C/N ratios. The results suggested that tetracycline could be degraded efficiently without using an additional organic carbon source. Most of the tetracycline (>80%), NH4+-N (>73%), TN (>68%), TP (>59%), and COD (>78%) were synchronously removed under the higher C/N ratios. The electron transport system activity (ETSA), dissolved organic matter (DOM), and extracellular polymeric substances (EPS) were evaluated for biofilm performance during aquaculture wastewater remediation. The results indicated that the protein (PN) and polysaccharide (PS) concentrations, and fluorescence intensities were significantly different because the influent C/N ratios changed the biofilm activity. The ETSA values were lowest when tetracycline was the sole carbon source, which suggested that tetracycline affected the nitrification activity of biofilms. Sphingobacteriia, Betaproteobacteria, and Alphaproteobacteria were identified as the dominant bacterial classes. This study provides a new strategy for the removal of tetracycline and nutrients from aquaculture wastewater. [ABSTRACT FROM AUTHOR]

Background: The green tea have antimicrobial activity against many types of bacteria It is considered a natural substance with few side effect. Aim of the Study: An in vitro study was carried out to investigate the ability of green tea extract and nicotine to inhibit growth, biofilm formation by salivary Mutans streptococci. Methods: This study included a convenient sample of 40 healthy Iraqi volunteers aged 18–23 years old from College of Dentistry / University of Baghdad. Green tea and nicotine aqueous extract were prepared in different concentration to use in agar diffusion method to detect the activity of extract, and ELISA reader in multi titer plate was used to determine the ability of salivary mutans Streptococci to form biofilm in the presence and absence of the extracts.to measure the biofilm inhibition rate. Results: Mutans Streptococci were sensitive to green tea and nicotine in different concentrations the diameters of the inhibition zone were effective in a dose dependent manner significantly. There was a significant difference between the concentrations of each extracts, antibacterial activity was in a dose dependent manner for the extracts. The minimum bactericidal concentration of green tea was (280 mg/ml) and minimum bactericidal concentration of nicotine was (45mg/ml). The study found that biofilm formation by Mutans Streptococci was markedly decreased in the presence of 1/2 minimum bactericidal concentration of both green tea and nicotine with mean of O.D 590 nm = 0.54 in comparison with green tea extracts and nicotine alone O.D 590 nm = 0.15, 0.68 respectively. Conclusions green tea and nicotine extracts in different concentration effectively reduced the biofilm formation of salivary Mutans streptococci. While the presence of nicotine has negatively impacted on the ability of green tea extracts in the inhibition of biofilm formation by Mutans Streptococci in vitro.

The present study evaluated the antibacterial activity of twenty essential oils from Algerian plants against the multi-drug resistant (MDR), the extended-drug resistant (XDR), the pan-drug resistant (PDR) and the wild strains of Acinetobacter baumannii: a major human pathogen for which only a few effective treatments are nowadays available. Special attention was also given to their effect on A. baumannii biofilm formation. The chemical composition of the essential oils was determined by gas chromatography and gas chromatography-mass spectrometry analysis, while the antibacterial activity was determined by disc diffusion and microdilution broth sensitivity assays. Microscopic visualization highlighted the effect of the most active essential oils on biofilm formation. Molecular docking was performed to investigate the binding mode of imipenem, thymol and cinnamaldehyde against target proteins (PBP1, OMPA and IMP2). Eight of the twenty essential oils showed very good activities against resistant A.baumannii with inhibition zones greater than 20 mm. Ammoides verticillata essential oil recorded the lowest minimum inhibitory concentrations, biofilm inhibition and biofilm eradication concentrations values no more than 0.217 mg/mL, 0.48 mg/mL, and 0.48 mg/mL, respectively. A. verticillata and C. cassia not only inhibited biofilm formation but also weakened and dissolved pre-formed biofilms. The in-silico and in-vitro studies showed that phytochemical analogues, thymol and cinnamaldehyde had improved physicochemical characteristics, greater binding affinities and, a better anti-Acinetobacter activity comapared to imipenem. The results of this study suggest that essential oils and their individual components can be used as therapeutic substances and as cleaning products since they are effective and eco-friendly. [ABSTRACT FROM AUTHOR]

Benzimidazole type N‐heterocyclic carbene molecules and their metal complexes have well‐known biological activity. Elemental silver and silver complexes also have antibacterial and antifungal activity. In this study, silver complexes with 1‐allyl 5,6‐dimethylbenzimidazolium derivative ligands were analyzed for their antimicrobial and antibiofilm activities. Additionally, bovine serum albumin (BSA) binding properties of the molecules were analyzed by spectrophotometric methods, and the details of interactions of the molecules with BSA were investigated by molecular docking methods. While N‐heterocyclic carbene salts showed moderate antifungal and antibiofilm activity, silver complexes of these salts have strong antimicrobial activity with <1.9–15.6 μg/ml minimal inhibitory concentration (MIC) values. On the other hand, carbene salts have better affinity against BSA than the complexes. Additionally, the interaction of the optimized complexes with SarA and BSA were analyzed by molecular docking methods. According to in vitro and in silico evaluation, the studied Ag complexes may be utilized for advanced studies. [ABSTRACT FROM AUTHOR]

Floating treatment wetlands (FTW) are an emerging Nature Based Solution that have exhibited promising nitrogen removal under different range of effluents pollutant concentrations. Despite the notable increase in the number of FTW studies in the last years, nitrogen (N) removal mechanisms within FTW have not been fully assessed. The present study aims to understand N removal in FTW and investigate their microbial biofilm activity through a pilot scale experiment for agri-food tertiary wastewater treatment. A conventional and a modified (with added cellular concrete (CC)) FTW were monitored over 7 months with respect to two control lagoons (conventional lagoons with or without CC hanging in the water column). Experimental results revealed that the best TN removal was achieved by the lagoon equipped with the modified FTW (20% mean removal increase compared to the conventional lagoon). Biofilm denitrification activity potential was up to 6.7–9.0 times higher within pilot lagoons equipped with FTW than that in control lagoon (LC without FTW), while nitrification activity potential was prominent in biofilms within the control pilot lagoons (exhibiting high dissolved oxygen (DO) concentration). Biofilms from plant roots exhibited the highest overall dissolved inorganic nitrogen treatment followed by the biofilms from sediments and CC material. Plant root biofilms exhibited both significant nitrification and denitrification activity potentials despite the overall low DO and COD concentrations within FTW pilot lagoons' water column. This suggests the existence of micro sites in the roots network which provide adequate aerobic conditions and access to organic carbon most probably through root exudates. Overall, N accumulation in the sediment was a minor removal mechanism for all pilot lagoons. Plant accumulation (accounting for one third of TN removal), nitrification and enhanced denitrification appeared to be the main removal mechanisms in pilot lagoons equipped with FTWs (with or without CC) while nitrification, algal assimilation and NH 4 -N volatilization may have been the major processes driving TN removal in the control pilot lagoons. Hence, FTW could be an interesting retrofit of existing lagoons to promote nitrogen removal through denitrification and plant assimilation, especially in the case of receiving bodies highly sensitive to nitrate input. Further research should address optimizing FTW design to guarantee stable N removal under changing water temperature and mitigate seasonal variations as well as investigate biofilm species for in-depth understanding of N cycle within FTWs. [ABSTRACT FROM AUTHOR]

This paper explores the performance of pilot-scale constructed wetland osmotic microbial fuel cell (CW-OMFC) in different gravel conditions. The performance was measured in terms of power generation, water flux, chemical oxygen demand (COD) removal, and coulombic efficiency. The CW-OMFC was divided into four sections based on the porosity of the materials. The surface area of materials at Side A, Side B, Side C, and Side D were 2.717 m2.g−1, 0.228 m2.g−1, 0.095 m2.g−1, and 0.072 m2.g−1, respectively. The CW-OMFC achieved maximum water flux, minimum reverse salt flux, high power density, and COD removal efficiency of 6.66 ± 0.5 L.m−2.h−1, 3.33 ± 1.2 g.m−2.h−1, 59.53 ± 10 mW.m−2 and 84.69%, respectively, by using high porous materials. The nutrients (nitrogen, phosphorus, and potassium) uptake by plants from wastewater were 12.17%, 12.01%, and 21.73%, respectively. [ABSTRACT FROM AUTHOR]

Biosynthesis is an important method for synthesizing nanoparticles at low cost, also they should be environmentally friendly, with tunable properties, and should possess potency applications than the synthetic method. The iron oxide nanoparticles were efficiently biosynthesized using the leaf extract of Celosia argentea. The phytochemicals in Celosia argentea leaves' extract were analyzed. The synthesized nanoparticles were characterized for knowing their structural, elemental, and optical properties using analytical techniques. The obtained results confirmed the formation of iron oxide nanoparticles with SPR band at 299 nm in high crystalline nature. The Fe–O bonding was validated. The particles formed in spherical shape with 5–10 nm size. The Fe and O occurrence was further confirmed from Fe and O spots in the mapping spectrum. The bioactive medicinal property of synthesized iron oxide nanoparticles was known from biofilm activity, antioxidant, anti-inflammatory, anti-diabetic, and larvicidal activities. The antibacterial activity which is depicted by the high zone of inhibition was observed at 19 mm (E. coli) and 25 mm (S. aureus) with 150 μg/mL concentration. At 150 μg/mL concentration, a higher inhibition rate was observed for biofilm activity. A higher activity was unveiled at 97% in 80 μg/mL concentration for antioxidant activity. The high activity was obtained at 93% and 87% in 500 μg/mL concentration for anti-inflammatory and anti-diabetic activities, respectively. An increased level of death rate of Anopheles subpictus, larvae were incurred at 24 h in 100 ppm and 48 h in 80 and 100 ppm. In MTT analysis, the high inhibition of 86% was achieved at 50 μg/mL concentration. Thus, all these results convey that the synthesized iron oxide nanoparticles may be utilized as antibiotic drugs and pesticides. [ABSTRACT FROM AUTHOR]

[Display omitted] • Performance of BE-UASB treating high-sulfate methanolic wastewater was evaluated. • BE-UASB exhibited COD removal of 93.6 % with 1.4-fold CH 4 yield of control. • Humics as main components of EPS on electrodes benefited the electron transfer. • Electrocatalysis induced synergy between Acetobacterium and SRB to reduce SO 4 2−. • BE-UASB restructured MPA to alleviate the competition with SRB for electron donors. A bioelectrochemical upflow anaerobic sludge blanket (BE-UASB) was constructed and compared with the traditional UASB to investigate the role of bioelectrocatalysis in modulating methanogenesis and sulfidogensis involved within anaerobic treatment of high-sulfate methanolic wastewater (COD/SO 4 2− ratio ≤ 2). Methane production rate for BE-UASB was 1.4 times higher than that of the single UASB, while SO 4 2− removal stabilized at 16.7%. Bioelectrocatalysis selectively enriched key functional anaerobes and stimulated the secretion of extracellular polymeric substances, especially humic acids favoring electron transfer, thereby accelerating the electroactive biofilms development of electrodes. Methanomethylovorans was the dominant genus (35%) to directly convert methanol to CH 4. Methanobacterium as CO 2 electroreduction methane-producing archaea appeared only on electrodes. Acetobacterium exhibited anode-dependence, which provided acetate for sulfate-reducing bacteria (norank Syntrophobacteraceae and Desulfomicrobium) through synergistic coexistence. This study confirmed that BE-UASB regulated the microbial ecology to achieve efficient removal and energy recovery of high-sulfate methanolic wastewater. [ABSTRACT FROM AUTHOR]

Aims: The current study aimed to screen Bacillus strains with wide‐spectrum quorum quenching (QQ) activity against N‐acyl‐l‐homoserine lactones (AHLs), helpful in controlling virulence traits in Gram‐negatives, including biofilm formation and also with anti‐biofilm activity against Gram‐positives. Methods and Results: A total of 94 halotolerant strains of Bacillus isolated from soil and salt‐lake sediment samples in Algeria were examined for the presence of QQ activity against AHLs, the presence of the aiiA gene, encoding an AHL lactonase enzyme typical of Bacillus spp., antimicrobial and anti‐biofilm activities against Pseudomonas aeruginosa and Streptococcus mutans. Of all strains of Bacillus spp. isolated, 48.9% showed antibacterial activity. In addition, 40% of these isolates showed a positive QQ activity against long‐chain AHLs, of which seven strains presented the aiiA gene. Among the species with broad‐spectrum QQ activity, the cell extract of Bacillus thuringiensis DZ16 showed antibiofilm activity against P. aeruginosa PAO1, reducing 60% using the Amsterdam active attachment (AAA) biofilm cultivation model. In addition, the cell extract of B. subtilis DZ17, also presenting a broad‐spectrum QQ activity, significantly reduced Strep. mutans ATCC 25175 biofilm formations by 63% and 53% in the xCELLigence and the AAA model, respectively, without affecting growth. Strain DZ17 is of particular interest due to its explicit halophilic nature because it can thrive at salinities in the range of 6%–30%. Conclusions: B. thuringiensis DZ16 and B. subtilis DZ17 strains have interesting antibacterial, QQ, and anti‐biofilm activities. The high range of salinities accepted by these strains increases their biotechnological potential. This may open up their use as probiotics, the treatment and prevention of conventional and emerging infectious diseases. Significance and Impact of Study: The use of safe, economical and effective probiotics is limited to control the infections related to multi‐resistant bacteria. In our study, we provide two promising agents with QQ, anti‐biofilm and antibacterial activities. [ABSTRACT FROM AUTHOR]

Probiotic microorganisms can release bioactive substances that can inhibit the growth and biofilm formation of pathogenic microorganisms such as Streptococcus mutans. Dental caries is a multi-factorial chronic infection disease, which starts with bacterial biofilm formation caused mainly by S. mutans. This study investigated the characteristics of Lactobacillus spp. strains as an oral probiotic. Twelve Lactobacillus spp. species obtained from fermented milk and dairy products were identified. Antimicrobial activity was determined with the Minimum Inhibition Concentration against S. mutans as an oral pathogen. Biofilm formation capabilities of the identified Lactobacillus strains in supernatant and culture media were determined. In addition, their ability to α-amylase tolerance and pH values (24h-48h) were determined. L.plantarum showed the highest antimicrobial activity compare other Lactobacillus strains. Also, L. plantarum inhibited biofilm formation.

Abstract—The relevance of this work consists in the necessity of improving the methods of service life prediction for structural materials in aquatic environments. This paper presents the results of studies concerning corrosion kinetics for certain structural metals in the seawater of the South China Sea. In this paper, the results are presented for the mathematical simulation of corrosion for St3 grade steel and copper-containing metals (copper, bronze, brass). It is shown that the most acceptable model for the corrosion rate K(t) is represented by the hyperbolic model K(t) = 6.06 t–0.21, R = 0.8, whereas the most acceptable model for specific corrosive loss M is represented by the power-law kinetic model M(t) = 181.9t0.79, R = 0.98. [ABSTRACT FROM AUTHOR]

Anode is a critical component in improving the performance of microbial fuel cells (MFC). Carbon nanotubes (CNTs) anodes of varying concentrations were employed to coat carbon felt (CF) using the dyeing method without the need of any binder agent. The anode's large and conductive electrode surface area enhances the flow of electrons from the yeast to the current collector and the adhesion/growth of the biofilm. Additionally, the enhanced bioelectrochemical activity was demonstrated by complete cell electrochemical measurements on the MFC using the synthesized anode. The CF/CNT2 electrode (4% w/v of CNT) is the optimum electrode because it produces MFC comparable performance to the CF/CNT3 electrode (6% w/v of CNT). Using CF/CNT2 electrodes, yeast MFC yields voltages and Maximum Power Densities (MPDs) of 0.255 ​V and 72.46 ​mW/m2, respectively. When compared to MFCs employing CF without any modification with CNTs, these outputs were roughly 40 and 436% higher, respectively. While the glucose on the MFC substrate decreases by 95.97 ​± ​0.14%, the conductive biofilm developing on the electrode surface increases by 255 ​± ​13 ​mg, which helps to boost electron transfer fairly nicely. That seems to be, the modified CF/CNT2 anode promoted the enrichment of electro-active microorganisms.

Microbial fuel cell (MFC) can utilize the metabolism of electroactive microorganisms to remove organic pollutants from wastewater, and the application of capacitive anodes can enhance the power generation capacity of MFC and the energy storage capacity of bioelectronics. This research aimed to create a capacitive anode with a large specific surface area and excellent electrical conductivity. To achieve this aim, iron-doped cross-linked puffed carbon (CPC–Fe) was prepared for the modification of carbon cloth (CC) substrates by a simple one-step expansion carbonization method using FeCl 3 ·6H 2 O and maltose as raw materials. The surface structure characterization confirms the successful incorporation of Fe atoms, with Fe 3 O 4 accounting for 79.61%. Fe 3 O 4 exhibits excellent specific capacitance characteristics and can also serve as a good conductor for the transmission or reception of electrons generated by electroactive bacteria. Furthermore, the mesoporous volume of CPC-Fe significantly increases, which contributes to the enhancement of the specific capacitance of material and the improvement of charge storage capacity. Based on these advantages, the maximum power density of MFC equipped with CPC-Fe/CC anode reaches 1850.50 mW m−2. The CPC-Fe/CC bioanode has a cumulative total charge of 1076.02 C m−2, showing good capacitive behaviour and exhibiting a significant enrichment effect on Geobacter species. This study demonstrates that the regulation of extracellular electron transfer (EET) process based on bioelectronic reception steps can not only enhance the power generation performance of MFC, but also effectively improve the energy storage capacity of MFC, which offers significant knowledge for the development of electrode design in other bioelectrochemical systems. [Display omitted] • Iron-doped cross-linked puffed carbon modification improve MFC performance. • CPC-Fe/CC anode increases MFC power density to 1850.50 mW m−2. • CPC-Fe/CC anode achieves the best electron harvesting capacity. • The cumulative total charge of CPC-Fe/CC bioanode reaches 1076.02 C m−2 • The relative abundance of typical electrogenic bacteria is improved. [ABSTRACT FROM AUTHOR]

A series of 1, 2, 4, 5-tetrasubstituted imidazole derivatives were synthesized and their antibiofilm potential against Candida albicans was evaluated in vitro . Two of the synthesized derivatives 5e ( IC 50  = 25 µg/mL) and 5m (IC 50  = 6 µg/mL),displayed better antifungal and antibiofilm potential than the standard drug Fluconazole (IC 50 = 40 µg/mL) against C. albicans . Based on the in vitro results, we escalated the real time polymerase chain reaction (RT-PCR) analysis to gain knowledge of the enzymes expressed in the generation and maintenance of biofilms and the mechanism of biofilm inhibition by the synthesized analogues. We then investigated the possible interactions of the synthesized compounds in inhibiting agglutinin-like proteins, namely Als3, Als4 and Als6 were prominently down-regulated using in-silico molecular docking analysis against the previously available crystal structure of Als3 and constructed structure of Als4 and Als6 using the SWISS-MODEL server. The stability and energy of the agglutinin-like proteins-ligand complexes were evaluated using molecular dynamics simulations (MDS). According to the 100 ns MDS, all the compounds remained stable, formed a maximum of 3, and on average 2 hydrogen bonds, and Gibb's free energy landscape analysis suggested greater affinity of the compounds 5e and 5m toward Als4 protein.Communicated by Ramaswamy H. Sarma.

Abstract Bioclogging is a main concern in infiltration systems as it may significantly shorten the service life of these low-technology water treatment methods. In porous media, biofilms grow to clog partially or totally the pore network. Dynamics of biofilm accumulation (e.g., by attachment, detachment, advective transport in depth) and their impact on both surface and deep bioclogging are still not yet fully understood. To address this concern, a 104 day-long outdoor infiltration experiment in sand tanks was performed, using secondary treated wastewater and two grain size distributions (GSDs): a monolayer system filled with fine sand, and a bilayer one composed by a layer of coarse sand placed on top of a layer of fine sand. Biofilm dynamics as a function of GSD and depth were studied through cross-correlations and multivariate statistical analyses using different parameters from biofilm biomass and activity indices, plus hydraulic parameters measured at different depths. Bioclogging (both surface and deep) was found more significant in the monolayer fine system than in the bilayer coarse-fine one, possibly due to an early low-cohesive biofilm formation in the former, driven by lower porosity and lower fluxes; under such conditions biomass is favorably detached from the top layer, transported and accumulated in depth, so that new biomass might colonize the surface. On the other hand, in the bilayer system, fluxes are highest, and the biofilm is still in a growing phase, with low biofilm detachment capability from the top sand layer and high microbial activity in depth, resulting in low bioclogging. Overall, the bilayer coarse-fine system allows infiltrating higher volume of water per unit of surface area than the monolayer fine one, minimizing surface and deep bioclogging, and thus increasing the longevity and efficiency of infiltration systems. Graphical abstract Unlabelled Image Highlights • Early biofilm formation in fine sands results in an early surface bioclogging. • Homogeneous grain size favors biomass transport in depth promoting deep bioclogging. • Coarse-fine system develops an active biofilm minimizing deep bioclogging. [ABSTRACT FROM AUTHOR]

Polycarbonate (PC) and polyethylene terephthalate (PET) thermoplastic polymer films were irradiated by low energy ion beams such as 100 keV Hydrogen (H+) ions and 350 keV Nitrogen (N+) ions at varied fluence from 1 × 1013 ions/cm2 to 5 × 1014 ions/cm2. The depth profile concentration of ions was calculated using Stopping and Range of Ions in Matter (SRIM) software code. Fourier Transform Infrared (FTIR) technique shows decrement in the intensity of peaks and disappearance of peaks mainly related to carbonyl stretching at 1770 cm−1 and C–C stretching at 1500 cm−1. Scanning electron microscopy (SEM) of irradiated polymers showed the formation of pores. X-ray diffraction (XRD) analysis has showed decrease in the intensity indicating the decrease in crystallinity after irradiation. Mechanical studies revealed that the molecular weight and microhardness decrease with increase in ion fluence due to increase in chain scission. The contact angle increased with increase in ion fluence indicating the hydrophobic nature of polymer after irradiation. Antibiofilm activity test of irradiated films shows resistance to Salmonella typhi (S. typhi) pathogen responsible for typhoid. The study shows that Nitrogen ion induces more damage compared to Hydrogen ions and PC films get more modified than PET films. [ABSTRACT FROM AUTHOR]

Background: The diffusion of antimicrobial resistance is a significant concern for public health worldwide. Staphylococcus aureus represents a paradigm microorganism for antibiotic resistance in that resistant strains appear within a decade after the introduction of new antibiotics. Methods: Fourteen S. aureus isolates from human specimens and twenty-one from samples of animal origin, were compared for their antimicrobial resistance and biofilm capability. In addition, they were characterized at the molecular level to detect the antimicrobial resistance mecA gene and genes related with enterotoxin, toxin, and biofilm production. Results: Both phenotypic and molecular analysis showed main differences among human- and animal-derived isolates. Among the human-derived isolates, more multidrug-resistant isolates were detected and mecA gene, enterotoxin, and toxin genes were more prevalent. Different genes involved in biofilm production were detected with bap present only in animal-derived isolates and sasC present in both isolates, however, with a higher prevalence in the human-derived isolates. Biofilm capability was higher in human-derived isolates mainly associated to the sasC gene. Conclusions: The overall results indicate that human S. aureus isolates are more virulent and resistant than the isolates of animal origin randomly selected with no infection anamnesis. This study confirms that selection for more virulent and resistant S. aureus strains is related to the clinical practice.

Improving the stimulation effect of electric current density (ECD) on microbial community is critical in designing and operating TDE-BAF. This study investigated the effect of ECD at 0.00, 4.08, 6.12, 12.20, 14.25, 16.30 and 20.20 A·m −2 on the removal performance, diversity and structure of microbial community in TDE-BAF. Results indicated that the ECD of 14.25 A·m −2 exhibited the highest COD, TOC and NH 4 + -N average removal rates with 93.33%, 91.26% and 93.87%, respectively; Under high ECD, especially exceeding 14.25 A·m −2 , the inhibition of growth and activity because of plasmatorrhexis was in agreement with the sharp biomass decline; there was no significant relation between community richness and diversity and removal efficiency below optimum ECD, while above optimal ECD, it was just the opposite; Microbial communities mainly including Hydrogenophaga, Saprospiraceae_uncultured, Delftia, Enterobacter, Pseudomonas, Pseudoxanthomonas, and Nitrosospira and physicochemical properties well explained the excellent removal performance at the optimum ECD. [ABSTRACT FROM AUTHOR]

Three new analogues of the fungal metabolite macrocidin Z, derived from homoserine, o-tyrosine and 5-hydroxytryptophan, rather than l -tyrosine were synthesised and tested for efficacy against selected pathogenic biofilms. They exhibited significant growth inhibitory and dispersal effects against S. aureus biofilms, comparable to those of the natural lead macrocidin Z, and even superior to those of non-natural normacrocidin Z, which they resemble more closely. Their low level of toxicity to human cells and bacteria warrants a more detailed assessment. [Display omitted] [ABSTRACT FROM AUTHOR]

Biofilm is central for biological water treatment processes in recirculating aquaculture systems (RAS). A lack of suitable methods for quantifying biofilm activity, however, makes it difficult to assess and compare the microbial status of biofilm. This type of information of the biofilm will be useful to assess the colonization status of nitrifying biocarriers or to evaluate the effect of disinfectants on the biofilm activity. Here we introduce a novel assay for rapid assessment of microbial activities in the biofilm attached on bioelements from a RAS biofilter. The assay consisted of an intermittent respirometer platform where biofilter elements were exposed to 10 mg/L hydrogen peroxide (H 2 O 2 ) for 1 h, following concurrent measurements of oxygen release from the decomposition of H 2 O 2 caused by biofilm-associated enzymes. A different number of colonized, mature bioelements from a moving bed biofilter in a freshwater RAS were tested with repeated H 2 O 2 exposure, and compared against their autoclaved forms. A substantial increase in dissolved oxygen (DO) concentration (0.92-2.31 mg O 2 /L) occurred with mature bioelements during 1 h of H 2 O 2 exposure, compared to small amounts of DO release (≤0.27 mg O 2 /L) with autoclaved bioelements. This substantiates that H 2 O 2 decomposition by biofilm is mainly governed by microbial enzymatic activities. A monomolecular model fitted well with the observed oxygen release profiles of tested mature bioelements after H 2 O 2 exposure (R 2  > 0.98). The kinetic rate constant of net oxygen release ( k or , h -1 ) was proportional (R 2 for linear fit = 0.99) to the number of mature bioelements tested. Repeated exposure of H 2 O 2 to the same bioelements did not change k or , which indicates that 10 mg/L H 2 O 2 with an exposure time of 1 h does not suppress enzymatic activity in biofilm. Our study provides a new rapid method that allows simple quantification of microbial activity in biofilm samples from aquaculture systems, which could potentially be also applied to study biofilm from wastewater treatment plants and other industries., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (©2023PublishedbyElsevierB.V.)

This study verified the effect of N-acyl homoserine lactone (AHL) concentrations on mature biofilm systems. Three concentrations of an AHL mixture were used in the batch test. Introducing of 5 nM AHLs significantly increased biofilm activity and increased sludge characteristics, which resulted in better pollutant removal performance, whereas exogenous 50 nM and 500 nM AHLs limited pollutant removal, especially COD and nitrogen removal. To further identify how exogenous signal molecular affects biofilm system nitrogen removal, analyzing of nitrifying bacteria through real-time polymerase chain reaction (RT-PCR) revealed that these additional signal molecules affect nitrifying to total bacteria ratio. In addition, the running state of the system was stable during 15 days of operation without an AHL dose, which suggests that the changes in the system due to AHL are irreversible. [ABSTRACT FROM AUTHOR]

A newly aerobic denitrifying bacterial strain,Pseudomonassp. X31, which was isolated from activated sludge, was added to a newly developed aerobic denitrification bio-ceramsite reactor as an inoculum to treat nitrate-polluted water and the denitrification activities of this system under different air–water ratio, hydraulic loading, and C/N (carbon/nitrogen ratio) conditions were investigated. It demonstrated excellent capability for denitrification in the bio-ceramsite reactor at air–water ratios that varied from 6.5:1 to 8:1. The optimal hydraulic loading for the bio-ceramsite reactor was 0.75 m/h with the optimum denitrification efficiency of 95.18%. The optimal C/N was 4.5:1 with a maximum nitrate removal efficiency of 98.48%. COD could be completely removed under the most appropriate condition (air–water ratio 6.5:1–8:1, hydraulic loading 0.75 m/h, and C/N 4.5:1). The quantity of the biomass in the reactor decreased along with flow, which was in accordance with the variety of the available substrate concentrations in the water. However, the biofilm activity was not proportional to the biomass in the bio-ceramsite reactor, but increased with the quantity of the biomass up to a peak value and then decreased. [ABSTRACT FROM AUTHOR]

• The high organic and ammonia wastewater mainly show effects of ammonium ion in MECs. • High ammonia loading inhibited substrate consumption but increased current output. • Peak anode electrochemical activity was obtained at ammonia loading of 1000 mg L–1. • High ammonia loading enriched exoelectrogens and hydrogenotrophic methanogens. • MECs can resist high ammonia loading under neutral pH with positive energy feedback. When facing wastewater with high organic and ammonia, e. g. swine wastewater, microbial electrolysis cell (MEC) is emerging for energy extraction as hydrogen and methane. However, the effects of highly concentrated ammonia on MEC haven't been fully evaluated. In this study, single-chamber MECs were operated with acetate and sucrose as substrates under various ammonia concentrations. The current generally increased with ammonia loading from 80 to 3000 mg L–1. Yet, the substrate consumption in MECs was inhibited with ammonia concentrations above 1000 mg L–1. As a combined result, the energy recovery efficiency of MECs was stable. The electrochemical activity of anode biofilm reached the peak under 1000 mg L–1 ammonia and was restricted under higher ammonia loadings. Under neutral pH, the NH 4 + increases the cell membrane permeability, which benefited the electrochemical activity of exoelectrogens to a proper extent. Nevertheless, the toxic ammonia also accelerated the anode biomass loss and stimulated the extracellular polymeric substance (EPS) secretion. Due to the current increase, the abundance of exoelectrogens generally raised with ammonia loading from 80 to 3000 mg L–1. However, except for anode biomass loss, the carbon and methane metabolism pathways were inhibited in acetate-fed MEC, while the glycolysis acted as the rate-limiting step for substrate degradation in sucrose-fed conditions. This study systematically examined the influences of high ammonia loading on MEC performances, bio-community and anode electrochemical activities, and evaluated practical feasibility and application inch of MECs for the energy recovery and pollutant removal of high concentration organic and ammonia wastewater. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: To improve hydrogen production performance, this paper describes a novel approach for fabricating a biofilm photobioreactor by adsorption of the photosynthetic bacteria (PSB) Rhodopseudomonas palustris CQK 01 on a hollow optical fiber (HOF) with a GeO2–SiO2–chitosan medium (GSCM) coating. The composition of the coating is analyzed using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The biocompatibility of the GSCM-coated HOF and the PSB in the hungry condition are examined. We also quantitatively investigate the biofilm dry weight; protein, polysaccharide, bacteriochlorophyll, carotenoid, and ATP contents of the biofilm cell; and average H2 production rates. The GSCM-coated HOF exhibits enhanced the biofilm biomass, improved the biofilm activity, and an increased H2 production rate. The proposed photobioreactor yielded fairly stable long-term performance with a hydrogen production rate of 2.65 mmol/L/h, which is 1.56 and 1.51 times higher than those of photobioreactors with an uncoated HOF and with a fiber having a roughened surface obtained by wrapping it in wire mesh, respectively. [Copyright &y& Elsevier]

Highlights: [•] Preparation of porous ceramsite using urban sludge and industrial waste. [•] Magnetic modified porous ceramsite with simply achievable method. [•] Magnetic modified porous ceramsite applied for the treatment of coking wastewater. [ABSTRACT FROM AUTHOR]

The article presents a research study on the in vitro biofilm activity of 66 Candida isolates from mastitic Anatolian buffalo milk in Western Turkey. The study reveals that Candida krusei, Candida rugosa, and Candida kefyr were the most common species found in the milk among the isolates. It states that the study can be beneficial to other studies involving mastitis caused by Candida species.

Abstract: Biofilm plays a crucial role on the biodegradation of organic matters in filter systems. In this study, two vermifilters (VFs, VF 1# was packed with 10∼13mm and 6∼9mm graded ceramic pellets, while VF 2# was packed with 6∼9mm ceramic pellets entirely) were operated in parallel. The variations of biofilm biomass and biofilm activity along the depth of the reactors were investigated. The results indicated that the biofilm biomass and the biofilm activity in both vermifilters decreased first and increased subsequently. The ratio of volatile suspended solids (VSS) to suspended solids (SS) were progressively declined from 0.60 to 0.53 in VF 1#, and from 0.57 to 0.44 in VF 2#. The sludge reduction of VF 2# was 40.4%, 6.2% higher than that of VF 1#. These findings indicated that the vermifilter filled with 6∼9mm ceramic pellets performed a better processing properties than the one filled with 10∼13mm and 6∼9mm graded ceramic pellets. [Copyright &y& Elsevier]

• Synthesis and characterization of new benzimidazolium molecules and their silver complexes • Antimicrobial and antibiofilm activities of NHC precursors and their Ag complexes • Molecular docking analysis against three target molecules of structural optimized molecules. In this study, we reported the synthesis of a new series of Silver(I)-N-heterocyclic carbene complexes which were obtained from the corresponding new N-heterocyclic carbene (NHC) precursors. All new compounds were characterized by elemental analysis, FT-IR, LC-MS, 1H NMR, and 13C{1H} NMR spectroscopy. These new N-heterocyclic carbene precursors and Ag(I)-NHC complexes were evaluated for their antibacterial, antifungal, and antibiofilm activities. The biological activities of synthesized products were compared with standard drugs. All compounds have moderate antibacterial and antibiofilm activities. In particular, while compound 2a was found to be the best inhibitor of E. coli biofilms, while compound 2d inhibited C. albicans biofilm at the highest rate. All the compounds were also analyzed by molecular docking methods with the certain target molecules. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: The partial dissipation of Gibbs energy as heat reflects the metabolic dynamic of biofilms in real time and may also allow quantitative conclusions about the chemical composition of the biofilm via Hess'' law. Presently, the potential information content of heat is hardly exploited due to the low flexibility, the low throughput and the high price of conventional calorimeters. In order to overcome the limitations of conventional calorimetry a miniaturized calorimeter for biofilm investigations has been evaluated. Using four thermopiles a heat production with spatial and temporal resolutions of 2.5 cm−1 and 2 s−1 could be determined. The limit of detection of the heat flow measurement was 20 nW, which corresponds to the cell density of an early stage biofilm (approx. 3×105 cells cm−2). By separating biofilm cultivation from the actual heat measurement, a high flexibility and a much higher throughput was achieved if compared with conventional calorimeters. The approach suggested allows cultivation of biofilms in places of interest such as technological settings as well as in nature followed by highly efficient measurements in the laboratory. Functionality of the miniaturized calorimeter was supported by parallel measurements with confocal laser scanning microscopy and a fiber optic based oxygen sensor using the oxycaloric equivalent (−460 kJ mol-O2 −1). [Copyright &y& Elsevier]

In our previous papers we have demonstrated that biofilm structure never reaches a steady state in biofilm reactors; in this paper we link this fact to biofilm detachment and to the oscillating pattern of biofilm accumulation. In one respect reactors supporting suspended microbial growth and reactors supporting attached microbial growth (biofilms) are similar: in both the biomass accumulates in the reactor and is disposed of with the effluent. However, while in reactors with suspended microbial growth biomass accumulation and disposal occur simultaneously, in biofilm reactors these two processes are separated in time. Biomass accumulation in biofilm reactors shows a distinct pattern composed of three phases: (1) growth, (2) detachment, (3) regrowth. Despite this distinct pattern of biofilm accumulation observed at the microscale, biofilm reactors do reach a steady state of substrate removal. [ABSTRACT FROM AUTHOR]

This article shows the results of research on microwave radiation as a factor affecting organic compounds removal in a reactor with a biofilm. In the experiment a bioreactor was situated inside a microwave tube and there exposed to radiation. Municipal wastes were supplied to the bioreactor from a retention tank, to which they returned having passed through the reactor's packing. The whole system operated in a time cycle comprising a 24-hour detention of the wastewaters supply. The research was based on the specific properties of microwave heating, i.e. their ability to heat only the substances of appropriate dielectric properties. As the reactor was properly constructed and the microwave generator work was synchronised with that of the volumetric pump, microwave energy was directed mostly to the biofilm. It was observed that as a result of microwave radiation the process of organic compounds removal, defined as Chemical Oxygen Demand COD, increased its rate nearly by half. Simultaneously the process efficiency increased by 7.7% at the maximum. While analysing the changes the organic compounds underwent it was revealed that the load in-built in the biomass decreased by over half as a result of microwave radiation input at 2.5 W s-1, which was optimal under the experimental conditions. Similarly the amount of pollutant remaining in the treated effluent decreased nearly by half, whereas the role of oxidation in removing organic pollutant increased in excess of 25% when compared to the control system. [ABSTRACT FROM AUTHOR]

We have examined whether assimilation of CO2 can be used as a measure of metabolic activity in planktonic and sessile heterotrophic bacteria. CO2 assimilation by environmental samples and pure cultures of heterotrophic bacteria was studied using 14CO2 and 13CO2 as tracers. Heterotrophic growth on complex organic substrates resulted in assimilation of CO2 into cell biomass by activated sludge, drinking water biofilm, and pure cultures of Escherichia coli ATCC 25922, Es. coli ATCC 13706, Rhodococcus ruber, Burkholderia sp., Bacillus circulans, Pseudomonas putida, Pseudomonas stutzeri, and Pseudomonas aeruginosa. Analysis of 13C-labelled phospholipid fatty acids (PLFAs) confirmed that heterotrophic bacteria may assimilate 13CO2 into cell macromolecules such as membrane lipids. All major PLFAs extracted from activated sludge and drinking water biofilm samples were enriched in 13C after incubation with CO2. Between 1.4% and 6.5% of the biomass produced by cultures of P. putida and a drinking water biofilm during growth in complex media was apparently derived from assimilation of CO2. Resting cells assimilated less CO2 compared to actively growing cells, and CO2 assimilation activity correlated with the amount of biomass produced during heterotrophic growth. The 14CO2 assimilation assay was evaluated as a tool to examine inhibitory effects of biocides on planktonic and sessile heterotrophs (biofilms). On the basis of 14CO2 assimilation activity, the minimum inhibitory concentration (MIC) of benzalkonium chloride was estimated to 21.1 and 127.2 mg l−1 for planktonic and biofilm samples, respectively. The results indicate that assimilation of isotopically labelled CO2 can be used as a relatively simple measure of metabolic activity in heterotrophic bacteria. CO2 assimilation assays may be used to study the effects of antimicrobial agents on growth and survival of planktonic and sessile heterotrophic organisms. [Copyright &y& Elsevier]

Quantitative parameters describing biofilm physical structure have been extracted from three-dimensional confocal laser scanning microscopy images and used to compare biofilm structures, monitor biofilm development, and quantify environmental factors affecting biofilm structure. Researchers have previously used biovolume, volume to surface ratio, roughness coefficient, and mean and maximum thicknesses to compare biofilm structures. The selection of these parameters is dependent on the availability of software to perform calculations. We believe it is necessary to develop more comprehensive parameters to describe heterogeneous biofilm morphology in three dimensions.This research presents parameters describing three-dimensional biofilm heterogeneity, size, and morphology of biomass calculated from confocal laser scanning microscopy images. This study extends previous work which extracted quantitative parameters regarding morphological features from two-dimensional biofilm images to three-dimensional biofilm images. We describe two types of parameters: (1) textural parameters showing microscale heterogeneity of biofilms and (2) volumetric parameters describing size and morphology of biomass. The three-dimensional features presented are average (ADD) and maximum diffusion distances (MDD), fractal dimension, average run lengths (in X, Y and Z directions), aspect ratio, textural entropy, energy and homogeneity. We discuss the meaning of each parameter and present the calculations in detail. The developed algorithms, including automatic thresholding, are implemented in software as MATLAB programs which will be available at www.erc.montana.edu site prior to publication of the paper. [Copyright &y& Elsevier]

We have evaluated the effects of selected minerals present in subsoil environment on the efficiency of lead removal from contaminated groundwaters using biofilms composed of sulfate-reducing microorganisms, and examined the stability of metal deposits after the biofilms had been temporarily exposed to the air. To quantify the studied effects, lead was immobilized in biofilms of Desulfovibrio desulfuricans grown anaerobically in two flat-plate flow reactors, one filled with hematite and the other with quartz. While the biofilms in both reactors were heterogeneous and consisted of voids and channels, the biofilms grown on hematite were denser, thicker, and more porous than those grown on quartz. The average H2S concentrations, measured using microelectrodes, were higher in the biofilms grown on quartz than those measured in the biofilms grown on hematite. During 18 weeks of operation, iron was continuously released from the hematite. Lead was immobilized more efficiently in the biofilms grown on quartz than it was in the biofilms grown on hematite. Lead deposits were partially reoxidized, especially in biofilms grown on hematite, and the biofilms in both reactors responded to the presence of oxygen by lowering their density and increasing the H2S production rate. [Copyright &y& Elsevier]

Bed segregation in a fluidized bed bioreactor profoundly influenced biofilm thickness and microbial activities of the biofilm along the bed height. Bioparticles coated with a thin biofilm, observed at the bottom of the reactor, had a higher specific activity in propylene glycol and n-propanol degradation than in thick biofilms developed at the top of the reactor. Although no significant difference was observed in specific activity for propionate and acetate along the reactor flow axis, more total propionate and acetate conversion occurred in regions of thicker biofilm accumulation. [ABSTRACT FROM AUTHOR]

An extracellular electron transfer (EET) process between an electroactive biofilm and an electrode is a crucial step for the performance of microbial fuel cells (MFCs), which is highly related to the enrichment of exoelectrogens and the electrocatalytic activity of the electrode. Herein, an efficient N- and Fe-abundant carbon cloth (CC) electrode with the comodification of iron porphyrin (FePor) and polyquaternium-7 (PQ) was synthesized using a facile solvent evaporation and immersion method and developed as an anode (named FePor-PQ) in MFCs. The surface structural characterizations confirmed the successful introduction of N and Fe atoms, whereas FePor-PQ achieved the N content of 9.59 at %, which may offer various active sites for EET. The introduction of PQ contributed to improving the surface hydrophilicity, providing the composite electrode good biocompatibility for bacterial attachment and colonization as well as substrate diffusion. Based on the advantages, the MFC with the FePor-PQ anode produced a maximum power density of 2165.7 mW m -2 , strikingly higher than those of CC (1124.0 mW m -2 ), PQ (1668.8 mW m -2 ), and FePor (1978.9 mW m -2 ). Furthermore, with the EET mediated by the binding of flavins and c-type cytochromes on the outer membrane was enhanced prominently, the typical exoelectrogen Geobacter was enriched up to 55.84% in the FePor-PQ anode biofilm. This work reveals a synergistic effect from heteroatom coating and surface properties tailoring to boost both the EET efficiency and exoelectrogen enrichment for enhancing MFC performance, which also provides valuable insights for designing electrodes in other bio-electrochemical systems.

Background: The diffusion of antimicrobial resistance is a significant concern for public health worldwide. Staphylococcus aureus represents a paradigm microorganism for antibiotic resistance in that resistant strains appear within a decade after the introduction of new antibiotics. Methods: Fourteen S. aureus isolates from human specimens and twenty-one from samples of animal origin, were compared for their antimicrobial resistance and biofilm capability. In addition, they were characterized at the molecular level to detect the antimicrobial resistance mecA gene and genes related with enterotoxin, toxin, and biofilm production. Results: Both phenotypic and molecular analysis showed main differences among human- and animal-derived isolates. Among the human-derived isolates, more multidrug-resistant isolates were detected and mecA gene, enterotoxin, and toxin genes were more prevalent. Different genes involved in biofilm production were detected with bap present only in animal-derived isolates and sasC present in both isolates, however, with a higher prevalence in the human-derived isolates. Biofilm capability was higher in human-derived isolates mainly associated to the sasC gene. Conclusions: The overall results indicate that human S. aureus isolates are more virulent and resistant than the isolates of animal origin randomly selected with no infection anamnesis. This study confirms that selection for more virulent and resistant S. aureus strains is related to the clinical practice. [ABSTRACT FROM AUTHOR]

Improving the stimulation effect of electric current density (ECD) on microbial community is critical in designing and operating TDE-BAF. This study investigated the effect of ECD at 0.00, 4.08, 6.12, 12.20, 14.25, 16.30 and 20.20A·m -2 on the removal performance, diversity and structure of microbial community in TDE-BAF. Results indicated that the ECD of 14.25A·m -2 exhibited the highest COD, TOC and NH 4 + -N average removal rates with 93.33%, 91.26% and 93.87%, respectively; Under high ECD, especially exceeding 14.25A·m -2 , the inhibition of growth and activity because of plasmatorrhexis was in agreement with the sharp biomass decline; there was no significant relation between community richness and diversity and removal efficiency below optimum ECD, while above optimal ECD, it was just the opposite; Microbial communities mainly including Hydrogenophaga, Saprospiraceae&#95;uncultured, Delftia, Enterobacter, Pseudomonas, Pseudoxanthomonas, and Nitrosospira and physicochemical properties well explained the excellent removal performance at the optimum ECD., (Copyright © 2017 Elsevier Ltd. All rights reserved.)