Home About us Contact
|
Home About us Contact | ||
|
|
||
Bacterial Degradation (bacterial + degradation)
Selected AbstractsShell disease in crustaceans , just chitin recycling gone wrong?ENVIRONMENTAL MICROBIOLOGY, Issue 4 2008Claire L. Vogan Summary The exoskeletons of aquatic crustaceans and other arthropods contain chitin, a biopolymer of ,-(1,4)-linked N -acetylglucosamine together with associated proteins. Despite the vast amounts of chitin within such animals little is found in sediments and open water because microorganisms rapidly degrade this following its loss after moulting or upon the animals' death. Shell disease syndrome is a worldwide disease condition that affects a wide range of crustaceans. It comes about as a result of bacterial degradation of the exoskeleton leading to unsightly lesions and even death if the underlying tissues become infected. There are at least two potential forms of the disease; one that appears to centre around chitin degradation and an additional form termed ,epizootic' shell disease, in which chitin degradation is of less significance. This account reviews our current understanding of the causative agents of this syndrome, assesses the potential economic consequences of the disease, and critically examines whether it is associated with anthropogenic disturbances including pollution. Overall, despite extensive studies during the last few decades, the potential links between faecal, heavy metal and insecticide pollution and shell disease are still unclear. [source] Perchlorate reduction by a novel chemolithoautotrophic, hydrogen-oxidizing bacteriumENVIRONMENTAL MICROBIOLOGY, Issue 10 2002Husen Zhang Summary Water treatment technologies are needed that can remove perchlorate from drinking water without introducing organic chemicals that stimulate bacterial growth in water distribution systems. Hydrogen is an ideal energy source for bacterial degradation of perchlorate as it leaves no organic residue and is sparingly soluble. We describe here the isolation of a perchlorate-respiring, hydrogen-oxidizing bacterium (Dechloromonas sp. strain HZ) that grows with carbon dioxide as sole carbon source. Strain HZ is a Gram-negative, rod-shaped facultative anaerobe that was isolated from a gas-phase anaerobic packed-bed biofilm reactor treating perchlorate-contaminated groundwater. The ability of strain HZ to grow autotrophically with carbon dioxide as the sole carbon source was confirmed by demonstrating that biomass carbon (100.9%) was derived from CO2. Chemolithotrophic growth with hydrogen was coupled with complete reduction of perchlorate (10 mM) to chloride with a maximum doubling time of 8.9 h. Strain HZ also grew using acetate as the electron donor and chlorate, nitrate, or oxygen (but not sulphate) as an electron acceptor. Phylogenetic analysis of the 16S rRNA sequence placed strain HZ in the genus Dechloromonas within the , subgroup of the Proteobacteria. The study of this and other novel perchlorate-reducing bacteria may lead to new, safe technologies for removing perchlorate and other chemical pollutants from drinking water. [source] Stability and detection of ,-pinene oxide in aqueous culture mediumENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 9 2000Kimberly K. Kajihara Abstract Methane consumption by methanotrophic bacteria was previously shown to be temporarily inhibited by ,-pinene. Based on literature considerations, loss of inhibition may be due to bacterial degradation of the monoterpene to ,-pinene oxide, an anticipated metabolite. However, since ,-pinene oxide is unstable in aqueous media, detection of its production by methanotrophs or other bacteria is problematic. Therefore, we used gas chromatography-mass spectrometry analysis to study the chemical breakdown of ,-pinene oxide in various buffer systems (Tris[hydroxymethyl]am inomethane, 3-[N-morpholino]propanesulfonic acid, phosphate; pH 7-9) suitable for bacterial whole-cell and cell-free experiments. In every case, aqueous phase ,-pinene oxide was unstable and its disappearance was accompanied by the appearance of five decomposition products in a characteristic fingerprint that was in part buffer dependent. However, this fingerprint was adequately stable in phosphate buffer such that its appearance could be used to infer the intermediacy of ,-pinene oxide if produced by the bacteria at or near their optimal pH. [source] Complementary pathways of dissolved organic carbon removal pathways in clear-water Amazonian ecosystems: photochemical degradation and bacterial uptakeFEMS MICROBIOLOGY ECOLOGY, Issue 1 2006André M. Amado Abstract Dissolved organic carbon (DOC) photochemical reactions establish important links between DOC and planktonic bacteria. We hypothesize that seasonal changes in DOC quality, related to the flood pulse, drive the effects of light,DOC interactions on uptake by planktonic bacteria uptake in clear-water Amazonian ecosystems. Water samples from two ecosystems (one lake and one stream) were incubated in sunlight during different hydrological periods and were then exposed to bacterial degradation. Photochemical and bacterial degradation were driven by seasonal DOC inputs. Bacterial mineralization was the main degradation pathway of autochthonous DOC in the lake, while allochthonous DOC was more available for photochemical oxidation. We suggest that sunlight enhances the bacterial uptake of refractory DOC but does not alter uptake of labile forms. We also observed a positive relationship between sunlight and bacterial degradation of DOC, instead of competition. We conclude that photochemical reactions and bacteria complementarily degrade the different sources of DOC during the flood pulse in Amazonian clear-water aquatic ecosystems. [source] Expression, purification, crystallization and preliminary X-ray analysis of para -nitrophenol 4-monooxygenase from Pseudomonas putida DLL-E4ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 10 2009Weidong Liu Para -nitrophenol 4-monooxygenase (PnpA) plays an important role in bacterial degradation of para -nitrophenol by oxidative release of the nitro group from the aromatic ring to form p -benzoquinone. In order to understand the structural basis of the function of this enzyme, PnpA was cloned, expressed in Escherichia coli and purified. PnpA was crystallized by the hanging-drop vapour-diffusion technique with PEG 4000 as precipitant. The PnpA crystals belonged to space group P212121, with unit-cell parameters a = 54.47, b = 77.56, c = 209.17,Ĺ, and diffracted to 2.24,Ĺ resolution. [source] Modulation of caspases and their non-apoptotic functions by Legionella pneumophilaCELLULAR MICROBIOLOGY, Issue 2 2010Amal O. Amer Summary Legionella pneumophila has become a model system to decipher the non-apoptotic functions of caspases and their role in immunity. In permissive cells, the L. pneumophila -containing vacuole evades endosomal traffic and is remodelled by the endoplasmic reticulum. Evasion of the endosomes is mediated by the Dot/Icm type IV secretion system. Upon L. pneumophila infection of genetically restrictive cells such as wild-type (WT) C57Bl/6J murine macrophages, flagellin is sensed by the NOD-like receptor Nlrc4 leading to caspase-1 activation by the inflammasome complex. Then, caspase-7 is activated downstream of the Nlrc4 inflammasome, promoting non-apoptotic functions such as L. pneumophila -containing phagosome maturation and bacterial degradation. Interestingly, caspase-3 is activated in permissive cells during early stages of infection. However, caspase-3 activation does not lead to apoptosis until late stages of infection because it is associated with potent Dot/Icm-mediated anti-apoptotic stimuli that render the infected cells resistant to external apoptotic inducers. Therefore, the role of caspase-1 and non-apoptotic functions of executioner caspases are temporally and spatially modulated during infection by L. pneumophila, which determine permissiveness to intracellular bacterial proliferation. This review will examine the novel activation pathways of caspases by L. pneumophila and discuss their role in genetic restriction and permissiveness to infection. [source] Using Rock-Eval 6 pyrolysis for tracking fossil organic carbon in modern environments: implications for the roles of erosion and weatheringEARTH SURFACE PROCESSES AND LANDFORMS, Issue 2 2006Yoann Copard Abstract This work relates to the debate on the fossil organic carbon (FOC) input in modern environments and its possible implication for the carbon cycle, and suggests the use of Rock-Eval 6 pyrolysis as a relevant tool for tracking FOC in such environments. Considering that such a delivery is mainly due to supergene processes affecting the continental surface, we studied organic matter in different reservoirs such as bedrocks, alterites, soils and rivers in two experimental catchments at Draix (Alpes de Haute Provence, France). Samples were subjected to geochemical (Rock-Eval 6 pyrolysis) investigations and artificial bacterial degradations. After comparing the geochemical fingerprint of samples, geochemical markers of FOC were defined and tracked in the different reservoirs. Our results confirm the contribution of FOC in modern soils and rivers and display the various influences of weathering and erosional processes on the fate of FOC during its exchange between these pools. In addition, the contrasting behaviour of these markers upon the supergene processes has also highlighted the refractory or labile characters of the fossil organic matter (FOM). Bedrock to river fluxes, controlled by gully erosion, are characterized by a qualitative and quantitative preservation of FOM. Bedrock to alterite fluxes, governed by chemical weathering, are characterized by FOC mineralization without qualitative changes in deeper alterites. Alterite to soils fluxes, controlled by (bio)chemical weathering, are characterized by strong FOC mineralization and qualitative changes of FOM. Thus weathering and erosional processes induce different FOM evolution and affect the fate of FOC towards the global carbon cycle. In this study, gully erosion would involve maintenance of an ancient sink for the global carbon cycle, while (bio)chemical processes provide a source of CO2. Finally, this study suggests that Rock-Eval 6 pyrolysis can be considered as a relevant tool for tracking FOC in modern environments. Copyright © 2006 John Wiley & Sons, Ltd. [source] | ||||||||||