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Inactivation Experiments (inactivation + experiment)

Distribution by Scientific Domains

Life Sciences	50%

Selected Abstracts

Virulent spores of Bacillus anthracis and other Bacillus species deposited on solid surfaces have similar sensitivity to chemical decontaminants

JOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2007
J-L. Sagripanti
Abstract Aims:, To compare the relative sensitivity of Bacillus anthracis and spores of other Bacillus spp. deposited on different solid surfaces to inactivation by liquid chemical disinfecting agents. Methods and Results:, We prepared under similar conditions spores from five different virulent and three attenuated strains of B. anthracis, as well as spores of Bacillus subtilis, Bacillus atrophaeus (previously known as Bacillus globigii), Bacillus cereus, Bacillus thuringiensis and Bacillus megaterium. As spore-surface interactions may bias inactivation experiments, we evaluated the relative binding of different spores to carrier materials. The survival of spores deposited on glass, metallic or polymeric surfaces were quantitatively measured by ASTM standard method E-2414-05 which recovers spores from surfaces by increasing stringency. The number of spores inactivated by each decontaminant was similar and generally within 1 log among the 12 different Bacillus strains tested. This similarity among Bacillus strains and species was observed through a range of sporicidal efficacy on spores deposited on painted metal, polymeric rubber or glass. Conclusions:, The data obtained indicate that the sensitivity of common simulants (B. atrophaeus and B. subtilis), as well as spores of B. cereus, B. thuringiensis, and B. megaterium, to inactivation by products that contain either: peroxide, chlorine or oxidants is similar to that shown by spores from all eight B. anthracis strains studied. Significance and Impact of the Study:, The comparative results of the present study suggest that decontamination and sterilization data obtained with simulants can be safely extrapolated to virulent spores of B. anthracis. Thus, valid conclusions on sporicidal efficacy could be drawn from safer and less costly experiments employing non-pathogenic spore simulants. [source]

Protein kinase C-, mediates von Willebrand factor secretion from endothelial cells in response to vascular endothelial growth factor (VEGF) but not histamine

JOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 11 2008
O. LORENZI
Summary.,Background:,Vascular endothelial growth factor (VEGF) and histamine induce von Willebrand factor (VWF) release from vascular endothelial cells. Protein kinase C (PKC) is involved in the control of exocytosis in many secretory cell types. Objectives:,We investigated the role of PKC and the interactions between PKC and Ca2+ signaling in both VEGF-induced and histamine-induced VWF secretion from human umbilical vein endothelial cells (HUVECs). Results:,Several PKC inhibitors (staurosporine, Ro31-8220, myristoylated PKC peptide inhibitor and Go6983) block VEGF-induced but not histamine-induced VWF secretion. PKC-, and novel PKCs (PKC-,, PKC-,, and PKC-,), but not PKC-,, are expressed in HUVECs. Both VEGF and histamine activate PKC-,. However, gene inactivation experiments using small interfering RNA indicate that PKC-, (but not PKC-,) is involved in the regulation of VEGF-induced but not histamine-induced secretion. Both VEGF and histamine induce a rise in cytosolic free Ca2+ ([Ca2+]c), but the response to VEGF is weaker and even absent in a significant subset of cells. Furthermore, VEGF-induced secretion is largely preserved when the rise in [Ca2+]c is prevented by BAPTA-AM. Conclusions:,Our study identifies striking agonist specificities in signal,secretion coupling. Histamine-induced secretion is dependent on [Ca2+]c but not PKC, whereas VEGF-induced secretion is largely dependent on PKC-, and significantly less on [Ca2+]c. Our data firmly establish the key role of PKC-, in VEGF-induced VWF release, but suggest that a third, VEGF-specific, signaling intermediate is required as a PKC-, coactivator. [source]

Deciphering regulatory mechanisms for secondary metabolite production in the myxobacterium Sorangium cellulosum So ce56

MOLECULAR MICROBIOLOGY, Issue 6 2007
Shwan Rachid
Summary Sorangium cellulosum strains produce approximately 50% of the biologically active secondary metabolites known from myxobacteria. These metabolites include several compounds of biotechnological importance such as the epothilones and chivosazols, which, respectively, stabilize the tubulin and actin skeletons of eukaryotic cells. S. cellulosum is characterized by its slow growth rate, and natural products are typically produced in low yield. In this study, biomagnetic bead separation of promoter-binding proteins and subsequent inactivation experiments were employed to identify the chivosazol regulator, ChiR, as a positive regulator of chivosazol biosynthesis in the genome-sequenced strain So ce56. Overexpression of chiR under the control of T7A1 promoter in a merodiploid mutant resulted in fivefold overproduction of chivosazol in a kinetic shake flask experiment, and 2.5-fold overproduction by fermentation. Using quantitative reverse transcription PCR and gel shift experiments employing heterologously expressed ChiR, we have shown that transcription of the chivosazol biosynthetic genes (chiA,chiF) is directly controlled by this protein. In addition, we have demonstrated that ChiR serves as a pleiotropic regulator in S. cellulosum, because mutant strains lack the ability to develop into regular fruiting bodies. [source]

Structure and Biosynthesis of Myxochromides S1,3 in Stigmatella aurantiaca: Evidence for an Iterative Bacterial Type I Polyketide Synthase and for Module Skipping in Nonribosomal Peptide Biosynthesis,

CHEMBIOCHEM, Issue 2 2005
Silke C. Wenzel Dipl.-Chem.
Abstract The myxobacterium Stigmatella aurantiaca DW4/3,1 harbours an astonishing variety of secondary metabolic gene clusters, at least two of which were found by gene inactivation experiments to be connected to the biosynthesis of previously unknown metabolites. In this study, we elucidate the structures of myxochromides S1,3, novel cyclic pentapeptide natural products possessing unsaturated polyketide side chains, and identify the corresponding biosynthetic gene locus, made up of six nonribosomal peptide synthetase modules. By analyzing the deduced substrate specificities of the adenylation domains, it is shown that module 4 is most probably skipped during the biosynthetic process. The polyketide synthase MchA harbours only one module and is presumably responsible for the formation of the variable complete polyketide side chains. These data indicate that MchA is responsible for an unusual iterative polyketide chain assembly. [source]