Tomicide adsorption on bacterial cells

The capacity of the bacteriocin-like factor of tomicid being adsorbed on microbial cells, depending on the sensitivity of test microorganisms to the preparation, its form and concentration, the duration of the contact of microbial cells with tomicid, the temperature and pH of the incubation medium, was studied. The bacteriocin-like factor of tomicid was found to be capable of nonspecific sorption on microbial cells (in an amount of 64-128 units per mg of dried cell mass). The decrease of the temperature of the incubation medium to 0 degrees C and its pH to 4.8 and 5.4 inhibited the process of binding this bacteriocin-like factor by microbial cells. The presence of the substance with lysozyme properties in the preparation influenced the process of the adsorption of the main antibacterial component on microbial cells sensitive to lysozyme.     

The application of confocal microscopy to the study of liposome adsorption onto bacterial biofilms

Confocal laser scanning microscopy has been used to visualise the adsorption of fluorescently labelled liposomes on immobilised biofilms of the bacterium Staphylococcus aureus. The liposomes were prepared with a wide range of compositions with phosphatidylcholines as the predominant lipids using the extrusion technique. They had weight average diameters of 125 +/- 5 nm and were prepared with encapsulated carboxyfluorescein. Cationic liposomes were prepared by incorporating dimethyldioctadecylammonium bromide (DDAB) or 3, beta [N-(N1,N1 dimethylammonium ethane)-carbamoyl] cholesterol (DC-chol) and anionic liposomes were prepared by incorporation of phosphatidylinositol (PI). Pegylated cationic liposomes were prepared by incorporation of DDAB and 1,2-dipalmitoylphosphatidylethanolamine-N-[polyethylene glycol)-2000]. Confocal laser scanned images showed the preferential adsorption of the fluorescent cationic liposomes at the biofilm-bulk phase interface which on quantitation gave fluorescent peaks at the interface when scanned perpendicular (z-direction) to the biofilm surface (x-y plane). The biofilm fluorescence enhancement (BFE) at the interface was examined as a function of liposomal lipid concentration and liposome composition. Studies of the extent of pegylation of the cationic liposomes incorporating DDAB, on adsorption at the biofilm-bulk phase interface were made. The results demonstrated that pegylation inhibited adsorption to the bacterial biofilms as seen by the decline in the peak of fluorescence as the mole% DPPE-PEG-2000 was increased in a range from 0 to 9 mole%. The results indicate that confocal laser scanning microscopy is a useful technique for the study of liposome adsorption to bacterial biofilms and complements the method based on the use of radiolabelled liposomes.     

The deposition of bacterial cells from laminar flows onto solid surfaces

In a previous article, the authors proposed a simple model for the rate of removal of bacterial cells from solid surfaces by fluid shear. This Model has been extended to include the deposition of cells from a flowing suspension. The theory is compared to experimentally obtained data for the deposition of Bacillus cereus cells onto the surface of glass capillaries. The effect of a hydrophobic surface, siliconized glass, and the addition of an antifoam agent to the suspension is also investigated.     

Deposition of bacterial cells onto glass and biofilm surfaces

Deposition rates of Pseudomonas putida and Hyphomicrobium ZV620 onto glass and biofilm surfaces were quantified. Both species deposited to glass at a much slower rate than to biofilm. A definite bias by depositing cells for biofilms of their own species was evident in the highest attachment rates observed in this study.     

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.Translated from Mikrobiologiya, Vol. 73, No. 6, 2004, pp. 810–816.Original Russian Text Copyright © 2004 by Samonin, Elikova.     

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.     

The deleterious metabolic and genotoxic effects of the bacterial metabolite p-cresol on colonic epithelial cells

p-Cresol that is produced by the intestinal microbiota from the amino acid tyrosine is found at millimolar concentrations in the human feces. The effects of this metabolite on colonic epithelial cells were tested in this study. Using the human colonic epithelial HT-29 Glc^–/+ cell line, we found that 0.8 mM p-cresol inhibits cell proliferation, an effect concomitant with an accumulation of the cells in the S phase and with a slight increase of cell detachment without necrotic effect. At this concentration, p-cresol inhibited oxygen consumption in HT-29 Glc^–/+ cells. In rat normal colonocytes, p-cresol also inhibited respiration. Pretreatment of HT-29 Glc^–/+ cells with 0.8 mM p-cresol for 1 day resulted in an increase of the state 3 oxygen consumption and of the cell maximal respiratory capacity with concomitant increased anion superoxide production. At higher concentrations (1.6 and 3.2 mM), p-cresol showed similar effects but additionally increased after 1 day the proton leak through the inner mitochondrial membrane, decreasing the mitochondrial bioenergetic activity. At these concentrations, p-cresol was found to be genotoxic toward HT-29 Glc^–/+ and also LS-174T intestinal cells. Lastly, a decreased ATP intracellular content was observed after 3 days treatment. p-Cresol at 0.8 mM concentration inhibits colonocyte respiration and proliferation. In response, cells can mobilize their “respiratory reserve.” At higher concentrations, p-cresol pretreatment uncouples cell respiration and ATP synthesis, increases DNA damage, and finally decreases the ATP cell content. Thus, we have identified p-cresol as a metabolic troublemaker and as a genotoxic agent toward colonocytes.     

Isolation of coliphage lambda ghosts able to adsorb onto bacterial cells

We have examined three methods of γ ghost production, starting with the [³H]eucine-labelled phage, purified by CsCl density gradient sedimentation. Ghosts obtained by the osmotic shock or by incubation in 5 M LiCl do not adsorb on bacteria. Ghosts obtained by the treatment with the chelating agent EDTA and purified by CsCl density gradient sedimentation posses well preserved adsorption properties and are virtually free of DNA and infectious phage particles.     

Thermodynamics of statherin adsorption onto hydroxyapatite

Statherin is a salivary protein that inhibits the nucleation and growth of hydroxyapatite crystals in the supersaturated environment of the oral cavity. The thermodynamics of adsorption of statherin onto hydroxyapatite crystals have been characterized here by isothermal titration calorimetry and equilibrium adsorption isotherm analysis. At 25 degrees C, statherin adsorption is characterized by an exothermic enthalpy of approximately 3 kcal/mol that diminishes to zero at approximately 25% surface coverage. The initial heat of statherin adsorption increases with temperature, displaying a positive heat capacity change of 194 +/- 7 cal K(-)(1) mol(-)(1) at 25 degrees C. The heat of adsorption during this initial phase is strongly dependent on the buffer species, and from the differential heats of buffer ionization, it can be calculated that approximately one proton is taken up by the crystal or protein upon adsorption. The free energy of adsorption is dominated at all coverages by a large positive entropy (>or=23 cal K(-)(1) mol(-)(1)), which may be partially due to the loss of organized water that hydrates the protein and the mineral surface prior to adsorption. These results are interpreted using a two-site model for adsorption of statherin onto the hydroxyapatite crystals.     

The pH dependence of calcium adsorption onto anionic phospholipid monolayers

The adsorption of ⁴⁵Ca to monolayers of phosphatidylinositol and dicetylphosphoric acid has been measured as a function of subphase pH with simultaneous recordings of surface pressure and interfacial potential. Below pH 3 little calcium was adsorbed and the films are assumed to be unionized. With acid subphases between pH 3 and 6.5 adsorption of calcium occurred initially, but it was then gradually lost due to an ageing process in the films. This time dependent change in the properties of the film was independent of the presence of Ca²⁺, but was dependent on the H⁺ concentration in the subphase; it was however not due to an acid hydrolysis of the monolayer. Ca²⁺ was permanently adsorbed at pH values above 6.5 with an increasing affinity up to pH 11.     

Competitive adsorption of Pb, Cd and Zn ions onto Eichhornia crassipes in binary and ternary systems

A batch sorption technique was used to study the biosorption of Pb²⁺, Cd²⁺ and Zn²⁺ ions onto the vastly abundant water hyacinth weed, Eichhornia crassipes biomass in binary and ternary systems at a temperature of 30 °C and pH 4.84. Mutual interference effects were probed using equilibrium adsorption capacity ratios, , where the prime indicates the presence of one or two other metal ions. The combined action of the metals was found to be antagonistic, and the metal sorption followed the order Pb²⁺  Cd²⁺  Zn²⁺. The behaviour of competitive biosorption for Pb–Cd and Pb–Zn combinations were successfully described by the Langmuir Competitive Model (CLM), whilst the model showed poor fitting to the Cd–Zn data. In conclusion, Pb²⁺ ions could still be effectively removed from aqueous solution in the presence of both Cd²⁺ and Zn²⁺ ions, but removal of the Cd²⁺ and Zn²⁺ ions would be suppressed in the presence of Pb²⁺.     

Selection of metastatic breast cancer cells based on adaptability of their metabolic state

A small subpopulation of highly adaptable breast cancer cells within a vastly heterogeneous population drives cancer metastasis. Here we describe a function-based strategy for selecting rare cancer cells that are highly adaptable and drive malignancy. Although cancer cells are dependent on certain nutrients, e.g., glucose and glutamine, we hypothesized that the adaptable cancer cells that drive malignancy must possess an adaptable metabolic state and that such cells could be identified using a robust selection strategy. As expected, more than 99.99% of cells died upon glutamine withdrawal from the aggressive breast cancer cell line SUM149. The rare cells that survived and proliferated without glutamine were highly adaptable, as judged by additional robust adaptability assays involving prolonged cell culture without glucose or serum. We were successful in isolating rare metabolically plastic glutamine-independent (Gln-ind) variants from several aggressive breast cancer cell lines that we tested. The Gln-ind cells overexpressed cyclooxygenase-2, an indicator of tumor aggressiveness, and they were able to adjust their glutaminase level to suit glutamine availability. The Gln-ind cells were anchorage-independent, resistant to chemotherapeutic drugs doxorubicin and paclitaxel, and resistant to a high concentration of a COX-2 inhibitor celecoxib. The number of cells being able to adapt to non-availability of glutamine increased upon prior selection of cells for resistance to chemotherapy drugs or resistance to celecoxib, further supporting a linkage between cellular adaptability and therapeutic resistance. Gln-ind cells showed indications of oxidative stress, and they produced cadherin11 and vimentin, indicators of mesenchymal phenotype. Gln-ind cells were more tumorigenic and more metastatic in nude mice than the parental cell line as judged by incidence and time of occurrence. As we decreased the number of cancer cells in xenografts, lung metastasis and then primary tumor growth was impaired in mice injected with parental cell line, but not in mice injected with Gln-ind cells.