Response of 19 Azolla strains to a high concentration of ammonium ions

The response of 19 Azolla strains from five species to 20 mM ammonium ions was examined. The response varied even among strains of the same species. The tolerance indexes of both relative growth rate and nitrogen fixation [(values for plants grown in the presence of ammonium ions)/(values for plants grown in the absence of ammonium ions)] showed that ammonium ions did not always simultaneously inhibit growth and nitrogen fixation of individual strains. The tolerance of each Azolla–Anabaena association to ammonium ions is assumed to be determined separately by both the host fern and the symbiotic Anabaena. The inhibitory effects of ammonium appeared predominantly in the mature region of Azolla–Anabaena associations. In the sensitive strains, both chlorophyll content and the number of cyanobionts were reduced only in the mature region when ammonium ions were present. Possible strains for treatment of wastewater, which contains a high concentration of ammonium ions, are discussed.     

Development of novel mass spectrometric methods for identifying HOCl‐induced modifications to proteins

Protein oxidation is thought to contribute to a number of inflammatory diseases, hence the development of sensitive and specific analytical techniques to detect oxidative PTMs (oxPTMs) in biological samples is highly desirable. Precursor ion scanning for fragment ions of oxidized amino acid residues was investigated as a label‐free MS approach to mapping specific oxPTMs in a complex mixture of proteins. Using HOCl‐oxidized lysozyme as a model system, it was found that the immonium ions of oxidized tyrosine and tryptophan formed in MS² analysis could not be used as diagnostic ions, owing to the occurrence of isobaric fragment ions from unmodified peptides. Using a double quadrupole linear ion trap mass spectrometer, precursor ion scanning was combined with detection of MS³ fragment ions from the immonium ions and collisionally‐activated decomposition peptide sequencing to achieve selectivity for the oxPTMs. For chlorotyrosine, the immonium ion at 170.1 m/z fragmented to yield diagnostic ions at 153.1, 134.1, and 125.1 m/z, and the hydroxytyrosine immonium ion at 152.1 m/z gave diagnostic ions at 135.1 and 107.1 m/z. Selective MS³ fragment ions were also identified for 2‐hydroxytryptophan and 5‐hydroxytryptophan. The method was used successfully to map these oxPTMs in a mixture of nine proteins that had been treated with HOCl, thereby demonstrating its potential for application to complex biological samples.     

Rat osseous plate alkaline phosphatase: mechanism of action of manganese ions

Polidocanol-solubilized osseous plate alkaline phosphatase was modulated by manganese ions in a similar way as by zinc ions. For concentrations up to 1.0 nm, the enzyme was stimulated by manganese ions, showing site-site interactions (n = 2.2). However, larger concentrations (> 0.1 m) were inhibitory. Manganese ions could play the role of zinc ions stimulating the enzyme synergistically in the presence of magnesium ions (K _d = 7.2 m; V = 1005.5 U mg^–1). Manganese ions could also play the role of magnesium ions, stimulating the enzyme synergistically in the presence of zinc ions (K _d = 2.2 m; V = 1036.7 U mg^–1). However, manganese ions could not substitute for zinc and magnesium at the same time since ion assymetry is necessary for full activity of the enzyme. A steady-state kinetic model for the modulation of enzyme activity by manganese ions is proposed.     

The effect of Cl- upon the sensitivity of starch-containing and starch-deficient stomata and guard cell protoplasts towards potassium ions,fusicoccin and abscisic acid

Chloride ions are necessary to compensate for the positively charged potassium ions imported into guard cells of Allium cepa L. during stomatal opening. Therefore an external Cl^- supply of intact Allium plants is important. But high levels of chloride have been found to reduce the sensitivity of the starch-lacking stomata and isolated guard cell protoplasts (GCPs) from Allium to potassium ions, fusicoccin and abscisic acid. Furthermore, with high levels of chloride, malate anions disappear from the guard cells of Allium, a finding which contrasts with situation in Vicia where the stomatal sensitivity to K⁺ ions, fusicoccin and ABA is not influenced by Cl^- ions and malate levels are unaffected. It is suggested that the absence of malate as a proton yielding primer inhibits the mechanism of H⁺/K⁺ exchange in Allium.Abbreviations ABA abscisic acid - FC fusicoccin - GCPs guard cell protoplasts     

Chemical stimulation of the virulence of entomopathogenic fungi

The effect of magnesium and manganese ions on the virulence of Beauveria bassiana, Metarhizium anisopliae, Paecilomyces farinosus, and Paecilomyces fumosoroseus entomopathogenic fungi was tested. The virulence of entomopathogenic fungi to Sitona lineatus (L) weevil, pupae and larvae, was increased by tested metal ions. Mg ions increased the virulence of B. bassiana against S. linatus (L) weevils 100%. The fungi exhibited various sensitivity to these metal ions.     

Removal of Chromium(VI) Ions from Synthetic Solutions by the Fungus Penicillium purpurogenum

The ability of Penicillium purpurogenum to bind high amounts of chromium(VI) from aqueous solutions is demonstrated. Cr(VI) adsorption capacity increases with time during the first four hours and then leveled off toward the equilibrium adsorption capacity. Biosorption of Cr(VI) ions reached equilibrium in four hours. Binding of Cr(VI) ions with Penicillium purpurogenum biomass was clearly pH dependent. Cr(VI) loading capacity increased with increasing pH. The adsorption of Cr(VI) ions reached a plateau value at a pH of approx. 6.0. The maximum capacity of adsorption of Cr(VI) ions onto the fungal biomass was 36.5 mg/g. Adsorption behavior of Cr(VI) ions can be approximately described with the Langmuir equation. When applying the Langmuir model, the maximum adsorption capacity (Q_max) and the Langmuir constant were found to be 40 mg/g and 3.9 × 10^–3 mg/L. Elution of Cr(VI) ions was performed by means of 0.5 M HCl. It was possible to use the biomass of Penicillium purpurogenum for six cycles for biosorption.     

Esterases in mycobacteria

Esterases ofMycobacterium phlei (acetic ester acetyl hydrolase E.C.3.1.6 and carboxylic esterhydrolase E.C.3.1.1.1.) obtained after separation on Sephadex G-100 can be temporarily, for a short time interval, activated by adding calcium ions. The activation of esterases isolated from cells was non-repeteable, whereas the temporary activation of esterases from the culture filtrate could be repeated by increasing concentrations of calcium ions. However, the value of activation gradually decreased. Similarly with calcium ions strontium ions were also effective, however, higher concentrations were required and the activation was non-repeatable. Magnesium ions were practically without any effect. Possible mechanisms of the temporary activation of esterases ofMycobacterium phlei are discussed.     

Effect of Calcium and Zinc on the Activity and Thermostability of Superoxide Dismutase

The effect of calcium and zinc ions on superoxide dismutase (SOD) from four plant species (Taxus baccata, Pinus sylvestris, Medicago rigidula, and Zea mays) was followed at three temperatures: optimal (20 °C), increased (50 °C), and high, inhibiting temperature (70 – 80 °C). At 20 and 50 °C in vitro added calcium increases SOD activity, but the degree was different for the plants investigated. The effect of zinc ions at the same temperatures varied in the investigated plants from activation to inhibition. An inhibiting effect of high temperature on SOD activity was diminished in the presence of calcium or zinc ions. It was shown that calcium and zinc ions can increase activity and thermostabilize different SOD isoforms.     

The relative biological effectiveness of densely ionizing heavy-ion radiation for inducing ocular cataracts in wild type versus mice heterozygous for the ATM gene

The accelerated appearance of ocular cataracts at younger ages has been recorded in both astronauts and airline pilots, and is usually attributed to high-energy heavy ions in galactic cosmic ray radiation. We have previously shown that high-LET 1-GeV/nucleon ⁵⁶Fe ions are significantly more effective than X-rays in producing cataracts in mice. We have also shown that mice haploinsufficient for ATM develop cataracts earlier than wild-type animals, when exposed to either low-LET X-rays or high-LET ⁵⁶Fe ions. In this paper we derive quantitative estimates for the relative biological effectiveness (RBE) of high energy ⁵⁶Fe ions compared with X-rays, both for wild type and for mice haploinsufficient for ATM. There is a clear trend toward higher RBE’s in haploinsufficient animals, both for low- and high-grade cataracts. Haploinsufficiency for ATM results in an enhanced sensitivity to X-rays compared with the wild type, and this enhancement appears even larger after exposure to high-LET heavy ions.Dedicated to the memory of Professor Basil V. Worgul, who passed away in January 2006, much missed by all his colleagues.     

Enzyme make-up of trichophyton rubrum and t. mentagrophytes

Summary Aldolase activity in the cell-free extracts of two dermatophytes,T. mentagrophytes andT. rubrum, was investigated. The kinetics of the enzyme and the effects of metal ions and metal-binders are also reported. The enzyme was more active inT. mentagrophytes than inT. rubrum. The optimum pH for the enzyme action was 7.2 and it was completely inactivated at 60° C. Cobalt and magnesium ions and cysteine activated the enzyme. Inhibition caused by EDTA and o-phenanthroline was partially reversed by cobalt ions. The dermatophyte aldolase resembles bacterial aldolase in its properties.     

Identification of genes required for gold and silver tolerance in Burkholderia cenocepacia H111 by transposon sequencing

Members of the genus Burkholderia show remarkable abilities to adapt to a wide range of environmental conditions and is frequently isolated from soils contaminated with heavy metals. In this study, we used a transposon sequencing approach to identify 138 and 164 genes that provide a benefit for growth of the opportunistic pathogen Burkholderia cenocepacia H111 in the presence of silver and gold ions respectively. The data suggest that arginine metabolism and citrate biosynthesis are important for silver tolerance, while components of an ABC transporter (BCAL0307-BCAL0308) and de novo cysteine biosynthesis are required for tolerance to gold ions. We show that determinants that affect tolerance to both metal ions include the two-component systems BCAL0497/99 and BCAL2830/31 and genes that are involved in maintaining the integrity of the cell envelope, suggesting that membrane proteins represent important targets of silver and gold ions. Furthermore, we show that that the P-type ATPase CadA (BCAL0055), which confers tolerance to cadmium contributes to silver but not gold tolerance. Our results may be useful for improving the antibacterial effect of silver and gold ions to combat drug-resistant pathogens.     

Enhancement of Lead(II) Biosorption by Microalgal Biomass Immobilized onto Loofa (Luffa cylindrica) Sponge

A unicellular green microalga, Chlorella sorokiniana, was immobilized on loofa (Luffa cylindrica) sponge and successfully used as a new biosorption system for the removal of lead(II) ions from aqueous solutions. The biosorption of lead(II) ions on both free and immobilized biomass of C. sorokiniana was investigated using aqueous solutions in the concentration range of 10–300 mg/L. The biosorption of lead(II) ions by C. sorokiniana biomass increased as the initial concentration of lead(II) ions increased in the medium. The maximum biosorption capacity for free and immobilized biomass of C. sorokiniana was found to be 108.04 and 123.67 mg lead(II)/g biomass, respectively. The biosorption kinetics were found to be fast, with 96 % of adsorption within the first 5 min and equilibrium reached at 15 min. The adsorption of lead(II) both by free and immobilized C. sorokiniana biomass followed the Langmuir isotherm. The biosorption capacities were detected to be dependent on the pH of the solution; and the maximum adsorption was obtained at a solution pH of about 5. The effect of light metal ions on lead(II) uptake was also studied and it was shown that the presence of light metal ions did not significantly affect lead(II) uptake. The loofa sponge‐immobilized C. sorokiniana biomass could be regenerated using 0.1 M HCl, with up to 99 % recovery. The desorbed biomass was used in five biosorption‐desorption cycles, and no noticeable loss in the biosorption capacity was observed. In addition, fixed bed breakthrough curves for lead(II) removal were presented. These studies demonstrated that loofa sponge‐immobilized biomass of C. sorokiniana could be used as an efficient biosorbent for the treatment of lead(II) containing wastewater.     

Kinetic study of the toxicity of zinc and lead ions to the heavy metals accumulating fungus Paecilomyces marquandii

Studies have been carried out to determine the toxicity of zinc and lead ions to germinating spores and hyphal growth of heavy metal accumulating fungus Paecilomyces marquandii (former Verticillium marquandii). Inhibitive concentration (IC₅₀) of zinc and lead ions was assayed by three different methods: image analysis, nephelometric on-line measurement and microcalorimetry. A kinetic model of spore germination and germ tube elongation was formulated and used as an auxiliary tool to determine IC₅₀ values upon image analysis data. The inhibitive effect of Zn²⁺ and Pb²⁺ to P. marquandii spores was mathematically described by the Edwards equation. Comparing the obtained IC₅₀ values, lead ions occurred to be more toxic to the germinating spores of P. marquandii than zinc ions (2.80 and 5.20 mM, respectively), although zinc ions induced a more significant delay in the development of the hyphae (13.84 h for 5 mM of Zn²⁺ and 9.30 h for 5 mM of Pb²⁺), which was demonstrated by the lengthened lag-phase (spore-swelling phase).     

Utilization in alginate beads for Cu(II) and Ni(II) adsorption of an exopolysaccharide produced by <Emphasis Type="Italic">Chryseomonas luteola</Emphasis> TEM05

Copper and nickel adsorption onto calcium alginate, sodium alginate with an extracellular polysaccharide (EPS) produced by the activated sludge bacterium Chryseomonas luteola TEM05 and the immobilized C. luteola TEM05 from aqueous solutions were studied. After that, the multi metal ions containing these ions together were prepared and partial competitive adsorptions of these mixtures were also investigated. The metal adsorption of gel beads were carried out at pH 6.0, 25 °C. The maximum adsorption capacities in Langmuir isotherm for calcium alginate, calcium alginate + EPS, calcium alginate + C. luteola TEM05 and calcium alginate + EPS + C. luteola TEM05 were 1.505, 1.989, 1.976, 1.937 mmol/g dry weight for Cu(II) and 0.996, 1.224, 1.078, 1.219 mol/g dry weight for Ni(II), respectively.The competitive biosorption capacities of the carrier for all metal ions were lower than single conditions.     

Inorganic ions and the hatching of Heterodera spp

Of various inorganic ions tested for their ability to stimulate hatching of eggs of the cyst nematodes of cereals (Heterodera avenae Woll), carrot (H. carotae Jones), cabbage (H. cruciferae Franklin), soybean (H. glycines Ichinohe), pea (H. goettingiana Liebs.), potato (H. rostochiensis Woll.), beet (H. schachtii Schm.), tobacco (H. tabacum Lownsbery & Lownsbery) and clover (H. trifolii Goffart), some were active. Zn²⁺ hatched many eggs of seven species and some of H. goettingiana, but inhibited hatch of H. avenae to below that in water. Zinc salts are the first recorded very active hatching stimulants for H. glycines in vitro. Many other metal ions stimulated hatching of H. schachtii eggs to varying extents; these also hatched some but not all of the other species. Vanadate ions were particularly effective for H. rostochiensis, more so than Zn²⁺. No ion increased the hatch of H. avenae to above that in water. The most active ions were not those most abundant in soil. The behaviour of different ions with different species did not suggest any obvious affinities between species, but the differences between the hatching of H. tabacum and H. rostochiensis add weight to the view that, despite morphological similarities and overlapping host ranges, they are distinct species rather than pathotypes of a single species. Ions and other hatching agents may be absorbed by materials within the egg or larva and alter the structure and function of these materials. The lack of correlation between the hatching of H. schachtii by ions and the known stability sequences of various biological metal-binding systems suggests that there may be several sites of action that differ in their response.     

The salt glands of Tamarix usneoides E. Mey. ex Bunge (South African Salt Cedar)

Tamarix usneoides is a halophyte tree endemic to south-western Africa. This species is known to excrete a range of ions from specialized glandular structures on its leaves. To understand the mechanisms involved in the transport, sequestration and excretion of ions by the glands, a study was performed on salt gland distribution and ultrastructure. The glands are vesiculated trichomes, comprised of eight cells viz. two basal collecting cells and six excretory cells, partially bounded by a secondary cell wall that could serve as an impermeable barrier, forcing excess ions to move from the apoplast of the surrounding tissue into the cytoplasm of the basal excretory cells. It was hypothesized that the ions are moved across the excretory cells in endocytotic vesicles that fuse with the plasmalemma or form junctional complexes, allowing ion movement from one excretory cell to the next. In the apical cell, the vesicles fuse with the plasmalemma, releasing the ions into the network of cell wall ingrowths which channel the ions to the outside surface of the cell. This study shows that there are distinct structural adaptations for the processing of ions for excretion, although the mechanism by which ions enter the cells still needs to be determined.     

Selective accumulation of silver by fungi

Summary APhoma sp., tolerating 1 mmol/l Ag⁺, and 32 other fungi from a culture collection (not selected for their metal tolerance), were tested for their ability to accumulate silver, cadmium, copper, nickel and lead ions from aqueous solutions. Silver was accumulated selectively. Bivalent ions Cu, Cd, Ni and Pb were partially released after about 50 min, whereas the monovalent Ag ion remained bound. The selectivity of thePhoma sp. for silver developed in the late linear growth phase and might be connected with the occurence of a slimy exopolymer. The mean accumulation of the five heavy element ions by 32 strains of fungi could not be correlated with the ionic radii of the ions.     

Electrohydrodynamic mortality of insects: a plausible mechanism

 An electrohydrodynamic (EHD) system with a point-to-plane electrode, which produced air ions within a strong electric field, was used to study mortalities of pupae, larvae, and adults of Tribolium confusum (TC) and larvae of Plodia interpunctella (PI). The treatments included a neutral air stream, negative ions, positive ions, and the air stream superimposed with ions of either polarity. The negative ions caused the maximum mortality in TC pupae and PI larvae whereas the TC adults were least affected, but the negative ion flux was higher than the positive one at the constant high voltage of the power supply used in the present experiments. The differences in the mean mortalities of the treatment groups were highly significant (P<0.0001). Mortality was primarily attributed to the body fluid losses caused by the electric wind of the EHD system. Mortality and weight loss relationships were linear with negative slopes (r ²=0.52, and r ²=0.98 for TC and PI, respectively). The superimposition of the air stream with either positive or negative ion fluxes increased the survival fractions compared with those of the ion fluxes alone. Received: 27 May 1996 / Accepted: 9 September 1996     

Electrohydrodynamic effects on two species of insects with economic importance to stored food products

An electrohydrodynamic (EHD) system which generated air ions within a strong electric field was used to study responses of stored-product insectsTribolium confusum (du Val) andPlodia interpunctella (Hübner). Larval mortality of both species generally increased with increased exposure time to ions of either polarity. The larvae and pupae ofT. confusum suffered a higher mortality rate than the adults. The insects initially exhibited distinct avoiding motions away from regions of high towards low fluxes of air ions of both polarity. Insects moved vigorously, tumbled, flipped, curled up, and aggregated when the EHD system was turned on. The control insects not exposed to air ions survived and showed a total absence of such behaviour. For bipolar exposures, the insects occupied the neutral zone where the effects were minimal due to cancellation of the fields. Prolonged exposures of more than 20 min produced a quiescent state. EHD-enhanced mass transfer of the liquid component from physical objects established in fluid mechanics was invoked as a possible cause for insect mortality and avoiding behaviour to ions. Body fluid losses increased linearly with time of exposure (R ²0.97) for all biological stages of insect growth. The larvae and pupae ofT. confusum lost 12 and 15% of their body fluids, respectively, after 80 min of exposure to negative air ions. Fluid losses of such a magnitude are likely to have contributed to insect fatality.     

Electrical noise from lipid bilayer membranes in the presence of hydrophobic ions

Summary In the presence of the hydrophobic ion dipicrylamine, lipid bilayer membranes exhibit a characteristic type of noise spectrum which is different from other forms of noise described so far. The spectral density of current noise measured at zero voltage increases in proportion to the square of frequency at low frequencies and becomes constant at high frequencies. The observed form of the noise spectrum can be interpreted on the basis of a transport model for hydrophobic ions in which it is assumed that the ions are adsorbed in potential-energy minima at either membrane surface and are able to cross the central energy barrier by thermal activation. Accordingly, current-noise results from random fluctuations in the number of ions jumping over the barrier from right to left and from left to right. On the basis of this model the rate constantk _i for the translocation of the hydrophobic ion across the barrier, as well as the mean surface concentrationN _t of adsorbed ions may be caluculated from the observed spectral intensity of current noise. The values ofk _i obtained in this way closely agree with the results of previous relaxation experiments. A similar, although less quantitative, agreement is also found for the surface concentrationN _t .