Ion mobility spectrometry (IMS) is currently in widespread use for the detection and identification of narcotic and explosive compounds without prior sample clean-up or concentration steps. IMS analysis is rapid, less than a minute, and sensitive, with detection limits in the nanogram to picogram range, depending on the target analyte. Our studies indicate that this technique has potential for detection of specific components of bacterial cells and for identification and differentiation of bacterial strains and species within a minute, and with no specialized test kits or reagents required. When microgram quantities of whole bacterial cells are thermally desorbed, complex positive or negative ion patterns (plasmagrams) are obtained. These plasmagrams differ reproducibly for different strains and species and for different conditions of growth, and can be used for the classification and differentiation of specific strains and species of bacteria, including pathogens. Methods for improved ion peak detection, most notably sequential sample desorption at stepped increases in temperature (programmed temperature ramping), are described. 相似文献
The aim of the present investigation was to compare the in vitro bacterial retention on saliva-coated implant materials (pure titanium grade 2 (cp-Ti) and a titanium alloy (Ti–6Al–4V) surfaces), presenting similar surface roughness, and to assess the influence of physico-chemical surface properties of bacterial strain and implant materials on in vitro bacterial adherence. Two bacterial strains (one hydrophilic strain and one hydrophobic strain) were used and the following were evaluated: bacterial cell adherence, SFE values as well as the Lifshitz-van-der Waals, the Lewis acid base components of SFE, the interfacial free energy and the non-dispersive interactions according to two complementary contact angle measurement methods: the sessile drop method and the captive bubble method.
Our results showed similar patterns of adherent bacterial cells on saliva-coated cp-Ti and saliva-coated Ti–6Al–4V. These findings could suggest that bacterial colonization (i.e. plaque formation) is similar on saliva-coated cp-Ti and Ti–6Al–4V surfaces and indicate that both materials could be suitable for use as transgingival abutment or healing implant components. The same physico-chemical properties exhibited by saliva-coated cp-Ti and TA6V, as shown by the sessile drop method and the captive bubble method, could explain this similar bacterial colonisation. Therefore, higher values of total surface free energy of saliva-coated cp-Ti and saliva-coated TA6V samples (γSV ≈65 mJ/m2) were reported using the captive bubble method indicating a less hydrophobic character of these surfaces than with the sessile drop method (γS ≈44.50 mJ/m2) and consequently possible differences in oral bacterial retention according the theory described by Absolom et al.
The number of adherent hydrophobic S. sanguinis cells was two-fold higher than that of hydrophilic S. constellatus cells. Our results confirm that physico-chemical surface properties of oral bacterial strains play a role in bacterial retention to implant materials in the presence of adsorbed salivary proteins. 相似文献
Bacterial sensors are indispensable in environmental monitoring, analysis of food and drink safety, prevention and treatment of pathogenic infections, antibiotic resistance screening, in combatting biocorrosion, and in biodefense. Recent discoveries within Human Microbiome project disclosed vital bacteria's role in human health and disease prognosis and treatment; they also placed in focus new analytical tools for bacterial analysis. Here, I discuss several basic concepts underlying the electrochemical bacterial biosensors: metabolic sensors, biosensors for DNA and RNA extracted from bacterial cells, and whole bacterial cell sensors, and their contribution to practically sought solutions for bacterial analysis. Current analytical issues and perspectives are outlined. 相似文献
Hydrogels are finding increasingly broad use, especially in biomedical applications. Their complex structure – a low-density network of microfibrils – defines their non-trivial mechanical behaviour. The focus of this work is on test-based quantification of mechanical behaviour of a bacterial cellulose (BC) hydrogel exposed to cyclic loading. Specimens for the tests were produced using Gluconacetobacter xylinus ATCC 53582 and tested in aqua under uniaxial cyclic loading conditions in a displacement-controlled regime. Substantial microstructural changes were observed in the process of deformation. A combination of qualitative microstructural observations with quantitative force-displacement relations allowed identification of main deformation mechanisms, confirming inelastic behaviour of the BC hydrogel under a loading-unloading-reloading regime. Elastic deformation was accompanied by non-elastic (viscoplastic) deformation in both tension and compression. This study also aims to establish a background for micromechanical modelling of overall properties of BC hydrogels. 相似文献
The binding behavior of acidic capsular polysaccharide (SPS), isolated from Klebsiella serotype K43, with oppositely charged dyes and surfactants have been studied by way of absorbance and emission spectroscopic measurements. Each repeating unit of the SPS consists of three D-mannose, one D-galactose, and one D-glucuronic acid residue. The anionic polysaccharide exhibited chromotropic character and induced strong metachromasy in the cationic dye, pinacyanol chloride (PCYN) through the formation of a 1:1 stoichiometric complex. Evaluation of thermodynamic parameters, viz., changes in free energy (ΔG), enthalpy (ΔH), and entropy (ΔS), for the formation of dye-polymer complex and studies on the effect of different cosolvents were also evaluated to shed light on the binding nature as well as the extent of stability of the dye-polymer complex. Fluorescence of the cationic dye acridine orange (AO) was quenched with the progressive addition of SPS, which was found to be of Stern-Volmer type. Cationic surfactants in their pure form as well as in the mixed state with nonionic surfactant (Tween-20), replaced the dye bound to the polymer matrices; thus the original band intensities of the dyes could be reverted. Such studies revealed the involvement of both electrostatic as well as hydrophobic interactions between the dye-polymer as well as surfactant-polymer aggregates. 相似文献
Transglucosylation reactions using sucrose as glucosyl donor and either N-acetyl-D-glucosamine, L-rhamnose, or methyl α -L-rhamnopyranoside as acceptors were carried out with recombinant glucansucrases from families 70 and 13 of glycoside-hydrolases. Depending on the enzyme specificity, various carbohydrate structures were synthesized and characterized including α -D-glucopyranosyl-(1 → 6)-N-acetyl-D-glucosamine, α -D-glucopyranosyl-(1 → 4)-N-acetyl-D-glucosamine, α -D-glucopyranosyl-(1 → 1)-β -L-rhamnopyranoside, α -D-glucopyranosyl-(1 → 4)-α -D-glucopyranosyl-(1 → 1)-β -L-rhamnopyranoside, methyl α -D-glucopyranosyl-(1 → 4)-α -L-rhamnopyranoside, and methyl α -D-glucopyranosyl-(1 → 3)-α -L-rhamnopyranoside. Disaccharides were obtained with yields going up to 64%. The structural diversity generated as well as the obtained yields appear to be related to enzyme active site architecture, which can be modulated and improved by enzyme engineering. Several of the obtained disaccharides enter in the composition of surface polysaccharides of pathogenic bacteria, among which is Shigella flexneri. Our results outline the potential of glucansucrases in the chemo-enzymatic synthesis of complex carbohydrates of biological interest whose chemical synthesis may be seen as a limitation. 相似文献
Bioleaching is a technology for the recovery of metals from minerals by means of microorganisms, which accelerate the oxidative dissolution of the mineral by regenerating ferric ions. Bioleaching processes take place at the interface of bacteria, sulfide mineral and leaching solution. The fundamental forces between a bioleaching bacterium and mineral surface are central to understanding the intricacies of interfacial phenomena, such as bacterial adhesion or detachment from minerals and the mineral dissolution. This review focuses on the current state of knowledge in the colloidal aspect of bacteria–mineral interactions, particularly for bioleaching bacteria. Special consideration is given to the microscopic structure of bacterial cells and the atomic force microscopy technique used in the quantification of fundamental interaction forces at nanoscale. 相似文献