SCREENING AND CHARACTERISATION OF SIDEROPHORE PRODUCING RHIZOBACTERIA FROM PADDY FIELD OF POONDI

To enhance the crop production and to manage plant diseases, many chemicals are being used. The use of such agrochemicals is hazardous to environment. To identify a viable alternate, biocontrol agent is necessary. Keeping this in point, the present investigation was undertaken to isolate PGPR bacteria from paddy rhizospheric soil. A total of 100 bacteria were isolated. On the basis of morphological, physiological and biochemical characterisation most of the isolates belong to Pseudomonas aeruginosa. The isolates were further screened for siderophores production by CAS method. In this 10 isolates showed positive results in siderophore production. The produced siderophore were further characterised based on their classi?cation such as hydroxylate, catecholate and carboxamate depending on the iron ligating group. In the present study, the effect of culture media components in the yield of siderophore was studied. Among the 10 isolates, 3 of were produced catecholate type of siderophore ef?ciently in succinate medium at neutral pH in low iron concentration. Potential siderophore producing isolates was further applied on Vigna radiata (Green gram). There was a signi?cant increase in the shoot and root length by roll towel method and Pot assay method

Identification of the metabolites from co-cultures of marine Streptomyces sp. IMB18-531 and Cladosporium sp. IMB19-099 / 药学学报

A new siderophore chelate (1) and 8 known compounds were identified from the liquid co-cultures of the marine-derived Streptomyces sp. IMB18-531 and Cladosporium sp. IMB19-099 by a combination of chromatography methods, including C18 reversed-phase medium pressure chromatography, gel column chromatography and HPLC. Their structures were determined by spectroscopic analysis and chemical methods as aluminioxamine E (1), desferrioxamine E (2), ferrioxamine E (3), terragine E (4), capsimicin (5), cyclo(L-prolinyl-L-tyrosine) (6), anthranilic acid (7), (Z)-14-methylpentadec-9-enoic acid (8), and (Z)-hexadec-8-enoic acid (9). Compound 2 showed inhibitory activities against the expression of liver fibrosis related genes COL1A1, MMP2, and TIMP2. Compounds 5, 8, and 9 displayed antibacterial activities against methicillin-resistant Staphylococcus aureus, S. epidermidis and Bacillus subtilis, with MICs of 16-64 μg·mL-1. Compound 5 showed cytotoxicities against human pancreatic cancer MIA Paca-2 and human colon cancer HT-29 cell lines with IC50 of 2.9 and 6.3 μmol·L-1, respectively.

Cryo-EM structures for the Mycobacterium tuberculosis iron-loaded siderophore transporter IrtAB

The adenosine 5'-triphosphate (ATP)-binding cassette (ABC) transporter, IrtAB, plays a vital role in the replication and viability of Mycobacterium tuberculosis (Mtb), where its function is to import iron-loaded siderophores. Unusually, it adopts the canonical type IV exporter fold. Herein, we report the structure of unliganded Mtb IrtAB and its structure in complex with ATP, ADP, or ATP analogue (AMP-PNP) at resolutions ranging from 2.8 to 3.5 Å. The structure of IrtAB bound ATP-Mg2+ shows a "head-to-tail" dimer of nucleotide-binding domains (NBDs), a closed amphipathic cavity within the transmembrane domains (TMDs), and a metal ion liganded to three histidine residues of IrtA in the cavity. Cryo-electron microscopy (Cryo-EM) structures and ATP hydrolysis assays show that the NBD of IrtA has a higher affinity for nucleotides and increased ATPase activity compared with IrtB. Moreover, the metal ion located in the TM region of IrtA is critical for the stabilization of the conformation of IrtAB during the transport cycle. This study provides a structural basis to explain the ATP-driven conformational changes that occur in IrtAB.

The effect of siderophore virulence gene entB on the virulence of Carbapenem-resistant Klebsiella pneumoniae / 中华检验医学杂志

Objective:To study the effect of the siderophore virulence gene entB on the virulence of carbapenem-resistant Klebsiella pneumonia (CRKP). Methods:CRKP-27 was selected as the experimental strain from 30 CRKP strains collected from the First Affiliated Hospital of Kunming Medical University. The knockdown strain (Δ entB) and complementing strain (C-Δ entB) were constructed by the clustered regularly interspaced short palindromic repeat-Cas9 technology, and verified by polymerase chain reaction (PCR). In order to initially understand the effect of entB on CRKP colony morphology and virulence phenotype, the colony morphology of CRKP-27, Δ entB, and C-Δ entB strains were observed and string test were tested. Draw the growth curve of the strains and determine the effect of entB on the growth of the CRKP strains. The siderophores production ability of the strains were detected quantitatively using chrome azurol S (CAS) detection solution. Mice model of inflammation was established to observe the survival rate of mice and intuitively understand the effect of entB on CRKP virulence. Results:The PCR results showed that the Δ entB strain and C-Δ entB stranin were constructed successfully. The entB has no significant effect on the colony morphology, capsule and virulence phenotype of CRKP. The growth rate of Δ entB was significantly faster than that of CRKP-27( P=0.008) and C-Δ entB ( P=0.001), which showed that entB weakened the growth ability of CRKP. Compared with CRKP-27( P=0.001) and C-Δ entB( P=0.001), the siderophore production of Δ entB was significantly decreased by 11.739 3% and 11.964 2%, indicating that entB gene increased the capacity of CRKP to produce siderophpres. In animal experiments, compared with CRKP-27( P=0.023) and C-Δ entB( P=0.024), the survival rate of mice in the Δ entB group was significantly increased, indicating that the entB increased the virulence of the CRKP. Conclusion:The siderophore virulence gene entB significantly weakened the growth ability of the strain, but clearly enhanced the siderophore production capacity and virulence of CRKP.

In vitro screening of siderophore-producing rice root endophytic bacteria from up-land paddies in north-western Vietnam for plant growth-promoting activities

Aims@#Endophytic bacteria (EB) living inside plant tissues possess different beneficial traits including siderophore production and other plant growth-promoting (PGP) activities. Siderophore-producing EB promote host plant growth by secreting ferrum in iron-deficient conditions. This study screened 19 siderophore producers in vitro, isolated from upland rice roots grown in mountain farms of Tung Village, Nậm Có Commune, Mù Cang Chải District, Yên Bái Province, Vietnam, for PGP traits, including phosphate solubilisation, indole-3-acetic acid (IAA), ammonia, gelatinase, amylase and catalase production.@*Methodology and results@#The bacteria were identified by Matrix assisted Laser Desorption Ionization Time of Flight mass spectrometry (MALDI-TOF MS). All 19 isolates were identified as genera Pseudomonas, Enterobacter, Pantoe, Bacillus, Burkholderia, Staphylococcus, Ralstonia and Cronotacter. The isolates produced catalase and ammonia. The amount of ammonia ranged from 60.74 ± 0.14 to 466.72 ± 0.18 mg/L. Out of the 19 siderophore producers, 17 (89.47%) were able to solubilise phosphate with solubilisation index (PSI) ranging from 1.12 ± 0.07 to 2.14 ± 0.15. The qualitative assays identified 12 isolates (63.15%) positive for IAA production with a tryptophan concentration of 5 mM, whereas 15 (78.94%) and 17 (89.47%) isolates were positive for gelatin and starch hydrolysis, respectively. Especially, 7 isolates were found to be positive for all tested assays in vitro including Pseudomonas rhodesiae (NC2), Enterobacter asburiae (NC50), Pantoea ananatis (NC63), Bacillus cereus (NC64), Burkholderia cenocepacia (NC110), Staphylococcus sciuri (NC112) and Ralstonia pickettii (NC122).@*Conclusion, significance and impact of study@#This study serves as crucial findings of multi-trait plant growth-promoting endophytic bacteria isolated from upland rice root in north-western Vietnam. The seven potential isolates positive for all tested assays could be effective PGP bacteria for bio-inoculants.

Cefiderocol: a novel siderophore cephalosporin against multi-drug resistant Gram-negative bacilli infections / 生物工程学报

Antimicrobial resistance is one of the critical public health issues in the world. There is an urgent need to develop effective broad-spectrum antibiotics to treat the infection of multi-drug resistant Gram-negative bacilli. Cefiderocol, developed by the Shionogi Inc. in Japan, is a new type of iron carrier cephalosporin antibiotics, which overcomes the drug resistance of Gram-negative bacilli due to the down-regulation of outer membrane pore protein and the up-regulation of efflux pump, and has good stability to serine- and metallo-carbapenemases. This drug has a broad spectrum and strong antibacterial activity against carbapenem-resistant Enterobacteriaceae (CRE), Pseudomonas aeruginosa, Acinetobacter baumannii, and Stenotrophomonas maltophilia. Cefiderocol can be used to treat complex urinary tract infections (including pyelonephritis), hospital-acquired pneumonia, and ventilator-associated pneumonia. By summarizing the chemical structure, antibacterial mechanism, in vitro antibacterial activity, pharmacokinetics, pharmacodynamics, and clinical treatment of cefiderocol, this review shows the application potential of cefiderocol as a new iron carrier cephalosporin in the treatment of multi-drug resistant Gram-negative bacilli infections.

Endophytic bacteria Bacillus safensis and Pseudomonas hibiscicola and their ability to increase rice seedling growth

Endophytic bacteria Bacillus safensis RS95 and Pseudomonas hibiscicola RS121 were evaluated for their ability to promote the growth of rice seedlings and produce indole-acetic acid (IAA) and siderophores and to solubilize phosphates. 'Guri' rice seeds were immersed in bacterial endophyte cell suspensions (separated and two-strain mixed), as well as in Escherichia coli DH5α, phosphate-buffered saline (PBS) and water treatments (negative controls). Seeds were sown on agar-water in Petri plates placed vertically at an angle of 65°. The ability of plant growth-promoting endophytic bacteria (PGPEB) to produce IAA and siderophores was determined by Salkowski colorimetric and chrome azurol S (CAS) assays, respectively. Mineral phosphate solubilization activity was calculated by inoculating the endophytes onto medium containing insoluble phosphate. PGPEB showed a positive effect on the growth of rice seedlings, causing a mean growth of shoots and primary-roots of 60 and 67%, respectively. Bacterial strains also showed positive traits for IAA and siderophore production, as well as phosphate-solubilization activity

Screening and characterization of siderophore producing endophytic bacteria from Cicer arietinum and Pisum sativum plants

Siderophores are low molecular weight iron chelating secondary metabolites synthesized by various groupsof microorganisms help in scavenging iron-limited conditions. Siderophores produced by endophytic bacteriafacilitate the plant growth by providing iron to plants. The objective of this study was to isolate and screenthe siderophore producing endophytes from nodules and roots of Cicer arietinum and Pisum sativum plants.Out of total 84 isolates, only 14 endophytes produced siderophore and quantitative analysis was also done.Ten best siderophore producers (above 65% siderophore units) were characterized for the type of siderophoreproduced. Most of them were producing hydroxamate and carboxylate type of siderophores. These 10 isolateswere evaluated for other plant growth promoting (PGP) traits in vitro. All of them were producing ammoniaand indole-3-acetic acid (IAA). Isolate CPFR10 was found to be positive for all the PGP traits viz. ammonia,organic acid, HCN, and IAA production. Diversity analysis of these 10 isolates using Amplified rDNARestriction Analysis profile revealed nine genotypes at 90% similarity

Impact of phosphate solubilizing bacteria on wheat (Triticum aestivum ) in the presence of pesticides / Impacto das bactérias solubilizantes de fosfato no trigo (Triticum aestivum ) na presença de pesticidas

Abstract Three phosphate solubilizing bacteria were isolated and identified by 16S rRNA sequencing as Pseudomonas putida, Pseudomonas sp and Pseudomonas fulva . The strains were subjected to plant biochemical testing and all the PGPR attributes were checked in the presence of pesticides (chlorpyrifos and pyriproxyfen). The phosphate solubilizing index of strain Ros2 was highest in NBRIP medium i.e 2.23 mm. All the strains showed acidic pH (ranges from 2.5-5) on both medium i.e PVK and NBRIP. Strain Ros2 was highly positive for ammonia production as well as siderophore production while strain Rad2 was positive for HCN production. The results obtained by the strains Rad1, Rad2 and Ros2 for auxin production were 33.1, 30.67 and 15.38 µg ml-1, respectively. Strain Rad1 showed 16% increase in percentage germination in comparison to control in the presence of pesticide stress. Most promising results for chlorophyll content estimation were obtained in the presence of carotenoids upto 6 mgg-1 without stress by both strains Rad1 and Rad2. Study suggests that especially strain Ros2 can enhance plant growth parameters in the pesticide stress.

Resumo Três bactérias solubilizantes de fosfato foram isoladas e identificadas por seqüenciamento de rRNA 16S como Pseudomonas putida, Pseudomonas sp e Pseudomonas fulva. As estirpes foram submetidas a testes bioquímicos de plantas e todos os atributos PGPR foram verificados na presença de pesticidas (clorpirifos e piriproxifeno). O índice de solubilização de fosfato da estirpe Ros2 foi mais elevado no meio NBRIP, isto é, 2,23 mm. Todas as estirpes apresentaram um pH ácido (varia de 2,5-5) em ambos os meios, isto é PVK e NBRIP. A estirpe Ros2 foi altamente positiva para a produção de amoníaco, bem como a produção de sideróforos enquanto a estirpe Rad2 foi positiva para a produção de HCN. Os resultados obtidos pelas estirpes Rad1, Rad2 e Ros2 para a produção de auxina foram 33,1, 30,67 e 15,38 μg ml-1 , respectivamente. A deformação Rad1 mostrou aumento de 16% na germinação percentual em comparação com o controlo na presença de stress de pesticida. Os resultados mais promissores para a estimativa do teor de clorofila foram obtidos na presença de carotenóides até 6 mgg-1 sem estresse por ambas as cepas Rad1 e Rad2. Estudo sugere que especialmente a estirpe Ros2 pode melhorar parâmetros de crescimento de plantas no estresse de pesticidas.

Prospecção de sideróforos do tipo hidroxamato e quinona para terapia de sobrecarga de ferro / Prospection of hydroxamate and quinone-type siderophores for iron overload chelation therapy

A sobrecarga de ferro é uma condição prejudicial para os pacientes, que apresentam uma diminuição significativa na qualidade de vida. Os fármacos quelantes são moléculas que têm capacidade de uso clínico para atuar como atenuadores da sobrecarga de metais. Neste trabalho apresentamos uma análise de sideróforos do tipo hidroxamato e quinona, com o objetivo de ampliar a gama de terapia de sobrecarga de ferro. Para cada composto foi realizado um ensaio competitivo com a sonda calce- ína para verificar a capacidade de ligação do ferro, e um ensaio antioxidante baseado na supressão da oxidação dependente de ferro da dihidrorrodamina (DHR) sob ascorbato. Foi observado que o hidroxamato cíclico piridoxatina apresentou capacidade de sequestrar ferro de substratos de alta afinidade, tanto em meio tamponado quanto em meio intracelular. Em ambas as situações também se mostrou um antioxidante eficiente. Entretanto, parece ser o mais tóxico do grupo dos hidroxamatos (que ainda continha o hidroxamato linear desferricoprogênio e o aromático desferriastercromo). Outros compostos naturais também foram estudados como possíveis candidatos a fármacos para sobrecarga de ferro. Complexos de ferro foram caracterizados por espectrofotometria para avaliar a estequiometria possível, considerando os sítios de ligação para cada composto. Ensaios de fluorescência revelaram que entre os quatro compostos em estudo (ácido clorogênico, lapachol, hemateína e hematoxilina), o complexo entre ferro e hemateína apresenta maior estabilidade relativa do que outros

Iron overload is a harmful condition for patients, who have a significant decrease in life quality. Chelating drugs are molecules that have the capacity for clinical use to act as attenuators of metal overload. In this work we present an analysis of hydroxamate and quinone-type siderophores, intending to broaden the range of iron overload therapy. For each compound it was conducted a competitive assay with the fluorescent probe calcein to verify the iron binding ability, and an antioxidant assay based on suppression of the iron-dependent oxidation of dihydrorhodamine (DHR) under ascorbate. It was observed that cyclic hydroxamate pyridoxatin displayed good ability to scavenge iron from high affinity substrates both in buffer and in intracellular medium. It was also an efficient antioxidant in both setups. However, pyridoxatin seems to be the most toxic from the hydroxamate group (composed also by the linear desferricoprogen and the aromatic desferriasterchrome). Other natural compounds have also been studied as possible candidates for iron-overload drug therapy. Iron complexes were characterized by spectrophotometry to assess the possible stoichiometry considering the binding sites for each compound. Fluorescence assays revealed that among the four compounds in study (chlorogenic acid, lapachol, hematein and hematoxylin), the complex between iron and hematein has higher relative stability than others

Dynamism of PGPR in bioremediation and plant growth promotion in heavy metal contaminated soil.

Heavy metal contamination, particularly of cultivable lands, is a matter of concern. Bioremediation helps in reversing such contamination to certain extent. Here, we report isolation, polyphasic identification and the role of siderophore producing rhizobacteria Alcaligenes feacalis RZS2 and Pseudomonas aeruginosa RZS3 in bioremediation of heavy metal contaminated soil and plant growth promotion activity in such contaminated soil. Siderophore produced by A. feacalis RZS2 and P. aeruginosa RZS3 strains chelated various heavy metal ions like MnCl2.4H2O, NiCl2.6H2O, ZnCl2, CuCl2 and CoCl2 other than FeCl3.6H2O at batch scale. Their bioremediation potential was superior over the chemical ion chelators like EDTA and citric acid. These isolates also promoted growth of wheat and peanut seeds sown in heavy metal contaminated soil. Effective root colonizing ability of these isolates was observed in wheat and peanut plants.

Determination of Siderophores in Seawater by High Performance Liquid Chromatography-Tandem Mass Spectrometry Coupled with Solid Phase Extraction / 分析化学

Siderophores were produced and secreted with marine microorganisms as the highly specific iron chelators. A method of liquid chromatography-tandem mass spectrometric detection coupled with solid phase extraction pretreatment was developed for the determination of siderophores in seawater. The samples were filtered through a 0. 22 μm membrane, extracted with an ENVI-18 cartridge and then eluted with methanol. The separation of the analytes was performed on a reversed phase SB-C18 column with a gradient elution program by using 0. 1% ( V/V) formic acid and methanol as the mobile phases. Qualitative analysis was performed in multiple-reaction monitoring mode. Good linearity (R2>0. 99) was obtained for Pyoverdines-Fe, Ferrichrome, Ferrioxamine E at the concentrations of 0. 001-3. 00 μg/mL, 0. 005-15. 00 μg/mL, 0. 001-3. 00 μg/mL, respectively. The instrumental detection limits and limits of quantification for the three analytes were 0. 08, 1. 76 and 1. 36 ng/mL; 0. 27, 5. 87 and 4. 53 ng/mL, respectively. The relative standard deviations were lower than 12%, while the recoveries were 12. 1%-18. 6% for Pyoverdines-Fe, 82. 0%-97. 7% for Ferrichrome, and 70. 0%-98. 3% for Ferrioxamine E.

Production of biocontrol traits by banana field fluorescent Pseudomonads and comparison with chemical fungicide.

Pseudomonas aeruginosa isolated from banana field rhizosphere produced different antifungal metabolites like bactriocin, hydrogen cyanide and siderophore. Bacteriocinogenic, siderophoregenic, and HCN rich broth of isolate inhibited the growth of phytopathogen like Aspergilus niger, Aspergilus flavus, Fusarium oxysporum and Alternaria alternata. The isolate exhibited more antifungal activity and comparatively low MIC vis-a-vis commonly used copper based systemic chemical fungicide;bil cop.

Characterization of plant growth-promoting bacteria inhabiting Vriesea gigantea Gaud. and Tillandsia aeranthos (Loiseleur) L.B. Smith (Bromeliaceae) / Caracterização de bactérias promotoras de crescimento vegetal em Vriesea gigantea Gaud. e Tillandsia aeranthos (Loiseleur) L.B. Smith (Bromeliaceae)

Microorganisms that live inside and around a plant can supply it with essential substances, such as phytohormones and essential nutrients. The present investigation aimed to isolate and characterize the phyllosphere, the endophytic, and the water tank bacteria associated with Vriesea gigantea and Tillandsia aeranthos. The bacteria were tested for siderophore and indole-3-acetic acid (IAA) production, phosphate solubilization, and presence of the nif H gene. Genetic diversity of the bacterial isolates was evaluated by rep-PCR. Sixty-eight bacterial strains were isolated from 3 different microhabitats of V. gigantea and from 2 microhabitats of T. aeranthos bromeliad plants. Gram-positive, spore-forming bacilli comprised most bacterial isolates. All isolates produced IAA in vitro in presence of very low amounts of tryptophan. More than 70% of the evaluated bacteria presented the ability of siderophore production and phosphate solubilization, and possessed the nif H gene. It was not possible to distinguish well-defined groups of isolates based on the bromeliad species and microhabitat they inhabit using genetic characterization by rep-PCR. Water tanks presented the most abundant diversity compared with phyllosphere and endophytes, probably due to the high nutrient concentration, which promotes an ideal environment for complex microbial communities.

Microrganismos que habitam o interior e a superfície podem fornecer substancias essenciais ao crescimento das plantas, como fitormônios e nutrientes essenciais. O presente trabalho teve como objetivo isolar e caracterizar as bactérias da filosfera, do ambiente endofítico e a água de tanque associadas à Vriesea gigantea e Tillandsia aeranthos. As bactérias foram submetidas a testes de verificação de produção de sideróforos e de ácido indol acético (AIA), solubilização de fosfatos, e a presença do gene nif H. A diversidade genética dos isolados bacterianos foi analisada por rep-PCR. Sessenta e oito microrganismos foram isolados de 3 microambientes distintos de V. gigantea e de 2 microambientes de T. aeranthos. A maioria das bactérias isoladas foram bacilos formadores de esporos, gram-positivos. Todos os isolados produziram AIA in vitro na presença de quantidades pequenas de triptofano. Mais de 70% das bactérias analisadas produziram sideróforos, solubilizaram fosfatos e possuíam o gene nif H. Não foi possível distinguir grupos definidos de microrganismos baseados no microhabitat e na espécie de bromélia de onde foram isolados usando rep-PCR. A água do tanque apresentou maior diversidade microbiana quando comparada com a filosfera e o ambiente endofítico, provavelmente devido à alta concentração de nutrientes, que promove um ambiente favorável para o desenvolvimento de comunidades microbianas complexas.

Accumulation of rare earth elements by siderophoreforming Arthrobacter luteolus isolated from rare earth environment of Chavara, India.

In this study, Arthrobacter luteolus, isolated from rare earth environment of Chavara (Quilon district, Kerala, India), were found to produce catechol-type siderophores. The bacterial strain accumulated rare earth elements such as samarium and scandium. The siderophores may play a role in the accumulation of rare earth elements. Catecholate siderophore and low-molecular-weight organic acids were found to be present in experiments with Arthrobacter luteolus. The influence of siderophore on the accumulation of rare earth elements by bacteria has been extensively discussed.

The exploration of the antibacterial mechanism of fe3+ against bacteria

This study demonstrated that the bacteria could adsorb Fe3+ and reduce Fe3+ to Fe2+. Iron had significant bacteriostatic effects, which were directly proportional to the iron concentration and under the influence of pH and chelator. It presumed that the inhibition of Fe3+ acts through the formation of hydroxyl free radicals.

Genetic diversity of siderophore-producing bacteria of tobacco rhizosphere / Diversidade genética de bactérias de rizosfera de tabaco produtoras de sideróforos

The genetic diversity of siderophore-producing bacteria of tobacco rhizosphere was studied by amplifiedribosomal DNA restriction analysis (ARDRA), 16S rRNA sequence homology and phylogenetics analysis methods. Studies demonstrated that 85% of the total 354 isolates produced siderophores in iron limited liquid medium. A total of 28 ARDRA patterns were identified among the 299 siderophore-producing bacterial isolates.The 28 ARDRA patterns represented bacteria of 14 different genera belonging to six bacterial divisions, namely β-, γ-, α-Proteobacteria, Sphingobacteria, Bacilli, and Actinobacteria. Especially, γ- Proteobacteria consisting of Pseudomonas, Enterobacter, Serratia, Pantoea, Erwinia and Stenotrophomonas genus encountered 18 different ARDRA groups. Results also showed a greater siderophore-producing bacterial diversity than previous researches. For example, Sphingobacterium (isolates G-2-21-1 and G-2-27-2), Pseudomonas poae (isolate G-2-1-1), Enterobacter endosymbiont (isolates G-2-10-2 and N-5-10), Delftia acidovorans (isolate G-1-15), and Achromobacter xylosoxidans (isolates N-46-11HH and N-5-20) were reported to be able to produce siderophores under low-iron conditions for the first time. Gram-negative isolates were more frequently encountered, with more than 95% total frequency. For Gram-positive bacteria, the Bacillus and Rhodococcus were the only two genera, with 1.7% total frequency. Furthermore, the Pseudomonas and Enterobacter were dominant in this environment, with 44.5% and 24.7% total frequency, respectively. It was also found that 75 percent of the isolates that had the high percentages of siderophore units (% between 40 and 60) belonged to Pseudomonas. Pseudomonas sp. G-229-21 screened out in this study may have potential to apply to low-iron soil to prevent plant soil-borne fungal pathogen diseases.

A diversidade genética de bactérias de rizosfera de tabaco produtoras de sideróforos foi estudada por meio da técnica de análise de restrição do DNA ribossomal amplificado (ARDRA), homologia de seqüência de 16s rRNA e métodos de análise filogenética. Observou-se que 85% do total de 354 isolados produziram sideróforos em meio liquido com restrição de ferro.Entre os 299 isolados produtores de sideróforos identificou-se 28 padrões ARDRA, que representaram 14 gêneros bacterianos diferentes, pertencentes a seis divisões bacterianas: β-, γ-, α-Proteobacteria, Sphingobacteria, Bacilli e Actinobacteria. γ- Proteobacteria, consistindo de Pseudomonas, Enterobacter, Serratia, Pantoea, Erwinia e Stenotrophomonas, pertenceram a 18 grupos ARDRA. Os resultados também mostraram uma diversidade maior de bactérias produtoras de sideróforos doque a relatada em outros estudos. Por exemplo, Sphingobacterium (isolados G-2-21-1 e G-2-27-2), Pseudomonaspoae (isolado G-2-1-1), Enterobacter endosymbiont (isolados G-2-10-2 e N-5-10), Delftia acidovorans (isolado G-1-15) e Achromobacter xylosoxidans (isolados N-46-1HH e N-5-20), capazes de produzir sideróforos em condições de baixa disponibilidade de ferro, foram relatados pela primeira vez. Isolados Gram negativos foram encontrados com maior freqüência, correspondendo a mais de 95% da freqüência total. Entre as bactérias Gram positivas, foram encontrados apenas os gêneros Bacillus e Rhodococcus, com 1,7% da freqüência total. Além disso, neste ambiente houve predominância de Pseudomonas e Enterobacter, com 44,5% e 24,7% da freqüência total, respectivamente. Verificou-se também que 75% dos isolados com alta porcentagem de unidades de sideróforos (% entre 40 e 60) pertenceram a Pseudomonas. Pseudomonas sp. G- 229-21, selecionado neste estudo, apresenta potencial de aplicação em solos com baixo teor de ferro para prevenção dedoenças fúngicas em plantas.

Siderophoregenic Acinetobacter calcoaceticus isolated from wheat rhizosphere with strong PGPR activity

Thirty-two bacterial isolates were obtained from wheat rhizosphere in black cotton soils of North Maharashtra region and subsequently tested for in-vitro siderophore production. Wheat isolate SCW1, being a strong siderophore producer, was selected, identified and confirmed as Acinetobacter calcoaceticus. The strain produced catechol type of siderophores during exponential phase which was influenced by iron content of medium. Seed bacterization with siderophoregenic A.calcoaceticus improved plant growth in pot and field studies. Such PGPR activity was attributed to the ability of strain to solubilise phosphates and produce IAA. Siderophore mediated antagonism was observed against common phytopathogens viz., Aspergillus flavus, A. niger, Colletotrichum capsicum and Fusarium oxysporum

Utilization of Transferrin-Bound Iron by Medically Important Staphylococcal Species

Staphylococcus aureus is able to utilize efficiently transferrin-bound iron as an iron source, whereas other staphylococci are not. The reason for this difference remains unclear. We compared the activity of siderophore-mediated iron-uptake systems among S. aureus, S. epidermidis, and S. saprophyticus. S. aureus was more susceptible to streptonigrin than the other two staphylococci. S. aureus was able to utilize efficiently transferrin-bound iron in proportion to the level of iron-saturation and produced siderophores in an inverse relation to iron-saturation. In contrast to S. aureus, S. epidermidis and S. saprophyticus were able to utilize only holotransferrin (HT; about 80% iron- saturated) and produced siderophores only in media containing HT. Moreover, they utilized HT less efficiently than S. aureus, though they produced greater amount of siderophores than S. aureus in media containing HT. The ability of the equivalent siderophores per se to capture iron from HT was not significantly different among the three species. Nevertheless, the siderophores from S. aureus stimulated the growth of the staphylococci to a greater degree than did the siderophores from S. epidermidis and S. saprophyticus. The siderophores from S. epidermidis and S. saprophyticus also stimulated the growth of S. aureus to a greater degree than those of the original bacteria which produced them. This indicates that S. aureus possesses a greater ability to produce more-efficient siderophores responding to very low iron-availability, as well as a greater ability to utilize iron-siderophore complexes, than the other two staphylococci. This explains in part the higher virulence of S. aureus compared to other staphylococci.

Transferrin Binding Protein of Staphylococcus aureus is not Essential for Iron-uptake from Transferrin in vitro / 감염과화학요법

BACKGROUND: Staphylococcus aureus produces siderophore and expresses transferring-binding protein for uptake of iron essentially required for multiplication under the iron-restricted conditions. We investigated which of the two iron-uptake systems is dominant or essential for S. aureus growth. METHODS: Streptonigrin-resistant mutant (SR-1) of S. aureus, isolated by repeated exposure to streptonigrin, was used in this study. SR-1 strain produced less amount of siderophore than the parent strain and did not express the transferring-binding protein. Growth and iron consumption of the two bacteria were compared during cultivation in the media containing various concentrations of iron, by measuring optical densities of the culture fluids at 600 nm and residual iron concentrations of the culture supernatants. RESULTS: Growth of the two bacteria in the iron-sufficient media containing various sources of iron was more active than in the iron-deficient media, in which iron concentration was 0.2 microgram/dL. Growth of SR-1 strain was markedly inhibited in the iron-deficient media with/without apotransferrin (0.5 mg/mL). However, growth of SR-1 strain did not show any difference in the iron-sufficient media containing FeCl3 (0.2 micrometer) and hemoglobin (0.5 mg/mL) as compared with that of the parental strain. Moreover, growth of the two bacteria did not show any difference in the media containing holotransferrin (0.5 mg/mL). There was no difference in iron consumption between the parental and mutant strains, evidenced by the residual iron concentration of the culture supernatants. CONCLUSION: Siderophore production is thought to be dominant or essential iron-uptake system for in vitro growth of S. aureus. The pathogenetic role of multifunctional transferring-binding protein, including transferring-binding activity and glycolytic enzyme activity, is expected to be established through further continued studies.