Suspension Of Microorganisms Research Articles

PHOTOFOCUSING OF MICROORGANISMS SWIMMING IN A FLOW WITH SHEAR

Some swimming microorganisms are sensitive to light, and this can affect the way in which they negotiate their environment. In particular, photophobic cells are repelled from unfavourable light conditions, and in a quiescent fluid environment this can be observed as elevated cell levels in regions away from these light conditions. This photoresponsive effect is of interest due to its potential technological applications. For example, the use of light to focus and direct cells could be used as a convenient means to separate out the algae used in biofuel production (for example, hydrogen), or exploited within devices for biodetection of environmental contaminants. However, in these types of situations the swimming cells will usually be suspended in a flow with shear. In this environment, it has previously been shown that cells can become hydrodynamically trapped in regions of high fluid shear, and so the extent to which photofocusing can occur under these conditions is not immediately clear. Moreover, in applications where the light must pass through appreciable volumes of the suspension, cells will typically absorb light and so shade each other from the illumination. As such, the intensity at any point in the flow is dependent upon the global cell concentration. Hence, in this study we model the coupled influence of fluid shear and cell photosensitivity on a suspension of swimming microorganisms, and ask under what circumstances a suspension of photophobic cells might be focused into high concentration regions.

Toxicity and Antimicrobial Properties of ZnO@ZIF-8 Embedded Silicone against Planktonic and Biofilm Catheter-Associated Pathogens

A ZnO@ZIF-8 powder on a gram scale was prepared via treatment of ZIF-8 with silver nitrate to induce spontaneous formation of ZnO nanorods on the surface of the ZIF-8 crystals. The crystal structure, phase purity, and physicochemical characteristics of ZnO@ZIF-8 were determined by X-ray diffraction, high-resolution electron microscopy, energy-dispersive spectroscopy, and nitrogen adsorption. The antimicrobial potential of ZnO@ZIF-8 for reduction of microorganisms often implicated with catheter-associated urinary tract infections (CAUTIs) was studied in detail using four target pathogens, Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, and Staphylococcus aureus. The ability of the compound to kill all four microorganisms in suspension was established, and a minimum bactericidal concentration of 0.25 mg mL–1 was determined for each microorganism. ZnO@ZIF-8 compound was found to be no more toxic to Galleria mellonella than distilled water, which was assessed by injection of Galleria with 10 μL of...

3D Casson nanofluid flow over slendering surface in a suspension of gyrotactic microorganisms with Cattaneo-Christov heat flux

A mathematical model is proposed to execute the features of the non-uniform heat source or sink in the chemically reacting magnetohydrodynamic (MHD) Casson fluid across a slendering sheet in the presence of microorganisms and Cattaneo-Christov heat flux. Multiple slips (diffusion, thermal, and momentum slips) are applied in the modeling of the heat and mass transport processes. The Runge-Kutta based shooting method is used to find the solutions. Numerical simulation is carried out for various values of the physical constraints when the Casson index parameter is positive, negative, or infinite with the aid of plots. The coefficients of the skin factors, the local Nusselt number, and the Sherwood number are estimated for different parameters, and discussed for engineering interest. It is found that the gyrotactic microorganisms are greatly encouraged when the dimensionless parameters increase, especially when the Casson fluid parameter is negative. It is worth mentioning that the velocity profiles when the Casson fluid parameter is positive are higher than those when the Casson fluid parameter is negative or infinite, whereas the temperature and concentration fields show exactly opposite phenomena.

Magnetohydrodynamic mixed thermo-bioconvection in porous cavity filled by oxytactic microorganisms

This article describes the steady magnetohydrodynamic mixed thermo-bioconvection in a square enclosure filled with a homogeneous and isotropic porous medium in the presences of oxytactic microorganisms. The model used for the oxytactic microorganisms is based on a continuum model of a suspension of oxytactic microorganisms. The mixed convection is resulting for the interaction between the buoyancy force and the moving of the top wall of the cavity with constant speed. The horizontal walls of the cavity are considered to be adiabatic while the vertical walls are differentially heated. The governing equations are solved using the finite volume method with SIMPLE technique. Comparisons with previously published works are performed and found to be in excellent agreements. It is found that the increase in both Richardson number and Hartmann number reduces the average Nusselt and Sherwood numbers.

Effects of beneficial microorganisms on lowland rice development.

Microorganisms can promote plant growth by increasing phytomass production, nutrient uptake, photosynthesis rates, and grain yield, which can result in higher profits for farmers. However, there is limited information available about the physiological characteristics of lowland rice after treatment with beneficial microorganisms in the tropical region. This study aimed to determine the effects of different beneficial microorganisms and various application forms on phytomass production, gas exchange, and nutrient contents in the lowland rice cultivar 'BRS Catiana' in a tropical region. The experiment was performed under greenhouse conditions utilizing a completely randomized design and a 7×3+1 factorial scheme with four replications. The treatments consisted of seven microorganisms, including the rhizobacterial isolates BRM 32113, BRM 32111, BRM 32114, BRM 32112, BRM 32109, and BRM 32110 and Trichoderma asperellum pooled isolates UFRA-06, UFRA-09, UFRA-12, and UFRA-52, which were applied using three different methods (microbiolized seed, microbiolized seed + soil drenched with a microorganism suspension at 7 and 15days after sowing (DAS), and microbiolized seed + plant spraying with a microorganism suspension at 7 and 15DAS) with a control (water). The use of microorganisms can provide numerous benefits for rice in terms of crop growth and development. The microorganism types and methods of application positively and differentially affected the physiological characteristics evaluated in the experimental lowland rice plants. Notably, the plants treated with the bioagent BRM 32109 on the seeds and on seeds + soil produced plants with the highest dry matter biomass, gas exchange rate, and N, P, Fe, and Mg uptake. Therefore, our findings indicate strong potential for the use of microorganisms in lowland rice cultivation systems in tropical regions. Currently, an additional field experiment is in its second year to validate the beneficial result reported here and the novel input sustainability.

Estimation of the light field inside photosynthetic microorganism cultures through Mittag-Leffler functions at depleted light conditions

Light attenuation within suspensions of photosynthetic microorganisms has been widely described by the Lambert–Beer equation. However, at depths where most of the light has been absorbed by the cells, light decay deviates from the exponential behaviour and shows a lower attenuation than the corresponding from the purely exponential fall. This discrepancy can be modelled through the Mittag–Leffler function, extending Lambert–Beer law via a tuning parameter α that takes into account the attenuation process.In this work, we describe a fractional Lambert–Beer law to estimate light attenuation within cultures of model organism Synechocystis sp. PCC 6803. Indeed, we benchmark the measured light field inside cultures of two different Synechocystis strains, namely the wild-type and the antenna mutant strain called Olive at five different cell densities, with our in silico results. The Mittag–Leffler hyper-parameter α that best fits the data is 0.995, close to the exponential case. One of the most striking results to emerge from this work is that unlike prior literature on the subject, this one provides experimental evidence on the validity of fractional calculus for determining the light field.We show that by applying the fractional Lambert–Beer law for describing light attenuation, we are able to properly model light decay in photosynthetic microorganisms suspensions.

Antimicrobial activity of disinfectants commonly used in the food industry in Mexico.

Disinfectants are widely used in food processing environments for microorganism control; their activity can vary according the microorganism and their used in the appropriated concentrations is vital. Hence, the aim of this study was determined the effectiveness and minimum inhibitory concentration (MIC) of 15 disinfectants commonly used in the food industry in Mexico. The antimicrobial activity and the MIC were determined according to AOAC and CLSI, respectively, with approved strains. Most disinfectants reduced 99.999% of microorganisms in suspension after 30s of contact, so reduction rate corresponded at least 5 Log10. Only for Pseudomonas aeruginosa ATCC 15442, did all disinfectants have 99.999% effectiveness. For the MIC, only the third generation quaternary ammonium compounds (QACs) in acid medium did not have values within the range in which is used in the food industry for Staphylococcus aureus ATCC 25923. In addition, for all disinfectants the MIC at 5min was two to four times greater than the concentration with the same effect at 10min; moreover, in most cases there was no difference in the MIC at 10 and 15min (p>0.05). At recommended concentrations, disinfectants had bactericidal activity for at least three of the six microorganisms evaluated. However, the MIC was affected by the exposure time: it was bigger at 5min than at 10min; moreover, in the majority of the cases, it was equal at 10 and 15min; with the results we could have a better understanding of disinfectants use in food processing environments.

Darcy–Brinkman bio-thermal convection in a suspension of gyrotactic microorganisms in a porous medium

On the basis of Darcy–Brinkman model, linear stability analysis is used to study bio-thermal convection in a suspension of gyrotactic microorganisms in a highly porous medium heated from below. A Galerkin method is performed to solve the governing equations generating a correlation between the traditional thermal Rayleigh number and the critical value of the bioconvection Rayleigh number. The effects of three variables including the bioconvection Peclet number, the gyrotaxis number and the modified Darcy number on both the wave number and the critical bioconvection Rayleigh number are analyzed and shown graphically. Results indicate that the critical bioconvection Rayleigh number becomes larger with increasing Darcy number.

Non-Gaussian limit fluctuations in active swimmer suspensions.

We investigate the hydrodynamic fluctuations in suspensions of swimming microorganisms (Chlamydomonas) by observing the probe particles dispersed in the media. Short-term fluctuations of probe particles were superdiffusive and displayed heavily tailed non-Gaussian distributions. The analytical theory that explains the observed distribution was derived by summing the power-law-decaying hydrodynamic interactions from spatially distributed field sources (here, swimming microorganisms). The summing procedure, which we refer to as the physical limit operation, is applicable to a variety of physical fluctuations to which the classical central limiting theory does not apply. Extending the analytical formula to compare to experiments in active swimmer suspensions, we show that the non-Gaussian shape of the observed distribution obeys the analytic theory concomitantly with independently determined parameters such as the strength of force generations and the concentration of Chlamydomonas. Time evolution of the distributions collapsed to a single master curve, except for their extreme tails, for which our theory presents a qualitative explanation. Investigations thereof and the complete agreement with theoretical predictions revealed broad applicability of the formula to dispersions of active sources of fluctuations.

Xenon-Water Interaction in Bacterial Suspensions as Studied by NMR

Xenon is a perspective gas for creation of oxygen free environment for different applications of biomaterials. To use xenon in suspensions and products properly it is necessary to know the molecular mechanisms of its interactions with water and cells. This work reports the study of bacterial suspensions of Escherichia coli in the presence of xenon using nuclear magnetic resonance (NMR). The work studied how the spin-lattice relaxation times of water protons in suspension change under xenon conditions. Xenon is able to form clathrate hydrates with water molecules at a temperature above the melting point of ice. The work studied NMR relaxation times which reflect the rotation freedom of water molecules in suspension. Lower relaxation times indicate reduced rotational freedom of water. Single exponential behavior of spin-lattice relaxation of protons in the suspensions of microorganisms has been registered. A recovery of longitudinal magnetization in cell suspensions with xenon clathrates has been characterized by two peaks in T1-distribution. Fast relaxing T1-component was related to the intracellular water and depended on the amount of xenon clathrates. The obtained results elucidate how the NMR method can monitor the process of clathrate formation and how the xenon atoms and hydrates interact with cells.

Aligned magnetic dipole in nonlinear radiative Falkner-Skan flow of Casson fluid over a wedge containing suspension of nanoparticles and microorganisms

Aligned magnetic dipole in nonlinear radiative Falkner-Skan flow of Casson fluid over a wedge containing suspension of nanoparticles and microorganisms

Aligned magnetic dipole in nonlinear radiative Falkner-Skan flow of Casson fluid over a wedge containing suspension of nanoparticles and microorganisms

This paper scrutinises the influences of aligned magnetic field and nonlinearly radiative flow of Falkner-Skan Casson liquid towards a wedge which is filled with microorganisms and nanoparticles. Following Buongiorno's model, the expressions of flow are developed and then transformed into self-similar form by utilising appropriate similarity transformations. Numerical outcomes are presented through plots and tabular form by enforcing Newton's and Runge-Kutta techniques. The impacts of arising constraints on liquid velocity, temperature, density of motile organisms and concentration are explored. For industrial and engineering interest, surface drag coefficient, rates of mass and heat transport, motile microorganism's density number are investigated. A comparative analysis for two cases namely aligned magnetic field (AMF) and magnetic field (MF) demonstrates that rate of heat and mass transfer are high in AMF case in comparison to MF case, and therefore desired results can be obtained by utilising AMF case.

Application of cinnamon bark emulsions to protect strawberry jam from fungi

The objective of the work was to evaluate the use of cinnamon bark-xanthan gum emulsions to preserve strawberry jam. The optimisation of the methodology used to prepare the emulsions and, the evaluation of their antimicrobial activity in culture media and in the strawberry jam were investigated. Emulsions were prepared in either a rotor-stator homogeniser or a magnetic stirrer combined with a high pressure homogeniser. Microorganism suspensions (103 and 106 CFU/mL), essential oil concentration and microbial sensitivity were decisive in the emulsions’ antimicrobial activity. The high stress applied to samples and their heating during homogenisation caused essential oil content losses. The jams prepared with the oil-in-water emulsions inoculated with Aspergillus flavus, Penicillium expansum, Zygosaccharomyces rouxii and Zygosaccharomyces bailii exhibited no growth during the 28 days of analysis The obtained results indicated the suitability of cinnamon bark oil-xanthan gum emulsions for preserving strawberry jam.

Biomass, gas exchange, and nutrient contents in upland rice plants affected by application forms of microorganism growth promoters.

Microorganisms are considered a genetic resource with great potential for achieving sustainable development of agricultural areas. The objective of this research was to determine the effect of microorganism application forms on the production of biomass, gas exchange, and nutrient content in upland rice. The experiment was conducted under greenhouse conditions in a completely randomized design in a factorial 7×3+1, with four replications. The treatments consisted of combining seven microorganisms with three application forms (microbiolized seed; microbiolized seed + soil drenched with a microorganism suspension at 7 and 15days after sowing (DAS); and microbiolized seed + plant sprayed with a microorganism suspension at 7 and 15DAS) and a control (water). Treatments with Serratia sp. (BRM32114), Bacillus sp. (BRM32110 and BRM32109), and Trichoderma asperellum pool provided, on average, the highest photosynthetic rate values and dry matter biomass of rice shoots. Plants treated with Burkolderia sp. (BRM32113), Serratia sp. (BRM32114), and Pseudomonas sp. (BRM32111 and BRM32112) led to the greatest nutrient uptake by rice shoots. Serratia sp. (BRM 32114) was the most effective for promoting an increase in the photosynthetic rate, and for the greatest accumulation of nutrients and dry matter at 84DAS, in rice shoots, which differed from the control treatment. The use of microorganisms can bring numerous benefits of rice, such as improving physiological characteristics, nutrient uptake, biomass production, and grain yield.

A radiative transfer modeling approach for accurate interpretation of PAM fluorometry experiments in suspended algal cultures.

The results of a numerical study on the simulation of pulse amplitude modulated (PAM) fluorometry within dense suspensions of photosynthetic microorganisms are presented. The Monte Carlo method was used to solve the radiative transfer equation in an algae-filled cuvette, taking into account absorption, anisotropic scattering, and fluorescence, as well as Fresnel reflections at interfaces. This method was used to simulate the transport of excitation and fluorescence light in a common laboratory fluorometer. In this fluorometer, detected fluorescence originates from a multitude of locations within the algal suspension, which can be exposed to very different fluence rates. The fluorescence-weighted fluence rate is reported, which is the local fluence rate of actinic light, averaged over all locations from which detected fluorescence originated. A methodology is reported for recovering the fluorescence-weighted fluence rate as a function of the transmittance of measuring light and actinic light through the sample, which are easily measured with common laboratory fluorometers. The fluorescence-weighted fluence rate can in turn be used as a correction factor for recovering intrinsic physiological parameters, such as the functional cross section of Photosystem II, from apparent (experimental) values. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:1601-1615, 2016.

Light-controlled flows in active fluids

Many photosynthetic microorganisms are able to detect light and move towards optimal intensities. This ability, known as phototaxis, plays a major role in ecology by affecting natural phytoplankton mass transfers, and has important applications in bioreactor and artificial micro-swimmers technologies. Here we show that this property can be exploited to generate macroscopic fluid flows using a localized light source directed towards shallow suspensions of phototactic microorganisms. Within the intensity range of positive phototaxis, algae accumulate beneath the excitation light, where collective effects lead to the emergence of radially symmetric convective flows. These flows can thus be used as hydrodynamic tweezers to manipulate small floating objects. At high cell density and layer depth, we uncover a new kind of instability, wherein the viscous torque exerted by self-generated fluid flows on the swimmers induces the formation of travelling waves. A model coupling fluid flow, cell concentration and orientation finely reproduces the experimental data. The ability of phototactic microorganisms to move towards optimal light intensities is exploited to generate fluid flows on scales several orders larger than the swimmers themselves. These flows are shown to function as hydrodynamic tweezers.

Studiu asupra influenţei radiaţiei laser la nivelul plăcii bacteriene comparativ cu clorhexidina 0,2% – analiză microbiologică şi microscopică

Objectives. The aim of this study was to evaluate de antimicrobian effect of laser radiation and chlorhexidine 0.2% treatment for reducing the number of pathogenic oral microorganisms, especially Streptococcus mutans, adjacent orthodontic brackets. Materials and methods. The suspension of microorganisms were obtained from patients orthodontic braces wearers. The probes were inoculated with this suspension and after that were exposed to decontamination methods represented by Erbium laser using two type of parameters: 80 mj - 15 Hz and 80 mj - 8 Hz, light emitting-diode (LED) 660 nm, surgery diode and 0.2% clorhexidine. After treatment, were harvesting probes around brackets and then were incubated aerobically at 37°C. To confirm the bactericid effect of treatment, it was adopted the colony forming units method. The Microsoft Excel program, one-way ANOVA and Tukey-Kramer test were used for statistical processing. Results. According to colony forming unit method the best bactericide effect was observed for the erbium laser group, following by surgery diode group comparatively with negative control group. Following one-way ANOVA analysis it can be remarked the significance difference from groups in terms of values resulted by application of different experimental treatments. Conclusions. The present study prove the highest efficiency of Er:YAG laser radiation on newly colony forming around orthodontic brackets decontamination.

Bioaugmentation of a sequencing batch reactor with Archaea for the treatment of reject water

In this study, the bioaugmentation of a sequencing batch reactor (SBR) for the treatment of reject water from wastewater treatment plant was evaluated. For the bioaugmentation step a product containing an enrichment of microorganisms from the Archaea domain was used to enhance the performance of the reactor for treating reject water. The experiment was carried out in two parallel lab-scale sequencing batch reactors. The first one (SBR A) was bioaugmented with a suspension of microorganisms from the Archaea domain, while the second reactor (SBR B) was not bioaugmented. The results here presented show that the SBR technology could sustain efficient NH 4 + –N and chemical oxyden demand removal rates and can be applied for the treatment of reject water. Moreover, the addition of microorganisms belonging to the Archaea domain improved the SBR overall operation, especially when the loading in the influent was increased. Administering Archaea to the reactor had also a positive effect on ammonia oxidation as well as on the nitrite removal.

Разработка реагента для оценки начальной стадии иммунного ответа на живую чумную вакцину

Objective of the study is to develop a reagent for the detection of lymphocytes with Yersinia pestis F1 antigen receptors. Materials and methods. Utilized have been: live plague vaccine based on the strain of Yersinia pestis EV NIIEG, formalin killed suspensions of microorganisms - Y. pestis , 3123, Y. enterocolitica O9 H-383 serovar, Y. pseudotuberculosis O1 2841 serovar; acetaldehyde-immobilized capsular antigen of Y. pestis F1 (obtained applying Baker methodology), lipopolysaccharide of Y. pestis K1, and bovine erythrocytes. Bovine erythrocyte F1 sensibilization has been performed using rivanol. Lymphocytes from blood have been isolated in density gradient ficoll-verografin 1.077. Lymphocytes with Yersinia pestis F1 antigen receptors have been detected by means of reagent adhesion onto the isolated lymphocytes. F1-free erythrocytes serve as controls. After the exposition, 7 evaluations of specificity to F1 and the lymphocytes, binding control reagent, have been carried out. Deployed have been 8 rabbits, immunized with live vaccine EV, and 2 rabbits, immunized with inactivated vaccine EV. Examined have been EV-vaccinated 5 persons. Results and conclusions. Identified is optimum sensibilizing dose of F1 antigen (250 µg/ml). Specificity of lymphocytes with receptors to F1 is demonstrated in inhibition experiments applying homologous and heterogeneous antigens. Lymphocytes with receptors to F1 (LRs) have been detected in peripheral blood of all rabbits and humans, immunized with vaccine EV. LRs have been registered since day 2 till day 35 in the rabbits, and in humans - since day 2 till day 14 after vaccination. It is shown that in case of revaccination of humans, LRs emerge and disappear earlier, than in case of primary immunization.

Magnetic field analysis in a suspension of gyrotactic microorganisms and nanoparticles over a stretching surface

The combine effects of magnetic field bioconvection, Brownian motion and thermophoresis on a free convection nanofluid flow over a stretching sheet containing gyrotactic microorganisms are investigated. The self-similar Buongiorno model is analyzed first time for stretching sheet numerically. The present results are compared with available data and are found in an excellent agreement. Pertinent results are presented graphically and discussed quantitatively with respect to variation in bioconvection parameters.