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1.
Background
Photorhabdus are Gram negative entomopathogenic bacteria that also have a mutualistic association with nematodes from the family Heterorhabditis. An essential part of this symbiosis is the ability of the bacterium to colonize the gut of the freeliving form of the nematode
called the infective juvenile (IJ). Although the colonization process (also called transmission) has been described phenomonologically
very little is known about the underlying molecular mechanisms. Therefore, in this study, we were interested in identifying
genes in Photorhabdus that are important for IJ colonization. 相似文献
2.
Iron has a central role in bioleaching and biooxidation processes. Fe 2+ produced in the dissolution of sulfidic minerals is re-oxidized to Fe 3+ mostly by biological action in acid bioleaching processes. To control the concentration of iron in solution, it is important to precipitate the excess as part of the process circuit. In this study, a bioprocess was developed based on a fluidized-bed reactor (FBR) for Fe 2+ oxidation coupled with a gravity settler for precipitative removal of ferric iron. Biological iron oxidation and partial removal of iron by precipitation from a barren heap leaching solution was optimized in relation to the performance and retention time ( τFBR) of the FBR. The biofilm in the FBR was dominated by Leptospirillum ferriphilum and “ Ferromicrobium acidiphilum.” The FBR was operated at pH 2.0 ± 0.2 and at 37 °C. The feed was a barren leach solution following metal recovery, with all iron in the ferrous form. 98–99% of the Fe 2+ in the barren heap leaching solution was oxidized in the FBR at loading rates below 10 g Fe 2+/L h ( τFBR of 1 h). The optimal performance with the oxidation rate of 8.2 g Fe 2+/L h was achieved at τFBR of 1 h. Below the τFBR of 1 h the oxygen mass transfer from air to liquid limited the iron oxidation rate. The precipitation of ferric iron ranged from 5% to 40%. The concurrent Fe 2+ oxidation and partial precipitative iron removal was maximized at τFBR of 1.5 h, with Fe 2+ oxidation rate of 5.1 g Fe 2+/L h and Fe 3+ precipitation rate of 25 mg Fe 3+/L h, which corresponded to 37% iron removal. The precipitates had good settling properties as indicated by the sludge volume indices of 3–15 mL/g but this step needs additional characterization of the properties of the solids and optimization to maximize the precipitation and to manage sludge disposal. 相似文献
3.
Background The Streptococcus pyogenes or Group A Streptococcus (GAS) genome encodes three ABC transporters, namely, FtsABCD, MtsABC, and HtsABC, which share homology with iron transporters.
MtsABC and HtsABC are believed to take up ferric (Fe 3+) and manganese ions and heme, respectively, while the specificity of FtsABCD is unknown. 相似文献
4.
Competitive binding of Fe 3+, Cr 3+, and Ni 2+ to transferrin (Tf) was investigated at various physiological iron to Tf concentration ratios. Loading percentages for these
metal ions are based on a two M
n+ to one Tf (i.e., 100% loading) stoichiometry and were determined using a particle beam/hollow cathode–optical emission spectroscopy
(PB/HC-OES) method. Serum iron concentrations typically found in normal, iron-deficient, iron-deficient from chronic disease,
iron-deficient from inflammation, and iron-overload conditions were used to determine the effects of iron concentration on
iron loading into Tf. The PB/HC-OES method allows the monitoring of metal ions in competition with Fe 3+ for Tf binding. Iron-overload concentrations impeded the ability of chromium (15.0 μM) or nickel (10.3 μM) to load completely
into Tf. Low Fe 3+ uptake by Tf under iron-deficient or chronic disease iron concentrations limited Ni 2+ loading into Tf. Competitive binding kinetic studies were performed with Fe 3+, Cr 3+, and Ni 2+ to determine percentages of metal ion uptake into Tf as a function of time. The initial rates of Fe 3+ loading increased in the presence of nickel or chromium, with maximal Fe 3+ loading into Tf in all cases reaching approximately 24%. Addition of Cr 3+ to 50% preloaded Fe 3+–Tf showed that excess chromium (15.0 μM) displaced roughly 13% of Fe 3+ from Tf, resulting in 7.6 ± 1.3% Cr 3+ loading of Tf. The PB/HC-OES method provides the ability to monitor multiple metal ions competing for Tf binding and will
help to understand metal competition for Tf binding. 相似文献
5.
Background Multifunctional magnetic nanoparticles are important class of materials in the field of nanobiotechnology, as it is an emerging
area of research for material science and molecular biology researchers. One of the various methods to obtain multifunctional
nanomaterials, molecular functionalization by attaching organic functional groups to nanomagnetic materials is an important
technique. Recently, functionalized magnetic nanoparticles have been demonstrated to be useful in isolation/detection of dangerous
pathogens (bacteria/viruses) for human life. Iron (Fe) based material especially FePt is used in the isolation of ultralow
concentrations (< 10 2 cfu/ml) of bacteria in less time and it has been demonstrated that van-FePt may be used as an alternative fast detection
technique with respect to conventional polymerase chain reaction (PCR) method. However, still further improved demonstrations
are necessary with interest to biocompatibility and green chemistry. Herein, we report the synthesis of Fe 3O 4 nanoparticles by template medication and its application for the detection/isolation of S. aureus bacteria. 相似文献
6.
Background The PmrAB (BasSR) two-component regulatory system is required for Salmonella typhimurium virulence. PmrAB-controlled modifications of the lipopolysaccharide (LPS) layer confer resistance to cationic antibiotic
polypeptides, which may allow bacteria to survive within macrophages. The PmrAB system also confers resistance to Fe 3+-mediated killing. New targets of the system have recently been discovered that seem not to have a role in the well-described
functions of PmrAB, suggesting that the PmrAB-dependent regulon might contain additional, unidentified targets. 相似文献
7.
To increase the antimicrobial activities of chitosan, chitosan nanoparticles loaded with Fe 2+ or Fe 3+ were prepared by surfactant‐assisted chitosan chelating Fe 2+, Fe 3+ and ionic gelation chitosan. Their chelating rates were determined by spectrophotometry. The particle sizes and zeta potentials of chitosan nanoparticles loaded with Fe 2+ or Fe 3+ were measured by size and zeta potential analysis. The nanoparticles antimicrobial activities were evaluated by different concentration against Escherichia coli, Staphylococcus aureus, Candida albicans in vitro. Results showed that the mean diameter of chitosan nanoparticles loaded with Fe 2+ or Fe 3+ were 206.4 and 195.2 nm, respectively. Their zeta potentials were +28.82 and +28.26 mV, respectively. The chelating rate of chitosan nanoparticles loaded with Fe 2+ was greatly higher than with Fe 3+. Their antimicrobial activity was showed greatly higher at lower concentrations compared to chitosan, and the antibacterial effect of chitosan nanoparticles loaded with Fe 2+ or Fe 3+ was preliminary observed. 相似文献
8.
Background Differentiating Dictyostelium discoideum amoebae respond upon cAMP-stimulation with an increase in the cytosolic free Ca 2+ concentration ([Ca 2+] i) that is composed of liberation of stored Ca 2+ and extracellular Ca 2+-influx. In this study we investigated whether intracellular cAMP is involved in the control of [Ca 2+] i. 相似文献
9.
Ferric binding protein, Fbp, serves an essential biological function in shuttling naked (hydrated) Fe 3+ across the periplasmic space of many Gram-negative bacteria. In this process, iron must be released at the cytoplasmic membrane to a permease. How iron is released from Fbp has yet to be resolved. Consequently, understanding the dynamics of iron release from Fbp is of both biological and chemical interest. Fbp requires an exogenous anion, e.g. phosphate when isolated from cell lysates, for tight iron sequestration. To address the role of exogenous anion identity and lability on Fe aq
3+ dissociation from Fbp, the kinetics of PO 4
3– exchange in Fe 3+
nFbp(PO 4) ( nFbp=recombinant Fbp from Neisseria meningitidis) were investigated by dynamic 31P NMR and the kinetics of Fe 3+ dissociation from Fe 3+
nFbp(X) (X=PO 4
3–, citrate anion) were investigated by stopped-flow pH-jump measurements. We justify the use of non-physiological low-pH conditions because a high [H +] will drive the Fe aq
3+ dissociation reaction to completion without using competing chelators, whose presence may complicate or influence the dissociation mechanism. For perspective, these studies of nFbp (which has been referred to as a bacterial transferrin) are compared to new and previously published kinetic and thermodynamic data for mammalian transferrin. Significantly, we address the lability of the Fe 3+ coordination shell in nFbp, Fe 3+
nFbp(X) (X=PO 4
3–, citrate), with respect to exogenous anion (X
n–) exchange and dissociation, and ultimately complete dissociation of the protein to yield naked (hydrated) Fe aq
3+. These findings are a first step in understanding the process of iron donation to the bacterial permease for transport across the cytoplasmic membrane.Electronic Supplementary Material Supplementary material is available in the online version of this article at . Abbreviations DTPP
diethylenetriaminepenta(methylenephosphonic acid)
- Fbp
ferric binding protein
- H 3cit
citric acid
-
hFbp
Fbp from Haemophilus influenzae
- H 2ox
oxalic acid
-
hTf
human serum transferrin
- 3,4-LICAMS
N, N, N-tris(5-sulfo-2,3-dihydroxybenzoyl)-1,5,10-triazadecane
-
nFbp
recombinant Fbp from Neisseria meningitidis
- NTA
nitrilotriacetic acid
- TRENSOX
tris[2-aminoethyl(8-hydroxyquinoline-5-sulfonato-7-carbonyl)]amine 相似文献
10.
Oxidative reactions can result in the formation of electronically excited species that undergo radiative decay depending on electronic transition from the excited state to the ground state with subsequent ultra‐weak photon emission (UPE). We investigated the UPE from the Fe 2+–EDTA (ethylenediaminetetraacetic acid)–AA (ascorbic acid)–H 2O 2 (hydrogen peroxide) system with a multitube luminometer (Peltier‐cooled photon counter, spectral range 380–630 nm). The UPE, of 92.6 μmol/L Fe 2+, 185.2 μmol/L EDTA, 472 μmol/L AA, 2.6 mmol/L H 2O 2, reached 1217 ± 118 relative light units during 2 min measurement and was about two times higher ( P < 0.001) than the UPE of incomplete systems (Fe 2+–AA–H 2O 2, Fe 2+–EDTA–H 2O 2, AA–H 2O 2) and medium alone. Substitution of Fe 2+ with Cr 2+, Co 2+, Mn 2+ or Cu 2+ as well as of EDTA with EGTA (ethylene glycol‐bis(β‐aminoethyl ether)‐ N, N, N′, N′‐tetraacetic acid) or citrate powerfully inhibited UPE. Experiments with scavengers of reactive oxygen species (dimethyl sulfoxide, mannitol, sodium azide, superoxide dismutase) revealed the dependence of UPE only on hydroxyl radicals. Dimethyl sulfoxide at the concentration of 0.74 mmol/L inhibited UPE by 79 ± 4%. Plant phenolics (ferulic, chlorogenic and caffec acids) at the concentration of 870 μmol/L strongly enhanced UPE by 5‐, 13.9‐ and 46.8‐times ( P < 0.001), respectively. It is suggested that augmentation of UPE from Fe 2+–EDTA–AA–H 2O 2 system can be applied for detection of these phytochemicals. 相似文献
11.
Background Mitochondria are dynamic organelles that move along actin filaments, and serve as calcium stores in plant cells. The positioning
and dynamics of mitochondria depend on membrane-cytoskeleton interactions, but it is not clear whether microfilament cytoskeleton
has a direct effect on mitochondrial function and Ca 2+ storage. Therefore, we designed a series of experiments to clarify the effects of actin filaments on mitochondrial Ca 2+ storage, cytoplasmic Ca 2+ concentration ([Ca 2+] c), and the interaction between mitochondrial Ca 2+ and cytoplasmic Ca 2+ in Arabidopsis root hairs. 相似文献
12.
Background Stimulation of Dictyostelium discoideum with cAMP evokes an elevation of the cytosolic free Ca 2+ concentration ([Ca 2+] i). The [Ca 2+] i-change is composed of liberation of stored Ca 2+ and extracellular Ca 2+-entry. The significance of the [Ca 2+] i-transient for chemotaxis is under debate. Abolition of chemotactic orientation and migration by Ca 2+-buffers in the cytosol indicates that a [Ca 2+] i-increase is required for chemotaxis. Yet, the iplA
- mutant disrupted in a gene bearing similarity to IP 3-receptors of higher eukaryotes aggregates despite the absence of a cAMP-induced [Ca 2+] i-transient which favours the view that [Ca 2+] i-changes are insignificant for chemotaxis. 相似文献
13.
This study investigates the impacts of influent ammonium concentrations on the microbial community in immobilized heterotrophic ammonium removal system. Klebsiella sp. FC61, the immobilized species, has the ability to perform simultaneous ammonium removal and Fe3+ reduction. It was found that average ammonium removal rate decreased from 0.308 to 0.157 mg/L/h, as the influent NH4
+-N was reduced from 20 to 10 mg/L. Meanwhile, at a total Fe3+ concentration of 20 mg/L, the average Fe3+ reduction removal efficiency and rate decreased from 44.61% and 0.18 mg/L/h, to 27.10% and 0.11 mg/L/h, respectively. High-throughput sequencing was used to observe microbial communities in bioreactor Samples B1, B2, and B3, after exposure to different influent NH4
+-N conditions. Results show that higher influent NH4
+-N concentrations increased microbial richness and diversity and that Klebsiella sp. FC61 play a functional role in the simultaneous removal of NH4
+-N and Fe3+ reduction in bioreactor systems. 相似文献
14.
Aims The aim of this study was to clarify the effects of homologous and heterologous extracellular DNAs (eDNAs) and histone‐like DNA‐binding protein (HLP) on Streptococcus intermedius biofilm development and rigidity. Methods and Results Formed biofilm mass was measured with 0·1% crystal violet staining method and observed with a scanning electron microscope. The localizations of eDNA and extracellular HLP (eHLP) in formed biofilm were detected by staining with 7‐hydoxyl‐9H‐(1,3‐dichloro‐9,9‐dimethylacridin‐2‐one) and anti‐HLP antibody without fixation, respectively. DNase I treatment (200 U ml ?1) markedly decreased biofilm formation and cell density in biofilms. Colocalization of eHLP and eDNA in biofilm was confirmed. The addition of eDNA (up to 1 μg ml ?1) purified from Strep. intermedius, other Gram‐positive bacteria, Gram‐negative bacteria, or human KB cells into the Strep. intermedius culture increased the biofilm mass of all tested strains of Strep. intermedius, wild‐type, HLP‐downregulated strain and control strains. In contrast, the addition of eDNA (>1 μg ml ?1) decreased the biofilm mass of all Strep. intermedius strains. Conclusions These findings demonstrated that eDNA and eHLP play crucial roles in biofilm development and its rigidity. Significance and Impact of the Study eDNA‐ and HLP‐targeting strategies may be applicable to novel treatments for bacterial biofilm‐related infectious diseases. 相似文献
15.
Background Associated with appropriate crop and soil management, inoculation of legumes with microbial biofertilizers can improve food
legume yield and soil fertility and reduce pollution by inorganic fertilizers. Rhizospheric bacteria are subjected to osmotic
stress imposed by drought and/or NaCl, two abiotic constraints frequently found in semi-arid lands. Osmostress response in
bacteria involves the accumulation of small organic compounds called compatible solutes. Whereas most studies on rhizobial
osmoadaptation have focussed on the model species Sinorhizobium meliloti, little is known on the osmoadaptive mechanisms used by native rhizobia, which are good sources of inoculants. In this work,
we investigated the synthesis and accumulations of compatible solutes by four rhizobial strains isolated from root nodules
of Phaseolus vulgaris in Tunisia, as well as by the reference strain Rhizobium tropici CIAT 899 T. 相似文献
17.
The degradation of fluoroacetate by microorganisms has been established for some time, although only a handful of dehalogenases
capable of hydrolyzing the stable C–F bond have been studied. Pseudomonas fluorescens DSM 8341 was originally isolated from soil and readily degrades fluoroacetate, thus it was thought that its dehalogenase
might have some desirable properties. The enzyme was purified from cell-free extracts and characterised: it is a monomer of
32,500 Da, with a pH optimum of 8 and is stable between pH 4 and 10; its activity is stimulated by some metal ions (Mg 2+, Mn 2+ and Fe 3+), but inhibited by others (Hg 2+, Ag 2+). The enzyme is specific for fluoroacetate, and the K
m
for this substrate (0.68 mM) is the lowest determined for enzymes of this type that have been investigated to date. 相似文献
18.
Aims To investigate community shifts of amoA‐encoding archaea (AEA) and ammonia‐oxidizing bacteria (AOB) in biofilter under nitrogen accumulation process. Methods and Results A laboratory‐scale rockwool biofilter with an irrigated water circulation system was operated for 436 days with ammonia loading rates of 49–63 NH 3 g m ?3 day ?1. The AEA and AOB communities were investigated by denaturing gradient gel electrophoresis, sequencing and real‐time PCR analysis based on amoA genes. The results indicated that changes in abundance and community compositions occurred in a different manner between archaeal and bacterial amoA during the operation. However, both microbial community structures mainly varied when free ammonia (FA) concentrations in circulation water were increasing, which caused a temporal decline in reactor performance. Dominant amoA sequences after this transition were related to Thaumarchaeotal Group I.1b, Nitrosomonas europaea lineages and one subcluster within Nitrosospira sp. cluster 3, for archaea and bacteria, respectively. Conclusions The specific FA in circulation water seems to be the important factor, which relates to the AOB and AEA community shifts in the biofilter besides ammonium and pH. Significance and Impact of the Study One of the key factors for regulating AEA and AOB communities was proposed that is useful for optimizing biofiltration technology. 相似文献
19.
Of various metal ions (Ca 2+, Cr 3+, Cu 2+, Fe 2+, Mg 2+, Mn 2+, Ni 2+ and Zn 2+) added to the culture medium of Agrobacterium tumefaciens at 1 mM, only Ca 2+ increased Coenzyme Q10 (CoQ 10) content in cells without the inhibition of cell growth. In a pH-stat fed-batch culture, supplementation with 40 mM of CaCO 3 increased the specific CoQ 10 content and oxidative stress by 22.4 and 48%, respectively. Also, the effect of Ca 2+ on the increase of CoQ 10 content was successfully verified in a pilot-scale (300 L) fermentor. In this study, the increased oxidative stress in A. tumefaciens culture by the supplementation of Ca 2+ is hypothesized to stimulate the increase of specific CoQ 10 content in order to protect the membrane against lipid peroxidation. Our results improve the understanding of Ca 2+ effect on CoQ 10 biosynthesis in A. tumefaciens and should contribute to better industrial production of CoQ 10 by biological processes. 相似文献
20.
Mammalian cells contain a pool of iron that is not strongly bound to proteins, which can be detected with fluorescent chelating
probes. The cellular ligands of this biologically important “chelatable”, “labile” or “transit” iron are not known. Proposed
ligands are problematic, because they are saturated by magnesium under cellular conditions and/or because they are not “safe”,
i.e. they allow iron to catalyse hydroxyl radical formation. Among small cellular molecules, certain inositol phosphates (Ins Ps) excel at complexing Fe 3+ in such a “safe” manner in vitro. However, we previously calculated that the most abundant Ins P, inositol hexakisphosphate, cannot interact with Fe 3+ in the presence of cellular concentrations of Mg 2+. In this work, we study the metal complexation behaviour of inositol 1,2,3-trisphosphate [Ins(1,2,3) P
3], a cellular constituent of unknown function and the simplest Ins P to display high-affinity, “safe”, iron complexation. We report thermodynamic constants for the interaction of Ins(1,2,3) P
3 with Na +, K +, Mg 2+, Ca 2+, Cu 2+, Fe 2+ and Fe 3+. Our calculations indicate that Ins(1,2,3) P
3 can be expected to complex all available Fe 3+ in a quantitative, 1:1 reaction, both in cytosol/nucleus and in acidic compartments, in which an important labile iron subpool
is thought to exist. In addition, we calculate that the fluorescent iron probe calcein would strip Fe 3+ from Ins(1,2,3) P
3 under cellular conditions, and hence labile iron detected using this probe may include iron bound to Ins(1,2,3) P
3. Therefore Ins(1,2,3) P
3 is the first viable proposal for a transit iron ligand.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
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