Nitrate (NO3−) affected perchlorate (ClO4−) reduction in a membrane batch biofilm reactor (MBBR), even though the electron donor, CH4, was available well in excess of its demand. For example, the ...perchlorate-reduction rate was 1.7 mmol/m2-d when perchlorate was the sole electron acceptor, but it dropped to 0.64 mmol/m2-d when nitrate also was present. The perchlorate-reduction rate returned to 1.60 mmol/m2-d after all nitrate was consumed. Denitratisoma and Azospirillum were main genera involved in perchlorate and nitrate reduction, and both could utilize NO3− and ClO4− as electron acceptors. Results of the reverse transcription-polymerase chain reaction (RT-PCR) showed that transcript abundances of nitrate reductase (narG), nitrite reductase (nirS), and perchlorate reductase (pcrA) increased when the perchlorate and nitrate concentrations were higher. Specifically, pcrA transcripts correlated to the sum of perchlorate and nitrate, rather than perchlorate individually. Analysis based on Density Functional Theory (DFT) suggests that bacteria able to utilize both acceptors, preferred NO3− over ClO4− due to nitrate reduction having lower energy barriers for proton and electron transfers.
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•NO3− reversibly inhibited ClO4− reduction when CH4 was in excess.•The narG/pcrA enzymes catalyzed nitrate reduction faster than perchlorate reduction.•Nitrate needs less energy than perchlorate for H+ and e− transfers during reduction.
Anaerobic ammonium oxidation (anammox) is recognized as the most cost-effective process for nitrogen removal from wastewater. In this study, effects of polyethylene plastics, nonwoven fabric, ...granular activated carbon (GAC) and polyurethane sponge as buoyant carriers were evaluated in lab-scale moving bed biofilm reactors (MBBRs). The overall performance of MBBRs with four types of carriers from priority to inferiority was noticed as, GAC, nonwoven fabrics, polyurethane sponge and polyethylene plastics under the same packing ratio of 20 v% and an average carrier size of 4 × 4 × 4 mm. The hydrophobic surface of GAC could selectively adsorb hydrophobic protein and favor anammox bacteria attachment, which contributed to achieving a total nitrogen removal rate of 0.40 kg-N/(m3·d) in 60 days. In conclusion, our results provide compelling evidence for achieving effective anammox process in an MBBR with GAC carriers and would benefit towards accomplishing a stable partial nitritation-anammox process in the future.
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•Anammox-MBBR with GAC achieved a TNRR 0.40 kg-N/(m3·d) in only 60 days.•GAC and nonwoven fabrics carrier could greatly enhance denitrification efficiency.•High positive correlations among EPS production, amx abundance and performance•Hydrophobic surface of GAC could selectively adsorb hydrophobic protein.•The anammox biofilm on GAC contributes to fast start-up and stable operation.
Removal of seven active pharmaceutical substances (ibuprofen, ketoprofen, naproxen, diclofenac, clofibric acid, mefenamic acid, and gemfibrozil) was assessed by batch experiments, with suspended ...biofilm carriers and activated sludge from several full-scale wastewater treatment plants. A distinct difference between nitrifying activated sludge and suspended biofilm carrier removal of several pharmaceuticals was demonstrated. Biofilm carriers from full-scale nitrifying wastewater treatment plants, demonstrated considerably higher removal rates per unit biomass (i.e. suspended solids for the sludges and attached solids for the carriers) of diclofenac, ketoprofen, gemfibrozil, clofibric acid and mefenamic acid compared to the sludges. Among the target pharmaceuticals, only ibuprofen and naproxen showed similar removal rates per unit biomass for the sludges and biofilm carriers. In contrast to the pharmaceutical removal, the nitrification capacity per unit biomass was lower for the carriers than the sludges, which suggests that neither the nitrite nor the ammonia oxidizing bacteria are primarily responsible for the observed differences in pharmaceutical removal. The low ability of ammonia oxidizing bacteria to degrade or transform the target pharmaceuticals was further demonstrated by the limited pharmaceutical removal in an experiment with continuous nitritation and biofilm carriers from a partial nitritation/anammox sludge liquor treatment process.
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► This study compares biofilm carrier and activated sludge removal of pharmaceuticals. ► Biofilm carriers show higher pharmaceutical removal, compared to activated sludge. ► Diclofenac and Clofibric acid were only removed with biofilm carriers. ► No clear link between pharmaceutical removal and nitrifying capacity was observed.
•The periphytic EPS were mainly composed of polysaccharides and proteins.•The periphytic EPS showed high turbidity removal capacity.•The periphytic EPS showed efficient aniline blue (AB) removal ...capacity.•The AB removal mechanism was a combined technique of “adsorption-flocculation”.•Periphytic biofilms were good sources for bioflocculants preparation.
The aim of this work was to study the characteristics and flocculating properties of extracellular polymeric substances (EPS) extracted from periphytic biofilms. The periphytic EPS, with an extracted yield of 491.8mg/g, were mainly composed of hetero-polysaccharides and proteins, and the elements C1s, N1s, and O1s. Polysaccharides represented 53.28% of the periphytic EPS. Proteins constituted 20.26% of the EPS, and contributed to at least 34.65% of the total flocculating activity. The periphytic EPS showed high turbidity removal capacity (86.76±1.52%, 10min) and efficient aniline blue (AB) removal capacity (56.46±1.41%, 30min). The mechanism of AB removal by the periphytic EPS seemed to be a combined technique of “adsorption-flocculation”. This study reveals the flocculating capability of periphytic EPS, and suggests that periphytic biofilms are novel sources for bioflocculants preparation.
Pseudomonas aeruginosa is a gram-negative bacterium that exists in various ecosystems, causing severe infections in patients with AIDS or cystic fibrosis. P. aeruginosa can form biofilm on a variety ...of surfaces, whereby the bacteria produce defensive substances and enhance antibiotic-resistance, making themselves more adaptable to hostile environments. P. aeruginosa resistance represents one of the main causes of infection-related morbidity and mortality at a global level. Iron is required for the growth of P. aeruginosa biofilm. This review summarises how the iron metabolism contributes to develop biofilm, and more importantly, it may provide some references for the clinic to achieve novel anti-biofilm therapeutics by targeting iron activities.
One of the leading causes for the failure of dental composite restorations is secondary caries. Effectively inhibiting cariogenic biofilms and reducing secondary caries could extend the service life ...of composite restorations. Dental composites releasing antibacterial agents such as chlorhexidine (CHX) have shown biofilm-inhibitory efficacy, but they usually have poor physical and mechanical properties. Herein, we present a study of a new method to encapsulate and release CHX from dental composite using mesoporous silica nanoparticles (MSNs). SBA-15 MSNs were synthesized according to a reported procedure. CHX (62.9 wt%) was encapsulated into dried MSN from 0.3 M CHX ethanol solution. The dental composites containing 0% (control), 3%, 5%, and 6.3% CHX or the same amounts of CHX entrapped in MSN (denoted as CHX@MSN) were fabricated with methacrylate monomers and silanized glass fillers (CHX or CHX@MSN + glass filler particle = 70 wt%). The monomer mixture consisted of bisphenol A glycidyl methacrylate (BisGMA), hexanediol dimethacrylate (HDDMA), ethoxylated bisphenol A dimethacrylate (EBPADMA), and urethane dimethacrylates (UEDMA) at a weight ratio of 40:30:20:10. The composites were tested for CHX release and recharge, flexural strength and modulus (at 24 hr and 1 mo), surface roughness, in vitro wear, and antibacterial activity against Streptococcus mutans and Lactobacillus casei (in both planktonic growth and biofilm formation). The results showed that the composites with CHX@MSN largely retained mechanical properties and smooth surfaces and showed controlled release of CHX over a long time. In contrast, the composites with directly mixed CHX showed reduced mechanical properties, rough surfaces, and burst release of CHX in a short time. The composites with CHX either directly mixed or in MSN showed strong inhibition to S. mutans and L. casei. This research has demonstrated the successful application of MSNs as a novel nanotechnology in dental materials to inhibit oral biofilm without sacrificing materials’ mechanical properties and surface integrity.
Staphylococcus aureus biofilms, a leading cause of persistent infections, are highly resistant to immune defenses and antimicrobial therapies. In the present study, we investigated the contribution ...of fibrin and staphylokinase (Sak) to biofilm formation. In both clinical S. aureus isolates and laboratory strains, high Sak-producing strains formed less biofilm than strains that lacked Sak, suggesting that Sak prevents biofilm formation. In addition, Sak induced detachment of mature biofilms. This effect depended on plasminogen activation by Sak. Host-derived fibrin, the main substrate cleaved by Sak-activated plasminogen, was a major component of biofilm matrix, and dissolution of this fibrin scaffold greatly increased susceptibility of biofilms to antibiotics and neutrophil phagocytosis. Sak also attenuated biofilm-associated catheter infections in mouse models. In conclusion, our results reveal a novel role for Sak-induced plasminogen activation that prevents S. aureus biofilm formation and induces detachment of existing biofilms through proteolytic cleavage of biofilm matrix components.
Biofilms are the most common cause of bacterial infections in humans and notoriously hard to treat due to their ability to withstand antibiotics and host immune defenses. To overcome the current lack ...of effective antibiofilm therapies and guide future design, the identification of novel biofilm-specific gene targets is crucial. In this regard, transcriptional regulators have been proposed as promising targets for antimicrobial drug design. Therefore, a Transposon insertion sequencing approach was employed to systematically identify regulators phenotypically affecting biofilm growth in
Pseudomonas aeruginosa
PA14 using the TnSeq analysis tools Bio-TraDIS and TRANSIT. A screen of a pool of 300,000 transposon insertion mutants identified 349 genes involved in biofilm growth on hydroxyapatite, including 47 regulators. Detection of 19 regulatory genes participating in well-established biofilm pathways validated the results. An additional 28 novel prospective biofilm regulators suggested the requirement for multiple one-component transcriptional regulators. Biofilm-defective phenotypes were confirmed for five one-component transcriptional regulators and a protein kinase, which did not affect motility phenotypes. The one-component transcriptional regulator
bosR
displayed a conserved role in
P. aeruginosa
biofilm growth since its ortholog in
P. aeruginosa
strain PAO1 was also required for biofilm growth. Microscopic analysis of a chromosomal deletion mutant of
bosR
confirmed the role of this regulator in biofilm growth. Overall, our results highlighted that the gene network driving biofilm growth is complex and involves regulators beyond the primarily studied groups of two-component systems and cyclic diguanylate signaling proteins. Furthermore, biofilm-specific regulators, such as
bosR
, might constitute prospective new drug targets to overcome biofilm infections.
Pseudomonas aeruginosa : all roads lead to resistance Breidenstein, Elena B.M; de la Fuente-Núñez, César; Hancock, Robert E.W
Trends in microbiology (Regular ed.),
08/2011, Letnik:
19, Številka:
8
Journal Article
Recenzirano
Pseudomonas aeruginosa is often resistant to multiple antibiotics and consequently has joined the ranks of ‘superbugs’ due to its enormous capacity to engender resistance. It demonstrates decreased ...susceptibility to most antibiotics due to low outer membrane permeability coupled to adaptive mechanisms and can readily achieve clinical resistance. Newer research, using mutant library screens, microarray technologies and mutation frequency analysis, has identified very large collections of genes (the resistome) that when mutated lead to resistance as well as new forms of adaptive resistance that can be triggered by antibiotics themselves, in in vivo growth conditions or complex adaptations such as biofilm growth or swarming motility.
•Isolation of biosurfactant producing lactic acid bacteria.•Antiadhesive potential of the lactic acid derived biosurfactants against biofilm forming pathogens.•Stability studies of biosurfactants.
...Various lactic acid bacteria (LAB) have been isolated and screened for biosurfactant production and their biomedical and food applications. Additionally, various different concentrations of the biosurfactant (0.625–25mgml−1) were used to evaluate its antimicrobial and antiadhesive potential against a range of pathogenic microorganisms. Biosurfactant was found to be stable to pH changes over a range of 4.0-12.0, being most effective at pH 7 and showed no apparent loss of surface tension and emulsification efficiency after heat treatment at 125°C for 15min. Present study demonstrated that biosurfactant obtained from Lactobacillus helveticus has the ability to counteract effectively the initial deposition of biofilm forming pathogens to silicone surfaces and to significantly sluggish biofilm growth.
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