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961.
Impact of aeration and heme-activated respiration on Lactococcus lactis gene expression: identification of a heme-responsive operon 总被引:1,自引:0,他引:1
Pedersen MB Garrigues C Tuphile K Brun C Vido K Bennedsen M Møllgaard H Gaudu P Gruss A 《Journal of bacteriology》2008,190(14):4903-4911
Lactococcus lactis is a widely used food bacterium mainly characterized for its fermentation metabolism. However, this species undergoes a metabolic shift to respiration when heme is added to an aerobic medium. Respiration results in markedly improved biomass and survival compared to fermentation. Whole-genome microarrays were used to assess changes in L. lactis expression under aerobic and respiratory conditions compared to static growth, i.e., nonaerated. We observed the following. (i) Stress response genes were affected mainly by aerobic fermentation. This result underscores the differences between aerobic fermentation and respiration environments and confirms that respiration growth alleviates oxidative stress. (ii) Functions essential for respiratory metabolism, e.g., genes encoding cytochrome bd oxidase, menaquinone biosynthesis, and heme uptake, are similarly expressed under the three conditions. This indicates that cells are prepared for respiration once O(2) and heme become available. (iii) Expression of only 11 genes distinguishes respiration from both aerobic and static fermentation cultures. Among them, the genes comprising the putative ygfCBA operon are strongly induced by heme regardless of respiration, thus identifying the first heme-responsive operon in lactococci. We give experimental evidence that the ygfCBA genes are involved in heme homeostasis. 相似文献
962.
963.
Alexandra Myari Gerasimos Malandrinos John Plakatouras Nick Hadjiliadis Imre Sóvágó 《Bioinorganic Chemistry and Applications》2003,1(1):99-112
His-Val-His and His-Val-Gly-Asp are two naturally occurring peptide sequences, present at the active site
of Cu,Zn-superoxide dismutase (Cu,Zn-SOD). We have already studied the interaction of His-Val-His=A
(copper binding site) with Cu(II) and of His-Val-Gly-Asp=B (zinc binding site) with Zn(II). As a
continuation of this work and for comparison purposes we have also studied the interaction of Zn(II) with
His-Val-His and Cu(II) with His-Val-Gly-Asp using both potentiometric and spectroscopic methods (visible,
EPR, NMR). The stoichiometry, stability constants and solution structure of the complexes formed have been
determined. Histamine type of coordination is observed for/ZnAH/2+, /ZnA/+, /ZnA2H/+ and/ZnA2/ in acidic pH while deprotonation of coordinated water molecules is observed at higher pH. /CUB/ species is
characterized by the formation of a macrochelate and histamine type coordination. Its stability results in the
suppression of amide deprotonation which occurs at high pH resulting in the formation of the highly distorted
from square planar geometry 4N complex/CuBH-3/3. 相似文献
964.
Helena Guasch Manel Leira Bernard Montuelle Anita Geiszinger Jean Luis Roulier Elisabet Tornés Alexandra Serra 《Hydrobiologia》2009,627(1):143-158
The aim of this study was to elucidate how the spatial scale and the set of variables included influence our ability to detect
the effects of different types of pollution on the biota. Using variance partitioning analysis, we assessed the individual
importance of a set of environmental factors (eutrophication and organic pollution) versus metal level pollution on the community
structure of diatom assemblages at different spatial scales. At regional scale, environmental factors did not explain more
of the variance compared to the watershed study. The results of the watershed scale field survey indicate that diatom community
composition was influenced by low metal concentrations, but this pattern was only observed by the inclusion of biofilm metal
concentration data. We recommend the analysis of metal traces in the water phase and the biota (fluvial biofilms) as well
as the use of the Diffusive Gradient in Thin films (DGT) technique to characterize low metal level pollution in freshwater
systems.
Handling editor: Judit Padisák 相似文献
965.
Mitochondrial Dysfunction and Psychiatric Disorders 总被引:1,自引:0,他引:1
Mitochondrial oxidative phosphorylation is the major ATP-producing pathway, which supplies more than 95% of the total energy
requirement in the cells. Damage to the mitochondrial electron transport chain has been suggested to be an important factor
in the pathogenesis of a range of psychiatric disorders. Tissues with high energy demands, such as the brain, contain a large
number of mitochondria, being therefore more susceptible to reduction of the aerobic metabolism. Mitochondrial dysfunction
results from alterations in biochemical cascade and the damage to the mitochondrial electron transport chain has been suggested
to be an important factor in the pathogenesis of a range of neuropsychiatric disorders, such as bipolar disorder, depression
and schizophrenia. Bipolar disorder is a prevalent psychiatric disorder characterized by alternating episodes of mania and
depression. Recent studies have demonstrated that important enzymes involved in brain energy are altered in bipolar disorder
patients and after amphetamine administration, an animal model of mania. Depressive disorders, including major depression,
are serious and disabling. However, the exact pathophysiology of depression is not clearly understood. Several works have
demonstrated that metabolism is impaired in some animal models of depression, induced by chronic stress, especially the activities
of the complexes of mitochondrial respiratory chain. Schizophrenia is a devastating mental disorder characterized by disturbed
thoughts and perception, alongside cognitive and emotional decline associated with a severe reduction in occupational and
social functioning, and in coping abilities. Alterations of mitochondrial oxidative phosphorylation in schizophrenia have
been reported in several brain regions and also in platelets. Abnormal mitochondrial morphology, size and density have all
been reported in the brains of schizophrenic individuals. Considering that several studies link energy impairment to neuronal
death, neurodegeneration and disease, this review article discusses energy impairment as a mechanism underlying the pathophysiology
of some psychiatric disorders, like bipolar disorder, depression and schizophrenia. 相似文献
966.
Dedman A Sharif-Naeini R Folgering JH Duprat F Patel A Honoré E 《European biophysics journal : EBJ》2009,38(3):293-303
The versatility of neuronal electrical activity is largely conditioned by the expression of different structural and functional
classes of K+ channels. More than 80 genes encoding the main K+ channel alpha subunits have been identified in the human genome. Alternative splicing, heteromultimeric assembly, post-translational
modification and interaction with auxiliary regulatory subunits further increase the molecular and functional diversity of
K+ channels. Mammalian two-pore domain K+ channels (K2P) make up one class of K+ channels along with the inward rectifiers and the voltage- and/or calcium-dependent K+ channels. Each K2P channel subunit is made up of four transmembrane segments and two pore-forming (P) domains, which are arranged in tandem
and function as either homo- or heterodimeric channels. This novel structural arrangement is associated with unusual gating
properties including “background” or “leak” K+ channel activity, in which the channels show constitutive activity at rest. In this review article, we will focus on the
lipid-sensitive mechano-gated K2P channel TREK-1 and will emphasize on the polymodal function of this “unconventional” K+ channel.
EBSA Satellite meeting: Ion channels, Leeds, July 2007. 相似文献
967.
Karreman MA Agronskaia AV Verkleij AJ Cremers FF Gerritsen HC Humbel BM 《Biology of the cell / under the auspices of the European Cell Biology Organization》2009,101(5):287-299
Background information. Treatment of cells with UVC radiation leads to the formation of DNA cross‐links which, if not repaired, can lead to apoptosis. γ‐H2AX and cleaved caspase 3 are proteins formed during UVC‐induced DNA damage and apoptosis respectively. The present study sets out to identify early morphological markers of apoptosis using a new method of correlative microscopy, ILEM (integrated laser electron microscopy). Cleaved caspase 3 and γ‐H2AX were immunofluorescently labelled to mark the cells of interest. These cells were subsequently searched in the fluorescence mode of the ILEM and further analysed at high resolution with TEM (transmission electron microscopy). Results. Following the treatment of HUVECs (human umbilical vein endothelial cells) with UVC radiation, in the majority of the cells γ‐H2AX was formed, whereas only in a subset of cells caspase 3 was activated. In severely damaged cells with high levels of γ‐H2AX a round, electron‐dense nuclear structure was found, which was hitherto not identified in UV‐stressed cells. This structure exists only in nuclei of cells containing cleaved caspase 3 and is present during all stages of the apoptotic process. Energy‐loss imaging showed that the nuclear structure accumulates phosphorus, indicating that it is rich in nucleic acids. Because the nuclear structure did not label for DNA and was not affected by regressive EDTA treatment, it is suggested that the UV‐induced nuclear structure contains a high amount of RNA. Conclusions. Because the UV‐induced nuclear structure was only found in cells labelled for cleaved caspase 3 it is proposed as an electron microscopic marker for all stages of apoptosis. Such a marker will especially facilitate the screening for early apoptotic cells, which lack the well‐known hallmarks of apoptosis within a cell population. It also raises new questions on the mechanisms involved in the UV‐induced apoptotic pathway. 相似文献
968.
Dimitra Kovala-Demertzi Vaso Dokorou Alexandra Primikiri Cristian Silvestru Mavroudis A. Demertzis 《Journal of inorganic biochemistry》2009,103(5):738-744
The complexes [Me2(Meclo)SnOSn(Meclo)Me2]2 (2) and [Ph3Sn(Meclo)] (3) where HMeclo is meclofenamic acid, N-(2,6-dichloro-m-tolylanthranilic acid)], have been prepared and structurally characterized by means of vibrational, 1H and 13C NMR spectroscopies. The crystal structure of complexes (2) and (3) have been determined by X-ray crystallography. Three distannoxane rings are present to the dimeric tetraorganodistannoxane of planar ladder arrangement of (2). The structure is centro symmetric and features a central rhombus Sn2O2 unit two additional tin atoms linked at the oxygen atoms. Five- and six-coordinated tin centers are present in the dimer distannoxane. X-ray analysis of (3) revealed a penta-coordinated structure containing Ph3Sn coordinated to the chelated carboxylato group. The polar imino hydrogen atom participates in intra-molecular hydrogen bonds. Complexes (2) and (3) are self-assembled via π → π, C-H-π, stacking interactions and intra-molecular hydrogen bonds. Meclofenamic acid and [Ph3Sn(Meclo)] have been evaluated for antiproliferative activity in vitro against three human cancer cell lines: MCF-7 (human breast cancer cell line), T24 (bladder cancer cell line), A-549 (non-small cell lung carcinoma) and a mouse L-929 (a fibroblast-like cell line cloned from strain L). The [Ph3Sn(Meclo)] complex exhibited high cytotoxic activity against all the cancer cell lines. Meclofenamic and [Ph3Sn(Meclo)] were tested for anti-mycobacterial activity against Mycobacterium tuberculosis H37Rv. The [Ph3Sn(Meclo)] complex was found to be a promising anti-mycobacterial lead compound, displaying high activity against M. tuberculosis H37Rv. 相似文献
969.
We examine the conditions necessary for the emergence of complex dynamic behavior in systems of microbial competition. In particular, we study the effect of spatial heterogeneity and substrate-inhibition on the dynamics of such a system. This is accomplished through the study of a mathematical model of two microbial populations competing for a single nutrient in a configuration of two interconnected chemostats. Microbial growth is assumed to follow substrate-inhibited kinetics for both species. Such a system with sterile feed has been shown in a previous work to exhibit stable periodic states. In the present work we study the system for the case of non-sterile feed, i.e., when the two species are present in the feed of the chemostats. The analysis is done by numerical bifurcation theory methods. We demonstrate that, in addition to periodic states, the system possesses stable quasi-periodic states resulting from Neimark-Sacker bifurcations of limit cycles. Also, periodic states may undergo successive period doublings leading to periodic states of increasing period and indicating that chaotic states might be possible. Multistability is also observed, consisting in the coexistence of several stable steady states and possibly stable periodic or quasi-periodic states for given operating conditions. It appears that substrate-inhibition, spatial heterogeneity and presence of microorganisms in the inflow are all necessary conditions for complex dynamics to arise in a microbial system of pure and simple competition. 相似文献
970.
Katja Fennel Damian Brady Dominic DiToro Robinson W. Fulweiler Wayne S. Gardner Anne Giblin Mark J. McCarthy Alexandra Rao Sybil Seitzinger Marie Thouvenot-Korppoo Craig Tobias 《Biogeochemistry》2009,93(1-2):159-178
Sediment denitrification is a major pathway of fixed nitrogen loss from aquatic systems. Due to technical difficulties in measuring this process and its spatial and temporal variability, estimates of local, regional and global denitrification have to rely on a combination of measurements and models. Here we review approaches to describing denitrification in aquatic sediments, ranging from mechanistic diagenetic models to empirical parameterizations of nitrogen fluxes across the sediment-water interface. We also present a compilation of denitrification measurements and ancillary data for different aquatic systems, ranging from freshwater to marine. Based on this data compilation we reevaluate published parameterizations of denitrification. We recommend that future models of denitrification use (1) a combination of mechanistic diagenetic models and measurements where bottom-waters are temporally hypoxic or anoxic, and (2) the much simpler correlations between denitrification and sediment oxygen consumption for oxic bottom waters. For our data set, inclusion of bottom water oxygen and nitrate concentrations in a multivariate regression did not improve the statistical fit. 相似文献