Biofilm Abundance Research Articles

Ferrihydrite regulated tire-wear microplastics biofilm for enhanced nitrogen transformation in surface water

Tire-wear microplastics (T-MPs) are increasingly present in surface water, which can intact with ferrihydrite and influence biofilm formation on T-MPs. However, the interaction of T-MPs and ferrihydrite on biofilm formation and its effect on nitrogen transformation in surface water is still unknown. In this paper, four sets of experiments were set up in simulated surface water inoculated with precultured bacteria, respectively, A: simulated surface water, B: addition of ferrihydrite, C: addition of T-MPs, and D: addition of both T-MPs and ferrihydrite. Characterization results showed that co-exposure of T-MPs and ferrihydrite increased roughness and decreased hydrophobicity in the surface of T-MPs, and resulted in higher biomass and EPS values in biofilm of T-MPs with ferrihydrite. Under co-exposure, the nitrate removal efficiency for 12 h was increased by 32.37 % and 25.74 % comparing with single ferrihydrite and T-MPs, and the accumulation and removal of nitrite as well as the production of higher concentrations of nitrous oxide indicated that the co-exposure contributed to the denitrification and stimulated nitrogen transformation. Furthermore, α-diversity index characterized a rich microbial community, especially the enrichment of functional microorganisms Firmicutes and Thauera, which were altered to enhance nitrogen transformation function (glutamine synthetase, nitronate monooxygenase). Ferrihydrite promoted complete denitrification process in the system and strengthened the role of nitrogen transformation microorganisms in the T-MPs biofilm. The abundance of key enzymes and functional genes (napA, nrtC, nirB, nosZ) increased with co-exposure T-MPs and ferrihydrite, and genes associated with nitrate and nitrite reduction (narG, narI) exhibited higher abundance in biofilm of T-MPs compared to the surrounding water. This research provided important insights into the effects of T-MPs co-exposure interactions with ferrihydrite on nitrogen transformation in surface water.

Enhanced nitrogen removal from low C/N municipal wastewater through nitrification, partial denitrification and anammox via a step-feed strategy: Synergistic contribution by bacteria in biofilm and floc sludge

Energy-efficient nitrogen removal from carbon-limited municipal wastewater poses challenges. This study developed a novel partial denitrification and anammox (PD/A) process using a step-feed strategy in a single-stage integrated fixed-biofilm activated sludge (IFAS) system operated under sequencing batch mode. Despite relatively low temperatures (15.9–21.6 °C), biological nitrogen removal efficiency reached 80.5 % without the addition of external carbon sources. With the total inorganic nitrogen (TIN) of 48.9 ± 1.2 mg N/L, and C/N of 4.0 in influent, the TIN in effluent achieved 9.6 ± 1.5 mg N/L. Anammox bacteria (AnAOB) activity in the biofilm was 27.96 mg N/(g VSS·d), which was threefold greater than in floc sludge. Candidatus Brocadia (AnAOB) presented a high relative abundance in biofilm (0.53 %), whereas denitrifying bacteria including Thauera and Candidatus Competibacter were mainly retained in floc sludge. Overall, the coupling of step-feed strategy and IFAS offers novel insights into the efficient nitrogen removal from low C/N domestic sewage for retrofitting of municipal wastewater treatment plants, not only saving the energy consumption for aeration, but also fully utilizing carbon sources and ammonium in the influent for the PD/A process.

Microbial Assemblages and Metabolic Activity in Organic‐Rich Subterranean Estuaries: Impact of Climate and Land Use Changes

AbstractMicrobial communities in subterranean estuaries mediate biogeochemical reactions of coastal groundwater discharging into the oceans; however, studies on their response to abrupt environmental changes caused by climate and land use alterations are still limited. In this study, we conducted a controlled laboratory study using combined geochemical and metagenomic approaches to investigate microbial structures and their metabolic pathways under a wide range of nitrate () inputs, saline solutions, and incubation times. These factors served as proxies for land use, salinization of the shallow aquifer, and climate changes. We found a highly reducing habitat and an amplification of genes related to denitrification, sulfate reduction, and methanogenesis processes. Core communities consisting of Clostridia, Bacilli, Alphaproteobacteria, Gammaproteobacteria, and Desulfobaccia were observed across all treatments. The metabolic prediction of plant‐derived organic matter (i.e., tannin and lignin) degradation was not affected by inputs or salinity because of it being implemented by core communities and the abundance of electron donors and acceptors. Quantification of denitrification genes shows that they are susceptible to inputs and seawater ions. Long‐term incubation allowed sufficient time for microbes to degrade less labile DOM, promoting the re‐release of buried solid phase organic matter into the active carbon cycle and increasing the relative abundance of biofilm or spore‐forming taxa while decreasing that of rare taxa. Our results illustrate the sensitivity of microbial assemblages to environmental changes and their capacity to altering the C and N cycles in coastal areas, further affecting coastal water quality and ecosystem‐scale biogeochemistry.

PVA-Based Films with Strontium Titanate Nanoparticles Dedicated to Wound Dressing Application.

Bioactive materials may be applied in tissue regeneration, and an example of such materials are wound dressings, which are used to accelerate skin healing, especially after trauma. Here, we proposed a novel dressing enriched by a bioactive component. The aim of our study was to prepare and characterize poly(vinyl alcohol) films modified with strontium titanate nanoparticles. The physicochemical properties of films were studied, such as surface free energy and surface roughness, as well as the mechanical properties of materials. Moreover, different biological studies were carried out, like in vitro hemo- and cyto-compatibility, biocidal activity, and anti-biofilm formation. Also, the degradation of the materials' utilization possibilities and enzymatic activity in compost were checked. The decrease of surface free energy, increase of roughness, and improvement of mechanical strength were found after the addition of nanoparticles. All developed films were cyto-compatible, and did not induce a hemolytic effect on the human erythrocytes. The PVA films containing the highest concentration of STO (20%) reduced the proliferation of Eschericha coli, Pseudomonas aeruginosa, and Staphylococcus aureus significantly. Also, all films were characterized by surface anti-biofilm activity, as they significantly lowered the bacterial biofilm abundance and its dehydrogenase activity. The films were degraded by the compost microorganism. However, PVA with the addition of 20%STO was more difficult to degrade. Based on our results, for wound dressing application, we suggest using bioactive films based on PVA + 20%STO, as they were characterized by high antibacterial properties, favorable physicochemical characteristics, and good biocompatibility with human cells.

Assessment of Biofilm Growth on Microplastics in Freshwaters Using a Passive Flow-Through System.

Biofilms that colonize on the surface of microplastics (MPs) in freshwaters may pose a potential health risk. This study examined factors that influence MP-associated biofilm growth, including polymer type, degree of weathering, and source water quality. Weathered MPs produced in-lab were employed in biofilm trials conducted on site using a passive flow-through system with raw water at drinking water treatment facility intakes. Adenosine triphosphate (ATP) was used to quantify biofilm abundance; biofilm composition was assessed via metagenomic sequencing. Biofilm growth was observed on all polymer types examined and most prevalent on polyvinyl chloride (PVC), where ATP levels were 6 to 12 times higher when compared to other polymers. Pathogen-containing species including Salmonella enterica and Escherichia coli were present on all polymers with relative abundance up to 13.7%. S. enterica was selectively enriched on weathered MPs in specific water matrices. These findings support the need to research the potential accumulation of pathogenic organisms on microplastic surfaces.

Freshwater algal biofilm assemblages are more effective than invertebrate assemblages at aggregating microplastics

Microplastics, plastic particles less than 5 mm in length, are a ubiquitous pollutant in the environment, but research on freshwater microplastic contamination is lacking. A possible fate of microplastics in freshwater environments is to become entangled or aggregated in biofilms, which are matrices of algae, bacteria, and micro invertebrates that grow on underwater surfaces, following a progression of settling algae, periphyton, and finally invertebrate colonization. This in-situ study at the Oasis Marina at National Harbor in Oxon Hill, Maryland, examined how the taxonomic assemblages of freshwater biofilms in the Potomac River are associated with the number of microplastics aggregated within them. Aluminum discs, acting as artificial substrate for biofilm growth, were deployed at the water's surface and at 2 m depth to survey biofilm assemblage and were sampled monthly from October 2021–October 2022. Microplastic abundances in the water column were measured every 2 weeks over the same period. Spatial and temporal trends in trapped and suspended microplastics, water quality parameters (temperature, dissolved oxygen, pH, salinity, conductivity, turbidity, ammonia, nitrate, and phosphate), and biofilm assemblages were measured and compared to explore factors affecting the abundance of microplastics and their partitioning between the water column and biofilms. Water quality had no measurable impact on microplastic abundance in the water column at either depth, but temperature was negatively correlated to microplastic abundance in biofilms. As the weather warmed and biofilms progressed to invertebrate settling, they tended to contain fewer microplastics. This may have occurred because less biologically rich biofilms, primarily composed of unicellular algal colonies, provide a favorable surface for microplastic deposition. Understanding seasonal changes in biofilm assemblage and microplastic abundance may help track the fate of microplastics in freshwater systems, particularly in their interactions with lower trophic organisms.

Biofilm-derived oxylipin 10-HOME-mediated immune response in women with breast implants.

This study investigates a mechanistic link of bacterial biofilm-mediated host-pathogen interaction leading to immunological complications associated with breast implant illness (BII). Over 10 million women worldwide have breast implants. In recent years, women have described a constellation of immunological symptoms believed to be related to their breast implants. We report that periprosthetic breast tissue of participants with symptoms associated with BII had increased abundance of biofilm and biofilm-derived oxylipin 10-HOME compared with participants with implants who are without symptoms (non-BII) and participants without implants. S. epidermidis biofilm was observed to be higher in the BII group compared with the non-BII group and the normal tissue group. Oxylipin 10-HOME was found to be immunogenically capable of polarizing naive CD4+ T cells with a resulting Th1 subtype in vitro and in vivo. Consistently, an abundance of CD4+Th1 subtype was observed in the periprosthetic breast tissue and blood of people in the BII group. Mice injected with 10-HOME also had increased Th1 subtype in their blood, akin to patients with BII, and demonstrated fatigue-like symptoms. The identification of an oxylipin-mediated mechanism of immune activation induced by local bacterial biofilm provides insight into the possible pathogenesis of the implant-associated immune symptoms of BII.

The potency of spores and biosurfactant of Bacillus clausii as a new biobased sol-gel coatings for corrosion protection of carbon steel ST 37 in water cooling systems

The structures of water cooling systems are prone to microbially-influenced corrosion (MIC) due to the favorable conditions for microbial growth. Biofilm formation accelerates corrosion, leading to reduced system efficiency, structural damage, and significant financial losses. Encapsulating viable bacterial spores and biosurfactant within a silica-based sol-gel coating offers an eco-friendly approach to prevent this type of corrosion. Bacillus clausii, known for its antimicrobial biosurfactant production capability, was utilized in this study to investigate the impact of spores and biosurfactant addition to silica-based sol-gel coatings in inhibiting biofilm formation and preventing corrosion in water cooling systems. Microbiological analysis of the biofilm was conducted using the total plate count method, while the corrosion process was analyzed through electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The viability of B. clausii spores within the sol-gel matrix was determined to be 20.8 %. The presence of bacterial spores and biosurfactant significantly increased the hydrophobicity of the sol-gel coating. Incorporating spores within the sol-gel matrix delayed biofilm formation for up to 12 days, while biosurfactant addition showed the smallest biofilm abundance (2.23×105 CFU/mL) at its maturation phase compare to others. After 180 days of incubation, analysis of Bode and Tafel plots demonstrated that the sol-gel coating containing biosurfactant maintained excellent anti-corrosion performance, exhibiting an impedance of 104 Ω cm2, Ecorr of -0.398 V vs SCE, and icorr of 0.51 µA/cm2. SEM-EDS analysis of the surface sample revealed a comparably smooth and uniform surface with a minimal abundance of exposed Fe atoms at 0.12 %. In conclusion, this study demonstrated the high potency of the sol-gel coating supplemented with biosurfactant in inhibiting biofilm formation and corrosion on metals in water cooling systems.

Enhancing the bioavailability of sulfur for denitrification in integrated floating-film and activated sludge (IFFAS) system filled with modified carriers under mixotrophic and autotrophic conditions

Sulfur autotrophic denitrification (SAD) holds application prospect in carbon-limited wastewater due to no additional carbon source, less sludge yield, and lower costs. However, the poor bioavailability of sulfur (S0) and the slow development of sulfur oxidizing bacteria (SOB) limit its wide application. Tween 80 is a nonionic surfactant with low toxicity and can regulate interface action between S0 and microorganisms. In this study, integrated floating-film and activated sludge (IFFAS) filled with graphene oxide (GO)-modified carriers was adopted and Tween 80 was introduced to enhance bioavailability of S0. When the influent C/N was below 0.7 and nitrogen loading was 0.24 Kg/(m3∙d), the total nitrogen removal efficiencies in reactors filled with GO-modified carriers and Tween 80 were above 90% while that of reactors filled with high density polyethylene (HDPE) carriers and 0.5 wt% GO-modified carriers was74.08 ± 12.8% and 81.87 ± 11.51%. Microbial analysis revealed that Tween 80 could enhance autotrophic denitrification bacteria relative abundance in biofilm at C/N ratios of < 0.7, such as Sulfurisoma (21.21%), Dechloromonas (8.42%) and Ignavibacterium (14.68%). Furthermore, predicted microbial functions analysis by PICRUSt showed that denitrification, sulfide oxidation, electron transfer and biofilm formation pathways were enhanced in reactors added Tween 80. This study demonstrated Tween 80 was able to improve the bioavailability of S0 and enhance the efficiency of SAD.

The exploitation of biofilm by migrant western sandpipers (Calidrismauri)

Assessing the quality of migratory shorebird stopover sites requires good measures of food availability. We developed simple methods to measure biofilm grazing by migrant western sandpipers (Calidris mauri), a species for which biofilm is an important dietary component. We used a field-portable chlorofluorometer to measure the density of chlorophyll-a (Chl-a) in surficial biofilms on Roberts Bank, a large intertidal mudflat in British Columbia, Canada, during northward migration.Chl-a density begins at a low level during each diurnal emersion period, and increases steadily during emersion at 4.1 mg m−2 h−1 for a total of ∼24.6 mg m−2 over a typical 6 h emersion period and ∼41 mg m−2 over a 10 h emersion period. Western sandpipers grazed at 1.35–1.45 mg Chl-a m−2 min−1, thus biofilm production supports 17.6 min m−2 of grazing time during a 6 h low tide period and 29.3 min m−2 during a 10 h period. During peak northward migration, the average grazing intensity of western sandpipers over an intertidal emersion period was 3.3–6.4 min m−2, suggesting that biofilm accumulation was 2.7–8.8 fold greater than the amount consumed. We found Chl-a density was highest (∼65 mg per m2) within 40 m of the shoreline. Grazing intensity was lowest close to shore, where predation risk from falcon attacks is highest. Grazing intensity peaked at 240 m and then declined, lowering Chl-a density at greater distances to a uniform level of ∼54 mg m−2. These results indicate that interactions between biofilm production and sandpiper grazing underlie spatio-temporal patterns in biofilm abundance on Roberts Bank.

Structural Characteristics and Functional Genes of Biofilms in Microbial Electrolysis Cells for Chlorobenzene Abatement

Chlorobenzene (CB) is typically emitted during industry and waste incineration, posing hazards to the safety of humans and the ecosystem. Successful CB elimination has been achieved in microbial electrolysis cells (MECs), whereas little is known about elimination effectiveness in response to the structural and functional characteristics of biofilms. Herein, the bacterial viability and functional gene abundance of biofilms in MECs with carbon cloth (CC), reticulated vitreous carbon (RVC), and nickel foam (NF) as cathodes are emphasized. Experimental results reveal that bacterial viability on RVC is 62 and 92% higher than that of CC and NF, respectively, achieving 30 and 65% superior CB removal efficiency. Notably, the MEC with RVC outperforms that with the highly conductive NF due to low electron loss, causing a twice as much increase in coulombic efficiency. Metagenomic analysis indicates that the CB degrader (i.e., Pandoraea), electrochemically active bacteria (i.e., Chryseobacterium), and genes responsible for CB metabolism (i.e., todD and clcB) in RVC biofilms increase by over 30%, fourfold, and 10%, respectively, compared to CC and NF. Moreover, CB degradation is found to occur via two possible pathways: (1) thorough elimination by dechlorination, hydrolysis, and oxidation after conversion to 3-chlorocatechol, and (2) conversion into phenol and benzoate for complete degradation.

Legionella relative abundance in shower hose biofilms is associated with specific microbiome members.

Legionella are natural inhabitants of building plumbing biofilms, where interactions with other microorganisms influence their survival, proliferation, and death. Here, we investigated the associations of Legionella with bacterial and eukaryotic microbiomes in biofilm samples extracted from 85 shower hoses of a multiunit residential building. Legionella spp. relative abundance in the biofilms ranged between 0-7.8%, of which only 0-0.46% was L. pneumophila. Our data suggest that some microbiome members were associated with high (e.g. Chthonomonas, Vrihiamoeba) or low (e.g. Aquabacterium, Vannella) Legionella relative abundance. The correlations of the different Legionella variants (30 Zero-Radius OTUs detected) showed distinct patterns, suggesting separate ecological niches occupied by different Legionella species. This study provides insights into the ecology of Legionella with respect to: (i) the colonization of a high number of real shower hoses biofilm samples; (ii) the ecological meaning of associations between Legionella and co-occurring bacterial/eukaryotic organisms; (iii) critical points and future directions of microbial-interaction-based-ecological-investigations.

Clostridium kluyveri enhances caproate production by synergistically cooperating with acetogens in mixed microbial community of electro-fermentation system

As a chain elongation (CE) model strain, Clostridium kluyveri has been used in the studies of bioaugmentation of caproate production. However, its application in the novel electro-fermentation CE system for bioaugmentation is still unclear. In this study, the CE performances, with or without bioaugmentation and in conventional or electro-fermentation systems were compared. And the mechanism of electrochemical-bioaugmentation by constructing a co-culture of Acetobacterium woodii and Clostridium kluyveri were further verified. Results demonstrated that the bioaugmentation treatments have better CE performance, especially in electro-fermentation system, with a highest caproate concentration of 4.68 g·L-1. Mechanism analysis revealed that C. kluyveri responded to the electric field and emerged synergy with the acetogens, which was proved by the increases of C. kluyveri colonization and the acetogens abundance in biofilm and supported by the co-culture experiment. This study provides a novel insight of microbial synergy mechanism of C. kluyveri during CE bioaugmentation in electro-fermentation system.

PMo12 as a redox mediator for bio-reduction of Cr(VI): Promotor or inhibitor?

Slow reduction rate and low reduction ability were the main limitations of bio-reduction of Cr(VI). As an efficient redox mediator, how phosphomolybdic acid (PMo12) affected bio-reduction of Cr(VI) was worthy of exploration. In this study, short-term and long-term effects of PMo12 on Cr(VI) reduction were investigated to reveal the relevant mechanism. After evaluating the short-term effect of PMo12 concentration from 0.05 to 1.00 mM on Cr(VI) bio-reduction, 0.50 mM was found to be optimum by improving Cr(VI) reduction rate by 16.3 % and microbial electron transport system activity (ETSA) by 43.0 % with Cr(VI) reduction efficiency of 100 % in short-term (22 h) batch experiments. By contrast, in long-term (28 days) continuous flow experiments, 0.50 mM PMo12 exhibited serious inhibition on Cr(VI) bio-reduction. The cumulative toxicity of Mo, strong oxidative stress (reactive oxygen species increased by 16.5 %), the inhibition of extracellular polymeric substances production and the reduction of microbial activity were proved to be the main inhibition mechanism. In terms of microbial electron transport system, the main electron carriers including flavin mononucleotide (FMN), nitrate reductase (NAR), nitrite reductase (NIR) were seriously inhibited. BugBase analysis confirmed that the relative abundance of biofilm forming bacteria decreased after PMo12 addition, and the relative abundance of oxidative stress tolerance bacteria continued to increase.

Evaluation of biofilm formation on acrylic resins used to fabricate dental temporary restorations with the use of 3D printing technology

BackgroundTemporary implant-retained restorations are required to support function and esthetics of the masticatory system until the final restoration is completed and delivered. Acrylic resins are commonly used in prosthetic dentistry and lately they have been used in three-dimensional (3D) printing technology. Since this technology it is fairly new, the number of studies on their susceptibility to microbial adhesion is low. Restorations placed even for a short period of time may become the reservoir for microorganisms that may affect the peri-implant tissues and trigger inflammation endangering further procedures. The aim of the study was to test the biofilm formation on acrylamide resins used to fabricate temporary restorations in 3D printing technology and to assess if the post-processing impacts microbial adhesion.MethodsDisk-shaped samples were manufactured using the 3D printing technique from three commercially available UV-curable resins consisting of acrylate and methacrylate oligomers with various time and inhibitors of polymerization (NextDent MFH bleach, NextDent 3D Plus, MazicD Temp). The tested samples were raw, polished and glazed. The ability to create biofilm by oral streptococci (S. mutans, S. sanguinis, S. oralis, S. mitis) was tested, as well as species with higher pathogenic potential: Staphylococcus aureus, Staphylococcus epidermidis and Candida albicans. The roughness of the materials was measured by an atomic force microscope. Biofilm formation was assessed after 72 h of incubation by crystal violet staining with absorbance measurement, quantification of viable microorganisms, and imaging with a scanning electron microscope (SEM).ResultsEach tested species formed the biofilm on the samples of all three resins. Post-production processing resulted in reduced roughness parameters and biofilm abundance. Polishing and glazing reduced roughness parameters significantly in the NextDent resin group, while glazing alone caused significant surface smoothing in Mazic Temp. A thin layer of microbial biofilm covered glazed resin surfaces with a small number of microorganisms for all tested strains except S. oralis and S. epidermidis, while raw and polished surfaces were covered with a dense biofilm, rich in microorganisms.ConclusionsUV-curing acrylic resins used for fabricating temporary restorations in the 3D technology are the interim solution, but are susceptible to adhesion and biofilm formation by oral streptococci, staphylococci and Candida. Post-processing and particularly glazing process significantly reduce bacterial biofilm formation and the risk of failure of final restoration.

Hidden interactions in the intertidal rocky shore: variation in pedal mucus microbiota among marine grazers that feed on epilithic biofilm communities.

In marine ecosystems, most invertebrates possess diverse microbiomes on their external surfaces, such as those found in the pedal mucus of grazing gastropods and chitons that aids displacement on different surfaces. The microbes are then transported around and placed in contact with free-living microbial communities of micro and other macro-organisms, potentially exchanging species and homogenizing microbial composition and structure among grazer hosts. Here, we characterize the microbiota of the pedal mucus of five distantly related mollusk grazers, quantify differences in microbial community structure, mucus protein and carbohydrate content, and, through a simple laboratory experiment, assess their effects on integrated measures of biofilm abundance. Over 665 Amplicon Sequence Variants (ASVs) were found across grazers, with significant differences in abundance and composition among grazer species and epilithic biofilms. The pulmonate limpet Siphonaria lessonii and the periwinkle Echinolittorina peruviana shared similar microbiota. The microbiota of the chiton Chiton granosus, keyhole limpet Fissurella crassa, and scurrinid limpet Scurria araucana differed markedly from one another, and form those of the pulmonate limpet and periwinkle. Flavobacteriaceae (Bacteroidia) and Colwelliaceae (Gammaproteobacteria) were the most common among microbial taxa. Microbial strict specialists were found in only one grazer species. The pedal mucus pH was similar among grazers, but carbohydrate and protein concentrations differed significantly. Yet, differences in mucus composition were not reflected in microbial community structure. Only the pedal mucus of F. crassa and S. lessonii negatively affected the abundance of photosynthetic microorganisms in the biofilm, demonstrating the specificity of the pedal mucus effects on biofilm communities. Thus, the pedal mucus microbiota are distinct among grazer hosts and can affect and interact non-trophically with the epilithic biofilms on which grazers feed, potentially leading to microbial community coalescence mediated by grazer movement. Further studies are needed to unravel the myriad of non-trophic interactions and their reciprocal impacts between macro- and microbial communities.

Mucoid Acinetobacter baumannii enhances anti-phagocytosis through reducing C3b deposition.

BackgroundMultidrug resistant (MDR) Acinetobacter baumannii causes serious infections in intensive care units and is hard to be eradicated by antibiotics. Many A. baumannii isolates are identified as the mucoid type recently, but the biological characteristics of mucoid A. baumannii and their interactions with host cells remains unclear.MethodsThe mucoid phenotype, antimicrobial susceptibility, biofilm-forming ability, acid resistance ability, peroxide tolerance, and in vivo toxicity of clinical ICUs derived A. baumannii isolates were first investigated. Secondly, the phagocytic resistance and invasive capacity of A. baumannii isolates to macrophages (MH-S, RAW264.7) and epithelial cells (A549) were analyzed. Furthermore, the abundance of C3b (complement factor C3 degradation product) deposition on the surface of A. baumannii was investigated. Last, the relationship between C3b deposition and the abundance of capsule in A. baumannii isolates were analyzed.ResultsThese A. baumannii strains showed different mucoid phenotypes including hyper mucoid (HM), medium mucoid (MM), and low mucoid (LM). All tested strains were MDR with high tolerance to either acid or hydrogen peroxide exposure. Notably, these mucoid strains showed the increase of mortality in the Galleria mellonella infection models. Besides, the HM strain exhibited less biofilm abundance, higher molecular weight (MW) of capsule, and greater anti-phagocytic activity to macrophages than the LM strain. Together with the increased abundance of capsule, high expression of tuf gene (associated with the hydrolysis of C3b), the HM strain effectively inhibits C3b deposition on bacterial surface, resulting in the low-opsonization phenotype.ConclusionCapsular characteristics facilitate the anti-phagocytic activity in hyper mucoid A. baumannii through the reduction of C3b deposition. Mucoid A. baumannii exhibits high phagocytosis resistance to both macrophages and epithelial cells.

Effects of pharmaceuticals on the fouling propensity of membrane bioreactor: Case of iodinated X-ray contrast media

Membrane bioreactor (MBR) has shown promising results in the abatement of pharmaceuticals, however, its fouling propensity has continued to put challenges in its wide-scale applicability. The present study is the first study that investigated the MBR fouling behaviour in the presence of iodinated X-ray contrast media (ICM). The study found that ICM aggravated the fouling issue by reducing the filtration cycle by 21 % and enhancing the production of key foulants- extracellular polymeric substances (EPS) and soluble microbial products (SMP). Size exclusion chromatography (SEC) results revealed the presence of a higher molecular weight (MW) organics in the EPS in ICM dosed phase. Also, excitation-emission matrix (EEM) contours of EPS showed that the exposure to ICM seemed to stimulate the secretion of aromatic proteins comprising tryptophan (28.7 %) and tyrosine (22.07 %) compared to the non-ICM dosed phase (25.10 % for tryptophan and 20.39 % for tyrosine). The floc size of the sludge was found to increase to 67.6 ± 10.2 µm from 22.4 ± 4.8 µm in the presence of ICM as a result of increased EPS content. Further, ICM addition resulted in a slight reduction of the sludge microbial activity (∼10 %). ICM also changed the microbial dynamics of the sludge by enriching the abundance of biofilm forming phyla such as Bacteroidetes and TM7. The findings of this study provide fundamental insights into the fouling propensity of MBR in presence of ICM, and highlight that the changes caused in the EPS secretion profile would be responsible for enhanced fouling.

Activated Carbon Facilitates Anaerobic Digestion of Furfural Wastewater: Effect of Direct Interspecies Electron Transfer

Anaerobic digestion of furfural wastewater suffers from toxicity to microbes, which reduces its performance. The toxic effects may be eliminated by a sustainable way of conductive material supplementation. In this study, the effect on anaerobic digestion of furfural (0.5–4 g/L) was investigated by adding 0–40 g/L granular activated carbon (GAC) in batch tests. The innovation of this current study is to explore the potential direct interspecies electron transfer (DIET) for the first time in furfural degradation as the sole substrate in anaerobic digestion. The results demonstrated that when furfural was the sole substrate, in the presence of GAC, the peak methane production rate was increased by 46.0%, while the specific methane yield was improved by 24.7%, compared with the control. Additionally, the electroactive Geobacter sulfurreducens abundance in biofilms attached to the surface of GAC was 19.0 folds higher than that in the control. The abundances of the related genes of methane metabolism and furfural degradation in biofilms were 1.1 and 5.8 folds higher than the control by metagenomic analysis, respectively. These lines of evidence suggested that the pathway of furfural metabolism to methane among Moorella species, G. sulfurreducens, and Methanothrix species based on DIET was likely established.

Surface Characteristics Together With Environmental Conditions Shape Marine Biofilm Dynamics in Coastal NW Mediterranean Locations

Microbial colonization of artificial substrates in coastal areas, which concerns hull ships, sensors as well as plastic debris, is of huge significance to attain a rational environmental management. Some surface and environmental drivers of biofilm development have previously been described but their relative impact on the formation of biofilms remains unknown while crucial. Especially, there is no evidence of the relative importance of physical surface properties (wettability, roughness, smoothness) compared to seawater characteristics in driving biofilm abundance and diversity. In addition, few studies have considered the temporal evolution of this complex form of colonization, which often prevent to globally understand the process. Using experimental facilities in two Mediterrranean locations, a multidisciplinary approach including surface characterizations as well as seawaterquality analyses, flow cytometry and 16S rDNA metabarcoding, allowed for the identification of the main drivers of colonization for two antifouling (AF) coatings. One AF coating released copper (SPC1) while the other limit colonization thanks to physical properties, namely a low surface energy, roughness and smoothness (FRC1). Results were obtained over 75 days and compared to a control surface (PVC). Biofilm development was observed on all surfaces, with increasing density from AF coatings to PVC. Pionneer bacteria were dissimilar within all three surface types, however, communities observed on FRC1 converged toward PVC ones overtime, whereas SPC1 communities remained highly specific. A remarkably low and unique diversity was found on SPC1 during the experiment as Alteromonas accounted for more than 90% of the community colonizing this substrate until 12 days, and remained one of the co-dominant taxa of mature biofilms. Moreover, clear differences were found between geographical locations. Low nutrients and higher hydrodymanics in Banyuls bay resulted in less dense biofilms overall compared to Toulon, but also in a the slower dynamic of biofilm formation. This is illustrated by the persistence of pioneer Alteromonas but also Hyphomonadacae after 75 days on SPC1. We concluded that, even if local environmental conditions influenced the composition of biofilm communities, particular physical features may control the biofilm density but not the diversity, while copper releasing coating controlled both. In addition, it is evident from these results that sequential biofilm dynamics should carefully be considered as initial processes of formation differed from the long-term ones.