Attenuation of metal toxicity by frankial siderophores
27 Jul 2010-Toxicological & Environmental Chemistry (Taylor & Francis Group)-Vol. 92, Iss: 7, pp 1339-1346
TL;DR: Siderophores minimize the metal-induced inhibition of growth in Frankia, likely due to regulation of nutritional imbalances and metabolic processes during adaptation towards metal stress and/or metal toxicity.
Abstract: In order to investigate the role of frankial siderophores in minimizing metal toxicity, Frankia strains were grown at different concentrations of Mg2+, Cu2+, and Zn2+. Growth was observed up to 500 µmol L−1 Mg2+, 10 µmol L−1 Cu2+, and 10 µmol L−1 Zn2+ while the maxima were at 200 µmol L−1 Mg2+, 1 µmol L−1 Cu2+, and 1 µmol L−1 Zn2+. The siderophore production was increased up to 500 µmol L−1 Mg2+, 10 µmol L−1 Cu2+, 100 µmol L−1 (hydroxamate type), and 200 µmol L−1 (catecholate type) Zn2+ while maximum production was found at Mg2+ (200 µmol L−1), Cu2+ (10 µmol L−1), and Zn2+ (10 µmol L−1). The results suggested that the growth was protected at higher concentrations of Mg2+ (up to 500 µmol L−1), Cu2+ (10 µmol L−1), and Zn2+ (10 µmol L−1), possibly due to enhanced siderophore production. Thus, siderophores minimize the metal-induced inhibition of growth in Frankia, likely due to regulation of nutritional imbalances and metabolic processes during adaptation towards metal stress and/or metal toxicity.
Citations
More filters
[...]
TL;DR: Each strain had a unique combination of metal import, binding, modification, and export genes that explain differences in patterns of metal resistance between strains.
Abstract: Frankia are actinobacteria that form a symbiotic nitrogen-fixing association with actinorhizal plants, and play a significant role in actinorhizal plant colonization of metal contaminated areas. Many Frankia strains are known to be resistant to several toxic metals and metalloids including Pb2+, Al+3, SeO2, Cu2+, AsO4, and Zn2+. With the availability of eight Frankia genome databases, comparative genomics approaches employing phylogeny, amino acid composition analysis, and synteny were used to identify metal homeostasis mechanisms in eight Frankia strains. Characterized genes from the literature and a meta-analysis of 18 heavy metal gene microarray studies were used for comparison. Unlike most bacteria, Frankia utilize all of the essential trace elements (Ni, Co, Cu, Se, Mo, B, Zn, Fe, and Mn) and have a comparatively high percentage of metalloproteins, particularly in the more metal resistant strains. Cation diffusion facilitators, being one of the few known metal resistance mechanisms found in the Frankia genomes, were strong candidates for general divalent metal resistance in all of the Frankia strains. Gene duplication and amino acid substitutions that enhanced the metal affinity of CopA and CopCD proteins may be responsible for the copper resistance found in some Frankia strains. CopA and a new potential metal transporter, DUF347, may be involved in the particularly high lead tolerance in Frankia. Selenite resistance involved an alternate sulfur importer (CysPUWA) that prevents sulfur starvation, and reductases to produce elemental selenium. The pattern of arsenate, but not arsenite, resistance was achieved by Frankia using the novel arsenite exporter (AqpS) previously identified in the nitrogen-fixing plant symbiont Sinorhizobium meliloti. Based on the presence of multiple tellurite resistance factors, a new metal resistance (tellurite) was identified and confirmed in Frankia. Each strain had a unique combination of metal import, binding, modification, and export genes that explain differences in patterns of metal resistance between strains. Frankia has achieved similar levels of metal and metalloid resistance as bacteria from highly metal-contaminated sites. From a bioremediation standpoint, it is important to understand mechanisms that allow the endosymbiont to survive and infect actinorhizal plants in metal contaminated soils.
18 citations
Cites background from "Attenuation of metal toxicity by fr..."
[...]
[...]
TL;DR: The results suggest that the siderophore produced by Anabaena oryzae can act as a biological sequestering agent for the mitigation of cadmium metal ions from the paddy fields to improve crop productivity.
Abstract: The efficacy of dihydroxamate siderophore in attenuation/mitigation of cadmium toxicity, an optimum level of cadmium under which cyanobacterium can grow and produce siderophore, complexation behaviour of cadmium and siderophore and kinetics of complexation along with in silico analysis have been investigated in paddy field cyanobacterium Anabaena oryzae under iron replete and deplete conditions. Results showed that cadmium concentration as 1.0 μM is optimum for growth as well as siderophore production in iron replete and deplete culture conditions. The complexation between cadmium–siderophore was evident in spectral scan. Kinetic studies as well as in silico docking analysis indicate that like iron, cadmium also forms a thermodynamically stable complex with siderophore. Thus our results suggest that the siderophore produced by Anabaena oryzae can act as a biological sequestering agent for the mitigation of cadmium metal ions from the paddy fields to improve crop productivity.
17 citations
[...]
TL;DR: Results suggest that the physiological approaches i.e., nitrogenase activity, glutamine synthetase activity and ammonia excretion are strain specific and might be helpful in rapid identification, in designing the marker for the specific strains as well as in improving nitrogen fixation in agroforestry.
Abstract: Different Frankia strains (HsIi2, HsIi4, HsIi5, HsIi8, HsIi9, HsIi10, HsIi11, HsIi12, HsIi13, HsIi14) nodulating Hippophae salicifolia D. Don, were characterized on the basis of physiological, biochemical and molecular attributes. Results suggest that the physiological approaches i.e., nitrogenase activity, glutamine synthetase (GS) activity and ammonia excretion are strain specific. The highest rate of nitrogen fixation and maximum production of ammonia with low GS makes the strain HsIi11, a suitable biofertilizer as compared to other strains. Analysis of total protein pattern (SDS–PAGE) revealed that the most closely related strains HsIi10 and HsIi4 were found to be most distantly related to the most similar strains HsIi14, HsIi5, HsIi13, HsIi11 and HsIi12. RAPD PCR analyses with an arbitrary primer 1253 produced distinct, unique and specific DNA fingerprints for each of the Frankia strain and 100% polymorphism was observed which uncovers the genetic diversity. These approaches might be helpful in rapid identification, in designing the marker for the specific strains as well as in improving nitrogen fixation in agroforestry.
13 citations
Cites background from "Attenuation of metal toxicity by fr..."
[...]
[...]
TL;DR: The basic understanding of the functioning and properties of Fur protein along with its role, interaction and regulation at various levels in cyanobacteria has been discussed in detail.
Abstract: The Ferric uptake regulator (Fur) protein is a global iron regulator found in most prokaryotes. Although the Fur protein is involved in a variety of metabolic pathways, it is specifically known for the regulation of several iron responsive genes. It binds to the highly conserved sequences located in the upstream promoter region known as iron boxes, using ferrous ion as a co-repressor. Apart from that, the Fur protein is also directly/indirectly involved in a variety of other crucial physiological pathways. Hence, understanding the mechanism of action and the mechanistic pathways of iron regulation by Fur is necessary and important. The basic understanding of the functioning and properties of Fur protein along with its role, interaction and regulation at various levels in cyanobacteria has been discussed in detail.
13 citations
Cites background from "Attenuation of metal toxicity by fr..."
[...]
[...]
TL;DR: The present study provides the first comprehensive overview of the complexity of Frankia's ligandosphere and opens a path to a deeper understanding of mechanisms that regulate metal homeostasis in frankiae.
Abstract: Frankia spp. are widespread nitrogen-fixing soil bacteria, which often live in symbiosis with a broad range of hosts. Metal homeostasis plays a crucial role in the success of the symbiosis regarding the acquisition of essential trace metals and detoxification of potentially toxic elements. We have hypothesised that Frankia releases many organic ligands with a broad spectrum of affinity for essential and toxic metals. We coined the term ‘ligandosphere’ to describe the entirety of excreted metal complexing agents and ligands derived from the dissolved organic matter. Using metal isotope-coded profiling (MICP); metallophores of physiological important and toxic trace metals were identified by the addition of stable metal isotope pairs such as 54Fe/58Fe, 63Cu/65Cu, 66Zn/68Zn or 95Mo/98Mo. Liquid chromatography coupled to a mass spectrometer revealed strong variations of the metallophore profile in between the 14 test-strains. In total, about 83 organic ligands were identified as binding to one of the tested metals. The predicted sum formula of the major Fe binding ligands and MS/MS experiments suggested that several metallophore candidates have a similar molecular backbone. Growth experiments with a hyper-producer of metallophores revealed a positive relationship between metallophore production and the concentration of Cu in the growth medium. The present study provides the first comprehensive overview of the complexity of Frankia's ligandosphere. It opens a path to a deeper understanding of mechanisms that regulate metal homeostasis in frankiae. Deciphering these mechanisms is important since the fitness of actinorhizal plants and their potential in ecological restoration relies heavily on their symbiosis with frankiae.
10 citations
References
More filters
Journal Article•
[...]
TL;DR: Procedures are described for measuring protein in solution or after precipitation with acids or other agents, and for the determination of as little as 0.2 gamma of protein.
Abstract: Since 1922 when Wu proposed the use of the Folin phenol reagent for the measurement of proteins, a number of modified analytical procedures utilizing this reagent have been reported for the determination of proteins in serum, in antigen-antibody precipitates, and in insulin. Although the reagent would seem to be recommended by its great sensitivity and the simplicity of procedure possible with its use, it has not found great favor for general biochemical purposes. In the belief that this reagent, nevertheless, has considerable merit for certain application, but that its peculiarities and limitations need to be understood for its fullest exploitation, it has been studied with regard to effects of variations in pH, time of reaction, and concentration of reactants, permissible levels of reagents commonly used in handling proteins, and interfering substances. Procedures are described for measuring protein in solution or after precipitation with acids or other agents, and for the determination of as little as 0.2 gamma of protein.
285,427 citations
"Attenuation of metal toxicity by fr..." refers methods in this paper
[...]
[...]
TL;DR: A broad overview of the evidence for an involvement of each mechanism in heavy metal detoxification and tolerance is provided.
Abstract: Heavy metals such as Cu and Zn are essential for normal plant growth, although elevated concentrations of both essential and non-essential metals can result in growth inhibition and toxicity symptoms. Plants possess a range of potential cellular mechanisms that may be involved in the detoxification of heavy metals and thus tolerance to metal stress. These include roles for the following: for mycorrhiza and for binding to cell wall and extracellular exudates; for reduced uptake or efflux pumping of metals at the plasma membrane; for chelation of metals in the cytosol by peptides such as phytochelatins; for the repair of stress-damaged proteins; and for the compartmentation of metals in the vacuole by tonoplast-located transporters. This review provides a broad overview of the evidence for an involvement of each mechanism in heavy metal detoxification and tolerance.
2,524 citations
"Attenuation of metal toxicity by fr..." refers background in this paper
[...]
[...]
[...]
[...]
[...]
[...]
1,253 citations
"Attenuation of metal toxicity by fr..." refers methods in this paper
[...]
[...]
TL;DR: The complement of efflux systems of 63 sequenced prokaryotes was compared with that of the heavy metal resistant bacterium Ralstonia metallidurans and showed that heavy metal resistance is the result of multiple layers of resistance systems with overlapping substrate specificities, but unique functions.
Abstract: What makes a heavy metal resistant bacterium heavy metal resistant? The mechanisms of action, physiological functions, and distribution of metal-exporting proteins are outlined, namely: CBA efflux pumps driven by proteins of the resistance–nodulation–cell division superfamily, P-type ATPases, cation diffusion facilitator and chromate proteins, NreB- and CnrT-like resistance factors. The complement of efflux systems of 63 sequenced prokaryotes was compared with that of the heavy metal resistant bacterium Ralstonia metallidurans. This comparison shows that heavy metal resistance is the result of multiple layers of resistance systems with overlapping substrate specificities, but unique functions. Some of these systems are widespread and serve in the basic defense of the cell against superfluous heavy metals, but some are highly specialized and occur only in a few bacteria. Possession of the latter systems makes a bacterium heavy metal resistant.
1,200 citations
"Attenuation of metal toxicity by fr..." refers background in this paper
[...]
[...]
[...]
TL;DR: Soil salinity is one of the most significant abiotic stresses for plant agriculture and genetically improving the salt tolerance of crop plants is an important part of basic plant biology, contributing to the understanding of subjects.
Abstract: Soil salinity is one of the most significant abiotic stresses for plant agriculture. Apart from the practical goal of genetically improving the salt tolerance of crop plants, salt tolerance research represents an important part of basic plant biology, contributing to our understanding of subjects
666 citations