Investigation of the porphyrins accumulation in barley leaves incubated with Mn cations and δ-aminolevulinic acid

In greening etiolated primary leaves of barley (Hordeum vulgare L.), Mn²⁺ ions have been shown to inhibit chlorophyll (Chl) accumulation in a dose dependent manner and to lead to an accumulation of protoporphyrin IX (Proto) and Mg-protoporphyrin IX monomethyl ester (MgPE). The amount of MgPE that accumulated, was 2 times higher than Proto. In the dark, Proto and MgPE were observed to have accumulated to high levels in seven-day old green and etiolated leaves in the presence of 5 mmol/L Mn²⁺, but only if 5 mmol/L δ-aminolevulinic acid (ALA) was present. The 24 hours of irradiation of the green barley leaves treated in this way, resulted in a photodynamic destruction of Proto and MgPE as well as of Chl and carotenoids (Car). The observed porphyrin accumulation caused by the Mn²⁺ ions was reversed in the presence of active iron (Fe²⁺). This effect was observed when the iron concentration in incubation solutions was half the Mn²⁺ concentration, most effective for porphyrin synthesis, i.e. 5 mmol/L. The action of Mn²⁺ on porphyrin accumulation is also discussed.     

Formation of Valine in the Presence of Sodium Acrylate Monomer by Glutamic Acid Producing Bacteria

Glutamic acid producing bacteria accumulated a large amount of valine in the presence of the excess biotin, when sodium acrylate monomer (Na-AM) was added at the earlier phase of culture. Brevibacterium roseum ATCC 13825, particularly, accumulated the large amount of valine among bacteria tested and the conditions of valine accumulation by this strain were investigated.

The most effective addition time of Na-AM was at the earlier phase of logarithmic phase. The optimal concentration of Na-AM for the accumulation of valine was 1.0 per cent (v/v). Most effective nitrogen sources were the combination of 1.0 per cent urea and 0.2 per cent ammonium sulphate. The additions of Mn²⁺ and Fe²⁺ increased valine accumulation. By the excess concentration of biotin for growth, 20 μg/liter or more, did not affected valine accumulation, while the presence of the suboptimal condition of biotin for growth was not good for the formation of valine even in the presence of Na-AM. The accumulation of valine reached 9.0 mg/ml from 75.0 mg/ml of glucose in the presence of 50 μg/liter of biotin and 1.0 per cent (v/v) of Na-AM.

This strain possessed considerable activity of valine formation regardless of the addition of Na-AM and promoted the accumulation of valine by the addition of Na-AM.     

Influence of some trace metals and stimulants on citric acid production from brewery wastes by Aspergillus niger

The addition of increasing levels of Mn²⁺, Fe³⁺, Zn²⁺, Co²⁺, Cu²⁺, Ca²⁺, sodium monofluoracetate and methanol during citric acid surface fermentation of spent grain liquor by Aspergillus niger (ATCC 9142) was investigated. For spent grain liquor the addition of 51 ppb Mn²⁺, 5 ppb Fe³⁺, 75 ppb Zn²⁺ and 4% (v/va) methanol caused a 4.9, 1.9, 10.9 and 16.8% increase in citric acid yield respectively. In all other fermentations the yield of citric acid was decreased whereas the biomass production in some cases was increased.     

Malformin A1 as a Mammalian Toxicant from Aspergillus niger

Culture conditions for guanosine production were studied with Bacillus subtilis MG–1 that exclusively accumulated guanosine. Of components investigated, KH₂PO₄, KC1, Fe⁺⁺, Mn⁺⁺, NH₄NO₃ and sodium glutamate have played important roles for guanosine production. The optimal concentrations in the culture medium were 2.0 g, 0.9 g, 7.5 mg, 7.5 mg, 20. 4 g and 6.0 g per liter, respectively.

In particular, the extremely minor concentration of Mn⁺⁺ 0.01 ppm completely repressed guanosine production although the cells grew sufficiently. Amino acids mixture was necessary for cell growth, but not essential for guanosine production.

Under these conditions, MG–1 accumulated 15 g of guanosine per liter in a weight yield of 18.8% of consumed sugar. However, a large amount of acetoin was also found as a byproduct.     

Citric acid fermentation from starch and dextrose syrups by a trace metal resistant mutant of Aspergillus niger

Potato starch and both untreated and decationized dextrose syrups were used as substrates for submerged citric acid biosynthesis using a mutant of Aspergillus niger. The same yield of product (80%) was achieved with both syrups and the starch despite having different trace metals content. The obtained mutant was more sensitive than the parent to Cd²⁺, Mo²⁺, and As³⁺, with decreasing yields of citric acid at 10 mg of ions l^–1. Fe²⁺, Mn²⁺, V²⁺ below 50 mg l^–1 and Cr³⁺, Ni²⁺, Cu²⁺ up to 100 mg l^–1, did not significantly inhibit citric acid production.     

Efficient itaconic acid production by Aspergillus terreus: Overcoming the strong inhibitory effect of manganese

Itaconic acid (IA), a building block platform chemical, is produced industrially by Aspergillus terreus utilizing glucose. Lignocellulosic biomass can serve as a low cost source of sugars for IA production. However, the fungus could not produce IA from dilute acid pretreated and enzymatically saccharified wheat straw hydrolyzate even at 100-fold dilution. Furfural, hydroxymethyl furfural and acetic acid were inhibitory, as is typical, but Mn²⁺ was particularly problematic for IA production. It was present in the hydrolyzate at a level that was 230 times over the inhibitory limit (50 ppb). Recently, it was found that PO₄³⁻ limitation decreased the inhibitory effect of Mn²⁺ on IA production. In the present study, a novel medium was developed for production of IA by varying PO₄³⁻, Fe³⁺ and Cu²⁺ concentrations using response surface methodology, which alleviated the strong inhibitory effect of Mn²⁺. The new medium contained 0.08 g KH₂PO₄, 3 g NH₄NO₃, 1 g MgSO₄·7H₂O, 5 g CaCl₂·2 H₂O, 0.83 mg FeCl₃·6H₂O, 8 mg ZnSO₄·7H₂O, and 45 mg CuSO₄·5H₂O per liter. The fungus was able to produce IA very well in the presence of Mn²⁺ up to 100 ppm in the medium. This medium will be extremely useful for IA production in the presence of Mn²⁺. This is the first report on the development of Mn²⁺ tolerant medium for IA production by A. terreus.     

Thiols as biomarkers of heavy metal tolerance in the aquatic macrophytes of Middle Urals,Russia

Aquatic macrophytes, viz. Sagittaria sagittifolia L., Lemna gibba L., Elodea canadensis Michx., Batrachium trichophyllum (Chaix.) Bosch., Ceratophyllum demersum L. and Potamogeton sp. (P. perfoliatus L., P. alpinus Balb., P. crispus L., P. berchtoldii Fieber, P. friesii Rupr., P. pectinatus L.) were collected from 11 sites for determining their metal accumulation and thiols content. Cu²⁺, Ni²⁺, Mn²⁺, Zn²⁺, and Fe³⁺ exceeded maximum permissible concentrations in chosen sites. Significant transfer of metals from water to leaves is observed in the order of Ni²⁺ < Cu²⁺ < Zn²⁺ < Fe³⁺ < Mn²⁺. The maximum variation of bioconcentration factor was noticed for manganese. The accumulation of heavy metals in leaves was correlated with non-protein and protein thiols, confirming their important role in metal tolerance. The largest contribution was provided by Cu²⁺ (on the average r = 0.88, p < 0.05), which obviously can be explained as an important role of these ions in thiols synthesis. Increased synthesis of thiols in the leaves allows the usage of SH-containing compounds as biomarkers of metal tolerance. Considering accumulation of metals and tolerance, B. trichophyllum, C. demersum and L. gibba are the most suitable species for phytoremediation of highly multimetal contamination, while E. canadensis and some species of Potamageton are suitable for moderately metal-polluted sites.     

不同浓度Fe2+与Zn2+对羊草幼苗生长和生理特性的影响

以羊草幼苗为研究对象,通过调整全营养培养基(CK,0.05 mmol/L Fe²⁺、0.015 mmol/L Zn²⁺)中铁或者锌含量设置0、10倍、20倍Fe²⁺(Zn²⁺)浓度处理Fe₀(Zn₀)、Fe₁₀(Zn₁₀)、Fe₂₀(Zn₂₀),以及在高铁培养基中单独添加0.15 mmol/L Zn²⁺或同时添加10 mmol/L Ca²⁺、5 mmol/L Mg²⁺、20 mmol/L K⁺处理,测定培养6 d后幼苗生长指标和矿质元素含量、以及高铁(Fe₂₀)处理下幼苗根中抗氧化指标和相关基因表达量,探究不同浓度Fe²⁺、Zn²⁺对羊草幼苗生长、矿质元素吸收积累及抗氧化指标、基因表达的影响。结果表明：(1)缺锌(Zn₀)显著抑制羊草幼苗鲜重的增加和Zn元素的积累,但促进Fe、Mg元素的积累;高浓度锌(Zn₁₀、Zn₂₀)显著促进幼苗叶片生长和Zn元素的积累;缺铁(Fe₀)显著抑制幼苗的根长、鲜重和Fe元素的积累,促进Mg、Zn元素的积累;高浓度铁(Fe₁₀、Fe₂₀)显著抑制羊草幼苗根叶生长、根毛发育和Ca、Zn、Mg、K元素的积累。(2)增加Zn²⁺和Ca²⁺、Mg²⁺、K⁺浓度无法恢复高铁胁迫对幼苗生长的抑制作用。(3)高浓度铁(Fe₂₀)处理羊草幼苗48 h后,根部过氧化物酶、超氧化物歧化酶、过氧化氢酶、抗坏血酸过氧化物酶、谷胱甘肽还原酶活性和丙二醛、抗坏血酸、还原型谷胱甘肽含量显著升高;烟酰胺合成酶基因、过氧化物酶基因表达量显著下调,植物类萌发素蛋白基因表达量显著上调。研究发现,羊草幼苗生长发育和矿质元素积累对环境中Zn²⁺浓度变化不敏感,却受到环境中高浓度Fe²⁺的显著抑制,并造成严重的氧化胁迫伤害,这种伤害无法在添加Zn²⁺或同时添加Ca²⁺、Mg²⁺、K⁺的条件下恢复。     

Nutritional factors regulating growth and accumulation of phenazine 1-carboxylic acid by Pseudomonas fluorescens 2-79

Summary Pseudomonas fluorescens strain 2-79 (NRRL B-15 132) is a biocontrol agent of take-all of wheat caused by the fungus Gaeumannomyces graminis var. tritici. Strain 2-79 produces the antibiotic phenazine 1-carboxylic acid, which acts as the primary mechanism of disease suppression. As a first step toward designing efficient methods of mass producing and formulating this biocontrol agent, the regulation of growth and antibiotic production by growth factors (including purines, pyrimidines, vitamins) and minerals (supplying B³⁺, Ca²⁺, Co²⁺, Cu²⁺, Fe²⁺, Mg²⁺, Mn²⁺, Mo⁶⁺, Zn²⁺) was examined in defined liquid culture. Additions of boric acid and sulfates of iron and magnesium enhanced both cell and associated antibiotic accumulation. However, accumulation of the antibiotic alone improved with additions of zinc sulfate, ammonium molybdate, and cytosine, but worsened with addition of adenine. Interactive effects involving the sulfates of iron, magnesium, and zinc were observed, and optimal iron-magnesium and iron-zinc combinations were demonstrated with respect to biomass and antibiotic accumulation, respectively.The mention of firm names or trade products does not imply that they are endorsed or recommended by the U. S. Department of Agriculture over other firms or similar products not mentioned Correspondence to: P. J. Slininger     

Biochemical studies of citric acid production and accumulation by Aspergillus niger mutants

The biochemical rationale for the inhibition of citric acid fermentation by Aspergillus niger in the presence of Mn²⁺ ions has been investigated using high citric acid-yielding, Mn²⁺ ion-sensitive as well as Mn²⁺ ion-tolerant mutant strains of A. niger. In the presence of Mn²⁺ (1.5 mg/l), citric acid production by the Mn²⁺ ion-sensitive strain (KCU 520) was reduced by about 75% with no apparent effect on citric acid yield by the Mn²⁺ ion-tolerant mutant strain (GS-III) of A. niger. The significantly increased level of the Mn²⁺ ion-requiring NADP⁺-isocitrate dehydrogenase activity in KCU 520 cells and the lack of effect on the activity level of the enzyme in GS-III mutant cells by Mn²⁺ ions during fermentation seem to be responsible for the Mn²⁺ ion inhibition of citric acid production by the KCU 520 strain and the high citric acid yield by the mutant strain GS-III of A. niger even in the presence of Mn²⁺.     

Production of Bacterial Cells from Methane

A mixed methane-oxidizing bacterial culture capable of stable and predictable growth in continuous culture was isolated. The culture consisted of two types of gram-negative nonsporulating rods resembling pseudomonads. The culture grew well at 45 C on an inorganic medium without asepsis. Specific metal requirements for Ca²⁺, Cu²⁺, MoO₄²⁻, Zn²⁺, Mn²⁺, Mg²⁺, and Fe³⁺ (or Fe²⁺) were shown. The cells grown in continuous culture contained 11.7 to 12.1% total nitrogen. From an animal nutrition standpoint, the distribution of amino acids was satisfactory. The continuous fermentation was operated over a range of steady-state dilution rates from 0.085 to 0.301 hr⁻¹. The maximum specific growth rate for the culture, μ_max, was 0.303 hr⁻¹ (doubling time 2.29 hr). The average yield for all fermentations analyzed was 0.616 g (dry weight of cells per g of methane used and 0.215 g (dry weight) of cells per g of oxygen used. The yields on both methane and oxygen were higher for the oxygen-limited than for the methane-limited fermentations. The maximum productivity attained in the fermentor was 2.39 g (dry weight) of cells per hr per liter at a dilution rate of 0.187 hr⁻¹ and a cell concentration of 12.8 g (dry weight) of cells per liter. The limit on maximum cell productivity was determined only by the mass transfer rate of oxygen in the fermentor. The simultaneous volumetric mass-transfer coefficients (k_La in hr⁻¹) for oxygen and methane were determined. The results appear to indicate an oxygen to methane mass-transfer coefficient ratio of approximately 1.4.     

Light emission from the Fe2+–EDTA–ascorbic acid–H2O2 system strongly enhanced by plant phenolic acids

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 Fe²⁺–EDTA (ethylenediaminetetraacetic acid)–AA (ascorbic acid)–H₂O₂ (hydrogen peroxide) system with a multitube luminometer (Peltier‐cooled photon counter, spectral range 380–630 nm). The UPE, of 92.6 μmol/L Fe²⁺, 185.2 μmol/L EDTA, 472 μmol/L AA, 2.6 mmol/L H₂O₂, 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 (Fe²⁺–AA–H₂O₂, Fe²⁺–EDTA–H₂O₂, AA–H₂O₂) and medium alone. Substitution of Fe²⁺ with Cr²⁺, Co²⁺, Mn²⁺ or Cu²⁺ 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 Fe²⁺–EDTA–AA–H₂O₂ system can be applied for detection of these phytochemicals.     

Lipid formation by Cryptococcus albidus in nitrogen-limited and in carbon-limited chemostat cultures

Summary Cryptococcus albidus var. Albidus CBS 4517 was grown in nitrogen-limited and in carbon-limited chemostat cultures. The effect of growth rate and limiting nutrient on lipid accumulation and fatty acid composition was investigated.The maximum lipid content in the biomass was, in both cultivation systems, observed at the lowest dilution rate (growth rate) tested. At this dilution rate, D=0.31 h^-1, cells from the nitrogen-limited culture contained 41% (w/w) lipid and cells from the carbon-limited culture 37%. These results indicate the ability of C. albidus, unlike other oleaginous yeasts, to accumulate lipid also in carbon-limited chemostats.The yield of lipid from carbon source was about the same at D=0.031 h^-1 in nitrogen-limited (Y _L/S=0.16 g/g) as in carbon-limited (Y _L/S=0.17 g/g) cultures and decreased with increasing growth rates. In the nitrogen-limited culture, the lipid productivity was about constant at low growth rates (0.031–0.056 h^-1) and a slight decrease was observed at D=0.08 h^-1, while the specific lipid productivity, q _L, increased to 27.5 mg/g per hour. In the carbon-limited culture, however, lipid productivity increased with increasing growth rates and reached its maximum value near _max, whereas q _L was about constant at 20 mg/g per hour.The fatty acid composition was influenced by the specific growth rate in nitrogen-limited as well as in carbon-limited cultures, although the changes were more pronounced during carbonlimitation. A decrease in the degree of unsaturation (/mole) was also observed with increasing lipid content in the cells.     

Purification and characterization of extracellular inulinase from a marine yeast <Emphasis Type="Italic">Pichia guilliermondii</Emphasis> and inulin hydrolysis by the purified inulinase

The extracellular inulinase of the marine yeast Pichia guilliermondii strain 1 was purified to homogeneity resulting in a 7.2-fold increase in specific inulinase activity. The molecular mass of the purified enzyme was estimated to be 50.0 kDa. The optimal pH and temperature for the purified enzyme were 6.0 and 60°C, respectively. The enzyme was activated by Mn²⁺, Ca²⁺, K⁺, Li⁺, Na⁺, Fe³⁺, Fe²⁺, Cu²⁺, and Co²⁺, but Mg²⁺, Hg²⁺, and Ag⁺ inhibited activity. The enzyme was strongly inhibited by phenylmethanesulphonyl fluoride (PMSF), iodoacetic acid, EDTA, and 1, 10-phenanthroline. The K _m and V _max values of the purified inulinase for inulin were 21.1 mg/mL and 0.08 mg/min, respectively. A large number of monosaccharides were detected after the hydrolysis of inulin. The deduced protein sequence from the cloned P. guilliermondii strain 1 inulinase gene contained the consensus motifs R-D-P-K-V-F-W-H and W-M-N-D-P-N-G, which are conserved among the inulinases from other microorganisms.     

A novel thermostable and halostable carboxymethylcellulase from marine bacterium <Emphasis Type="Italic">Bacillus licheniformis</Emphasis>AU01

A novel thermostable, halostable carboxymethylcellulase (CMCase) from a marine bacterium Bacillus licheniformisAU01 was purified 10.4-fold with 18% yield with a specific activity of 88.43 U/mg and the molecular weight was estimated as 37 kDa. The enzyme was optimally active at pH 9–10 and temperature 50–60°C and it was most stable up to pH 12 and 20–30% of NaCl concentration. The enzyme activity was reduced when treated with Hg²⁺, Fe²⁺ and EDTA and stimulated by Co²⁺, Mn²⁺, Mg²⁺ and Ca²⁺. Various cationic, anionic detergents and commercial detergents were not much affected CMCase activity.     

Equilibrium and Kinetics of Adsorption of Mn2+ by Haloarchaeon Halobacterium sp. GUSF (MTCC3265)

The coastal waters of countries bordering on an ocean show increases in manganese pollution due to runoff from mining activity and from industries dealing with production of ferroalloys, steel, iron, petrochemicals, and fertilizers. One gram of dried cells of haloarchaeon Halobacterium sp. GUSF (MTCC3265) adsorbed 99% Mn²⁺ in 60 min at pH 6.8 and 30ºC on contact with 109.54 mg Mn²⁺ per liter in saline solution. Adsorbed Mn²⁺ was quantified by atomic absorption spectrometry and demonstrated on the cell surface by SEM-EDX. Mn²⁺ adsorbed to functional groups of the adsorbent was studied by FTIR. The adsorption process of Mn²⁺ showed saturation and followed pseudo–second-order kinetics; was consistent with the homogeneity of the Langmuir model (R² of 0.99); exhibited a Q_max of 62.5 mg g^?1 and a binding energy of 0.018 L mg^?1. The Mn²⁺adsorption was also consistent with the heterogeneity of the Freundlich model by exhibiting a K_f of 1.0 mg g^?1 with an n value of 1.1. Adsorption efficiency of 99% was retained even after a third adsorption-desorption cycle. This is the first report on metal ion adsorption, using Mn²⁺ as an example, by the haloarchaeon Halobacterium sp. GUSF (MTCC3265) in the domain Archaea.     

锰对外生菌根真菌生长、养分吸收、有机酸分泌和菌丝体中锰分布的影响

外生菌根真菌对于酸性和锰污染土壤的植树造林和生态恢复有重要作用。采用液体培养方法,以大白菇Rd Fr(Russula delica Fr.)、彩色豆马勃Pt 715(Pisolithus tinctorius 715)、土生空团菌Cg Fr(Cenococcum geophilum Fr.)和厚环粘盖牛肝菌Sg Kl S(Suillus grevillei(Kl.)Sing)为供试对象,研究了Mn2+对外生菌根真菌生长、养分吸收、有机酸和氢离子分泌的影响,以及锰在菌丝细胞内外的分布情况。结果表明:在0—800 mg Mn2+/L的培养液中,Mn2+对Rd Fr生长无显著影响;低浓度的Mn2+刺激Sg Kl S生长,中、高浓度无抑制作用;但大幅度降低Pt 715和Cg Fr的生物量,说明Rd Fr和Sg Kl S抗(耐)锰的能力较强。在Mn2+胁迫下,供试菌株的氮、钾含量和吸收量显著降低;含磷量和吸收量,以及草酸和柠檬酸的分泌速率因菌株不同而表现出多样性,说明在减轻Mn2+毒的过程中,磷酸盐(或聚磷酸盐)对Mn2+固定作用和有机酸的络合作用因菌株不同而异。但是,Mn2+显著降低Rd Fr和Sg Kl S的氢离子分泌速率,菌丝和原生质中的含Mn量显著低于敏感性菌株,说明降低Mn2+的活性和减少吸收可能是外生菌根真菌抗(耐)Mn2+的重要机制。此外,菌丝吸收的Mn2+绝大部份存在于质外体,少量进入细胞,前者是后者的5.23—9.21倍,说明原生质膜是外生菌根真菌防御Mn2+进入细胞的重要屏障。     

Using Taguchi experimental design methods to optimize trace element composition for enhanced surfactin production by Bacillus subtilis ATCC 21332

In this work, optimizing trace element composition was attempted as a primary strategy to improve surfactin production from Bacillus subtilis ATCC 21332. Statistical experimental design (Taguchi method) was applied for the purpose of identifying optimal trace element composition in the medium. Of the five trace elements examined, Mg²⁺, K⁺, Mn²⁺, and Fe²⁺ were found to be more significant factors affecting surfactin production by the B. subtilis strain. In the absence of Mg²⁺ or K⁺, surfactin yield decreased to 0.4 g/l, which was only 25% of the value obtained from the control run. When Mn²⁺ and Fe²⁺ were both absent, the production yield also dropped to ca. 0.6 g/l, approximately one-third of the control value. However, when only one of the two metal ions (Fe²⁺ or Mn²⁺) was missing, the B. subtilis ATCC 21332 strain was able to remain over 80% of original surfactin productivity, suggesting that some interactive correlations among the selected metal ions may involve. Taguchi method was thus applied to reveal the interactive effects of Mg²⁺, K⁺, Mn²⁺, Fe²⁺ on surfactin production. The results show that interaction of Mg²⁺ and K⁺ reached significant level. By further optimizing Mg²⁺ and K⁺ concentrations in the medium, the surfactin production was boosted to 3.34 g/l, which nearly doubled the yield obtained from the original control.     

Application of an M13 bacteriophage displaying tyrosine on the surface for detection of Fe3+ and Fe2+ ions

Ferric and ferrous ion plays critical roles in bioprocesses,their influences in many fields have not been fully explored due to the lack of methods for quantification of ferric and ferrous ions in biological system or complex matrix.In this study,an M13 bacteriophage(phage) was engineered for use as a sensor for ferric and ferrous ions via the display of a tyrosine residue on the P8 coat protein.The interaction between the specific phenol group of tyrosine and Fe~(3+)./ Fe~(2+).was used as the sensor.Transmission electron microscopy showed aggregation of the tyrosine-displaying phages after incubation with Fe~(3+) and Fe~(2+).The aggregated phages infected the host bacterium inefficiently.This phenomenon could be utilized for detection of ferric and ferrous ions.For ferric ions,a calibration curve ranging from 200 nmol/L to 8 μmol/L with a detection limit of 58 nmol/L was acquired.For ferrous ions,a calibration curve ranging from 800 nmol/L to 8μmol/L with a detection limit of 641.7 nmol/L was acquired.The assay was specific for Fe~((3+)) and Fe~((2+)) when tested against Ni~(2+),Pb~(2+),Zn~(2+),Mn~(2+),Co~(2+),Ca~(2+),Cu~(2+),Cr~(3+),Ba~(2+),and K~+.The tyrosine displaying phage to Fe~(3+) and Fe~(2+) interaction would have plenty of room in application to biomatenals and bionanotechnology.     

Vacuolar membrane transporters OsVIT1 and OsVIT2 modulate iron translocation between flag leaves and seeds in rice

The plant vacuole is an important organelle for storing excess iron (Fe), though its contribution to increasing the Fe content in staple foods remains largely unexplored. In this study we report the isolation and functional characterization of two rice genes OsVIT1 and OsVIT2, orthologs of the Arabidopsis VIT1. Transient expression of OsVIT1:EGFP and OsVIT2:EGFP protein fusions revealed that OsVIT1 and OsVIT2 are localized to the vacuolar membrane. Ectopic expression of OsVIT1 and OsVIT2 partially rescued the Fe²⁺‐ and Zn²⁺‐sensitive phenotypes in yeast mutant Δccc1 and Δzrc1, and further increased vacuolar Fe²⁺, Zn²⁺ and Mn²⁺ accumulation. These data together suggest that OsVIT1 and OsVIT2 function to transport Fe²⁺, Zn²⁺ and Mn²⁺ across the tonoplast into vacuoles in yeast. In rice, OsVIT1 and OsVIT2 are highly expressed in flag leaf blade and sheath, respectively, and in contrast to OsVIT1, OsVIT2 is highly responsive to Fe treatments. Interestingly, functional disruption of OsVIT1 and OsVIT2 leads to increased Fe/Zn accumulation in rice seeds and a corresponding decrease in the source organ flag leaves, indicating an enhanced Fe/Zn translocation between source and sink organs, which might represent a novel strategy to biofortify Fe/Zn in staple foods.