Modeling Virus Adsorption in Batch and Column Experiments

Experiments with batch suspensions, recirculating columns and flow-through columns have been carried out involving a sandy soil and five bacteriophages: MS2, PRD1, X174, Q and PM2. In batch and recirculating column experiments, attachment and detachment rate coefficients were determined by fitting a two-parameter (attachment and detachment) model. In general, attachment and detachment rate coefficients were not found to be significantly different between the two kinds of experiments. There was one exception, however: MS2 appeared to detach faster in the presence of strong advective flow. In the case of flow-through column experiments, it is shown that a two-site model, with adsorption to equilibrium and kinetic sites, fits the breakthrough curves of all the phages, except PM2, satisfactorily. A one-site kinetic model was found to be appropriate for phage PM2. A small proportion of bacteriophages MS2, PRD1, and Q adsorbed to equilibrium sites, whereas a large proportion of X174 adsorbed to equilibrium sites. Such a distinction between adsorption to equilibrium and kinetic sites cannot be made in the case of batch or recirculating column experiments. Kinetic attachment rate coefficients were found to be significantly higher for the bacteriophages with presumably stronger negative charge. This may be ascribed to the presence of multivalent cations. Under these conditions, bacteriophage X174 appears to behave more conservatively than more negatively charged viruses, and may then be a better choice as a relatively conservative tracer for virus transport through the subsurface.     

Interaction of Mycoplasma with Viruses I. Primary Adsorption of Virus Is Ionic in Mechanism

We have studied the adsorption of the Gourlay Acholeplasma virus MVL-1 to the host cell Acholeplasma laidlawii JA-1. Successful adsorption depends primarily on some unknown action of the serum factor in the medium, but evaluation of various physical parameters indicates clearly that given this factor the kinetics is pseudo first order (K = 3 x 10(-9) cm(3)/min) and the mechanism ionic. Chiefly important are the ionic strength of the cation and pH (optimal Na(+) = 0.08 M, pH = 6). The system seems indifferent to whether the cation is Na, K, NH(4), Ca, or Mg. There is little effect of temperature over the range 0 to 42 C. The diffusion constant of the virus, calculated from its geometry or its maximum adsorption rate, is consistent with its reported size and shape.     

Effect of Ionic Strength on the Binding of Sindbis Virus to Chick Cells

Sindbis virus can adsorb to chicken embryo fibroblasts in two different ways. "Loosely" bound virus can be washed off the cell with buffers of ionic strength 0.2 or greater, whereas "tightly" bound virus remains attached under these conditions. When Sindbis virus is adsorbed to chick cells at 4 C from a buffer of ionic strength 0.17, 40 to 50% of the adsorbed virus is loosely bound, the remainder tightly bound. Infection of chick cells by Sindbis virus has only small effects on the total amount of virus that can be bound to the cells. However, the amount of Sindbis virus that can be tightly bound declines rapidly beginning at 2 to 3 h after infection. By 7 h after infection, the amount of virus that can be tightly bound is only 10 to 20% of the amount bound to uninfected cells. The adsorption (and penetration) of virus at 37 C is most efficient at an ionic strength of 0.15 to 0.17; at this ionic strength most of the adsorbed virus is tightly bound. At higher ionic strengths the virus adsorbs poorly. At lower ionic strengths most of the virus is loosely bound. A second enveloped virus, vesicular stomatitis virus, has been studied for the purposes of comparison; its adsorption behavior differs from that of Sindbis virus.     

Effect of Grewia Gum as a Suspending Agent on Ibuprofen Pediatric Formulation

The purpose of this work was to evaluate the potential of grewia gum (GG) as a suspending agent in pharmaceutical oral formulation using ibuprofen as model drug. Ibuprofen pediatric suspension (25 mg/5 mL) was formulated with grewia gum (0.5% w/v) as the suspending agent. Similar suspensions of Ibuprofen containing either sodium carboxymethylcellulose (Na-CMC) or hydroxymethylpropylcellulose (HPMC) were also produced. The suspensions were evaluated for ease of redispersion, sedimentation, rheological properties, and the effect of aging on the rheological properties at 25°C. The particle size and particle size distributions of the dispersed solute were determined. The redispersion time was 19, 11, and 0.5 min, respectively, for formulation containing Na-CMC, HPMC, and GG .The sedimentation volumes were 0.05, 0.05, and 0.125 mL, respectively, for Na-CMC, HPMC, and GG . Viscosities of suspensions at spindle speed of 25 rpm were of the order: GG > HPMC > Na-CMC when freshly prepared and of the order: HPMC > GG > Na-CMC within 6 months of storage. The particles size was 72.72, 73.82, 81.93, and 83.41 μm, respectively, for suspensions containing Na-CMC, ibuprofen alone, HPMC, and GG. Greatest hysteresis was observed in formulation containing HPMC. All the formulations were stable. It was our conclusion that the difference in the physicochemical properties of ibuprofen pediatric formulations was influenced more by the suspending agent used in the formulations than the drug. GG combined better redispersion with minimal changes in viscosity on storage compared to Na-CMC and HPMC as suspending agent. Thus GG may serve as a good suspending agent requiring no further aid in suspension redispersibility.KEY WORDS: grewia gum, oral pharmaceutical formulations, physicochemical properties, potential suspending agent     

Ionic Composition of Microdialysis Perfusing Solution Alters the Pharmacological Responsiveness and Basal Outflow of Striatal Dopamine

While using the technique of in vivo microdialysis, we have assessed the effect of the ionic composition of the perfusing solution on extracellular dopamine levels during resting conditions and following a pharmacological manipulation. Our results indicate that perfusion with solutions containing the ionic composition of commercially available Ringer's solution, which mimic the ionic composition of plasma as opposed to brain extracellular fluid, alters the turnover rate and basal release of dopamine. Moreover, perfusion with solutions containing higher calcium levels, i.e., 3.4 mM, than the amount we have determined to be present in the extracellular fluid of striatum (1.2 mM) alters the pharmacological responsiveness of the nigrostriatal dopamine system to synthesis inhibition.     

Effect of Different Ammonia Concentrations on Community Succession of Ammonia-oxidizing Microorganisms in a Simulated Paddy Soil Column

Ammonia oxidation is performed by both ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA). To explore the effect of ammonia concentration on the population dynamic changes of ammonia-oxidizing microorganisms, we examined changes in the abundance and community composition of AOA and AOB in different layers. Most of the archaeal amoA sequences were Nitrosotalea-related and the proportion that Nitrosotalea cluster occupied decreased in the surface layer and increased in the deep layer during the cultivation process. Nitrosopumilus-related sequences were only detected in the deep layer in the first stage and disappeared later. Both phylogenetic and quantitative analysis showed that there were increased Nitrosomonas-related sequences appeared in the surface layer where the ammonia concentration was the highest. Both AOA and AOB OTU numbers in different layers decreased under selective pressure and then recovered. The potential nitrification rates were 25.06 μg·N·L(-1)·g(-1) dry soil·h(-1) in the mid layer which was higher than the other two layers. In general, obvious population dynamic changes were found for both AOA and AOB under the selective pressure of exogenous ammonia and the changes were different in three layers of the soil column.     

Transport of Surface-modified Carbon Nanotubes through a Soil Column

Carbon nanotubes (CNTs) are widely manufactured nanoparticles, which are being utilized in a number of consumer products, such as sporting goods, electronics and biomedical applications. Due to their accelerating production and use, CNTs constitute a potential environmental risk if they are released to soil and groundwater systems. It is therefore essential to improve the current understanding of environmental fate and transport of CNTs. The transport and retention of CNTs in both natural and artificial media have been reported in literature, but the findings widely vary and are thus not conclusive. There are a number of physical and chemical parameters responsible for variation in retention and transport. In this study, a complete procedure of selected multiwalled carbon nanotubes (MWCNTs) is presented starting from their surface modification to a complete set of laboratory column experiments at critical physical and chemical scenarios. Results indicate that the stability of the commercially available MWCNTs are critical with their attached surface functional group which can also influence the transport and retention of MWCNT through the surrounding medium.     

Effect of Agricultural Operations and Precipitation on Vertical Distribution of a Nuclear Polyhedrosis Virus in Soil

TheAnticarsia gemmatalisnuclear polyhedrosis virus (AgNPV) was released in two soybean plots in September, 1991; the soil in the plots was then sampled periodically through July, 1992, to determine the effects of normal agricultural soil manipulations and precipitation on vertical distribution of the polyhedral occlusion bodies (POBs). The amount of AgNPV increased at all depths down to 37.5–50 cm as long as there was virus-contaminated plant matter, even dead soybean refuse, above the soil surface. Agricultural operations (disking, harrowing, mowing, planting, cultivating) had no effect on the amount or vertical distribution of AgNPV in soil. After the crop refuse was disked into the soil in November, the amount of POBs began decreasing at all depths; these decreases continued over winter and at times appeared to be associated with precipitation. The POBs were no longer detected below 37.5 cm by April, 1992, or below 25 cm by July, 1992. However, in July there were still 274 POBs/g in the top 2.5 cm of soil. Thus, agricultural operations should not hinder contamination of soybean leaves by AgNPV from its soil reservoir.     

New Culture Medium Containing Ionic Concentrations of Nutrients Similar to Concentrations Found in the Soil Solution

A new growth medium which closely approximates the composition of the soil solution is presented. This soil solution equivalent (SSE) medium contains the following components (millimolar): NO₃, 2.5; NH₄, 2.5; HPO₄, 0.005; Na, 2.5; Ca, 4.0; Mg, 2.0; K, 0.503; Cl, 4.0; SO₄, 5.0; ethylenediamine-di(o-hydroxyphenylacetic acid), 0.02; and MES [2-(N-morpholino)ethanesulfonic acid] (to maintain the pH at 6.0), 10, plus 0.1% arabinose. The advantages of the SSE medium are discussed.     

Bacterial Community Composition in the Water Column of a Lake Formed by a Former Uranium Open Pit Mine

Mining of pyrite minerals is a major environmental issue involving both biological and geochemical processes. Here we present a study of an artificial lake of a former uranium open pit mine with the aim to connect the chemistry and bacterial community composition (454-pyrosequencing of 16S rRNA genes) in the stratified water column. A shift in the water chemistry from oxic conditions in the epilimnion to anoxic, alkaline, and metal and sulfide-rich conditions in the hypolimnion was corresponded by a strong shift in the bacterial community, with few shared operational taxonomic units (OTU) between the water layers. The epilimnetic bacterial community of the lake (～20?years old) showed similarities to other temperate freshwater lakes, while the hypolimnetic bacterial community showed similarity to extreme chemical environments. The epilimnetic bacterial community had dominance of Actinobacteria and Betaproteobacteria. The hypolimnion displayed a higher bacterial diversity and was dominated by the phototrophic green sulphur bacterium of the genus Chlorobium (ca. 40?% of the total community). Deltaproteobacteria were only represented in the hypolimnion and the most abundant OTUs were affiliated with ferric iron and sulfate reducers of the genus Geobacter and Desulfobulbus, respectively. The chemistry is clearly controlling, especially the hypolimnetic, bacterial community but the community composition also indicates that the bacteria are involved in metal cycling in the lake.     

The Effect of Lanthanum on the Composition of Methanotrophic Community of Sod-Podzolic Soil

Microbiology - While lanthanum is known to regulate the metabolism of microorganisms using single-carbon compounds, there is no information about its effect on soil communities. This is the first...     

Effect of Different Carbon Sources on Community Composition of Bacterial Enrichments from Soil

Soil is a highly heterogeneous matrix, which can contain thousands of different bacterial species per gram. Only a small component of this diversity (maybe <1%) is commonly captured using standard isolation techniques, although indications are that a larger proportion of the soil community is in fact culturable. Better isolation techniques yielding greater bacterial diversity would be of benefit for understanding the metabolic activity and capability of many soil microorganisms. We studied the response of soil bacterial communities to carbon source enrichment in small matrices by means of terminal restriction fragment length polymorphism (TRFLP) analysis. The community composition of replicate enrichments from soil displayed high variability, likely attributable to soil heterogeneity. An analysis of TRFLP data indicated that enrichment on structurally similar carbon sources selected for similar bacterial communities. The same analysis indicated that communities first enriched on glucose or benzoate and subsequently transferred into medium containing an alternate carbon source retained a distinct community signature induced by the carbon source used in the primary enrichment. Enrichment on leucine presented a selective challenge that was able to override the imprint left by primary enrichment on acetate. In a time series experiment community change was most rapid 18 hours after inoculation, corresponding to exponential growth. Community composition did not stabilize even 4 days after secondary enrichment. Four different soil types were enriched on four different carbon sources. TRFLP analysis indicated that in three out of four cases communities enriched on the same carbon source were more similar regardless of which soil type was used. Conversely, the garden soil samples yielded similar enrichment communities regardless of the enrichment carbon source. Our results indicate that in order to maximize the diversity of bacteria recovered from the environment, multiple enrichments should be performed using a chemically diverse set of carbon sources.     

Characterization of Virus Adsorption by Using DEAE-Sepharose and Octyl-Sepharose†

Viruses were characterized by their adsorption to DEAE-Sepharose or by their elution from octyl-Sepharose by using buffered solutions of sodium chloride with different ionic strengths. Viruses whose adsorption to DEAE-Sepharose was reduced most rapidly by an increase in the sodium chloride concentration were considered to have the weakest electrostatic interactions with the solids; these viruses included MS2, E1, and X174. Viruses whose adsorption to DEAE-Sepharose was reduced least rapidly were considered to have the strongest electrostatic interactions with the column; these viruses included P1, T4, T2, and E5. All of the viruses studied adsorbed to octyl-Sepharose in the presence of 4 M NaCl. Viruses that were eluted most rapidly following a decrease in the concentration of NaCl were considered to have the weakest hydrophobic interactions with the column; these viruses included X174, CB4, and E1. Viruses that were eluted least rapidly from the columns after the NaCl concentration was decreased were considered to have the strongest hydrophobic interactions with the column; these viruses included f2, MS2, and E5.     

Influence of Salts on Virus Adsorption to Microporous Filters

We investigated the direct and indirect effects of mono-, di-, and trivalent salts (NaCl, MgCl₂, and AlCl₃) on the adsorption of several viruses (MS2, PRD-1, X174, and poliovirus 1) to microporous filters at different pH values. The filters studied included Millipore HA (nitrocellulose), Filterite (fiberglass), Whatman (cellulose), and 1MDS (charged-modified fiber) filters. Each of these filters except the Whatman cellulose filters has been used in virus removal and recovery procedures. The direct effects of added salts were considered to be the effects associated with the presence of the soluble salts. The indirect effects of the added salts were considered to be (i) changes in the pH values of solutions and (ii) the formation of insoluble precipitates that could adsorb viruses and be removed by filtration. When direct effects alone were considered, the salts used in this study promoted virus adsorption, interfered with virus adsorption, or had little or no effect on virus adsorption, depending on the filter, the virus, and the salt. Although we were able to confirm previous reports that the addition of aluminum chloride to water enhances virus adsorption to microporous filters, we found that the enhanced adsorption was associated with indirect effects rather than direct effects. The increase in viral adsorption observed when aluminum chloride was added to water was related to the decrease in the pH of the water. Similar results could be obtained by adding HCl. The increased adsorption of viruses in water at pH 7 following addition of aluminum chloride was probably due to flocculation of aluminum, since removal of flocs by filtration greatly reduced the enhancement observed. The only direct effect of aluminum chloride on virus adsorption that we observed was interference with adsorption to microporous filters. Under conditions under which hydrophobic interactions were minimal, aluminum chloride interfered with virus adsorption to Millipore, Filterite, and 1MDS filters. In most cases, less than 10% of the viruses adsorbed to filters in the presence of a multivalent salt and a compound that interfered with hydrophobic interactions (0.1% Tween 80 or 4 M urea).     

Bioreduction of Hexavalent Chromium from Soil Column Leachate by Pseudomonas stutzeri

Bioreduction of Cr(VI) to less toxic Cr(III) by chromate-reducing bacteria has offered an ecological and economical option for chromate detoxification. The present study reports isolation of chromate-resistant bacterial strain Cr8 from chromium slag, identified as Pseudomonas stutzeri, based on 16S rRNA gene sequencing and their potential use in Cr(VI) reduction. The reduced product associated with bacterial cell was characterized by scanning electron microscopy–energy-dispersive x-ray spectroscopy (SEM-EDS) and x-ray diffraction (XRD) analyses. At initial concentrations of 100 and 200 mg L^?1 Cr(VI), P. stutzeri Cr8 reduced Cr(VI) completely within 24 h, whereas it reduced almost 1000 mg L^?1 Cr(VI) at the end of 120 h. Further, soil column leaching experiments were performed and found that bacterial cells reduced Cr(VI) leachate at faster rate that almost disappeared at the end of 168 h. The leachate precipitates also revealed efficient chromate bioreduction. The remediation process utilizing P. stutzeri could be considered as a viable alternative to reduce Cr(VI) contamination, especially emanating from the overburden dumps of chromite ores and mine drainage.     

Effect of Yeast Cell Morphology,Cell Wall Physical Structure and Chemical Composition on Patulin Adsorption

The capability of yeast to adsorb patulin in fruit juice can aid in substantially reducing the patulin toxic effect on human health. This study aimed to investigate the capability of yeast cell morphology and cell wall internal structure and composition to adsorb patulin. To compare different yeast cell morphologies, cell wall internal structure and composition, scanning electron microscope, transmission electron microscope and ion chromatography were used. The results indicated that patulin adsorption capability of yeast was influenced by cell surface areas, volume, and cell wall thickness, as well as 1,3-β-glucan content. Among these factors, cell wall thickness and 1,3-β-glucan content serve significant functions. The investigation revealed that patulin adsorption capability was mainly affected by the three-dimensional network structure of the cell wall composed of 1,3-β-glucan. Finally, patulin adsorption in commercial kiwi fruit juice was investigated, and the results indicated that yeast cells could adsorb patulin from commercial kiwi fruit juice efficiently. This study can potentially simulate in vitro cell walls to enhance patulin adsorption capability and successfully apply to fruit juice industry.     

Carbohydrate Composition of Vesicular Stomatitis Virus

Analysis by gas-liquid chromatography of the trimethylsilylated sugar residues of purified vesicular stomatitis virus grown in L cells or chick embryo cells revealed the presence in the whole virion of four hexoses (glucose, galactose, mannose, and fucose), two hexosamines (glucosamine and galactosamine), and 34 to 40% neuraminic acid. The isolated viral glycoprotein was devoid of galactosamine and fucose, both of which sugars were present in whole virions presumably as part of the membrane glycolipids.     

Effects of the Ionic Composition and Water Potential of Aqueous Solution on the Activity and Survival of Orrina phyllobia

The activity and survival of Orrina phyllobia fourth-stage juveniles (J4) were examined in aqueous solutions representing 96 combinations of eight predominant soil solution ions at total concentrations of 100, 200, and 1,000 meq/liter. Various water potentials were imposed by the addition of mannitol or polyethylene glycol to ionic solutions. Nematode longevity increased as water potential was decreased. Longevity was approximately doubled at a water potential of -23 × 10⁵ Pa and more than tripled at -60 × 10⁵ Pa. No combination oflons at 200 meq/liter was lethal after a 6-day exposure. Several ion combinations significantly increased longevity at -10 and -23 × 10⁵ Pa. Single cation Na⁺ solutions consistently inhibited activity and more than doubled nematode longevity.