Mineral Scaling on Reverse Osmosis Membranes: Role of Mass, Orientation, and Crystallinity on Permeability.

Prior mineral scaling investigations mainly studied the effects of membrane surface properties rather than on the mineral properties and their impact on membrane permeability. In our study, mass, crystal growth orientation, and crystallinity of mineral precipitates on membranes, as well as their effects on membrane permeability have been investigated. Gypsum scaling tests on bare and bovine serum albumin (BSA)-conditioned membranes were conducted under different saturation indices. Results show that a longer scaling period was required for BSA-conditioned membranes to reach the same membrane permeate flux decline as bare membranes. Though the final reduced permeability was the same for both two membranes, the masses of the mineral precipitates on BSA-conditioned membranes were around two times more than those on bare membranes. Further mineral characterizations confirmed that different permeability decay rates of both types of the membrane were attributed to the differences in growth orientations rather than amounts of gypsum precipitates. Moreover, BSA-conditioned layers with high carboxylic density and specific molecular structure could stabilize bassanite and disrupt the oriented growth to inhibit the formation of needle-like gypsum crystals as observed on bare membranes, thus resulting in lower surface coverage with scales on membranes and alleviating the detrimental scaling effect on membrane permeability.

Aerobic degradation of dichlorinated dibenzo-p-dioxin and dichlorinated dibenzofuran by bacteria strains obtained from tropical contaminated soil.

Bacterial diversity and aerobic catabolic competence of dioxin-degrading bacterial strains isolated from a polluted soil in the tropics were explored. Isolation of bacteria occurred after 12 months of consecutive enrichment, with dioxin congeners serving as the only sources of carbon and energy. Seventeen strains that were isolated were subsequently screened for dioxin metabolic competence. Among these isolates, five had unique amplified ribosomal DNA restriction analysis (ARDRA) patterns out of which two exhibiting good metabolic competence were selected for further investigation. The two strains were identified as Bacillus sp. SS2 and Serratia sp. SSA1, based on their 16S rRNA gene sequences. Bacterial growth co-occurred with dioxin disappearance and near stoichiometric release of chloride for one ring of the chlorinated congeners. The overall percentage removal of dibenzofuran (DF) by strain SS2 was 93.87%; while corresponding values for 2,8-dichlorodibenzofuran (2,8-diCDF) and 2,7-dichlorodibenzo-p-dioxin (2,7-diCDD) were 86.22% and 82.30% respectively. In the case of strain SSA1, percentage removal for DF, 2,8-diCDF and 2,7-diCDD were respectively 98.9%, 80.97% and 70.80%. The presence of two dioxin dioxygenase catabolic genes (dxnA1 and dbfA1) was investigated. Only the dbfA1 gene could be amplified in SS2 strain. Results further revealed that strain SS2 presented higher expression levels for the alpha-subunit of DF dioxygenase (dbfA1) gene during growth with dioxins. The expression level for dbfA1 gene was higher when growing on DF than on the other chlorinated analogs. This study gives an insight into dioxin degradation, with the catabolic potential of strains SS2 and SSA1 (an enteric bacterium) within the sub-Sahara Africa. It further shows that dioxin catabolic potential might be more prevalent in different groups of microorganisms than previously believed. Few reports have demonstrated the degradation of chlorinated congeners of dioxins, particularly from sub-Saharan African contaminated systems.

Investigation of Thermal Properties of Graphene-Coated Membranes by Laser Irradiation to Remove Biofoulants.

In the present study, we take advantage of the high thermal conductivity of graphene nanomaterials to develop a filter that can be easily cleaned via laser irradiation after biofouling occurs. In this investigation, the intensity of the laser beam and the amount of graphene used for membrane coating were investigated with Bacillus subtilis to achieve the most efficient removal of biofoulants. Thermographic measurements of glass microfiber filters coated with 500 µg of graphene showed an increase in temperature of about 328 ± 9 °C in about 6 s when the filters were irradiated with a 21.6 W/cm-2 laser intensity, which allowed successful removal of biofoulants. The thermal cleaning was effective for at least four filtrations without impacting the subsequent microbial removals, which were of ∼5 log for each filtration step followed by laser irradiation. Additionally, the permeability of the coated filters only dropped from 17.8 to 15.9 L/m2s after the laser cleaning procedure. The cleaning procedure was validated by using bayou water with a complex composition of biofoulants. Graphene-coated membranes coupled with laser irradiation afford a very fast and nonhazardous approach to clean biofoulants on graphene-coated membranes.

Level of Fimbriation Alters the Adhesion of Escherichia coli Bacteria to Interfaces.

Adhesion of bacteria to interfaces is the first step in pathogenic infection, in biofilm formation, and in bioremediation of oil spills and other pollutants. Bacteria use a variety of surface structures to promote interfacial adhesion, with the level of expression of these structures varying in response to local conditions and environmental signals. Here, we investigated how overexpression of type 1 fimbriae, one such appendage, modifies the ability of Escherichia coli to adhere to solid substrates, via biofilm formation and yeast agglomeration, and to oil/water interfaces, via a microbial adhesion to hydrocarbon assay. A plasmid that enables inducible expression of E. coli MG1655 type 1 fimbriae was transformed into fimbriae-deficient mutant strain MG1655ΔfimA. The level of fimH gene expression in the engineered strain, measured using quantitative real-time PCR, could be tuned by changing the concentration of inducer isopropyl ß-d-1-thiogalactopyranoside (IPTG), and was higher than that in strain MG1655. Increasing the degree of fimbriation only slightly modified the surface energy and zeta potential of the bacteria, but enhanced their ability to agglomerate yeast cells and to adhere to solid substrates (as measured by biofilm formation) and to oil/water interfaces. We anticipate that the tunable extent of fimbriation accessible with this engineered strain can be used to investigate how adhesin expression modifies the ability of bacteria to adhere to interfaces and to actively self-assemble there.

Relationship of Biodiversity with Heavy Metal Tolerance and Sorption Capacity: A Meta-Analysis Approach.

Microbial remediation of metals can alleviate the concerns of metal pollution in the environment. The microbial remediation, however, can be a complex process since microbial metal resistance and biodiversity can play a direct role in the bioremediation process. This study aims to understand the relationships among microbial metal resistance, biodiversity, and metal sorption capacity. Meta-analyses based on 735 literature data points of minimum inhibitory concentrations (MIC) of Plantae, Bacteria, and Fungi exposed to As, Cd, Cr Cu, Ni, Pb, and Zn showed that metal resistance depends on the microbial Kingdom and the type of heavy metal and that consortia are significantly more resistant to heavy metals than pure cultures. A similar meta-analysis comparing 517 MIC values from different bacterial genera (Bacillus, Cupriavidus, Klebsiella, Ochrobactrum, Paenibacillus, Pseudomonas, and Ralstonia) confirmed that metal tolerance depends on the type of genus. Another meta-analysis with 195 studies showed that the maximum sorption capacity is influenced by microbial Kingdoms, the type of biosorbent (whether consortia or pure cultures), and the type of metal. This study also suggests that bioremediation using microbial consortia is a valid option to reduce environmental metal contaminations.

Recent advances in graphene-based biosensor technology with applications in life sciences.

Graphene's unique physical structure, as well as its chemical and electrical properties, make it ideal for use in sensor technologies. In the past years, novel sensing platforms have been proposed with pristine and modified graphene with nanoparticles and polymers. Several of these platforms were used to immobilize biomolecules, such as antibodies, DNA, and enzymes to create highly sensitive and selective biosensors. Strategies to attach these biomolecules onto the surface of graphene have been employed based on its chemical composition. These methods include covalent bonding, such as the coupling of the biomolecules via the 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide reactions, and physisorption. In the literature, several detection methods are employed; however, the most common is electrochemical. The main reason for researchers to use this detection approach is because this method is simple, rapid and presents good sensitivity. These biosensors can be particularly useful in life sciences and medicine since in clinical practice, biosensors with high sensitivity and specificity can significantly enhance patient care, early diagnosis of diseases and pathogen detection. In this review, we will present the research conducted with antibodies, DNA molecules and, enzymes to develop biosensors that use graphene and its derivatives as scaffolds to produce effective biosensors able to detect and identify a variety of diseases, pathogens, and biomolecules linked to diseases.

Efficacy of carbonaceous materials for sorbing polychlorinated biphenyls from aqueous solution.

Interest in incorporating nanomaterials into water treatment technologies is steadily growing, driving the necessity to understand the interaction of these new materials with specific water contaminants. In the present study, five different carbonaceous materials: activated carbon (AC), charcoal (BC), carbon nanotubes (CNT), graphene (GE), and graphene oxide (GO) were investigated as sorbent materials for 11 polychlorinated biphenyl (PCB) congeners in aqueous concentrations in the pg-µg/L range. Sorbent-water distribution coefficients (Ks) calculated in aqueous concentrations of ng/L show that AC is superior to GE, GO, CNT, and BC for the 11 PCB congeners investigated by an average of 1.1, 1.1, 1.3, and 2.5 orders of magnitude, respectively. Additionally, maximum capacity and sorption affinity parameters from the Langmuir, Freundlich, and Polanyi-Dubinin-Manes (PDM) models show a similar result. Interestingly, however, the effect of molecular planarity has greater impact on PCB sorption to the nanomaterials, such that the planar congeners form stronger bonds with CNT, GE, and GO compared to AC and BC. This work demonstrated superior PCB sorption by AC as compared with the nanomaterials examined such that substantial post production modifications would be necessary for the nanomaterials to out-perform AC.

Toxicity of functionalized single-walled carbon nanotubes on soil microbial communities: implications for nutrient cycling in soil.

Culture-dependent and -independent methods were employed to determine the impact of carboxyl-functionalized single-walled carbon nanotubes (SWNTs) on fungal and bacterial soil microbial communities. Soil samples were exposed to 0 (control), 250, and 500 µg of SWNTs per gram of soil. Aliquots of soil were sampled for up to 14 days for culture-dependent analyses, namely, plate count agar and bacterial community level physiological profiles, and culture-independent analyses, namely, quantitative real-time polymerase chain reaction (qPCR), mutliplex-terminal restriction fragment length polymorphism (M-TRFLP), and clone libraries. Results from culture-independent and -dependent methods show that the bacterial soil community is transiently affected by the presence of SWNTs. The major impact of SWNTs on bacterial community was observed after 3 days of exposure, but the bacterial community completely recovered after 14 days. However, no recovery of the fungal community was observed for the duration of the experiment. Physiological and DNA microbial community analyses suggest that fungi and bacteria involved in carbon and phosphorus biogeochemical cycles can be adversely affected by the presence of SWNTs. This study suggests that high concentrations of SWNTs can have widely varying effects on microbial communities and biogeochemical cycling of nutrients in soils.

Diversity of fungal microbiome obtained from plant rhizoplanes.

Microbial communities, and their ecological importance, have been investigated in several habitats. However, so far, most studies could not describe the closest microbial interactions and their functionalities. This study investigates the co-occurring interactions between fungi and bacteria in plant rhizoplanes and their potential functions. The partnerships were obtained using fungal-highway columns with four plant-based media. The fungi and associated microbiomes isolated from the columns were identified by sequencing the ITS (fungi) and 16S rRNA genes (bacteria). Statistical analyses including Exploratory Graph and Network Analysis were used to visualize the presence of underlying clusters in the microbial communities and evaluate the metabolic functions associated with the fungal microbiome (PICRUSt2). Our findings characterize the presence of both unique and complex bacterial communities associated with different fungi. The results showed that Bacillus was associated as exo-bacteria in 80 % of the fungi but occurred as putative endo-bacteria in 15 %. A shared core of putative endo-bacterial genera, potentially involved in the nitrogen cycle was found in 80 % of the isolated fungi. The comparison of potential metabolic functions of the putative endo- and exo-communities highlighted the potential essential factors to establish an endosymbiotic relationship, such as the loss of pathways associated with metabolites obtained from the host while maintaining pathways responsible for bacterial survival within the hypha.

Graphene nanocomposite for biomedical applications: fabrication, antimicrobial and cytotoxic investigations.

Materials possessing excellent bacterial toxicity, while presenting low cytotoxicity to human cells, are strong candidates for biomaterials applications. In this study, we present the fabrication of a nanocomposite containing poly(N-vinylcarbazole) (PVK) and graphene (G) in solutions and thin films. Highly dispersed PVK-G (97-3 w/w%) solutions in various organic and aqueous solvents were prepared by solution mixing and sonication methods. The thermal properties and morphology of the new composite were analyzed using thermal gravimetry analysis (TGA) and atomic force microscopy (AFM), respectively. PVK-G films were immobilized onto indium tin oxide (ITO) substrates via electrodeposition. AFM was used to characterize the resulting topography of the nanocomposite thin films, while cyclic voltammetry and UV-vis were used to monitor their successful electrodeposition. The antimicrobial properties of the electrodeposited PVK-G films and solution-based PVK-G were investigated against Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis). Microbial growth after exposure to the nanocomposite, metabolic assay and live-dead assay of the bacterial solutions exposed to PVK-G presented fewer viable and active bacteria than those exposed to pure PVK or pure graphene solutions. The PVK-G film inhibited about 80% of biofilm surface coverage whereas the PVK- and G-modified surfaces allowed biofilm formation over almost the whole coated surface (i.e. > 80%). The biocompatibility of the prepared PVK-G solutions on NIH 3T3 cells was evaluated using the MTS cell proliferation assay. A 24 h exposure of the PVK-G nanocomposite to the NIH 3T3 cells presented ~80% cell survival.

Antimicrobial applications of electroactive PVK-SWNT nanocomposites.

The antibacterial properties of a nanocomposite containing an electroactive polymer, polyvinyl-N-carbazole (PVK) (97 wt %), and single-walled carbon nanotubes (SWNT) (3 wt %) was investigated as suspensions in water and as thin film coatings. The toxic effects of four different PVK-SWNT (97:3 wt %) nanocomposite concentrations (1, 0.5, 0.05, and 0.01 mg/mL) containing 0.03, 0.015, 0.0015, and 0.0003 mg/mL of SWNT, respectively, were determined for planktonic cells and biofilms of Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis). The results showed that the nanocomposite PVK-SWNT had antibacterial activity on planktonic cells and biofilms at all concentration levels. Higher bacterial inactivation (94% for E. coli and 90% for B. subtilis) were achieved in planktonic cells at a PVK-SWNT concentration of 1 mg/mL. Atomic force microscopy (AFM) imaging showed significant reduction of biofilm growth on PVK-SWNT coated surfaces. This study established for the first time that the improved dispersion of SWNTs in aqueous solutions in the presence of PVK enhances the antimicrobial effects of SWNTs at very low concentrations. Furthermore, PVK-SWNT can be used as an effective thin film coating material to resist biofilm formation.

Effect of Endosymbiotic Bacteria on Fungal Resistance Toward Heavy Metals.

Most studies on metal removal or tolerance by fungi or bacteria focus on single isolates, without taking into consideration that some fungi in nature may be colonized by endobacteria. To address this knowledge gap, we investigated the tolerance and removal of diverse metals with two fungal species: Linnemannia elongata containing Burkholderia-related endobacteria and Benniella erionia containing Mollicute-related endobacteria. Isogenic lines of both species were generated with antibiotic treatments to remove their respective endobacteria. Experiments involved comparing the isogenic lines and wild type fungi in relation to the minimum inhibitory concentration for the metals, the fungal ability to remove these different metals via atomic adsorption spectroscopy, and the interaction of the metals with specific functional groups of the fungi and fungi-bacteria to determine the role of the bacteria via attenuated total reflection fourier transformed infrared (ATR-FTIR). Finally, we determined the influence of different metal concentrations, associated with moderate and high fungal growth inhibition, on the presence of the endobacteria inside the fungal mycelium via quantitative real-time PCR. Results showed that the presence of the endosymbiont increased B. erionia resistance to Mn2+ and increased the removal of Fe2+ compared to isogenic lines. The absence of the endosymbiont in L. elongata increased the fungal resistance toward Fe2+ and improved the removal of Fe2+. Furthermore, when the bacterial endosymbiont was present in L. elongata, a decrease in the fungal resistance to Ca2+, Fe2+, and Cr6+was noticeable. In the ATR-FTIR analysis, we determined that C-H and C = O were the major functional groups affected by the presence of Cu2+, Mn2+, and Fe2+ for L. elongata and in the presence of Cu2+ and Ca2+ for B. eronia. It is noteworthy that the highest concentration of Pb2+ led to the loss of endobacteria in both L. elongata and B. eronia, while the other metals generally increased the concentration of endosymbionts inside the fungal mycelium. From these results, we concluded that bacterial endosymbionts of fungi can play a fundamental role in fungal resistance to metals. This study provides the first step toward a greater understanding of symbiotic interactions between bacteria and fungi in relation to metal tolerance and remediation.

Elevated Adsorption of Lead and Arsenic over Silver Nanoparticles Deposited on Poly(amidoamine) Grafted Carbon Nanotubes.

An efficient adsorbent, CNTs-PAMAM-Ag, was prepared by grafting fourth-generation aromatic poly(amidoamine) (PAMAM) to carbon nanotubes (CNTs) and successive deposition of Ag nanoparticles. The FT-IR, XRD, TEM and XPS results confirmed the successful grafting of PAMAM onto CNTs and deposition of Ag nanoparticles. The absorption efficiency of CNTs-PAMAM-Ag was evaluated by estimating the adsorption of two toxic contaminants in water, viz., Pb(II) and As(III). Using CNTs-PAMAM-Ag, about 99 and 76% of Pb(II) and As(III) adsorption, respectively, were attained within 15 min. The controlling mechanisms for Pb(II) and As(III) adsorption dynamics were revealed by applying pseudo-first and second-order kinetic models. The pseudo-second-order kinetic model followed the adsorption of Pb(II) and As(III). Therefore, the incidence of chemisorption through sharing or exchanging electrons between Pb(II) or As(III) ions and CNTs-PAMAM-Ag could be the rate-controlling step in the adsorption process. Further, the Weber-Morris intraparticle pore diffusion model was employed to find the reaction pathways and the rate-controlling step in the adsorption. It revealed that intraparticle diffusion was not a rate-controlling step in the adsorption of Pb(II) and As(III); instead, it was controlled by both intraparticle diffusion and the boundary layer effect. The adsorption equilibrium was evaluated using the Langmuir, Freundlich, and Temkin isotherm models. The kinetic data of Pb(II) and As(III) adsorption was adequately fitted to the Langmuir isotherm model compared to the Freundlich and Temkin models.

Distinguishing nanoparticle drug release mechanisms by asymmetric flow field-flow fractionation.

This research demonstrates the development, application, and mechanistic value of a multi-detector asymmetric flow field-flow fractionation (AF4) approach to acquire size-resolved drug loading and release profiles from polymeric nanoparticles (NPs). AF4 was hyphenated with multiple online detectors, including dynamic and multi-angle light scattering for NP size and shape factor analysis, fluorescence for drug detection, and total organic carbon (TOC) to quantify the NPs and dissolved polymer in nanoformulations. The method was demonstrated on poly(lactic-co-glycolic acid) (PLGA) NPs loaded with coumarin 6 (C6) as a lipophilic drug surrogate. The bulk C6 release profile using AF4 was validated against conventional analysis of drug extracted from the NPs and complemented with high performance liquid chromatography - quadrupole time-of-flight (HPLC-QTOF) mass spectrometry analysis of oligomeric PLGA species. Interpretation of the bulk drug release profile was ambiguous, with several release models yielding reasonable fits. In contrast, the size-resolved release profiles from AF4 provided critical information to confidently establish the release mechanism. Specifically, the C6-loaded NPs exhibited size-independent release rate constants and no significant NP size or shape transformations, suggesting surface desorption rather than diffusion through the PLGA matrix or erosion. This conclusion was supported through comparative experimental evaluation of PLGA NPs carrying a fully entrapped drug, enrofloxacin, which showed size-dependent diffusive release, along with density functional theory (DFT) calculations indicating a higher adsorption affinity of C6 onto PLGA. In summary, the development of the size-resolved AF4 method and data analysis framework fulfills salient analytical gaps to determine drug localization and release mechanisms from nanomedicines.

Complete genome sequence of the Thermophilic Bacterium Exiguobacterium sp. AT1b.

Here we present the genome of strain Exiguobacterium sp. AT1b, a thermophilic member of the genus Exiguobacterium whose representatives were isolated from various environments along a thermal and physicochemical gradient. This genome was sequenced to be a comparative resource for the study of thermal adaptation with a psychroactive representative of the genus, Exiguobacterium sibiricum strain 255-15, that was previously sequenced by the U.S. Department of Energy's (DOE's) Joint Genome Institute (JGI) (http://genome.ornl.gov/microbial/exig/).

Asymmetric flow field-flow fractionation (AF4) with fluorescence and multi-detector analysis for direct, real-time, size-resolved measurements of drug release from polymeric nanoparticles.

Polymeric nanoparticles (NPs) are typically designed to enhance the efficiency of drug delivery by controlling the drug release rate. Hence, it is critical to obtain an accurate drug release profile. This study presents the first application of asymmetric flow field-flow fractionation (AF4) with fluorescence detection (FLD) to quantify release profiles of fluorescent drugs from polymeric NPs, specifically poly(lactic-co-glycolic acid) NPs loaded with enrofloxacin (PLGA-Enro NPs). In contrast to conventional measurements requiring separation of the NPs and dissolved drugs (typically by dialysis) prior to quantification, AF4 provides in situ removal of unincorporated drugs, while the judicious combination of online FLD and UV detection selectively provides the entrapped drug and PLGA NP concentrations, respectively, and hence the drug loading. NP size and shape factors are simultaneously obtained by online dynamic and multi-angle light scattering (DLS, MALS) detectors. The AF4 and dialysis approaches were compared to evaluate drug release from PLGA-Enro NPs containing a high proportion (≈ 94%) of unincorporated (burst release) drug at three temperatures spanning the glass transition temperature (Tg ≈ 33 °C) of the NPs. The AF4 method clearly captured the temperature dependence of the drug release relative to Tg (from no release at 20 °C to rapid release at 37 °C). In contrast, dialysis was not able to distinguish differences in the extent or rate of release of the entrapped drug because of interferences from the burst release, as well as the dialysis lag time, as supported through a diffusion model and validation experiments on purified NPs with low burst release. Finally, the multi-detector AF4 analysis yielded unique size-dependent release profiles across the entire NP size distribution, with smaller NPs showing faster release consistent with radial diffusion from the NPs. Overall, this study demonstrates the novel application and advantages of multi-detector AF4 methods, particularly AF4-FLD, to obtain direct, size-resolved release profiles of fluorescent drugs from polymeric NPs.

Prevention of infection caused by enteropathogenic E. coli O157:H7 in intestinal cells using enrofloxacin entrapped in polymer based nanocarriers.

Poor bioavailability of antibiotics, toxicity, and development of antibiotic-resistant bacteria jeopardize antibiotic treatments. To circumvent these issues, drug delivery using nanocarriers are highlighted to secure the future of antibiotic treatments. This work investigated application of nanocarriers, to prevent and treat bacterial infection, presenting minimal toxicity to the IPEC-J2 cell line. To accomplish this, polymer-based nanoparticles (NPs) of poly(lactide-co-glycolide) (PLGA) and lignin-graft-PLGA (LNP) loaded with enrofloxacin (ENFLX) were synthesized, yielding spherical particles with average sizes of 111.8 ± 0.6 nm (PLGA) and 117.4 ± 0.9 nm (LNP). The releases of ENFLX from PLGA and LNP were modeled by a theoretical diffusion model considering both the NP and dialysis diffusion barriers for drug release. Biocompatible concentrations of ENFLX, enrofloxacin loaded PLGA(Enflx) and LNP(Enflx) were determined based on examination of bacterial inhibition, toxicity, and ROS generation. Biocompatible concentrations were used for treatment of higher- and lower-level infections in IPEC-J2 cells. Prevention of bacterial infection by LNP(Enflx) was enhanced more than 50% compared to ENFLX at lower-level infection. At higher-level infection, PLGA(Enflx) and LNP(Enflx) demonstrated 25% higher prevention of bacteria growth compared to ENFLX alone. The superior treatment achieved by the nanocarried drug is accredited to particle uptake by endocytosis and slow release of the drug intracellularly, preventing rapid bacterial growth inside the cells.

Democratization of fungal highway columns as a tool to investigate bacteria associated with soil fungi.

Bacteria-fungi interactions (BFIs) are essential in ecosystem functioning. These interactions are modulated not only by local nutritional conditions but also by the physicochemical constraints and 3D structure of the environmental niche. In soils, the unsaturated and complex nature of the substrate restricts the dispersal and activity of bacteria. Under unsaturated conditions, some bacteria engage with filamentous fungi in an interaction (fungal highways) in which they use fungal hyphae to disperse. Based on a previous experimental device to enrich pairs of organisms engaging in this interaction in soils, we present here the design and validation of a modified version of this sampling system constructed using additive printing. The 3D printed devices were tested using a novel application in which a target fungus, the common coprophilous fungus Coprinopsis cinerea, was used as bait to recruit and identify bacterial partners using its mycelium for dispersal. Bacteria of the genera Pseudomonas, Sphingobacterium and Stenotrophomonas were highly enriched in association with C. cinerea. Developing and producing these new easy-to-use tools to investigate how bacteria overcome dispersal limitations in cooperation with fungi is important to unravel the mechanisms by which BFIs affect processes at an ecosystem scale in soils and other unsaturated environments.

Widespread bacterial diversity within the bacteriome of fungi.

Knowledge of associations between fungal hosts and their bacterial associates has steadily grown in recent years as the number and diversity of examinations have increased, but current knowledge is predominantly limited to a small number of fungal taxa and bacterial partners. Here, we screened for potential bacterial associates in over 700 phylogenetically diverse fungal isolates, representing 366 genera, or a tenfold increase compared with previously examined fungal genera, including isolates from several previously unexplored phyla. Both a 16 S rDNA-based exploration of fungal isolates from four distinct culture collections spanning North America, South America and Europe, and a bioinformatic screen for bacterial-specific sequences within fungal genome sequencing projects, revealed that a surprisingly diverse array of bacterial associates are frequently found in otherwise axenic fungal cultures. We demonstrate that bacterial associations with diverse fungal hosts appear to be the rule, rather than the exception, and deserve increased consideration in microbiome studies and in examinations of microbial interactions.

Microbially-induced mineral scaling in desalination conditions: Mechanisms and effects of commercial antiscalants.

Reverse osmosis (RO) technology is promising in the sustainable production of fresh water. However, expansion of RO use has been hindered by membrane fouling, mainly inorganic fouling known as scaling. Although membrane mineral scaling by chemical means have been investigated extensively, mineral scaling triggered by microbial activity has been largely neglected. In this study, the simultaneous biomineralization of CaCO3 and CaSO4 in the presence of three different microbial communities from fresh water, wastewater, and seawater was investigated. In the presence of either 13 or 79 mM of Ca2+ and SO42- in the media, the fresh water microbial community produced calcite/vaterite and vaterite/gypsum, respectively; the wastewater community produced vaterite and vaterite/gypsum, respectively; and the seawater community produced aragonite in both conditions. The results showed that the concentration of salts and the microbial composition influence the types of precipitates produced. The mechanisms of crystal formation of CaCO3 and gypsum by these communities were also investigated by determining the need for metabolic active cells, the effect of a calcium channel blocker, and the presence of extracellular polymeric substances (EPS). The results showed that metabolically active cells can lead to production of EPS and formation of Ca2+ gradient along the cells through calcium channels, which will trigger formation of biominerals. The prevention of biomineralization by these consortia was also investigated with two common polymeric RO antiscalants, i.e. polyacrylic acid (PAA) and polymaleic acid (PMA). Results showed that these antiscalants do not prevent the formation of the bio-precipitates suggesting that novel approaches to prevent biomineralization in RO systems still needs to be investigated.