Suspensions Of Bacteria Research Articles

Phase separation in mixed suspensions of bacteria and nonadsorbing polymers.

The shapes of bacteria can vary widely; they may, for instance, be spherical, rod-like, string-like, or curved. In general, bacilli are highly anisotropic. For research and (bio)technological purposes, it can be useful to concentrate bacteria, which is possible by adding nonadsorbing polymers. The induced phase separation originates from a polymer-mediated depletion interaction, first understood by Asakura and Oosawa. Here, it is shown that free volume theory (FVT) can semi-quantitatively describe the phase transitions observed when adding sodium polystyrene sulfonate polymers to E. coli bacteria [Schwarz-Linek et al., Soft Matter 6, 4540 (2010)] at high ionic strength. The E. coli bacteria are described as short, hard spherocylinders. FVT predicts that the phase transitions of the mixtures result from a fluid-ABC crystal solid phase coexistence of a hard spherocylinder-polymer mixture.

In English

A promising direction for long-term storage of cells at relatively high temperatures may be their encapsulation with nanoscale biologically inert materials capable of creating a shell around microdroplets of a cell suspension, which, on the one hand, provides the possibility of gas exchange between the suspension and the external environment, and on the other hand, inhibits the processes of cell life, so transferring them to a state close to suspended animation. The method of low-temperature 1H NMR spectroscopy was used to study the process of hydration of lactobacilli, the effect of a weakly polar organic medium on it and the encapsulation of cells with silica. The aim of this work was to study the hydration of cell suspensions and the viability of lactic acid bacteria cells encapsulated with silica and the penetration possibility of such an active substance as trifluoroacetic acid into them. As a result of the studies carried out, it has been shown that the spectral parameters of water in concentrated cell suspensions of lactic acid bacteria strongly depend on the concentration of the suspension, which is probably associated with the possibility of the formation of a stable cell gel, which can be encapsulated by silica particles without its destruction in both air and a chloroform medium with addition of trifluoroacetic acid. The radial distribution curves of non-freezing water clusters have two maxima corresponding to R = 2 and 20–100 nm. The contribution to the distribution of the second maximum increases with increasing water concentration.

Succession of Bacterial Community During the Initial Aerobic, Intense Fermentation, and Stable Phases of Whole-Plant Corn Silages Treated With Lactic Acid Bacteria Suspensions Prepared From Other Silages.

The present study was aimed at investigating the bacterial community in lactic acid bacteria (LAB) suspensions prepared from whole-plant corn silage (LAB suspension-CS) and Elymus sibiricus silage (LAB suspension-ES) and the bacterial community succession of whole-plant corn silages inoculated with LAB suspension-CS or LAB suspension-ES during initial aerobic phase, intense fermentation phase, and stable phase. The LAB suspensions were cultured in sterile Man, Rogosa, Sharpe broth at 37°C for 24 h and used as inoculants for ensiling. The chopped whole-plant corn was treated with distilled water (CK), LAB suspension-CS (CSL), or LAB suspension-ES (ESL) and then ensiled in vacuum-sealed plastic bags containing 500 g of fresh forage. Silages were sampled at 0 h, anaerobic state (A), 3 h, 5 h, 10 h, 24 h, 2 days, 3 days, 10 days, 30 days, and 60 days of ensiling with four replicates for each treatment. The results showed that Lactobacillus, Weissella, and Lachnoclostridium_5 dominated the bacterial community in LAB suspension-CS; Lactobacillus was the most predominant bacterial genus in LAB suspension-ES. During the initial aerobic phase (from 0 h to A) of whole-plant corn silage, the pH and the abundances of Pantoea, Klebsiella, Rahnella, Erwinia, and Serratia increased. During the intense fermentation phase (from A to 3 days), the pH decreased rapidly, and the microbial counts increased exponentially; the most predominant bacterial genus shifted from Pantoea to Weissella, and then to Lactobacillus; inoculating LAB suspensions promoted the bacterial succession and the fermentation process, and LAB suspension-CS was more effective than LAB suspension-ES. During the stable phase (from 3 to 60 days), the pH and the microbial counts decreased, and Lactobacillus dominated the bacterial community with a little decrease. The results also confirmed the existence of LAB fermentation relay during fermentation process, which was reflected by Weissella, Lactococcus, and Leuconostoc in the first 5 h; Weissella, Lactococcus, Leuconostoc, Lactobacillus, and Pediococcus between 5 and 24 h; and Lactobacillus from 24 h to 60 days.

The Minimum Inhibitory Concentration (MIC) And Minimum Bactericidal Concentration (MBC) Of Sambiloto Leaf Extract Against Enterococcus Faecalis

Background: Enterococcus faecalis is a bacterium that causes failure of the root canal treatment. Sodium hypochlorite is often used as irrigation, but it caused irritate the tissue. The chemical compounds in sambiloto leaf are tanin, saponin, alkaloid, flavonoid and andrographolide which have antibacterial potency. Purpose: To determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of sambiloto leaf extract against Enterococcus faecalis. Methods: Sambiloto leaf extract was made up to 5 concentrations which are 1,56%, 2,09%, 2,61% and 3,125%. 5 tubes consist of BHIB and 0,1 ml suspension of bacteria, 1 tube consist only with BHIB. 5 tubes added with sambiloto leaf extract in variated concentrations. The tube was incubated in anaerobic jar at 37o C for 24 hours. Then the suspension of bacteria was subcultured in nutrient agar. Minimum inhibitory consentration (MIC) and minimum bactericidal concentration (MBC) counted manually. Results: Sambiloto leaf extract at a concentration of 1,56% showed inhibition of bacterial growth while the concentrations of 2,09% showed no bacterial growth. Conclusion: Sambiloto leaf extract has antibacterial effect at minimum inhibitory concentration of 1,56% and minimum bactericidal concentration of 2,09%

Biosorption of lead by bacteria isolated from abattoir wastewater

Six bacteria were isolated from abattoir wastewater collected from Minna central abattoir. Lead tolerant bacteria were isolated from the wastewater. The isolates were then characterized on the basis of their colonial appearance and reaction to various biochemical tests. The lead tolerance profile of the isolates was carried out using agar diffusion method, with concentrations of Lead nitrate ranging from 50-250 mg/L. Two resistant isolates identified as species of Bacillus and Neisseria were selected for biosorption studies. Lead concentration was determined using Atomic Absorption Spectrophotometry. The lead biosorption capacity of the two isolates was studied by inoculating 2 mL of 24 hours old bacteria suspension in 50mL Nutrient broth, containing varying concentrations of lead (500 and 1000 mg/L) at varying pH (7 and 8), with representative samples being withdrawn at day 4, 8 and 12. The results showed that highest biosorption rate was recorded on day 10, at pH 7, in solution containing 500 mg/L of lead with 75.3% and 66% by Bacillus sp. and Neisseria sp. respectively. These results show that Bacillus sp. had better sorption capacity than Neisseria sp. Both organisms can be used for the removal of lead.
 Keywords: Wastewater, Biosorption, Abattoir, heavy metal, Bacteria

Motility-induced clustering and meso-scale turbulence in active polar fluids

Meso-scale turbulence was originally observed experimentally in various suspensions of swimming bacteria, as well as in the collective motion of active colloids. The corresponding large scale dynamical patterns were reproduced in a simple model of a polar fluid, assuming a constant density of active particles. Recent, more detailed studies in a variety of experimental realizations of active polar fluids revealed additional interesting aspects, such as anomalous velocity statistics and clustering phenomena. Those phenomena cannot be explained by currently available models for active polar fluids. Herein, we extend the continuum model suggested by Dunkel et al to include density variations and a local feedback between the local density and self-propulsion speed of the active polar particles. If the velocity decreases strong enough with the density, a linear stability analysis of the resulting model shows that, in addition to the short-wavelength instability of the original model, a long-wavelength instability occurs. This is typically observed for high densities of polar active particles and is analogous to the well-known phenomenon of motility-induced phase separation (MIPS) in scalar active matter. We determine a simple phase diagram indicating the linear instabilities and perform systematic numerical simulations for the various regions in the corresponding parameter space. The interplay between the well understood short-range instability (leading to meso-scale turbulence) and the long-range instability (associated with MIPS) leads to interesting dynamics and novel phenomena concerning nucleation and coarsening processes. Our simulation results display a rich variety of novel patterns, including phase separation into domains with dynamically changing irregularly shaped boundaries. Anomalous velocity statistics are observed in all phases where the system segregates into regions of high and low densities. This offers a simple explanation for their occurrence in recent experiments with bacterial suspensions.

Ultrafiltration for environmental safety in shellfish production: A case of bloom emergence

The process of ultrafiltration (UF) of natural seawater often encounters the problems of variation in water quality and coastal blooms. To validate the feasibility of UF in shellfish farms, this study compared the hydraulic performance and pollutant removal efficiency of the UF process with those of the commonly used treatments that combine several filtration steps with ultraviolet (UV) disinfection. The comparison was conducted in the cases of natural seawater and a coastal bloom. Given that the UF process encountered the specific type of pollution, this study evaluated the filtration performance of the UF process and the retention of total suspended solids (TSS), bacteria, phytoplankton, and zooplankton. A real coastal bloom was considered in the case study of an experimental shellfish hatchery/nursery in France. The results show that both treatments were able to eliminate approximately 50% of TSS. However, in contrast with UV treatment combined with filtration, the UF process retained total amounts of phytoplankton, zooplankton, and bacteria in the bloom. Although the hydraulic performance of the UF process was impacted by the coastal bloom, the fouling was eliminated through chemical cleaning conducted at a frequency less than once per 12 h. Despite the severe pollution, this study confirmed the pollution resistance and treatment performance of the UF process, indicating that UF has the potential to enhance the biosecurity level.

Utilization of Indole-3-acetic acid–Secreting Bacteria in Algal Environment to Increase Biomass Accumulation of Ochromonas and Chlorella

Application of plant hormones is an effective strategy to further improve the accumulation of microalgae biomass. In this study, the IAA (indole-3-acetic acid) production capacity of symbiotic bacteria isolated from the culture system of Ochromonas and Chlorella was detected and compared, with the bacterial community structure revealed. The results demonstrated that Algoriphagus, Porphyrobacter, Roseococcus, and Rhizobium were the dominant bacterial genera both in Ochromonas and Chlorella system, distributed in Proteobacteria and Bacteroidetes. Sixteen of 40 strains classified into 15 genera isolated from the two genera of microalgae could produce IAA, with Agrobacterium and Rhizobium as the main representatives with highest IAA production level (22.53–34.18 mg/L in 30 h). And through determination of changes of chlorophyll content in the co-culture system of microalgae and the supernatant of IAA high-yielding bacteria suspension from medium with or without tryptophan (synthetic precursor of IAA), Rhizobium (C-3) and Agrobacterium (O-16, C-2) were proved to promote the growth of Ochromonas and Chlorella through secreting IAA. The biomass yield of Ochromonas and Chlorella could be respectively increased by 78.98% and 72.73% through the co-culture with Agrobacterium (C-2), by 68.15% and 69.93% for Rhizobium (C-3) and by 80.89% and 65.73% for Agrobacterium (O-16). Moreover, compared with the application of exogenous IAA to improve the microalgae biomass, it is more efficient and economical to construct algae bacteria symbiosis system using IAA secretory bacteria commonly existed in microalgae culture system. In addition, the growth promoting effect of IAA secretory bacteria on microalgae was different among the species of algae.

Comparison of disinfectants for drinking water: chlorine gas vs. on-site generated chlorine

The feasibility of on-site generated chlorine (OSG chlorine) as an alternative disinfectant to chlorine gas was evaluated in terms of total organic carbon (TOC) removal, disinfection efficiency, biofilm control, disinfection by-products (DBPs) formation, chlorine decay rate, and volatility. Chlorine gas decreased the pH of the treated water by -0.1 per mg/L of free available chlorine (FAC) while OSG chlorine increased the pH by + 0.06 per mg/L. OSG chlorine with more hypochlorite ion (OCl-) at higher pH was less effective in the inactivation of suspended bacteria and TOC removal but remained in the distribution system longer and controlled biofilm formation more effectively than chlorine gas. The DBPs formation by OSG chlorine was not significantly different from that by chlorine gas except for the reduction of Haloacetonitriles. Hypochlorous acid (HOCl) was more volatile than OCl-, indicating the lower volatility of FAC in the OSG chlorine-treated water. Two types of OSG systems, “Mixed oxidants” and OSG hypochlorite, did not show any significant difference in disinfection, DBPs formation, and chlorine decay rate (paired t-test, p = 0.40, 0.11 ~ 0.70, > 0.42). A significant synergy effect by oxidants other than FAC cannot be expected in the use of “mixed oxidants” at a water treatment plant.

Marginal Adaptation and Microbial Leakage at Conometric Prosthetic Connections for Implant-Supported Single Crowns: An In Vitro Investigation

Encouraging clinical results were reported on a novel cone-in-cone coupling for the fixation of dental implant-supported crowns (Acuris, Dentsply Sirona Implants, Mölndal, Sweden). However, the presence or absence of a microgap and a potential bacterial leakage at the conometric joint has not yet been investigated. A misfit and a resulting gap between the conometric components could potentially serve as a bacterial reservoir that promotes plaque formation, which in turn may lead to inflammation of the peri-implant tissues. Thus, a two-fold study set-up was designed in order to evaluate the bidirectional translocation of bacteria along conometrically seated single crowns. On conometric abutments filled with a culture suspension of anaerobic bacteria, the corresponding titanium nitride-coated (TiN) caps were fixed by friction. Each system was sterilized and immersed in culture medium to provide an optimal environment for microbial growth. Positive and negative controls were prepared. Specimens were stored in an anaerobic workstation, and total and viable bacterial counts were determined. Every 48 h, samples were taken from the reaction tubes to inoculate blood agar plates and to isolate bacterial DNA for quantification using qrt-PCR. In addition, one Acuris test system was subjected to scanning electron microscopy (SEM) to evaluate the precision of fit of the conometric coupling and marginal crown opening. Throughout the observational period of one week, blood agar plates of the specimens showed no viable bacterial growth. qrt-PCR, likewise, yielded a result approaching zero with an amount of about 0.53 × 10−4 µg/mL DNA. While the luting gap/marginal opening between the TiN-cap and the ceramic crown was within the clinically acceptable range, the SEM analysis failed to identify a measurable microgap at the cone-in-cone junction. Within the limits of the in-vitro study it can be concluded that the Acuris conometric interface does not allow for bacterial translocation under non-dynamic loading conditions.

Effect of the biogenic precipitation of calcium carbonate on bacterial transport in sand columns

Prediction of bacteria transport to riparian shallow groundwater is very important to prevent the pollution of water resources by coliform bacteria. The objective of this study was to investigate the effectiveness of microbially induced calcium carbonate precipitation (MICCP) in reducing bacteria (Escherichia coli and Pseudomonas fluorescens) transport. To perform the MICCP process, air-dried sterile sand was poured into polyvinyl chloride (PVC) cylinders (4.8 × 14.92 cm) and incubated for 3 days in the presence of Sporosarcina pasteurii (~108 Cell g−1sand), urea and CaCl2 (1.5 M). A pulse (0.1 pore volume (PV)) of bacteria suspension (108 CFU mL−1) was added on top of the sand columns (MICCP treated and control) and leaching experiments were followed at steady-state, saturated flow condition. Culturable bacteria were determined in the leachate and the sand extracts (resident bacteria) by colony count method. The MICCP treatment reduced saturated hydraulic conductivity (Ks) value 3.9 times compared to the control and thereby reduced bacteria leaching. Bioprecipitated calcium carbonate in MICCP columns increased bacteria straining compared to control columns especially in surface layer (0-3 cm). MICCP process increased filtration coefficient (λf), and relative adsorption index (SR), and decreased maximum depth of bacteria transport (Zmax). The average (Cav) and cumulative cell density (Ccum) of both bacteria passed from the MICCP column decreased around 3.9-fold compared to the control. Overall, the MICCP process has potential in bacteria filtration in the porous media reducing the risk of groundwater pollution.

Thermodynamic Inhibition in a Biofilm Reactor with Suspended Bacteria.

We formulate a biofilm reactor model with suspended bacteria that accounts for thermodynamic growth inhibition. The reactor model is a chemostat style model consisting of a single replenished growth promoting substrate, a single reaction product, suspended bacteria, and wall attached bacteria in the form of a bacterial biofilm. We present stability conditions for the washout equilibrium using standard techniques, demonstrating that analytical results are attainable even with the added complexity from thermodynamic inhibition. Furthermore, we numerically investigate the longterm behaviour. In the computational study, we investigate model behaviour for select parameters and two commonly used detachment functions. We investigate the effects of thermodynamic inhibition on the model and find that thermodynamic inhibition limits substrate utilization/production both inside the biofilm and inside the aqueous phase, resulting in less suspended bacteria and a thinner biofilm.

Влияние совместной обработки эндофитным штаммом бактерий Bacillus thuringiensis B-5351 и салициловой кислотой на устойчивость растений картофеля к Phytophthora infestans (Mont.) de Bary

Влияние совместной обработки эндофитным штаммом бактерий Bacillus thuringiensis B-5351 и салициловой кислотой на устойчивость растений картофеля к Phytophthora infestans (Mont.) de Bary

Onsager's variational principle in active soft matter.

Onsagers variational principle (OVP) was originally proposed by Lars Onsager in 1931 [L. Onsager, Phys. Rev., 1931, 37, 405]. This fundamental principle provides a very powerful tool for formulating thermodynamically consistent models. It can also be employed to find approximate solutions, especially in the study of soft matter dynamics. In this work, OVP is extended and applied to the dynamic modeling of active soft matter such as suspensions of bacteria and aggregates of animal cells. We first extend the general formulation of OVP to active matter dynamics where active forces are included as external non-conservative forces. We then use OVP to analyze the directional motion of individual active units: a molecular motor walking on a stiff biofilament and a toy two-sphere microswimmer. Next we use OVP to formulate a diffuse-interface model for an active polar droplet on a solid substrate. In addition to the generalized hydrodynamic equations for active polar fluids in the bulk region, we have also derived thermodynamically consistent boundary conditions. Finally, we consider the dynamics of a thin active polar droplet under the lubrication approximation. We use OVP to derive a generalized thin film equation and then employ OVP as an approximation tool to find the spreading laws for the thin active polar droplet. By incorporating the activity of biological systems into OVP, we develop a general approach to construct thermodynamically consistent models for better understanding the emergent behaviors of individual animal cells and cell aggregates or tissues.

Rheology of bacterial superfluids in viscous environments.

Viscous environments are ubiquitous in nature and in engineering applications, from mucus in lungs to oil recovery strategies in the earth's subsurface - and in all these environments, bacteria also thrive. The behavior of bacteria in viscous environments has been investigated for a single bacterium, but not for active suspensions. Dense populations of pusher-type bacteria are known to create superfluidic regimes where the effective viscosity of the entire suspension is reduced through collective motion, and the main purpose of this study is to investigate how a viscous environment will affect this behavior. Using a Couette rheometer, we measure shear stress as a function of the applied shear rate to define the effective viscosity of suspensions of Escherichia coli (E. coli), while varying both the bacterial density within the suspension and the viscosity of the suspending fluid. We document the remarkable observation that E. coli decreases the effective suspension viscosity to near-zero (superfluidic regime) for all solvent viscosities tested (1-17 mPa s). Specifically, we observe that the bacterial density needed to trigger this superfluidic regime and the maximum shear rate under which this regime can be sustained both decrease with increasing solvent viscosity. We find that the resulting rheograms can be well approximated by the Carreau-Yasuda law. Using this, we propose a constitutive model as a function of the solvent viscosity and the bacterial concentration only. This model captures the onset of the superfluidic regime and offers promising avenues for the modelling of flow of bacterial suspensions in viscous environments.

Suspended solids and bacteria removal mechanisms in ceramic filter and pervious concrete filter: a review

The need for drinking water with affordable access is increasing nowadays. The poor water quality problems can be solved by several water treatment methods, i.e. ceramic filter (CF) and pervious concrete filter (PCF). Those two mentioned technologies work based on the pores that exist within the filter. This study aimed to review (1) the influence of the material composition of the CF and PCF on hydraulic characteristics (porosity, permeability, pore size, pore structure, pore connectivity/ distribution) and its removal effectiveness, and (2) the removal mechanisms of suspended solids and bacteria based on its hydraulic characteristics. The study reviewed 45 literature, including books, reports, and published articles. The type, mineral, and sources of clay and the type, shape, proportion, and size of combustible materials on CF will affect its hydraulic characteristic. The shape, size, and type of aggregate, the ratio of water to cement, and the ratio of aggregate to cement on PCF will affect its hydraulic characteristics. The removal mechanisms of suspended solids are straining on the surface and trapping on the deadlocked pores. On the other hand, the bacteria removal mechanisms strain the bacteria in the dirt layer and trap the bacteria in the pores.

AgNPs@ZIF‐8 Hybrid Material‐Modified Polyethersulfone Microfiltration Membranes for Antibiofouling Property and Permeability Improvement

AbstractMembrane fouling is a major hindrance to the effective application of polyethersulfone (PES) membranes. Synthetic silver nanoparticles @ zeolitic imidazolate framework‐8 (AgNPs@ZIF‐8) hybrid crystals were used to modify the PES microfiltration membranes for mitigating membrane fouling and better water permeability. The surface modification of AgNPs@ZIF‐8 hybrid crystals improved the antifouling property of the membranes. The number of live bacteria in the bacteria suspension was over 90 % less than that of control membranes. Furthermore, after surface modification, the membrane permeability was enhanced, which was due to increased surface hydrophilization of the membranes which could partly explain the improved antifouling property. The results demonstrate that the use of AgNPs@ZIF‐8 hybrid crystals is a feasible and attractive approach for the development of antifouling membranes.

A meta-analysis of metal biosorption by suspended bacteria from three phyla

Biosorption of heavy metals by bacterial biomass has been the subject of significant research interest in last decades due to its efficiency, relatively low cost and minimal negative effects for the surrounding environment. In this meta-analysis, the biosorption efficiencies of different bacterial strains for Cu(II), Cd(II), Zn(II), Cr(III), Mn(II), Pb(II) and Ni(II) were evaluated. Optimum conditions for the biosorption process such as initial metal concentration, temperature, pH, contact time, metal type, biomass dosage and bacterial phyla, were evaluated for each heavy metal. According to the results, the efficiencies of bacterial biomass for removal of heavy metal were as follows: Cd(II) > Cr(III) > Pb(II) > Zn(II) > Cu(II) > Ni(II) > Mn(II). Firmicute phyla showed the highest overall (living and dead) biosorption efficiency for heavy metals. Living biomass of Proteobacteria had the best biosorption performance. Living bacterial biomass was significantly more efficient in biosorption of Cu(II), Zn(II) and Pb(II) than dead biomass. The maximum biosorption efficiency of bacterial strains for Cd(II), Pb(II) and Zn(II) was achieved at pH values between 6 and 7.5. High temperatures (>35 °C) reduced the removal efficiencies for Cu(II) and Zn(II) and increased the efficiencies for Cd(II) and Cr(III) ions. The maximum biosorption efficiency of non-essential heavy metals occurred with short contact times (<2 h). Essential metals such as Zn and Cu were more efficiently removed with long biosorption durations (>24 h). The mean biosorption capacity of bacterial biomass was between 71.26 and 125.88 mg g−1. No publication bias existed according to Egger’s and Begg’s test results.

A journey of wastewater to clean hydrogen: A perspective

A journey of wastewater to clean hydrogen: A perspective

Enhanced biodegradation of hydrocarbons by Pseudomonas aeruginosa-encapsulated alginate/gellan gum microbeads

Pseudomonas aeruginosa-encapsulated alginate/gellan gum microbeads (PAGMs) were prepared at the condition of 10 g/L alginate, 1 g/L gellan gum, and 2.57 mM calcium ions, and investigated for the biodegradation of a diesel-contaminated groundwater. The degradation of diesel with PAGMs reached 71.2% after 10days in the aerobic condition, while that of suspended bacteria was only 32.0% even after 30days. The kinetic analysis showed that PAGMs had more than two-order higher second-order kinetic constant than that of the suspended bacteria. Interestingly, the degradation of diesel was ceased due to the depletion of the dissolved oxygen after 10 day in the PAGM reactor, but the microbial degradation activity was immediately restored after the addition of oxygen to 10.5 mg/L. The change in ATP concentration and the viability of bacteria showed that the microbial activity in PAGMs were maintained (66.4%, and 84.3%, respectively) even after 30days of experiment with PAGMs due to the protective barrier of the microbeads, whereas those of suspended bacteria showed significant decrease to 6.2% and 14.4% of initial value, respectively, due to the direct contact to toxic hydrocarbons. The results suggested that encapsulation of bacterial cells could be used for the enhanced biodegradation of diesel hydrocarbons in aqueous systems.