Search results for "bacteria."
showing 10 items of 4757 documents
A role for Rho in receptor- and G protein-stimulated phospholipase C Reduction in phosphatidylinositol 4,5-bisphosphate by Clostridium difficile toxi…
1996
Receptors coupled to heterotrimeric guanine nucleotide-binding proteins (G proteins) activate phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2)-hydrolyzing phospholipase C (PLC) enzymes by activated alpha of free beta gamma subunits of the relevant G proteins. To study whether low molecular weight G proteins of the Rho family are involved in receptor signaling to PLC, we examined the effect of Clostridium difficile toxin B, which glucosylates and thereby inactivates Rho proteins, on the regulation of PLC activity in human embryonic kidney (HEK) cells stably expressing the m3 muscarinic acetylcholine receptor (mAChR) subtype. Toxin B treatment of HEK cells did not affect basal PLC activi…
Restoration of Clostridium difficile toxin-B-inhibited phospholipase D by phosphatidylinositol 4,5-bisphosphate.
1996
Receptor signalling to phospholipase D (PLD) in human embryonic kidney (HEK) cells stably expressing the m3 muscarinic acetylcholine receptor apparently involves Rho proteins. Since phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] has been recognized as an essential cofactor for PLD activity and since activated Rho proteins have been reported to stimulate the synthesis of PtdIns(4,5)P2, we studied whether in HEK cells PLD activity is regulated by PtdIns(4,5)P2 and, in particular, whether PtdIns(4,5)P2 can restore PLD activity inhibited by Clostridium difficile toxin B, which inactivates Rho proteins. Addition of MgATP to permeabilized HEK cells increased basal PLD activity and potentia…
Control of cellular phosphatidylinositol 4,5-bisphosphate levels by adhesion signals and Rho GTPases in NIH 3T3 fibroblasts
2000
The involvement of small GTPases of the Rho family in the control of phosphoinositide metabolism by adhesion signals was examined in NIH 3T3 fibroblasts. Abrogation of adhesion signals by detachment of cells from their substratum resulted in a time-dependent decrease in the cellular level of PtdIns(4,5)P2 by approximately 50%. This effect could be mimicked by treatment of adherent cells with Clostridium difficile toxin B and toxin B-1470, which inhibit specific subsets of Rho and Ras GTPases. Detachment of cells that had been pretreated with the clostridial toxins did not cause a further reduction in PtdIns(4,5)P2 levels, suggesting that the target GTPases are integrated into the control of…
The ability of soil-borne fungi to degrade organophosphonate carbon-to-phosphorus bonds
1997
The ability of a wide variety of soil-borne fungal strains to degrade four structurally different compounds containing P-C bonds, namely the naturally occurring amino acid ciliatine, the popular herbicide glyphosate, phosphonoacetic acid and 2-amino-3-phosphonopropionic acid, was studied in order to show that soil fungi may play an important role in the biodegradation of organophosphonates. Most of the strains appeared to utilize ciliatine as the sole source of phosphorus for growth. Only a limited number of strains were able to grow on the other phosphonates used in this work. The strains of Trichoderma harzianum, Scopulariopsis sp. and Aspergillus niger chosen for more detailed study show…
Enhanced chemiluminescent determination of chloramphenicol and related nitro compounds by ‘on-line’ photochemical reaction
2000
The viability of tandem photochemical reaction-chemiluminescence detection was studied for a heterogeneous family of nitro compounds using chloramphenicol as a test substance. The 'on-line' chemical photodegradation of chloramphenicol was performed in a flow injection assembly by using a photoreactor consisting of a 725 cm x 0.5 mm id piece of PTFE tubing coiled around an 8 W low-pressure mercury lamp. Photodegraded chloramphenicol was detected by oxidizing photo-fragments from the parent compound and their subsequent reaction with a luminol-Co(II) system. The calibration graph was linear up to 3 x 10(-5) mol l-1 chloramphenicol, the limit of detection was 3 x 10(-9) mol l-1, the relative s…
Through space singlet energy transfers in the light harvesting systems and cofacial bisporphyrin dyads
2010
Recent discoveries from our research groups on the photophysics of a few cofacial bisporphyrin dyads for through space singlet and triplet energy transfers raised several important investigations about the mechanism of energy transfers and energy migration in light-harvesting devices, notably LH II, in the heavily investigated purple photosynthetic bacteria. The key feature is that for face-to-face and slipped dyads with controlled structure using rigid spacers or spacers with limited flexibilities, our fastest rates for singlet energy transfer are in the 10 × 109 s -1 (i.e. 100 ps time scale) for donor-acceptor distances of ~3.5–3.6 Å. The time scale for energy transfers between different…
Comments on the through space singlet energy transfers and energy migration (exciton) in the light harvesting systems
2008
Recent findings on the photophysical investigations of several cofacial bisporphyrin dyads for through space singlet and triplet energy transfers raised several serious questions about the mechanism of the energy transfers and energy migration in the light harvesting devices, notably LH II, in the heavily studied purple photosynthetic bacteria. The key issue is that for simple cofacial or slipped dyads with controlled geometry using rigid spacers or spacers with limited flexibilities, the fastest possible rates for singlet energy transfer for three examples are in the 10 x 10(9)s(-1) (i.e. just in the 100 ps time scale) for donor-acceptor distances approaching 3.5-3.6 A. The reported time s…
Quantum Chemical Simulations of Excited-State Absorption Spectra of Photosynthetic Bacterial Reaction Center and Antenna Complexes
2011
The semiempirical ZINDO/S CIS configuration interaction method has been used to study the ground- and excited-state absorption spectra of wild type and heterodimer M202HL reaction centers from purple bacterium Rhodobacter sphaeroides as well as of peripheral LH2 and LH3 light harvesting complexes from purple bacterium Rhodopseudomonas acidophila. The calculations well reproduce the experimentally observed excited-state absorption spectra between 1000 and 17,000 cm(-1), despite the necessarily limited number of chromophores and protein subunits involved in the calculations. The electron density analysis reveals that the charge transfer between adjacent chromophores dominates the excited-stat…
Shedding light on biogas: Phototrophic biofilms in anaerobic digesters hold potential for improved biogas production
2019
Conventional anaerobic digesters intended for the production of biogas usually operate in complete darkness. Therefore, little is known about the effect of light on their microbial communities. In the present work, 16S rRNA gene amplicon Nanopore sequencing and shotgun metagenomic sequencing were used to study the taxonomic and functional structure of the microbial community forming a biofilm on the inner wall of a laboratory-scale transparent anaerobic biodigester illuminated with natural sunlight. The biofilm was composed of microorganisms involved in the four metabolic processes needed for biogas production, and it was surprisingly rich in Rhodopseudomonas faecalis, a versatile bacterium…
Chloroplast DNA evidence for introgression and long distance dispersal in the desert annualSenecio flavus (Asteraceae)
1995
Phylogenetic analysis of chloroplast DNA (cpDNA) restriction site variation supports a close genetic relationship between the Southwest AsianSenecio flavus subsp.breviflorus and the North AmericanS. mohavensis. The intercontinental disjunct distribution of these two desert annuals may have originated via long distance dispersal. The chloroplast genomes of the Southern and North AfricanS. flavus subsp.flavus and subsp.breviflorus differ by at least ten restriction sites, while at most two restriction sites differentiate the cpDNA genomes of subsp.breviflorus and the outgroupS. squalidus. This suggests that the cpDNA genome ofS. flavus subsp.breviflorus may have resulted from introgression an…