Adsorption Of Bacterial Cells Research Articles

Atrazine biodegradation modulated by clays and clay/humic acid complexes

The fate of pesticides in the environment is strongly related to the soil sorption processes that control not only their transfer but also their bioavailability. Cationic (Ca-bentonite) and anionic (Layered Double Hydroxide) clays behave towards the ionisable pesticide atrazine (AT) sorption with opposite tendencies: a noticeable sorption capacity for the first whereas the highly hydrophilic LDH showed no interactions with AT. These clays were modified with different humic acid (HA) contents. HA sorbed on the clay surface and increased AT interactions. The sorption effect on AT biodegradation and on its metabolite formation was studied with Pseudomonas sp. ADP. The biodegradation rate was greatly modulated by the material's sorption capacity and was clearly limited by the desorption rate. More surprisingly, it increased dramatically with LDH. Adsorption of bacterial cells on clay particles facilitates the degradation of non-sorbed chemical, and should be considered for predicting pesticide fate in the environment.

Surface Thermodynamics and Extended DLVO Theory of Acidithiobacillus ferrooxidans Cells Adhesion on Pyrite and Chalcopyrite

The adhesion of Acidithiobacillus ferrooxidans bacterial cells have been assessed by following the thermody- namic and extended DLVO theoretical approaches. Surface potential, interfacial tension and contact angle parameters that are necessary for the calculation of free energy of adhesion have been determined experimentally. The Hamaker constant involved in the Lifshitz-van der Waals interaction energy has been estimated by microscopic and macroscopic methods. The free energy of adhesion found to be negative on pyrite and chalcopyrite minerals indicating the adsorption of bacterial cells on these minerals. The potential energy diagrams of total interaction energy versus separation distance curves also il- lustrate the feasibility of bacterial cells adhesion except in a pH region where the bacterial species and minerals possess similar surface charge with high magnitude. The present theoretical analysis of bacterial adhesion on mineral surfaces found to be in good agreement with the experimental results and previous findings in the literature. Thus, the bacterial ad- hesion behavior on minerals can be judged and explained by considering the physico-chemical interaction forces.

Langmuir adsorption of bacterial cells to the oil surface for green technologies

Langmuir adsorption of bacterial cells to the oil surface for green technologies

Selective adsorption of bacterial cells onto zeolites

Zeolites adsorb microbial cells on their surfaces and selective adsorption for specific microorganisms was seen with certain zeolites. Tests for the adsorption ability of zeolites were conducted using various established microbial cell lines. Specific cell lines were shown to selectively absorb to certain zeolites, species to species. In order to understand the selectivity of adsorption, we tested adsorption under various pH conditions and determined the zeta-potentials of zeolites and cells. The adsorption of some cell lines depended on the pH, and some microorganisms were preferentially adsorbed at acidic pH. The values of zeta-potentials were used for calculating the electric double layer interaction energy between zeolites and microbial cells. There was a correlation between the experimental adsorption results and the interaction energy. Moreover, we evaluated the surface hydrophobicity of bacterial cells by using the microbial adherence to hydrocarbon (MATH) assay. In addition, we also applied this method for zeolites to quantify relative surface hydrophobicity. As a result, we found a correlation between the adsorption results and the hydrophobicity of bacterial cells and zeolites. These results suggested that adsorption could be explained mainly by electric double layer interactions and hydrophobic interactions. Finally, by using the zeolites Na-BEA and H-Y, we succeeded in clearly separating three representative microbes from a mixture of Escherichia coli, Bacillus subtilis and Staphylococcus aureus. Zeolites could adsorb each of the bacterial cell species with high selectivity even from a mixed suspension. Zeolites can therefore be used as effective carrier materials to provide an easy, rapid and accurate method for cell separation.

Spectroelectrochemical Examination of the Interaction between Bacterial Cells and Gold Electrodes

The interaction between bacterial cells of Pseudomonas fluorescens (ATCC 17552) and gold electrodes was analyzed by cyclic voltammetry (CV) and attenuated total reflection-surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS). The voltammetric evaluation of cell adsorption showed a decrease in the double-layer capacitance of polyoriented single-crystal gold electrodes with cell adhesion. As followed by IR spectroscopy in the ATR configuration, the adsorption of bacterial cells onto thin-film gold electrodes was mainly indicated by the increase in intensity with time of amide I and amide II protein-related bands at 1664 and 1549 cm(-1), respectively. Bands at 1448 and 2900 cm(-1) corresponding to the scissoring and the stretching bands of CH2 were also detected, together with a minor peak at 1407 cm(-1) due to the vs COO- stretching. Weak signals at 1237 cm(-1) were due to amide III, and a broad band between 1100 and 1200 cm(-1) indicated the presence of alcohol groups. Bacteria were found to displace water molecules and anions coadsorbed on the surface in order to interact with the electrode intimately. This fact was evidenced in the SEIRAS spectra by the negative features appearing at 3450 and 3575 cm-1, corresponding to interfacial water directly interacting with the electrode and water associated with chloride ions adsorbed on the electrode, respectively. Experiments in deuterated water confirmed these assignments and allowed a better estimation of amide absorption bands. In CV experiments, an oxidation process was observed at potentials higher than 0.4 V that was dependent on the exposure time of electrodes in concentrated bacterial suspensions. Adsorbed bacterial cells were found to get closer to the gold surface during oxidation, as indicated by the concomitant increment in the main IR bacterial signals including amide I, a sharp band at 1240 cm(-1), and a broad one at 1120 cm(-1) related to phosphate groups in the bacterial membranes. It is proposed to be due to the oxidation of lipopolysaccharides on the outermost bacterial surface.

Development and characterization of porous silver‐incorporated hydroxyapatite ceramic for separation and elimination of microorganisms

A novel filter material for separating and eliminating microorganisms in water and gas was fabricated by incorporating silver ions into porous hydroxyapatite (HA) ceramics prepared by a starch additive technique. The porous ceramics reveal a microstructure of both large and small pores. Microorganism separating and eliminating properties of the porous silver-incorporated HA ceramics (PHA-Ag) were investigated by bacterial and viral filtration tests. The PHA-Ag demonstrated excellent separating and antibacterial effects on Escherichia coli and the mechanisms were studied. Adsorption of bacterial cells to the HA and the barricading effect of small pores contribute to the separating property of PHA-Ag, while the Ag+ ions equip the ceramics with antibacterial property. Furthermore, the PHA-Ag exhibited an observable virus-eliminating property and its probable mechanism was also discussed.

Immobilization of cells with nitrilase activity from a thermophilic bacterial strain

Cells of the moderately thermophilic Bacillus sp. UG-5B strain, producing nitrilase (EC3.5.5.1), which converts nitriles directly to the corresponding acid and ammonia, were immobilized using different types of matrices and techniques. A variety of sol-gel silica hybrids were tested for entrapment and adsorption of bacterial cells as well as chemical binding on polysulphone membranes. Activation of the matrix surface with formaldehyde led to an increase in immobilization efficiency and operational stability of the biocatalysts. Among the supports screened, membranes gave the best results for enzyme activity and especially operational stability, with retention of 100% activity after eight reaction cycles.

A study of the adsorption of bacterial cells on porous materials

The paper presents experimental data on the adsorption of bacterial cells on porous materials.

Surface charge and metal adsorption of bacterial cells

Surface charge and metal adsorption of bacterial cells

Evidence for interfacial uptake in hexadecane degradation by Rhodococcus equi: the importance of cell flocculation.

The kinetics of hexadecane degradation were studied in four strains of Rhodococcus equi that did not produce biosurfactants. The aim was to analyse the characteristics of alkane uptake and their relevance to a mechanism of interfacial uptake. The kinetic studies involved continuous determination of degradation by electrolytic respirometry in a diphasic system where the hydrophobic phase was hexadecane or a solution of hexadecane in a non-toxic, non-biodegradable solvent, either 2,2,4,4,6,8,8-heptamethylnonane or silicone oil. The technique allowed large variations in interfacial area between the aqueous and hydrophobic phases. For the four strains, the kinetics obtained were reproducible and showed, in almost all cases, an initial short phase of exponential growth, followed by a long phase of linear growth. Specific growth rates during exponential growth varied amongst the strains from 0.11 to 0.20 h(-1) and were independent of interfacial area, in accordance with the very strong adsorption of bacterial cells at the interface of solvent and aqueous media. The degradation rates during linear growth did not increase with interfacial area but increased with efficiency of stirring. These characteristics can be explained by the formation of cellular flocs due to the hydrophobicity of the strains. These flocs were observed during growth on hexadecane in almost all conditions. In one case, with a non-flocculating culture, a kinetic pattern with a longer exponential phase, closer to that expected for simple interfacial uptake, was observed. The results show that strictly interfacial uptake, limited by floc formation (occurring at moderate and higher cell densities, and controlled by stirring efficiency) is a common pattern for growth on long-chain alkanes of micro-organisms that do not produce biosurfactants.

Changes in Pre-Formed Granule Composition and Structure in a Sulphidogenic UASB Treating a Synthetic Ferric Oxalate Wastewater

The effect of treatment of an acidic, high sulphate/iron bearing, oxalate wastewater on pre-formed granule composition and structure in an upflow anaerobic sludge blanket (UASB) reactor was studied. The results indicated that this wastewater did not lead to the formation of new granules in a pre-seeded reactor. Ferrous precipitates which accumulated at the base of the reactor acted as a surface for adsorption of bacterial cells, and a majority of the substrate degradation occurred in this lower region. The presence of Desulfosarcina on the precipitate surface confirmed the sulphidogenic nature of the system, and these organisms outcompeted the methanogens present. After 18 months of operation compressed ellipsoidal granules were identified in the upper layers of the sludge bed, and these were proposed to be the original inoculum granules following displacement from the reactor bed and compression caused by precipitate build up.

Effect of the clay minerals montmorillonite and kaolinite on the genetic transformation of competentBacillus subtilis cells

The effect of the clay minerals montmorillonite and kaolinite on the transformation of competentBacillus subtilis cells with chromosomal DNA was studied. Clay particles were found to substantially increase the transformation frequency of competent cells, as well as the rate of their spontaneous chromosomal and plasmid transformation. The effect was ascribed to the adsorption of bacterial cells on the surface of mineral particles.

Adsorption of bacterial cells onto activated sludge flocs

The adsorption of 9 species of bacteria onto laboratory-activated sludge flocs were investigated and a kinetic model describing the adsorption process was proposed in order to design an effective bioaugmentation strategy. The typical time course of bacterial adsorption, which is a triphasic process, consisted of lag, rapid adsorption, and stationary phases. The equilibrium of the cells in the stationary phase obeyed the Freundlich isotherm. The reversible and nonlinear model could describe the process to a certain degree and the Freundlich parameters and specific sorption rates were estimated for each bacterial strain. There was no apparent relationship between the estimated parameters and characteristics of the bacterial strains, such as specific growth rate, hydrophobicity of the cells, and flocculation activity against kaolin clays. However, the high floc formation ability of the bacterial strains was observed to be related to high cell concentrations although a longer lag time was required.

Antimicrobial activity of UV-irradiated nylon film for packaging applications

Antimicrobial packaging could enhance food storage life and safety. An antimicrobial moiety that is permanently bound to the polymer surface and does not leach has particular appeal. The use of 193 nm UV irradiation to convert amide groups on the surface of nylon to amines having antimicrobial activity has been reported previously. We prepared materials accordingly and explored their mode of action and activity against pathogens. Three food related bacterial strains, Staphylococcus aureus, Pseudomonas fluorescens and Enterococcus faecalis were exposed to antimicrobial film in 0.2 M sodium phosphate buffer (pH 7.0). Samples were held shaken at 100 r.p.m. in a 25°C incubator. The antimicrobial film was effective in reduction of microbial concentration in the bulk fluid for all food-related bacteria tested. The effectiveness was dependent on the bacterial strain. Adsorption of bacterial cells diminished the effectiveness of amine groups. Experimental results indicate that the decrease in concentration of bacterial cells in bulk fluid is more likely to be the bactericidal action than adsorption of live cells. © 1998 John Wiley & Sons, Ltd.

Antimicrobial activity of UV‐irradiated nylon film for packaging applications

Antimicrobial packaging could enhance food storage life and safety. An antimicrobial moiety that is permanently bound to the polymer surface and does not leach has particular appeal. The use of 193 nm UV irradiation to convert amide groups on the surface of nylon to amines having antimicrobial activity has been reported previously. We prepared materials accordingly and explored their mode of action and activity against pathogens. Three food related bacterial strains, Staphylococcus aureus, Pseudomonas fluorescens and Enterococcus faecalis were exposed to antimicrobial film in 0.2 M sodium phosphate buffer (pH 7.0). Samples were held shaken at 100 r.p.m. in a 25°C incubator. The antimicrobial film was effective in reduction of microbial concentration in the bulk fluid for all food-related bacteria tested. The effectiveness was dependent on the bacterial strain. Adsorption of bacterial cells diminished the effectiveness of amine groups. Experimental results indicate that the decrease in concentration of bacterial cells in bulk fluid is more likely to be the bactericidal action than adsorption of live cells. © 1998 John Wiley & Sons, Ltd.

Removal and recovery of nickel ion (Ni 2+) from aqueous solution by magnetite-immobilized cells of Enterobacter sp. 4-2

Cells of Enterobacter sp. 4-2 which could remove large amounts of nickel ion (Ni 2+) from aqueous solution were immobilized on magnetites. The optimal conditions for the adsorption of bacterial cells onto magnetites were a cell:magnetite ration greater than 1:10 (dry weight basis), Tris buffer with pH ⩽6.5, and temperature at 25°C. Under selected conditions (cell:magnetite ratio of 1:10, pH 6.0, and temperature at 25°C), more than 90% of the bacterial cells were immobilized onto magnetites. The optimal conditions for immobilized cells to remove Ni 2+ from aqueous solution were Tris buffer at an alkaline pH, the temperature higher than 37°C, and the retention time longer than 30 min. Under selected conditions (temperature at 25°C and retention time of 10 min), 50–90% of Ni 2+ was removed by immobilized cells from the buffer at pHs 7–9. Complete recovery of adsorbed Ni 2+ from immobilized cells was achieved by washing the Ni 2+-cell-magnetite complexes with diluted citric acid.

Effect of Solution Ionic Strength and Iron Coatings on Mineral Grains on the Sorption of Bacterial Cells to Quartz Sand

Understanding the interaction between bacterial cells and solid surfaces is essential to our attempts to quantify and predict the transport of microbes in groundwater aquifers, whether from the point of view of contamination or from that of bioremediation. The sorption of bacterial cells suspended in groundwater to porous medium grains was examined in batch studies. Bacterial sorption to clean quartz sand yielded equilibrium, linear, adsorption isotherms that varied with the bacterial strain used and the ionic strength of the aqueous solution. Values of K(d) (the slope of the linear sorption isotherm) ranged from 0.55 to 6.11 ml g, with the greatest sorption observed for the highest groundwater ionic strength. These findings are consistent with the interpretation that an increasingly compressed electrical double layer results in stronger adsorption between the like-charged mineral surface and the bacterial cells. When iron-oxyhydroxide-coated sand was used, however, all of the added bacteria were adsorbed up to a threshold of 6.93 x 10 cells g of coated sand, beyond which no further adsorption occurred. The irreversible, threshold adsorption is the result of a strong electrostatic attraction between the sesquioxide coating and the bacterial cells. Experimental results of adsorption in mixtures of quartz and Fe(III)-coated sand were successfully predicted by a simple additive model for sorption by the two substrate phases. Even small amounts of Fe(III)-coated sand in a mixture influenced the extent of adsorption of bacterial cells. A quantitative description of adsorption in the mixtures can be realized by using a linear isotherm for reversible adsorption to the quartz grains with a y intercept that represents the number of cells irreversibly adsorbed to the Fe(III)-coated sand.

Adsorption of bacterial cells to crystal particles of heavy metals: Role of electrostatic interaction

Several species of bacterial cells were found to adsorb to crystal particles of heavy metals, such as cadmium, zinc, copper, and iron. In particular, Thiobacillus sp. strain 13-1, isolated from a corroded concrete sewer, was rapidly adsorbed to crystal particles of cadmium. Observation under a light microscope revealed that cells of Thiobacillus sp. strain 13-1 were adsorbed aggregately on the surface of crystal particles of cadmium. The bacterial cells that adsorbed were released into the aqueous phase by the addition of carboxylic acid containing negatively charged hydroxyl groups or compounds. Since hydroxycarboxylic acid seems to prevent the tenacious adsorption of the bacterial cells on the crystal particles of heavy metals, the adsorption of bacterial cells to such particles may be attributed to the electrostatic interaction between them.

Kinetics and mechanism of the adsorption of Sulfolobus acidocaldarius on coal surfaces

The adsorption of Sulfolobus acidocaldarius on five types of coals (with different sulfur contents) was investigated to define the kinetics of the bacterial cell adsorption and to clarify the mechanism of the adsorption involved in biological desulfurization of coals. A kinetic model, in which two stages of adsorption are considered, is proposed on the basis of the experimental results. The estimated values of the maximum cell numbers adsorbed per unit area of coal surface (including internal surface area of pores larger than 0.5 μm), [Sm], showed a good correlation with the pyritic sulfur content of the coals. The mechanism of the adsorption was studied by investigating the effects of pH, ζ potentials of coal particles and the bacteria, a specific inhibitor of membrane-bound ATPase (20 mM NaF), a surfactant (Tween 80, 0.05%), and heat treatment (121 °C, 15 min) of the bacteria. From these observations, it was concluded that the rapid adsorption in the first stage was related with the physical force of hydrophobicity and the adsorption in the second stage was strongly related with the oxidation of pyrite. An electromicrographic study on the erosion of pyrite surfaces by the bacterial cells was also conducted. The micrographs of the pyrite particles after 5 days of the incubation showed that surfaces of pyrite minerals were eroded by adsorbed cells.

Factors affecting adsorption of Azospirillum brasilense Cd to root hairs as compared with root surface of wheat

Electron microscopy of wheat (Triticum aestivum) roots inoculated with Azospirillum brasilense Cd revealed massive adsorption of bacterial cells to the root surface and less adsorption to root hairs. Quantitative analysis of A. brasilense Cd adsorption to root surface and to root hairs, confirmed qualitatively by light microscopy observations, revealed a bacterial adsorption ratio of 5 (+2): 1 (root surface: root hairs). Extreme bacterial adsorption ratios were recorded when bacteria were previously grown in the presence of KNO3 (27:1) or when bacterial cells were inoculated under hydroponic plant growth conditions (80:1). Adsorption of A. brasilense Cd to roots was directly related to the bacterial growth phase, with logarithmic phase cultures demonstrating a greater adsorption than stationary phase cultures. Adsorption to root hairs was dependent mainly on the number of root hairs developed under certain growth conditions. When very few root hairs had developed, most of the bacterial cells were adsorbed to the root surface. Factors such as starvation, bacteria grown in culture in the presence of KNO3, addition of several nutrients, and protease or NaEDTA treatments of bacterial cells before the adsorption assay decreased bacterial adsorption to root hairs. Other factors such as microaerophilic growth conditions, addition of several bacterial chemoattractants, and cellulase-treated root hairs enhanced bacterial adsorption. It is proposed that although A. brasilense Cd adsorbed to every part of the root system, more cells adsorbed to the root surface of wheat than to the root hairs.Key words: associative bacteria, Azospirillum, bacterial adsorption, beneficial bacteria, rhizosphere bacteria, root-hair colonization.