Investigating antibacterial effects of garlic (Allium sativum) concentrate and garlic-derived organosulfur compounds on Campylobacter jejuni by using Fourier transform infrared spectroscopy, Raman spectroscopy, and electron microscopy.

Fourier transform infrared (FT-IR) spectroscopy and Raman spectroscopy were used to study the cell injury and inactivation of Campylobacter jejuni from exposure to antioxidants from garlic. C. jejuni was treated with various concentrations of garlic concentrate and garlic-derived organosulfur compounds in growth media and saline at 4, 22, and 35°C. The antimicrobial activities of the diallyl sulfides increased with the number of sulfur atoms (diallyl sulfide < diallyl disulfide < diallyl trisulfide). FT-IR spectroscopy confirmed that organosulfur compounds are responsible for the substantial antimicrobial activity of garlic, much greater than those of garlic phenolic compounds, as indicated by changes in the spectral features of proteins, lipids, and polysaccharides in the bacterial cell membranes. Confocal Raman microscopy (532-nm-gold-particle substrate) and Raman mapping of a single bacterium confirmed the intracellular uptake of sulfur and phenolic components. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to verify cell damage. Principal-component analysis (PCA), discriminant function analysis (DFA), and soft independent modeling of class analogs (SIMCA) were performed, and results were cross validated to differentiate bacteria based upon the degree of cell injury. Partial least-squares regression (PLSR) was employed to quantify and predict actual numbers of healthy and injured bacterial cells remaining following treatment. PLSR-based loading plots were investigated to further verify the changes in the cell membrane of C. jejuni treated with organosulfur compounds. We demonstrated that bacterial injury and inactivation could be accurately investigated by complementary infrared and Raman spectroscopies using a chemical-based, "whole-organism fingerprint" with the aid of chemometrics and electron microscopy.

Infrared and Raman spectroscopic studies of the antimicrobial effects of garlic concentrates and diallyl constituents on foodborne pathogens.

The antimicrobial effects of garlic (Allium sativum) extract (25, 50, 75, 100, and 200 µL/ml) and diallyl sulfide (5, 10, and 20 µM) on Listeria monocytogenes and Escherichia coli O157:H7 cultivated in tryptic soy broth at 4, 22, and 35 °C for up to 7 days were investigated. L. monocytogenes was more resistant to garlic extract and diallyl compounds treatment than E. coli O157:H7. Fourier transform infrared (FT-IR) spectroscopy indicated that diallyl constituents contributed more to the antimicrobial effect than phenolic compounds. This effect was verified by Raman spectroscopy and Raman mapping on single bacteria. Scanning electron microscope (SEM) and transmission electron microscope (TEM) showed cell membrane damage consistent with spectroscopic observation. The degree of bacterial cell injury could be quantified using chemometric methods.

Using of infrared spectroscopy to study the survival and injury of Escherichia coli O157:H7, Campylobacter jejuni and Pseudomonas aeruginosa under cold stress in low nutrient media.

The inactivation and sublethal injury of Escherichia coli O157:H7, Campylobacter jejuni and Pseudomonas aeruginosa at three temperatures (22 °C, 4 °C and -18 °C) were studied using traditional microbiological tests and mid-infrared spectroscopy (4000-400 cm(-1)). Bacteria were cultivated in diluted nutrient matrices with a high initial inoculation (∼10(7) CFU/ml) levels. Both E. coli O157:H7 and P. aeruginosa survived and cell numbers increased at 22 °C for 5 days while C. jejuni numbers decreased one log(10) CFU/ml. A two log CFU/ml decrease was observed for the three pathogens held at 4 °C for 12 days. C. jejuni survived poorly following incubation at -18 °C for 20 days while levels of E. coli O157:H7 and P. aeruginosa remained high (10(4) CFU/ml). Temperature stress response of microbes was observed by infrared spectroscopy in polysaccharide, protein, lipid, and nucleic acid regions and was strain specific. Level of cold injury could be predicted using cluster, discriminant function and class analog analysis models. Pathogens may produce oligosaccharides and potentially other components in response to stress as indicated by changes in spectral features at 1200-900 cm(-1) following freezing.

Substrate effects on the wettability of electrospun titania-poly(vinylpyrrolidone) fiber mats.

Titania-poly(vinylpyrrolidone) (PVP) core-shell nano/microfibers are electrospun on substrates of differing hydrophilicity and conductivity in order to investigate the connection between these substrate properties and the apparent water contact angles against the fiber mats. The focus of this study compares current data from silicon- and aluminum foil-supported mats to extant data from ITO and glass-supported fibers to detail the complexities of apparent contact angle dependence on mat structure related to substrate properties. Electrospinning time and collection distance were controlled parameters for producing thicker and denser mats. In all cases, contact angles increased with collection time for a given substrate series. A morphological wettability study of the fiber mat surface was conducted by applying Rhodamine B dye solution droplets. Using fluorescence microscopy, the stained fibers indicate the extent of true wetting contact and the lack of penetration into the fiber layers. Image comparisons with bright-field illumination confirms that even some fibers of the top layers are not wetted.

Wettability of electrospun poly(vinylpyrrolidone)-titania fiber mats on glass and ITO substrates in aqueous media.

Networks of nano/microfibers (fiber mats) have been electrospun from solutions of dispersed poly(vinylpyrrolidone) (PVP) and a titania precursor onto glass and indium-tin oxide (ITO) plates to study their wettability. Collection time and electrode separation are the two key fabrication parameters investigated, along with the flow rate, polymer molecular weight, and drying conditions, to determine the effects on network morphology and the relationship to contact angles. Measurements indicate that the fiber mats on both glass and ITO increase in thickness and contact angle for longer spinning time and shorter distance, resulting in an extreme case of apparent ultrahydrophobicity on ITO of up to 169.9 degrees with water. The fiber mats are shown by optical microscopy to exhibit differences in morphology for insulating glass (straight) and conductive ITO (loopy) substrates responsible for the wide-ranging and well-controlled wettability to within 1-2 degrees. Fiber mats baked at 200 degrees C for 24 h show excellent mechanical stability with wetting even against frequent heavy rinsing, conducive for reusable aqueous applications such as biosensors or cellular scaffolding.

Increases in renal epsilon-(gamma-glutamyl)-lysine crosslinks result from compartment-specific changes in tissue transglutaminase in early experimental diabetic nephropathy: pathologic implications.

Diabetic nephropathy (DN) is characterized by an early, progressive expansion and sclerosis of the glomerular mesangium leading to glomerulosclerosis. This is associated with parallel fibrosis of the renal interstitium. In experimental renal scarring, the protein cross-linking enzyme, tissue transglutaminase (tTg), is up-regulated and externalized causing an increase in its crosslink product, epsilon-(gamma-glutamyl)-lysine, in the extracellular space. This potentially contributes to the extracellular matrix (ECM) accumulation central to tissue fibrosis by increasing deposition and inhibiting breakdown. We investigated if a similar mechanism may contribute to the ECM expansion characteristic of DN using the rat streptozotocin model over 120 days. Whole kidney epsilon-(gamma-glutamyl)-lysine (HPLC analysis) was significantly increased from Day 90 (+337%) and peaked at Day 120 (+650%) (p < 0.05). Immunofluorescence showed this increase to be predominantly extracellular in the peritubular interstitial space, but also in individual glomeruli. Total kidney transglutaminase (Tg) was not elevated. However, using a Tg in situ activity assay, increased Tg was detected in both the extracellular interstitial space and glomeruli by Day 60, with a maximal 53% increase at Day 120 (p < 0.05). Using a specific anti-tTg antibody, immunohistochemistry showed a similar increase in extracellular enzyme in the interstitium and glomeruli. To biochemically characterize glomerular changes, glomeruli were isolated by selective sieving. In line with whole kidney measurement, there was an increase in glomerular epsilon-(gamma-glutamyl) lysine (+361%); however, in the glomeruli this was associated with increases in Tg activity (+228%) and tTg antigen by Western blotting (+215%). Importantly, the ratio of glomerular epsilon-(gamma-glutamyl) lysine to hydroxyproline increased by 2.2-fold. In DN, changes in the kidney result in increased translocation of tTg to the extracellular environment where high Ca(2+) and low GTP levels allow its activation. In the tubulointerstitium this is independent of increased tTg production, but dependent in the glomerulus. This leads to excessive ECM cross-linking, contributing to the renal fibrosis characteristic of progressive DN.