Search results for "Bacterial"
showing 10 items of 3246 documents
Levansucrases from Pseudomonas syringae pv. tomato and P. chlororaphis subsp. aurantiaca: Substrate specificity, polymerizing properties and usage of…
2011
Levansucrases of Pseudomonas syringae pv. tomato DC3000 (Lsc3) and Pseudomonas chlororaphis subsp. aurantiaca (also Pseudomonas aurantiaca) (LscA) have 73% identity of protein sequences, similar substrate specificity and kinetic properties. Both enzymes produce levan and fructooligosaccharides (FOS) of varied length from sucrose, raffinose and sugar beet molasses. A novel high-throughput chip-based nanoelectrospray mass spectrometric method was applied to screen alternative fructosyl acceptors for levansucrases. Lsc3 and LscA could both transfructosylate D-xylose, D-fucose, L- and D-arabinose, D-ribose, D-sorbitol, xylitol, xylobiose, D-mannitol, D-galacturonic acid and methyl-α-D-glucopyra…
Pyrocoll, an Antibiotic, Antiparasitic and Antitumor Compound Produced by a Novel Alkaliphilic Streptomyces Strain
2003
A new secondary metabolite was detected in the culture extract of Streptomyces sp. AK 409 by HPLC-diode-array screening. The metabolite was identified as pyrocoll, which is known to be a constituent of cigarette smoke. Pyrocoll is known as a synthetic compound, but until now had not been isolated as a natural product from a microorganism. The compound showed biological activity against various Arthrobacter strains, filamentous fungi, several pathogenic protozoa, and some human tumor cell lines.
Effect of heat activation and inactivation conditions on germination and thermal resistance parameters of Bacillus cereus spores.
2001
The effect of isothermal and non-isothermal heat activation on germination and thermoresistance of two strains of Bacillus cereus spores was studied. Results indicated that the germination after isothermal activation was lower than after non-isothermal heating. The activation rate affected the z value, which increased with faster heating rates. For each temperature and inactivation rate, the non-isothermal activation at rate of 2 degrees C/min resulted in larger D values (D90 = 4.70 min) than isothermal activation (D90 = 4.04 min). The two mathematical equations used to analyse non-isothermal data produced similar predicted D and z values, nevertheless the Hayakawa equation modified in this…
Thermal inactivation kinetics of Bacillus stearothermophilus spores using a linear temperature program.
1999
A systematic study of the inactivation kinetics of Bacillus stearothermophilus spores was carried out in nonisothermic heating conditions using a linear temperature increase program and analyzing the experimental data by means of a one-step nonlinear regression. The D and z values estimated are close to those obtained in isothermic conditions and estimated by using a two-step model, first D values are calculated, and then in the second step a z value is deduced (D(121 degrees C) = 3.08 and 4.38 min, respectively, and z = 7 and 7.9 degrees C, respectively). No convergence problems were observed when using the one-step nonlinear regression proposed. The results indicated that the methodology …
High gas pressure: An innovative method for the inactivation of dried bacterial spores
2012
In this article, an original non-thermal process to inactivate dehydrated bacterial spores is described. The use of gases such as nitrogen or argon as transmission media under high isostatic pressure led to an inactivation of over 2 logs CFU/g of Bacillus subtilis spores at 430 MPa, room temperature, for a 1 min treatment. A major requirement for the effectiveness of the process resided in the highly dehydrated state of the spores. Only a water activity below 0.3 led to substantial inactivation. The solubility of the gas in the lipid components of the spore and its diffusion properties was essential to inactivation. The main phenomenon involved seems to be the sorption of the gas under pres…
Pathogenicity of intrathoracically administrated Bacillus thuringiensis spores in Blatta orientalis.
2006
Abstract The ability of Bacillus thuringiensis to produce septicaemia in Periplaneta americana and Blatta orientalis has been investigated. Spores and crystals from several wild-type strains as well as spores of a B. thuringiensis crystal-deficient mutant, were first orally administrated at high doses, and no significant mortality was recorded. Intrathoracic injection of spore suspensions in P. americana revealed that this species is not very susceptible to B. thuringiensis spores. B. orientalis , by contrast, was found to be very susceptible to B. thuringiensis , with a LD 50 of about 35,000 spores, that is similar to that reported on Lepidoptera challenged with parenterally injected B. th…
Bacterial growth and biological properties of Cymbopogon schoenanthus and Ziziphus lotus are modulated by extraction conditions
2020
Abstract The present study aims to evaluate the antibacterial activity and biological properties of two traditional Saharian plants (Cymbopogon schoenanthus and Ziziphus lotus). The plant extracts were obtained by using a different combination of extraction methods (conventional vs. ultrasound-assisted) and solvents (water vs. ethanol:water (50:50, v/v)). The antioxidant profile, anti-inflammatory activity and impact on bacterial growth (foodborne and probiotic bacteria) of the obtained extracts were assessed. The plant species showed the hierarchically more important role in determining the biological properties of the extracts, followed by extraction solvent and extraction conditions. Con…
Characterization of antimicrobial properties on the growth of S. aureus of novel renewable blends of gliadins and chitosan of interest in food packag…
2007
The biocide properties of chitosan-based materials have been known for many years. However, typical antimicrobial formulations of chitosan, mostly chitosonium salts, are known to be very water sensitive materials which may impair their use in many application fields such as food packaging or food coating applications. This first work reports on the development and characterization of the antimicrobial properties of novel fully renewable blends of chitosan with more water-resistant gliadin proteins isolated from wheat gluten. Chitosan release to the nutrient broth from a wide range of blends was studied making use of the ninhydrin method. The results indicated that both pure chitosan and its…
Alpha-toxin of Staphylococcus aureus
1991
Alpha-toxin, the major cytotoxic agent elaborated by Staphylococcus aureus, was the first bacterial exotoxin to be identified as a pore former. The protein is secreted as a single-chain, water-soluble molecule of Mr 33,000. At low concentrations (less than 100 nM), the toxin binds to as yet unidentified, high-affinity acceptor sites that have been detected on a variety of cells including rabbit erythrocytes, human platelets, monocytes and endothelial cells. At high concentrations, the toxin additionally binds via nonspecific absorption to lipid bilayers; it can thus damage both cells lacking significant numbers of the acceptor and protein-free artificial lipid bilayers. Membrane damage occu…
Pyrrolomycins as antimicrobial agents. Microwave-assisted organic synthesis and insights into their antimicrobial mechanism of action
2019
Abstract New compounds able to counteract staphylococcal biofilm formation are needed. In this study we investigate the mechanism of action of pyrrolomycins, whose potential as antimicrobial agents has been demonstrated. We performed a new efficient and easy method to use microwave organic synthesis suitable for obtaining pyrrolomycins in good yields and in suitable amount for their in vitro in-depth investigation. We evaluate the inhibitory activity towards Sortase A (SrtA), a transpeptidase responsible for covalent anchoring in Gram-positive peptidoglycan of many surface proteins involved in adhesion and in biofilm formation. All compounds show a good inhibitory activity toward SrtA, havi…