Oxytoca Strain Research Articles

Arsenate and arsenite removal from contaminated water by iron oxides nanoparticles formed inside a bacterial exopolysaccharide

In the last decades, the presence of high As levels in groundwaters poses a serious limitation to the use of this resources for drinking purposes in several parts of the world. Treatment of As-rich waters selected iron oxides filters as more effective, low cost and selective technology. Green and biologically-driven pathways to synthetize new nanostructured iron oxy-hydroxides are becoming always more attractive. We tested the suitability of FeOOH nanoparticles (9–15 nm) produced by Klebsiella oxytoca strain DSM 29614 and encapsulated in EPS gel structure to treat arsenic rich water. Different gel:water volume ratios were tested to treat 5000 μg As/L solution. 20% FeEPS solution was able to remove 95% of As(V) while in 5% solution removal was reduced to 60%. Arsenic adsorption was very fast and follows pseudo-2nd order kinetic with maximum adsorption capacity reached at about 30 min. Adsorption followed Langmuir model for As(V) with qmax = 31.8 mgAs/gFe and BET for As(III) with 8 mgAs/gFe for the first layer in 10% FeEPS solution. FeEPS dried into powder showed noticeable removal only after 2 h, hence not suitable for drinking water treatment. Treatment of natural As levels in mimicked groundwaters showed 87–95% As(V) and 45–61% As(III) removal after 5 min. FeEPS gel immobilized onto bivalve shell debris was used in packed-bed filters. It retained 49.8 mgAs/gFe from 150 μg/L As(V) spiked groundwater before reaching breakthrough at 8000 BVs. Biologically produced FeEPS gel showed good potentialities as eco-friendly material to remove As from contaminated groundwater.

Cloning and characterization of a Flavin-free oxygen-insensitive azoreductase from Klebsiella oxytoca GS-4-08.

This study reports the identification of a new bacterial azoreductase (AzoR) from Klebsiella oxytoca GS-4-08, its heterologous production in Escherichia coli and the decolorization of azo dyes. The AzoR, as a flavin-free, oxygen-insensitive enzyme, has a molecular mass of 22kDa and a high substrate specificity for methyl red (MR). In the presence of 5mM of NADH, the enzyme activity for decolorization of 50mgl-1 of MR reached 5.61μmolmin-1 mg protein-1. Double-reciprocal plots indicated that the NADH and MR reductions proceed by ping-pong mechanism. The calculated Vm was 8.17μMmin-1 mg protein-1, and the AzoR retained over 75% of relative activity under temperature range from 20 to 50°C. This study for the first time identified an AzoR from Klebsiella oxytoca strain, which enabled efficient degradation of azo dyes by strain GS-4-08.

Bioreduction of azo dyes was enhanced by in-situ biogenic palladium nanoparticles

Biogenic nanoparticles are promising materials for their green synthesis method and good performance in stimulation on reduction of environmental contaminants. In this study, Pd(0) nanoparticles (bio-Pd) were generated by Klebsiella oxytoca GS-4-08 in fermentative condition and in-situ improved the azo dye reduction. The bio-Pd was mainly located on cell membrane with a size range of 5–20 nm by TEM and XRD data analyses. Anthraquinone-2-disulfonate (AQS) greatly increased the reduction rate of Pd(II) with a reduction efficiency as high as 96.54 ± 0.23% in 24 h. The quinone respiration theory, glucose metabolism and the biohydrogen pathway were used to explain the enhancement mechanism of the in-situ generated bio-Pd on azo dye reduction. These results indicate that the in-situ generated bio-Pd by K. oxytoca strain is efficient for azo dye reduction without complex preparation processes, which is of great significance for the removal and subsequent safe disposal of hazardous environmental compounds.

Four novel strains of cellulolytic symbiotic bacteria isolated and characterized from GI tract of marine fishes of various feeding habits

Abstract Selected marine fishes with different feeding habits were screened for the presence of symbiotic cellulolytic bacteria in their gut. Four cellulolytic species of symbiotic bacteria were isolated from GI tract of marine fishes namely Carangoides praeustus, Filimanus similis, Sardinella longiceps and Sillago sihama. The strains were identified after polyphasic phenotypic and genotypic (16S rRNA gene) characterization as Bacillus subtilis strain TCPC1, Vibrio alginolyticus strain CFSS2C2, Pseudomonas stutzeri strain KSLS4C3 and Klebsiella oxytoca strain MSSC4. (Genbank Accession nos.: JN710380, JN710378, JN710377, JN712301).The results indicated the presence of cellulolytic bacteria in GI tract of marine fishes of carnivorous, phytoplanktivorous and omnivorous feeding habits. Cellulolytic activity was the maximum for B. subtilis strain TCPC1 (0.45 mg glucose ml−1) and V. alginolyticus strain CFSS2C2 (0.24 mg glucose ml−1) at 234 h. While P. stutzeri strain KSLS4C3 showed the maximum utilization (0.22 mg glucose ml−1) from 240 to 258 h. K. oxytoca strain MSSC4 (0.47 mg glucose ml−1) showed three peaks during the study. The maximum rate of cellulose utilization was shown by P. stutzeri strain KSLS4C3 (0.05 mg glucose ml−1 medium h−1) followed by K. oxytoca strain MSSC4 (0.03 mg glucose ml−1 medium h−1).

Carbapenemase-producing Enterobacteriaceae in Mexico: report of seven non-clonal cases in a pediatric hospital

BackgroundCarbapenemases-producing Enterobacteriaceae (CPE) are a worldwide public health emergency. In Mexico, reports of CPE are limited, particularly in the pediatric population. Here, we describe the clinical, epidemiological, and molecular characteristics of seven consecutive cases in a third-level pediatric hospital in Mexico City over a four-month period during 2016.ResultsThe Enterobacteriaceae identified were three Escherichia coli strains (producing OXA-232, NDM-1 and KPC-2), two Klebsiella pneumoniae strains (producing KPC-2 and NDM-1), one Klebsiella oxytoca strain producing OXA-48 and one Enterobacter cloacae strain producing NDM-1. The majority of patients had underlying disesases, three were immunocompromised, and three had infections involved the skin and soft tissues. Half patients died as a result of CPE infection.ConclusionsThis study represents the first report of E. coli ST131-O25b clone producing NDM-1 in Latin America. In addition, this study is the first finding of K. oxytoca producing OXA-48 and E. coli producing OXA-232 in Mexican pediatric patients.

Development of a semi-continuous two-stage simultaneous saccharification and fermentation process for enhanced 2,3-butanediol production by Klebsiella oxytoca.

There is growing interest in the production of 2,3-butanediol (2,3-BD) from renewable resources by microbial fermentation because of its wide applications to specialty and commodity chemical industries. Klebsiella oxytoca usually produces 2,3-BD as a major end product during the fermentation of carbohydrates. This is the first study to provide a high-efficiency simultaneous saccharification and 2,3-BD fermentation process. Also, this study proves the stability of a metabolically engineered 2,3-BD overproducing K. oxytoca strain for industrial application.

KlebsiellaBacteria Isolated from the Genital Chamber ofPhyllophaga obsoleta

Females of Phyllophaga obsoleta Blanchard (Coleoptera: Melolonthidae) display a typical “calling” behavior by protruding the abdominal tip and exposing their genital chamber. This is the moment when the sex pheromone is released into the environment. The genital chamber and accessory glands have a specialized epithelia involved in production of the chemicals. In other species of the group (e.g., Costelytra zealandica White), bacteria have been confirmed to be involved. We identified the microorganisms in the genital chamber of females of P. obsoleta. Two types of bacterial colonies were isolated from the inside of the genital chamber and identified using the 16S rRNA gene sequence. The sequence of one of the bacterial colonies was a 97% match with the Klebsiella oxytoca strain HP1 sequence, while the sequence of the other bacterial colony was a 98% match with the Klebsiella michiganensis strain VITSW4 sequence. Microbiological and biochemical tests were used for taxonomic identification. Both bacteria produce indole and acetoin, chemicals that have been reported as attractants and sex pheromones in other insects, showing they can potentially participate in production of sex pheromone of P. obsoleta.

Medfly Gut Microbiota and Enhancement of the Sterile Insect Technique: Similarities and Differences of Klebsiella oxytoca and Enterobacter sp. AA26 Probiotics during the Larval and Adult Stages of the VIENNA 8D53+ Genetic Sexing Strain

The Mediterranean fruit fly, Ceratitis capitata, is a major agricultural pest worldwide. The development of genetic sexing strains (GSSs) for this species that allows male-only sterile insects releases has boosted the effectiveness of the environmental friendly pest control method known as the sterile insect technique. The last generation of these strains, the VIENNA 7 and VIENNA 8, are currently used in all mass rearing facilities worldwide and are considered as models for such pest control applications. The sterile insect technique depends on the rearing of sufficient numbers of adequate “biological quality” laboratory flies to be released in the field. Currently, there is an increasing amount of studies focusing on the characterization of the symbiotic communities and development of probiotic diets. In our study, two bacterial isolates, an Enterobacter sp. (strain AA26) and a Klebsiella oxytoca strain, were used as probiotics in larval and adult diet. These strains have been shown to be beneficial, affecting several aspects related to the rearing efficiency and biological quality of the medfly VIENNA 8D53+ GSS. Our results demonstrate the effect of K. oxytoca on the developmental duration of the immature stages and, to some extent, on flight ability. On the other hand, our study does not support the presence of any beneficial effect of (a) K. oxytoca on pupal and adult recovery and adults’ survival under stress conditions when provided as a larval diet supplement and (b) K. oxytoca and Enterobacter sp. AA26 on mating competitiveness when provided as adult diet supplements. Possible explanations for inconsistencies with previous studies and the need for universalizing protocols are discussed. Our findings, combined with previous studies can support the sterile insect technique, through the improvement of different aspects of mass rearing and biological properties of laboratory reared insect pests.

Bacteriological pollution indicators in Ogun River flowing through Abeokuta Metropolis

Water resources are significant part of integrated community development policy and good health. Hence, the need to reduce the impact of natural and anthropogenic pollution causes so as to enhance water quality. The bacteriological quality of the Ogun River was investigated to determine the sanitary conditions of the water body between March and August, 2014. Total heterotrophic bacteria counts (THBC), total coliform counts (TCC) and total Escherichia coli counts (TEC) using standard plate count and Most Probable Number (MPN) techniques were determined. The isolates were identified using 16SrRNA gene. Total heterotrophic bacteria counts varied between 1.13 × 106 and 4.1 × 107 CFU/ml, TCC ranged between 2.5 × 105 and 2.33× 107 CFU/ml and TEC was between 5 × 104 and 1.3 × 106 CFU/ml. Most Probable Number of coliforms in all samples varied between 120 and 1600 MPN/100 ml. Isolated microorganisms include Escherichia coli strain SUS9EC, Escherichia coli O157:H7 strain SSI7, Escherichia coli strain BW25113, Escherichia coli strain C-X1B, and Klebsiella oxytoca strain KU-5. One-wayanalysis of variance showed significant difference within the samples at (P<0.05).The results revealed high bacteria counts which is higher than the recommended value of 1.2 × 102 for THBC, a zero E. coli count and not more than 10 coliforms per 100 ml by World Health Organization standards for drinking water.Keywords: Water, bacteria, Escherichia coli, pollution

Isolation and Characterization of Hydrocarbon-utilizing Bacteria from Petroleum Sludge Samples obtained from Crude Oil Processing Facility in Nigeria

The isolation and characterization of hydrocarbon-utilizing bacteria from petroleum oily sludge collected from crude oil processing plant in Rivers State, Nigeria was carried out. Microbiological analysis of the sludge sample showed that the microbial load consisted average of 2.5 x 106 cfu/g total heterotrophic bacterial (THB) count, while the hydrocarbon utilizing bacterial (HUB) count was average of 2.0 x 103 cfu/g. Phenotypic characteristics and phylogenetic analysis of the 16S rRNA gene sequence of the isolates revealed that they were related to members of the species Klebsiella pneumonia, Klebsiella oxytoca and Alcaligenes faecalis. The 16S rRNA of the isolates showed percentage similarities to the type strains (99% sequence similarities) of the following; Klebsiella pneumonia strain B21 (gi: 922317936), Klebsella pneumonia strain ICB-C183 (gi: 908478837), Klebsella oxytoca strain BCNAI (gi: 846993354), Klebsella oxytoca strain BC4 (gi: 884060138), Alcaligenes faecalis strain IOU PMR (gi: 686028963) and Alcaligenes faecalis strain AQ-I (gi: 816845513). Of the six hydrocarbon utilizing bacteria identified, 4(67%) were Klebsiella species while 2(33%) were identified as Alcaligenes sp of different strains. The result suggest that these isolated organisms from the petroleum sludge can be explored and used to promote environmentally friendly technology clean-up of petroleum hydrocarbon polluted sites in the Niger Delta region of Nigeria.Keywords: Hydrocarbon -utilizing bacteria, Petroleum sludge, 16S rRNA, Phylogenetic, Gene sequence.

Gut eradication of VIM-1 producing ST9 Klebsiella oxytoca after fecal microbiota transplantation for diarrhea caused by a Clostridium difficile hypervirulent R027 strain

We report the fecal carriage eradication of a VIM-1-producing ST9 Klebsiella oxytoca strain in a pluripathological 84-year-old woman after fecal microbiota transplantation to control relapsing R027 hypervirulent Clostridium difficile infections. The donor was her son, in which the absence of fecal carbapenemase-producing bacteria was corroborated.

ISOLATION AND CHARACTERIZATION OF A MOLYBDENUM-REDUCING AND GLYPHOSATE-DEGRADING Klebsiella oxytoca STRAIN SAW-5 IN SOILS FROM SARAWAK

Bioremediation of pollutants including heavy metals and xenobiotics is an economic and environmentally friendly process. A novel molyb-denum-reducing bacterium with the ability to utilize the pesticide glyphosate as a carbon source is reported. The characterization works were carried out utilizing bacterial resting cells in a microplate format. The bacterium reduces molybdate to Mo-blue optimally between pH 6.3 and 6.8 and at 34 o C. Glucose was the best elec-tron donor for supporting molybdate reduction followed by lactose, maltose, melibiose, raffinose, d-mannitol, d-xylose, l-rhamnose, l-arabinose, dulcitol, myo-inositol and glycerol in descending order. Other requirements include a phosphate concentration at 5.0 mM and a molybdate concentration between 20 and 30 mM. The molybdenum blue exhibited an absorption spec-trum resembling a reduced phospho-molybdate. Molybdenum reduction was inhibited by mercury, silver, cadmium and copper at 2 ppm by 45.5, 26.0, 18.5 and 16.3%, respectively. Biochemical analysis identified the bacterium as Klebsiella oxytoca strain Saw-5. To conclude, the capacity of this bacterium to reduce molybdenum into a less toxic form and to grow on glyphosate is novel and makes the bacterium an important instrument for bioremediation of these pollutants.

Enhanced reduction of Fe(III) oxides and methyl orange by Klebsiella oxytoca in presence of anthraquinone-2-disulfonate.

Klebsiella oxytoca GS-4-08 is capable of azo dye reduction, but its quinone respiration and Fe(III) reduction abilities have not been reported so far. In this study, the abilities of this strain were reported in detail for the first time. As the biotic reduction of Fe(III) plays an important role in the biogeochemical cycles, two amorphous Fe(III) oxides were tested as the sole electron acceptor during the anaerobic respiration of strain GS-4-08. For the reduction of goethite and hematite, the biogenic Fe(II) concentrations reached 0.06 and 0.15mM, respectively. Humic acid analog anthraquinone-2-disulfonate (AQS) was found to serve as an electron shuttle to increase the reduction of both methyl orange (MO) and amorphous Fe(III) oxides, and improve the dye tolerance of the strain. However, the formation of Fe(II) was not accelerated by biologically reduced AQS (B-AH2QS) because of the high bioavailability of soluble Fe(III). For the K. oxytoca strain, high soluble Fe(III) concentrations (above 1mM) limit its growth and decolorization ability, while lower soluble Fe(III) concentrations produce an electron competition with MO initially, and then stimulate the decolorization after the electron couples of Fe(III)/Fe(II) are formed. With the ability to respire both soluble Fe(III) and insoluble Fe(III) oxides, this formerly known azo-reducer may be used as a promising model organism for the study of the interaction of these potentially competing processes in contaminated environments.

Isolation and characterization of a molybdenum-reducing and SDSdegrading Klebsiella oxytoca strain Aft-7 and its bioremediation application in the environment

Masdor N, Shukor MSA, Khan A, Halmi MIE, Abdullah SRS, Shamaan NA, Shukor MY. 2015. Taxonomy and distribution of species of the genus Acanthus (Acanthaceae) in mangroves of the Andaman and Nicobar Islands, India. Biodiversitas 16: 238-246.Pollution as a result of anthropogenic activities is a severe global issue. These activities including inappropriate disposal, industrialand prospecting activities and unnecessary use of agricultural chemicals have triggered international initiatives to eliminate thesecontaminants. In this work we screen the ability of a molybdenum-reducing bacterium isolated from contaminated soil to grow andreduce molybdenum on various detergents. The bacterium was able to grow on SDS as a carbon source although the compound did notsupport molybdenum reduction. The bacterium reduces molybdate to Mo-blue optimally between pH 5.8 and 6.3 and between 25 and34oC. Glucose was the best electron donor for supporting molybdate reduction followed by sucrose, D-mannitol, D-sorbitol, lactose,salicin, trehalose, maltose and myo-Inositol in descending order. Other requirements include a phosphate concentration between 5.0 and7.5 mM and a molybdate concentration between 5 and 20 mM. The absorption spectrum of the Mo-blue produced was similar toprevious Mo-reducing bacterium, and closely resembles a reduced phosphomolybdate. Molybdenum reduction was inhibited by mercury(ii), silver (i) and copper (ii) at 2 ppm by 62.1, 33.9 and 33.6%, respectively. Biochemical analysis resulted in a tentative identificationof the bacterium as Klebsiella oxytoca strain Aft-7. The ability of this bacterium to detoxify molybdenum and degrade detergent makesthis bacterium an important tool for bioremediation.

Intracellular azo decolorization is coupled with aerobic respiration by a Klebsiella oxytoca strain.

Reduction of azo dye methyl red coupled with aerobic respiration by growing cultures of Klebsiella oxytoca GS-4-08 was investigated. In liquid media containing dye and 0.6% glucose in a mineral salts base, 100mgl(-1) of the dye are completely removed in 3h under shaking conditions. The dye cannot be aerobically decolorized by strain GS-4-08 without extra carbon sources, indicating a co-metabolism process. Higher initial dye concentration prolonged the lag phase of the cell growth, but final cell concentrations of each batches reached a same level with range from 6.3 to 7.6mgl(-1) after the dye adaption period. This strain showed stronger dye tolerance and decolorization ability than many reported strains. Furthermore, a new intracellular oxygen-insensitive azoreductase was isolated from this strain, and the specific activity of enzyme was 0.846 and 0.633Umg(-1) protein in the presence of NADH and NADPH, respectively. N,N dimethyl-p-phenylenediamine and anthranilic acid were stoichiometrically released from MR dye, indicating the breakage of azo bonds accounts for the intracellular decolorization. Combining the characteristics of azoreductase, the stoichiometry of EMP, and TCA cycle, the electron transfer chain theory of aerobic respiration, and the possible mechanism of aerobic respiration coupled with azo reduction by K. oxytoca GS-4-08 are proposed. This study is expected to provide a sound theoretical basis for the development of the K. oxytoca strain in aerobic process for azo dye containing wastewaters.

Characterisation of biosynthesised silver nanoparticles by scanning electrochemical microscopy (SECM) and voltammetry

Silver nanoparticles (AgNPs) were biosynthesised by a Klebsiella oxytoca strain BAS-10, which, during its growth, is known to produce a branched exopolysaccharide (EPS). Klebsiella oxytoca cultures, treated with AgNO3 and grown under either aerobic or anaerobic conditions, produced silver nanoparticles embedded in EPS (AgNPs-EPS) containing different amounts of Ag(0) and Ag(I) forms. The average size of the AgNPs-EPS was determined by transmission electron microscopy, while the relative abundance of Ag(0)- or Ag(I)-containing AgNPs-EPS was established by scanning electrochemical microscopy (SECM). Moreover, the release of silver(I) species from the various types of AgNPs-EPS was investigated by combining SECM with anodic stripping voltammetry. These measurements allowed obtaining information on the kinetic of silver ions release from AgNPs-EPS and their concentration profiles at the substrate/water interface.

Cytotoxic and pathogenic properties of Klebsiella oxytoca isolated from laboratory animals.

Klebsiella oxytoca is an opportunistic pathogen implicated in various clinical diseases in animals and humans. Studies suggest that in humans K. oxytoca exerts its pathogenicity in part through a cytotoxin. However, cytotoxin production in animal isolates of K. oxytoca and its pathogenic properties have not been characterized. Furthermore, neither the identity of the toxin nor a complete repertoire of genes involved in K. oxytoca pathogenesis have been fully elucidated. Here, we showed that several animal isolates of K. oxytoca, including the clinical isolates, produced secreted products in bacterial culture supernatant that display cytotoxicity on HEp-2 and HeLa cells, indicating the ability to produce cytotoxin. Cytotoxin production appears to be regulated by the environment, and soy based product was found to have a strong toxin induction property. The toxin was identified, by liquid chromatography-mass spectrometry and NMR spectroscopy, as low molecular weight heat labile benzodiazepine, tilivalline, previously shown to cause cytotoxicity in several cell lines, including mouse L1210 leukemic cells. Genome sequencing and analyses of a cytotoxin positive K. oxytoca strain isolated from an abscess of a mouse, identified genes previously shown to promote pathogenesis in other enteric bacterial pathogens including ecotin, several genes encoding for type IV and type VI secretion systems, and proteins that show sequence similarity to known bacterial toxins including cholera toxin. To our knowledge, these results demonstrate for the first time, that animal isolates of K. oxytoca, produces a cytotoxin, and that cytotoxin production is under strict environmental regulation. We also confirmed tilivalline as the cytotoxin present in animal K. oxytoca strains. These findings, along with the discovery of a repertoire of genes with virulence potential, provide important insights into the pathogenesis of K. oxytoca. As a novel diagnostic tool, tilivalline may serve as a biomarker for K oxytoca-induced cytotoxicity in humans and animals through detection in various samples from food to diseased samples using LC-MS/MS. Induction of K. oxytoca cytotoxin by consumption of soy may be in part involved in the pathogenesis of gastrointestinal disease.

The study of Nickel Resistant Bacteria (NiRB) isolated from wastewaters polluted with different industrial sources

BackgroundPollution due to the heavy metals is a problem that may have negative consequences on the hydrosphere. One of the best procedures in removing the toxic metals from the environment is using metal resistant bacteria.ResultsIn the present study eight nickel resistant bacteria were isolated from industrial wastewaters. Three of them were selected as the most resistant based on their Maximum tolerable concentration (8, 16 and 24 mM Ni2+). Their identification was done according to morphological, biochemical characteristics and 16SrDNA gene sequencing and they were identified as Cupriavidus sp ATHA3, Klebsiella oxytoca ATHA6 and Methylobacterium sp ATHA7. The accession numbers assigned to ATHA3, ATHA6 and ATHA7 strains are JX120152, JX196648 and JX457333 respectively. The Growth rate of the most resistant isolate, Klebsiella oxytoca strain ATHA6, in the presence of Ni2+ and the reduction in Ni2+ concentration was revealed that K oxytoca ATHA6 could decrease 83 mg/mL of nickel from the medium after 3 days.ConclusionIt can be concluded that the identified Ni resistant bacteria could be valuable for the bioremediation of Ni polluted waste water and sewage.

Mutagenesis at α-423Ile of MoFe protein reduces the catalytic activity of nitrogenase in Klebsiella oxytoca

Nitrogenase catalyzes the ATP-dependent reduction of dinitrogen to ammonia, the central process of biological nitrogen fixation. The mechanism of electron transfer from the P-cluster to the iron-molybdenum cofactor (FeMo-co) during the process of substrate reduction remains unclear. Based on our previous hypothesis, the dual pathway model, three mutants of Klebsiella oxytoca strain M5al (termed Nβ102A, Kα431H and Iα423P) were constructed to map the H+/e− transfer pathway, in which β-102Asn, α-431Lys and α-423Ile of the molybdenum-iron (MoFe) protein of nitrogenases were replaced by alanine, histidine and proline, respectively. All three substitutions affected the diazotrophic growth, especially of the Iα423P strain with very low capability of diazotrophic growth and C2H2 reduction activity. In a 42-L fermenter, the Iα423P strain was induced to the maximal C2H2 reduction activity, which was only ~17 % of that of M5al. However, the transcription level of the nifD gene was approximately four-fold higher than that of the M5al strain, indicating that the low C2H2 reduction activity of Iα423P was not because of downregulation of nifD expression. The maximal C2H2 and H+ reduction activities of the Iα423P MoFe protein were 13 % and 21 % of those of the wild-type MoFe protein, respectively. In conclusion, we propose that the changed properties of the Iα423P MoFe protein are related to the disruption of hydrogen bond formation between α-423Ile and homocitrate, and that α-423Ile serves as a gate to the Mo site in FeMo-co during the H+/e− transfer in nitrogenase.

Ferric citrate fermentation by a Klebsiella oxytoca strain isolated from pyrite mine drainage producing a relevant exopolysaccharide and its potential applications

Ferric citrate fermentation by a Klebsiella oxytoca strain isolated from pyrite mine drainage producing a relevant exopolysaccharide and its potential applications