Dual Species Research Articles

Bonding antimicrobial rhamnolipids onto medical grade PDMS: A strategy to overcome multispecies vascular catheter-related infections

In clinic there is a demand to solve the drawback of medical devices multispecies related infections. Consequently, different biomaterial surfaces, such as vascular catheters, urgently need improvement regarding their antifouling/antimicrobial properties. In this work, we covalently functionalized medical grade polydimethylsiloxane (PDMS) with antimicrobial rhamnolipids to investigate the biomaterial surface activity towards mono and dual species biofilms. Preparation of surfaces with “piranha” oxidation, followed by APTES bonding and carbodiimide reaction with rhamnolipids effectively bonded these compounds to PDMS surface as confirmed by FTIR-ATR and XPS analysis. Generated surfaces were active towards S. aureus biofilm formation showing a 4.2 log reduction while with S. epidermidis and C. albicans biofilms a reduction of 1.2 and 1.0 log reduction, respectively, was observed. Regarding dual-species testing the higher biofilm log reduction observed was 1.9. Additionally, biocompatibility was assessed by cytocompatibility towards human fibroblastic cells, low platelet activation and absence of vascular irritation.Our work not only sheds light on using covalently bonded rhamnolipids towards dual species biofilms but also highlights the biocompatibility of the obtained PDMS surfaces.

A microplate‐based Response Surface Methodology model for growth optimization and biofilm formation on polystyrene polymeric material in a Candida albicans and Escherichia coli co‐culture

AbstractBiofilm formation is one of the crucial factors for virulence in Candida albicans, Escherichia coli and their polymicrobial biofilm formed on medical prosthetics. In this study, high biofilm forming C. albicans M207 from a case of invasive candidiasis and a standard strain of bacterial culture E. coli ATCC 39936 were used for initial screening and media optimization using One Variable at a time (OVAT) and Response Surface Methodology (RSM) models, respectively, in polystyrene microtiter plates for in vitro biofilm studies. Sucrose and peptone significantly affected biofilm formation when screened by OVAT. Media optimization by Central Composite Design (CCD) showed that pH significantly affected biofilm formation for all the cultures which was further validated at critical parameters. Biofilm was quantified by growth OD measurements, MTT and CV assays in the presence and absence of FBS precoating and compared with standard Trypticase Soy Broth (TSB) media which did not show any significant difference. This high throughput polystyrene microtiter plate assay for preliminary screening of nutritional components using OVAT and media optimization using RSM model is being reported for the first time for biofilm formation by C. albicans and E. coli in a single and dual species environment. This study is essential for functional analysis of in‐vitro growth and biofilm formation by these two pathogenic strains on polymeric hospital equipments and to develop suitable control measures to inhibit biofilm formation by C. albicans and E. coli single species and their co‐culture.

Carrier-free nanoprodrug for p53-mutated tumor therapy via concurrent delivery of zinc-manganese dual ions and ROS.

Human cancers typically express a high level of tumor-promoting mutant p53 protein (Mutp53) with a minimal level of tumor-suppressing wild-type p53 protein (WTp53). In this regard, inducing Mutp53 degradation while activating WTp53 is a viable strategy for precise anti-tumor therapy. Herein, a new carrier-free nanoprodrug (i.e., Mn-ZnO2 nanoparticles) was developed for concurrent delivery of dual Zn-Mn ions and reactive oxygen species (ROS) within tumor to regulate the p53 protein for high anti-tumor efficacy. In response to the mild tumor acidic environment, the released Zn2+ and H2O2 from Mn-ZnO2 NPs induced ubiquitination-mediated proteasomal degradation of Mutp53, while the liberative Mn2+ and increased ROS level activated the ATM-p53-Bax pathway to elevate WTp53 level. Both in vitro and in vivo results demonstrated that pH-responsive decomposition of Mn-ZnO2 NPs could effectively elevate the intracellular dual Zn-Mn ions and ROS level and subsequently generate the cytotoxic hydroxyl radical (•OH) through the Fenton-like reaction. With the integration of multiple functions (i.e., carrier-free ion and ROS delivery, tumor accumulation, p53 protein modulation, toxic •OH generation, and pH-activated MRI contrast) in a single nanosystem, Mn-ZnO2 NPs demonstrate its superiority as a promising nanotherapeutics for p53-mutated tumor therapy.

Synergism With ε-Polylysine Hydrochloride and Cinnamon Essential Oil Against Dual-Species Biofilms of Listeria monocytogenes and Pseudomonas lundensis.

Various pathogenic and spoilage bacteria frequently coexist in meat processing environments and can form multispecies biofilms, causing significant health and economic issues. Despite the prevalence and coexistence, only less is known about possible interactions between Listeria monocytogenes (LM) and spoilers like Pseudomonas species, and their community-wide resistance against natural preservatives. This study evaluates the interactions between mono- or dual-species biofilms formed by LM and Pseudomonas lundensis (PL), as well as the sensitivity of these bacteria in dual-species biofilms to ε-polylysine hydrochloride (ε-PLH) alone or combined with cinnamon essential oil (CEO). The results showed that the biofilm cell density of P. lundensis in dual species was higher (p < 0.05) than LM, constituting about 85% of the total population. More biofilms and exopolysaccharide both in mono- or dual species of the two psychrotrophic strains were greatly produced at 15°C than at 30°C. The biomass, biovolume, and thickness of dual-species biofilms were significantly lower than single PL biofilm when tested using crystal violet staining, confocal laser scanning microscopy, and scanning electron microscopy, indicating the competitive interactions between them prevail. Additionally, ε-PLH significantly reduced the biofilm development as mono- and dual species in a concentration-dependent manner, especially single LM biofilm, which was consistent with the decrease in autoinducer-2 (AI-2) activity. LM as dual-species biofilms exhibited lower sensitivity to ε-PLH than its mono-biofilm probably due to protective effect conferred by PL. ε-PLH in combination with CEO, at the maximum sublethal concentrations (MSCs), showed enhanced inhibitory activity against dual-species biofilm formation, as evidenced by thin spare spatial structures and reduced AI-2 activity. In addition, the preformed dual biofilms were dramatically eradicated following treatment with ε-PLH combined with CEO at higher than minimum inhibitory concentration in comparison with either of the compounds used alone, indicating the synergistic antibiofilm of the two preservatives. This study reveals the competitive interactions between the two strains in dual-species biofilms, in which the dominant PL significantly contributed toward the tolerance of LM to ε-PLH, and the use of combined preservatives shows it is an effective strategy to control the multispecies biofilms in meat processing.

Studying the Penetration Ability of Various Pathogenic Bacteria into Raw Beef Meat Surface and the Antibacterial Effect of Ozonated Water

Colonization of meat with bacterial pathogens potentially affects the quality of the meat products. This study aimed to determine the penetration ability of psychrotolerant bacterial pathogens into the surface of red beef meat. The penetration experiment was carried out on raw beef meat to see how different time intervals (1 day, 2 days, and 3 days) and temperatures (5°C, 15°C, and 20°C) affected the penetration process. When bacteria are found at a depth of about 2 cm in the tested meat block, this is considered a positive penetration occurrence. In this study, the action of ozone treatment (at variable exposition times) on the bacterial loads of beef meat samples in which bacterial penetration occurred was evaluated. The formation of ozone was accomplished by utilizing an O3 generator (A2Z/AQUA-6, USA). The O3(ppm) concentration in water was defined using the HI 38054 Ozone Test Kit (Hanna Instrument®, USA). The results of bacterial penetrability suggest that at low temperatures, the rate of germ penetration onto the meat surface decreases. The results revealed that the penetration rate increased in the case of dual and triple bacterial species. This can be explained by the fact that all the bacterial species that were used in the study are actively motile and have proteolytic activity. These proprieties together absolutely play a major role in the acceleration of the penetration process by these bacteria, or even so, their existence together is synergistic for migration deeper into meat. To ensure freshness and public health protection, raw meat must be treated and processed in a sanitary manner. Under the conditions used in this study, a concentration of 0.5 ppm of O3 was found to be highly effective in reducing the bacterial count in meat blocks. This decline was aided by rising the exposing time to 45 minutes to achieve 3 log10 CFU/ml-1, and the bacterial count diminished with increased exposure time to ozonated water at the same concentration. These results suggest that O3 treatment could be used to lay the groundwork for a new method of reducing meat contamination by foodborne bacterial pathogens.

Heme cross-feeding can augment Staphylococcus aureus and Enterococcus faecalis dual species biofilms

The contribution of biofilms to virulence and as a barrier to treatment is well-established for Staphylococcus aureus and Enterococcus faecalis, both nosocomial pathogens frequently isolated from biofilm-associated infections. Despite frequent co-isolation, their interactions in biofilms have not been well-characterized. We report that in combination, these two species can give rise to augmented biofilms biomass that is dependent on the activation of E. faecalis aerobic respiration. In E. faecalis, respiration requires both exogenous heme to activate the cydAB-encoded heme-dependent cytochrome bd, and the availability of O2. We determined that the ABC transporter encoded by cydDC contributes to heme import. In dual species biofilms, S. aureus provides the heme to activate E. faecalis respiration. S. aureus mutants deficient in heme biosynthesis were unable to augment biofilms whereas heme alone is sufficient to augment E. faecalis mono-species biofilms. Our results demonstrate that S. aureus-derived heme, likely in the form of released hemoproteins, promotes E. faecalis biofilm formation, and that E. faecalis gelatinase activity facilitates heme extraction from hemoproteins. This interspecies interaction and metabolic cross-feeding may explain the frequent co-occurrence of these microbes in biofilm-associated infections.

DNA methylation clocks for dogs and humans

DNA methylation profiles have been used to develop biomarkers of aging known as epigenetic clocks, which predict chronological age with remarkable accuracy and show promise for inferring health status as an indicator of biological age. Epigenetic clocks were first built to monitor human aging, but their underlying principles appear to be evolutionarily conserved, as they have now been successfully developed for many mammalian species. Here, we describe reliable and highly accurate epigenetic clocks shown to apply to 93 domestic dog breeds. The methylation profiles were generated using the mammalian methylation array, which utilizes DNA sequences that are conserved across all mammalian species. Canine epigenetic clocks were constructed to estimate age and also average time to death. We also present two highly accurate human–dog dual species epigenetic clocks (R = 0.97), which may facilitate the ready translation from canine to human use (or vice versa) of antiaging treatments being developed for longevity and preventive medicine. Finally, epigenome-wide association studies here reveal individual methylation sites that may underlie the inverse relationship between breed weight and lifespan. Overall, we describe robust biomarkers to measure aging and, potentially, health status in canines.

Effects of Dual‐Species Biofilm Formation on Plastic Degradation by Ideonella sakaiensis

As of 2015, nearly 80% of the world’s virgin plastic ended up in a landfill or the natural environment, a majority accredited to the packaging industry. Due to the composition of the durable plastic, polyethylene terephthalate (PET), the primary polymer found in single‐use packaging, is not naturally biodegradable and thus accumulates. Recently, several microbes were discovered that could degrade the plastic compounds within their gut with no signs of toxicity. Ideonella sakaiensisis a novel bacterium capable of depolymerizing PET using a hydrolase termed PETase. An additional enzyme, MHETase, aids in converting dimers for the complete recovery of monomers within I. sakaiensis. Ultimately, efficiency in degrading PET of varying crystallinity occurs with a preference of low crystallinity PET, in opposition to other species currently known. During degradation, I. sakaiensisforms a thin biofilm over the plastic. It is known that the cells contain special appendages to adhere to the plastic surface, however, little research has been conducted on how the biofilm formation affects the degradation process. Multi‐species biofilms have been shown to create complex communities for enhanced PET degradation in marine plastic debris using other bacterial strains.This research aims to study the biofilm formation as well as its effects on its degradation properties of I. sakaiensisas an isolate, as well as a dual species biofilm with known biofilm forming bacteria: Stenotrophomonas maltophilia, Staphylococcus aureus, and Pseudomonas aeruginosa. The first half of the project characterized the effects of introducing biofilm forming bacteria on I. sakaiensis’ biofilm growth. The second half of the project analyzes the biofilm growth along with a degradation assay to determine the effects of these bacterial strains on the degradation process of I. sakaiensis. These effects were then evaluated to determine the role of biofilm formation in the degradation process. This study provides a foundation that can be used by the biotech, environmental, and molecular communities to lead to a commercialization of plastic degradation products, ultimately creating a circular and stable economy within the consumer world.

Potentials Distribution and Origin of Lablab [Lablab purpureus (L.) Sweet]: A Review

The review summarizes the potential, distribution and origin of Lablab purpureus. Forage legume has potentials for the production and productivities of arable land by suppling nitrogen for the living organisms in the soil those allowed to obtain their own feed in the symbiotic relationships. Further the soil become fertile for the next cropping season even at the time of intercropping the yield would be improved than mono-cropping systems. It also supplies the protein requirement of livestock and human consumption as vegetable or as seed sources. It is summer growing annual trifoliate forage legume. The origin of lablab is considered to be in Africa because in large parts of tropical Africa wild type cultivated lablab exists. Then it is heavily distributed to the corner side of the continent and Southeast Asia for seed and vegetable production. Even though the origin and distribution of lablab initiated in the African continent the applicability and degree of uses of the species were not well recognized across countries in the continent. Therefore further conservation and evaluation of this dual purpose species give priority by governmental and non-governmental bodies.

In vitro effect of farnesol on planktonic cells and dual biofilm formed by Candida albicans and Escherichia coli

Many biofilm studies have focused on axial biofilms, however biofilms in nature and in vivo environment are multi-species. Farnesol is a sesquiterpene alcohol found in many essential oils. This study investigated the in vitro effects of farnesol on planktonic cells and biofilms of Candida albicans and Escherichia coli. The ultrastructural morphology of farnesol treated cells was evaluated by TEM. According to the XTT results, farnesol caused a significant decrease in metabolic activity and scanning electron microscope images confirmed a reduction in the preformed biofilm as a result of farnesol treatment for single species C. albicans and E. coli biofilms. Although farnesol has less effect on dual species biofilm compared to the single species biofilms, its effect on the dual biofilm was found to be stronger than amphotericin B or ampicillin. Further studies are needed to clarify the role of farnesol on fungal-bacterial biofilms.

Moment analysis of unsteady bi-component species (drug) transport with coupled chemical reaction in non-Newtonian blood flow

Motivated by exploring the fluid dynamics of dual drug delivery systems in biomedicine, a mathematical analysis of the bi-component species transport (convective-diffusion) in rheological blood flow with bulk chemical reaction through a two-dimensional rigid vessel is presented. Two different bulk degradation reaction rates are included for the dual species (pharmacological agents, A, B). An analytical expression for axial velocity is derived using a perturbation method. The decoupled convection-diffusion equations are then analyzed with the Aris – Barton approach. The mean concentration of the species is estimated using the first five concentration moments with the aid of fourth order Hermite polynomials. A finite difference technique based on the Crank Nicholson implicit scheme is employed to handle the pth order moment of the general concentration. The analysis reveals that increasing reversible transfer rate and irreversible bulk degradation result in a reduction in the total mass of the species over time. The mass of both species decreases with an increase in reversible transfer rate, even though the mass of species A depletes faster than the mass of species B. The skewness of the concentration distribution decreases as yield stress increases and the distributions in all scenarios are positively skewed and tend to zero over time, implying that the distribution tends to symmetry over time. The kurtosis decreases over time from positive to negative values and eventually approaches zero. Mean concentration peaks for both species A and B are elevated with increasing yield stress, although magnitudes are significantly higher for species A. With increasing values of the distribution coefficient between two species, mean concentration peaks are elevated for species (component) A whereas they are depleted for species B, although substantially greater magnitudes are computed for species B. Good correlation of the skewness with earlier Newtonian results is achieved. The results provide some useful insight into the bi-component drug transport in smaller vessel pharmacodynamics where hemorheology is important.

Interaction of Bdellovibrio bacteriovorus with Gram-Negative and Gram-Positive Bacteria in Dual Species and Polymicrobial Communities.

The interaction of Bdellovibrio bacteriovorus PF13 with mixed bacterial communities, consisting of Gram-negative (Pseudomonas fluorescens and Klebsiella pneumoniae) and Gram-positive (Staphylococcus aureus and Enterococcus faecium) bacteria, was investigated to determine if this wild-type predator preferentially preys on certain bacteria and whether the presence of Gram-positive organisms influences its predation efficiency. In co-culture with P. fluorescens and K. pneumoniae, the cell counts (PFU/mL) of PF13 increased by 5.79 and 5.17 logs (48 h), respectively, while in the dual species assay (P. fluorescens, K. pneumoniae and PF13), the cell counts of PF13 increased by 1.95 logs (24 h). Using ethidium monoazide bromide quantitative polymerase chain reaction (EMA-qPCR), the concentration of PF13 increased by 1.25 to 3.62 logs in the co-culture experiments, by 1.41 to 5.05 logs in dual species cultures and by 2.65 logs in a polymicrobial culture. However, PF13 preferentially preyed on K. pneumoniae in the dual species and polymicrobial cultures, highlighting that the presence of Gram-positive bacteria did not affect the predation efficiency of PF13. This is significant as it implies that the predator can be applied in mixed microbial communities to target Gram-negative pathogens which may pose a health risk to patients, consumers or for the treatment of contaminated water.

Iron phthalocyanine-derived nanozyme as dual reactive oxygen species generation accelerator for photothermally enhanced tumor catalytic therapy

Nanozymes are artificial enzymes that mimic natural enzyme-like activities and show great promise for tumor catalytic therapy. However, new nanozymes with multiple catalytic activities for multifunctional nanotheranostic use remain challenging to design. Herein, for the first time, iron phthalocyanine (Fe(II)Pc) was assembled with poly(l-lactide-co-glycolide)-block-poly(ethylene glycol) to prepare an Fe(II)Pc assembly (denoted as Fe(II)Pc-A). The obtained Fe(II)Pc-A could be applied as a smart near-infrared (NIR) light-responsive nanotheranostic for simultaneous photoacoustic imaging-guided photothermal therapy. Notably, Fe(II)Pc-A possessed peroxidase, catalase, and oxidase mimicking activities, which could not only catalyze the conversion of intratumoral H2O2 to •OH, but also degrade H2O2 to generate O2 and continuously catalyze the conversion of O2 to cytotoxic O2•-. Impressively, the dual reactive oxygen species (ROS) generation of Fe(II)Pc-A was further remarkably enhanced by the endogenous acidity of the tumor microenvironment and the exogenous NIR light-responsive photothermal effect. Moreover, the O2 self-supplying ability of Fe(II)Pc-A led to increased generation of O2•- for enhancing catalytic therapy in hypoxic tumor. These collective properties of Fe(II)Pc-A nanozyme enabled it to be a dual ROS generation accelerator for photothermally enhanced tumor catalytic therapy. Thus, a new type of high-performance nanozyme for multifunctional nanotheranostic use toward cancer was presented.

Induction of hydrolytic enzyme production and antibiosis via a culture of dual fungal species isolated from soil rich with the residues of woody plants in Saudi Arabia

Inducing hydrolytic enzymes production and antibiosis is an attractive process for industrial applications. The approach can be used to repress pathogenic microorganisms. Using a dual culture of Aspergillus fumigatus and Aspergillus flavus, the activities of cellulase, polygalacturonase, chitinase, β-1,3-glucanases, protease, xylanase, and β-glucosidase were 1.78, 3.87, 2.98, 2.79, 6.91, 2.89 U, and 1.43 U∙mg-1 of protein. Meanwhile, the activities were 0.87, 2.78, 0.58, 1.69, 4.45, 2.06, and 0.89 U.mg-1 of protein for A. flavus alone and 0.98, 2.98, 0.87, 1.89, 4.98, 2.58, and 0.91 U.mg-1 of protein for A. fumigatus alone. The cellulase, polygalacturonase, and chitinase activities were studied at different temperatures; 40 °C and 50 °C, which were better temperatures than 20 °C in terms of enzymes activity for A. fumigatus and the dual culture compared to A. flavus. The highest antimicromial activity was observed using the dual fungal culture, where the inhibition zones were 3.13, 3.47, 2.27, 1.77, 1.03, and 2 mm compared with A. fumigatus alone or A. flavus alone, against Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Aspergillus fumigatus, Mucor circinelloides, and Fusarium moniliforme, respectively.

Strain-specific interspecies interactions between co-isolated pairs of Staphylococcus aureus and Pseudomonas aeruginosa from patients with tracheobronchitis or bronchial colonization

Dual species interactions in co-isolated pairs of Staphylococcus aureus and Pseudomonas aeruginosa from patients with tracheobronchitis or bronchial colonization were examined. The genetic and phenotypic diversity between the isolates was high making the interactions detected strain-specific. Despite this, and the clinical origin of the strains, some interactions were common between some co-isolated pairs. For most pairs, P. aeruginosa exoproducts affected biofilm formation and reduced growth in vitro in its S. aureus counterpart. Conversely, S. aureus did not impair biofilm formation and stimulated swarming motility in P. aeruginosa. Co-culture in a medium that mimics respiratory mucus promoted coexistence and favored mixed microcolony formation within biofilms. Under these conditions, key genes controlled by quorum sensing were differentially regulated in both species in an isolate-dependent manner. Finally, co-infection in the acute infection model in Galleria mellonella larvae showed an additive effect only in the co-isolated pair in which P. aeruginosa affected less S. aureus growth. This work contributes to understanding the complex interspecies interactions between P. aeruginosa and S. aureus by studying strains isolated during acute infection.

Bacterial-Specific Induction of Inflammatory Cytokines Significantly Decreases upon Dual Species Infections of Implant Materials with Periodontal Pathogens in a Mouse Model.

Cytokine profiles are often perturbed after infections of medical implants. With a non-invasive in vivo imaging system, we report in a mouse model that interferon expression after infection of subcutaneous implants with Streptococcus oralis, Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, and Treponema denticola (alone or as a combination) was species-specific, persisted longer in the presence of implants, and notably decreased upon dual species infections. This type I interferon expression disappeared within two weeks; however, histology of implant–tissue interface indicated high recruitment of immune cells even after three weeks. This was suggestive that biomaterial-associated infections could have prolonged effects, including the systemic stimulation of inflammatory cytokines. The present study investigated the systemic impact of this chronic peri-implant inflammation on the systemic expression of inflammatory cytokines (23) using a multiplex assay. Initially, the cytokine measurement in murine fibroblasts exposed to periodontal pathogens remained limited to the expression of five cytokines, namely, IL-6, G-CSF, CXCL-1/KC, MCP-1 (MCAF), and IL-12 (p40). The systemic determination of cytokines in mice increased to 19 cytokines (IL-1α, IL-2, IL-3, IL-5, IL-6, IL-9, IL-12 (p40), IL-12 (p70), IL-13, IL-17A, CCL-11/Eotaxin, G-CSF, IFN-γ, CXCL1/KC, MCP-1 (MCAF), MIP-1α/CCL3, MIP-1β/CCL4, CCL5/RANTES, and TNF-α). Systemic induction of cytokines was species-specific in the mouse model. The cytokine induction from infected implants differed significantly from sole tissue infections and sterile implants. Notably, systemic cytokine induction decreased after infections with dual species compared to single species infections. These findings describe the systemic effect of chronic peri-implant inflammation on the systemic induction of inflammatory cytokines, and this effect was strongly correlated to the type and composition of initial infection. Systemic modulations in cytokine expression upon dual species infections exhibit an exciting pattern that might explain the complications associated with biomaterial-related infection in patients. Moreover, these findings validate the requirement of multispecies infections for pre-clinical studies involving animal models.

Interspecies Interactions of the 2,6-Dichlorobenzamide Degrading Aminobacter sp. MSH1 with Resident Sand Filter Bacteria: Indications for Mutual Cooperative Interactions That Improve BAM Mineralization Activity.

Bioaugmentation often involves an invasion process requiring the establishment and activity of a foreign microbe in the resident community of the target environment. Interactions with resident micro-organisms, either antagonistic or cooperative, are believed to impact invasion. However, few studies have examined the variability of interactions between an invader and resident species of its target environment, and none of them considered a bioremediation context. Aminobacter sp. MSH1 mineralizing the groundwater micropollutant 2,6-dichlorobenzamide (BAM), is proposed for bioaugmentation of sand filters used in drinking water production to avert BAM contamination. We examined the nature of the interactions between MSH1 and 13 sand filter resident bacteria in dual and triple species assemblies in sand microcosms. The residents affected MSH1-mediated BAM mineralization without always impacting MSH1 cell densities, indicating effects on cell physiology rather than on cell number. Exploitative competition explained most of the effects (70%), but indications of interference competition were also found. Two residents improved BAM mineralization in dual species assemblies, apparently in a mutual cooperation, and overruled negative effects by others in triple species systems. The results suggest that sand filter communities contain species that increase MSH1 fitness. This opens doors for assisting bioaugmentation through co-inoculation with "helper" bacteria originating from and adapted to the target environment.

Axisymmetric radiative titanium dioxide magnetic nanofluid flow on a stretching cylinder with homogeneous/heterogeneous reactions in Darcy-Forchheimer porous media: Intelligent nanocoating simulation

Modern nanomaterials coating processes feature high temperature environments and complex chemical reactions required for the precise synthesis of bespoke designs. Such flow processes are extremely complex and feature both heat and mass transfer in addition to viscous behaviour. Intelligent nano-coatings exploit magnetic nanoparticles and can be manipulated by external magnetic fields. Mathematical models provide an inexpensive insight into the inherent characteristics of such coating dynamics processes. Motivated by this, in the current work, a novel mathematical model is developed for dual catalytic reactive species diffusion in axisymmetric coating enrobing forced convection boundary layer flow from a linearly axially stretching horizontal cylinder immersed in a homogenous non-Darcy porous medium saturated withmagnetic nanofluid. Homogeneous and heterogeneous reactions, heat source (e.g. laser source) and non-linear radiative transfer are included. The Tiwari-Das nanoscale model is deployed. A Darcy-Forchheimerdrag force formulation is utilized to simulate both bulk porous drag and second order inertial drag of the porous medium fibres. The magnetic nanofluid is an aqueous electroconductive polymer comprising base fluid water and magnetic TiO2 nanoparticles. The TiO2 nanoparticles are one chemically reacting species (A) and a second species (B) is also present (e.g. oxygen) which also reacts chemically. Viscous heating and Ohmic dissipation are also included to produce a more physically realistic thermal analysis. The non-linear conservation equations proposed here with species diffusion (species A and B) are transformed via an appropriate stream function and scaling variables into a set of non-linear united multi-degree ODEs. The rising nonlinear ordinary differential boundary value problem is solved with four-point Gauss-Lobotto formulae in the MATLAB bvp5c routine. Validation is conducted with an Adams-Moulton predictor–corrector numerical scheme (AM2 coded in Unix). The widespread visualization of velocity, temperature, species A concentration, species B concentration, skin friction, local Nusselt number and species A and B local Sherwood numbers is included. For the higher Schmidt number the momentum diffusion rate exceeds the species diffusion rate and this will produce a depression in concentration values. Further, increasing Darcian parameter retards the local Nusselt number magnitudes since higher permeability corresponds to sparsity in the solid fibres, reduction in thermal conduction and a concomitant cooling of the cylinder surface.

Flow characteristics in a parallel-plate porous channel under convective boundary conditions and triple diffusion for the non-Darcy porous matrix

This article inspects the effect of triple diffusion in a vertical conduit encapsulated with porous matrix and subjected to third kind boundary conditions. Third kind boundary condition is a combination of Dirichlet and Neumann boundary conditions which specifies a linear combination of function and its derivative values on the boundary. Homogeneous chemical reaction along with viscous and Darcy dissipation effects are included. Adapting the Boussinesq approximation, the soultal buoyancy effects due to concentration gradients of the dispersed components are taken into account. Applying suitable transformations, the conservation equations are reduced into dimensionless form and the dimensionless parameters evolved are thermal Grashof number (0≤Λ1≤20), solutal Grashof number (for species 1 and 2, 0≤Λ2,Λ3≤20), porous (2≤σ≤8) and inertial parameters (0≤I≤6), Biot numbers (at the left and right walls, 1≤Bi1,Bi2≤10), Brinkman number (0≤Br≤1), Schmidt numbers (0≤Sc1,Sc2≤6), Soret numbers (Sr1=Sr2=1) and temperature difference ratio (RT=1). Adopting perturbation technique, the analytical solutions which are applicable only when the Brinkman number is less than one is appraised. However for any values of the Brinkman number, Runge-Kutta shooting method is operated. The impact of selected parameters on the momentum, heat and dual species concentration fields are presented in the form of pictures. The solutions computed by numerical method are justified by comparing with the analytical method. The numerical and analytical solutions are equal in the absence of Darcy and viscous dissipations and the discrepancy advances as the Brinkman number expands. Further the solutions obtained are also justified by comparing the results with Zanchini [1] in the absence of chemical reaction for clear fluid. The thermal field is augmented with the Brinkman number for symmetric and asymmetric Biot numbers. However the profiles are highly distinct at the cold plate for unequal Biot numbers in comparison with equal Biot numbers. The conclusions are admissible to materials processing and chemical transport phenomena.

Nanoparticle carrier co-delivery of complementary antibiofilm drugs abrogates dual species cariogenic biofilm formation in vitro

ABSTRACT Background Dental caries is a multifactorial disease caused by pathogenic biofilm. In particular, Streptococcus mutans synthesizes biofilm exopolysaccharides, while Candida albicans is associated with the development of severe carious lesions. Aim This study aimed to prevent the formation of S. mutans and C. albicans biofilms by exploiting pH-sensitive nanoparticle carriers (NPCs) with high affinity to exopolysaccharides to increase the substantivity of multi-targeted antibiofilm drugs introduced topically in vitro. Methods Dual-species biofilms were grown on saliva-coated hydroxyapatite discs with sucrose. Twice-daily, 1.5 min topical treatment regimens of unloaded and drug-loaded NPC were used. Drugs included combinations of two or three compounds with distinct, complementary antibiofilm targets: tt-farnesol (terpenoid; bacterial acid tolerance, fungal quorum sensing), myricetin (flavonoid; exopolysaccharides inhibitor), and 1771 (lipoteichoic acid inhibitor; bacterial adhesion and co-aggregation). Biofilms were evaluated for biomass, microbial population, and architecture. Results NPC delivering tt-farnesol and 1771 with or without myricetin completely prevented biofilm formation by impeding biomass accumulation, bacterial and fungal population growth, and exopolysaccharide matrix deposition (vs. control unloaded NPC). Both formulations hindered acid production, maintaining the pH of spent media above the threshold for enamel demineralization. However, treatments had no effect on pre-established dual-species biofilms. Conclusion Complementary antibiofilm drug-NPC treatments prevented biofilm formation by targeting critical virulence factors of acidogenicity and exopolysaccharides synthesis.