Survival and death of Chara internodal cells in electrolyte solutions and calcium release from the cell wall

Abstract. Survival and death of Chara internodal cells were investigated in one of the alkali metal salts KCl, some of the alkali earth metal salts CaCl₂, Ca(NO₃)₂, MgCl₂, Mg(NO₃)₂, SrCl₂, Sr(NO₃)₂, BaCl₂ and Ba(NO₃)₂, potassium phosphate pH buffer solution (pH 7.0), Tris-maleate pH buffer solution (pH 7.0), HEPES (N-2-hydroxyethylpiperazine-N′-2-ethanesulphonic acid)-KOH (pH 7.0) pH buffer solution, calcium buffer solutions, and deionized water. Most of the internodal cells died within a day or a few days in KCl, MgCl₂, Mg(NO₃)₂, BaCl₂ and Ba(NO₃)₂ solutions of higher concentrations, calcium buffer solutions of pCa 6.0, 10.0 mol m^-3 potassium phosphate pH buffer solution and 10.0 mol m^-3 Trismaleate pH buffer solution. However, all of the internodal cells survived more than 10 d in deionized water, 80.0 mol m^-3 CaCl₂, 80.0 mol m^-3 Ca(NO₃)₂, 80.0 mol m^-3 SrCl₂, 80.0 mol m^-3 Sr(NO₃)₂ calcium buffer solutions of pCa 4.0 and pCa 5.0, and 10.0 mol m^-3 HEPES-KOH (pH 7.0) pH buffer solution. Addition of Ca²⁺ or Sr²⁺ to K⁺, Mg²⁺ and Ba²⁺ salt solutions increased the survival rates of the internodal cells. Calcium release from the internodal cell wall was measured in deionized water, KCl, NaCl, MgCl₂, CaCl₂, SrCl₂ and BaCl₂ solutions. Except in deionized water and CaCl₂ solution, most of the calcium binding to the cell wall was released within one or a few hours in respective electrolyte solutions. Thus, survival and death of the internodal cells in the electrolyte solutions tested were interpreted in terms of the calcium release from the cell wall and the cell membrane, and intrinsic ability of Sr²⁺ to maintain the cell membrane normal.     

NOTE ON THE EXCITATION AND INHIBITION OF LUMINESCENCE IN BER?

1. The ions of Ca and K condition general luminescence, and are therefore necessary to the conduction of the impulse. 2. In van''t Hoff''s solution from which Mg is omitted, Berœ shows hyperirritability with respect to luminescence. This is the result of the action of Ca and K ions unantagonized by Mg. 3. The luminescent material spread on filter paper does not show luminescence in sea water, NaCl, MgCl₂, or saccharose solutions isotonic with sea water. In solutions of CaCl₂, SrCl₂, BaCl₂, KCl, and K₂SO₄ the indicator paper glows with a bright luminescence. 4. In dark adapted Berœ, luminescence is inhibited by a certain quantity of light. This quantity has an average value of 57,285 meter-candle-minutes, which is twelve times the value given by Mnemiopsis.     

Über die Wirkung von ADP und einigen Kationen auf die Rotationsströmung in den Wurzelhaaren der Gerste (Hordeum vulgare L.)

Zusammenfassung In getrennten Versuchen wurde die Wirkung von ADP, Ca⁺⁺, Mg⁺⁺, K⁺ und Cu⁺⁺ auf die Rotationsströmung in den Wurzelhaaren der Gerste (Hordetim vulgare L.) untersucht. Das in verschiedenen Konzentrationen fortdauernd verabreichte ADP bedingte eine Stimulation der Plasmaströmung. Die Beschleunigung der Rotationsströmung war der ADP-Konzentration gegenüber umgekehrt proportional (Abb. 3).Von den untersuchten Kationen hatte nur Ca⁺⁺ (1·10^–3 Mol) eine Stimulationswirkung. Diese Stimulationswirkung wird der Aktivierung eines Enzyms bzw. eines kontraktilen Proteins mit ATPase-Eigenschaften zugeschrieben.Die Rolle von ADP und einigen Kationen bei der Stimulation der Rotation wurde dann mit Hilfe einer gemischten Behandlung untersucht. Diese bestand in der gleichzeitigen Verabreichung von ADP (1·10^–6 Mol) und CaCl₂, MgCl₂, KCl (1 · 10^–3 Mol) oder CuCl₂ (1·10^–6 Mol). Es wurde festgestellt, daß Mg⁺⁺ und Ca⁺⁺ eine antagonistische Wirkung ausüben. Ca⁺⁺ hebt die durch ADP induzierte Stimulation auf und reduziert die Rotationsgeschwindigkeit plötzlich bis auf den Kontrollwert. Die Mg⁺⁺-Wirkung bewirkt, nach einer zeitweiligen Beibehaltung der Stimulation, ebenfalls eine Abnahme der Geschwindigkeit. K⁺ hat eine ähnliche Wirkung wie Ca⁺⁺. Cu⁺⁺ beeinträchtigt die ADP-induzierte Stimulation in geringem Maße.Die gleichzeitige Einwirkung von ADP und einigen Kationen erlaubt die Aufstellung folgender Hypothese. Die Rotationsstimulation erfolgt dank dem ATP, das auf Kosten des von außen absorbierten ADP in den Mitochondrien synthetisiert wird. Die zusätzliche ATP-Synthese kann durch gleichzeitige Ca⁺⁺-Behandlung unterbunden werden. NachHanson und Mitarb, sollen Ca⁺⁺ und ADP um ein phosphoryliertes Zwischenprodukt in Kompetition treten, so daß es zu einer Ansammlung von Ca⁺⁺ und P_a in der Zelle kommt. Andererseits könnte teilweise auch die aktive, energieverbrauchende Salzabsorption die Geschwindigkeitsabnahme der Rotation bei gemischter Behandlung erklären.

---

The effect of ADP and some cations on rotational streaming in barley (Hordeum vulgare L.) root hairs

Summary The effect of ADP, Ca⁺⁺, Mg⁺⁺, K⁺, and Cu⁺⁺ upon rotational streaming within barley (Hordeum vulgäre L.) root hairs was separately studied. It was shown that various solutions of ADP may stimulate the streaming after continuous treatment. The rate increase of the rotational streaming was inverse proportional to ADP concentration (Fig. 3).From the investigated cations only Ca⁺⁺ (1·10^–3M) caused a stimulation of streaming after continuous treatment. This effect is probably due to enzymic activation of a contractile proteine which has ATPase feature.The role of ADP and of the investigated cations in the stimulation of the rotational streaming was studied by means of mixed treatment. This kind of treatment consists in a simultaneous administration of ADP (1 · 10^–6M) and CaCl₂, MgCl₂, KCl (1 · 10^–3M), or CuCl₂ (1 · 10^–6M) solutions. Ca⁺⁺ and Mg⁺⁺ showed an antagonistic action. Ca⁺⁺ brings about an immediately suppress of ADP induced stimulation. Suddenly the rate of streaming comes back to control. Mg⁺⁺ after a temporary maintaining of stimulation, also causes the lowering of the streaming. The action of K⁺ was very similar to those of Ca⁺⁺. Cu⁺⁺ changes to a little extent the stimulation caused by ADP.The simultaneous action of ADP and of the investigated cations allow us to express the following hypothesis. The stimulation of the rotational streaming after ADP treatment probably is due to ATP synthetized in mitochondria on the account of ADP. The additional synthesis of ATP can be prevented by simultaneous administration of Ca⁺⁺. According toHanson and his coworkers Ca⁺⁺ would compete with ADP for a phosphorylated intermediate product. From a such competition would result the Ca⁺⁺ and P_i accumulation. The active uptake of salts which require energy would also explain the lowering of the rotational streaming rate after the mixed treatment.

     

Distribution of calcium in the suctorian Discophrya collini: An X-ray microanalytical study

Discophrya collini is a free-living suctorian with tentacles which can be induced to contract by means of a range of experimental stimuli, including the application of CaCl₂ and MgCl₂ but not BaCl₂. X-ray microanalysis of glutaraldehydeonly fixed cells shows Ca to be present in the cytoplasmic ground substance and elongate dense bodies (EDB). In 10^?1 M CaCl₂-treated cells, calcium levels remain unchanged except for a three-fold increase in the EDB. Treatment of cells with 10^?1 M MgCl₂ and 10^?1 M BaCl₂ does not result in their detection in the cell. It is suggested that EDB may act as reservoirs controlling levels of calcium.     

Volume changes,ion exchanges,and fragilities of human red cells in solutions of the chlorides of the alkaline earths

1. Concentrations of BaCl₂, MgCl₂, SrCl₂, and CaCl₂ can be found in which the volume of washed human red cells remains almost unchanged for short periods of time; in more concentrated solutions the cells shrink, and in less concentrated ones they swell. Between tonicities of about 1.5 and 0.75, the van't Hoff-Mariotte law applies roughly, but at lower tonicities the red cell volume is anomalously great, sometimes in the absence of hemolysis. 2. If the cells are allowed to stand at 4°C. in the media of different tonicities, the volume changes are not maintained. The volumes decrease in a complex way, and the decreases are accompanied by a loss of K from the cells and an entry of the external cation into them. 3. With two exceptions, these ion exchanges are not accompanied by any important changes in the osmotic, mechanical, or heat fragility of the red cells. The exceptions are a marked effect of BaCl₂ on heat fragmentation, and of CaCl₂ on osmotic and mechanical fragilities.     

Tentacle contraction and ultrastructure inDiscophrya collini: The response to cations

Summary Discophrya collini is a suctorian protozoan with contractile tentacles containing a microtubule-lined canal and microfilaments. The effects of a range of cations on tentacle contraction and ultrastructure have been determined. Treatment with 80 mM CaCl₂ and 95 mM MgCl₂ causes contraction to 28% and 57% of the control length respectively. Re-extension takes over 4 hours in the culture medium, but CaCl₂-treated tentacles are re-extended after a 5 minutes treatment with 10^–2 M EDTA or 5 × 10^–3 M EGTA. CuCl₂ causes a significant contraction at 10^–5 M (to 77%); LaCl₃ at 10^–4 M (to 65%); ZnCl₂ at 10^–2 M (to 65%), but BaCl₂, CoCl₂, MnCl₂, NiCl₂, and SrCl₂ cause significant changes only at 10^–1 M.The cytoplasm of CaCl₂-treated cells contains two forms of membraneous structures when viewed in TEM; that of MgCl₂-treated cells reveals granular areas of medium electron density. None of these features are seen in control cells. The microtubules of the tentacle canal appear to be intact upon its retraction into the cell with no change occurring in the numbers or relative positions of the microtubules. The tentacle cortex is wrinkled. It is suggested from this and previous work that tentacle contraction may be mediated by a microfilament-based mechanism, and that calcium may be involved.     

Cessation of cytoplasmic streaming follows an increase of cytoplasmic Ca2+ during action potential inNitella

Summary Taking advantage of prolonged action potential under low temperature, we studied temporal relationship among the action potential, increase of cytoplasmic Ca²⁺ concentration and cessation of cytoplasmic streaming inNitella. The Ca²⁺ concentration began to increase at a very early stage of the action potential and the cessation of streaming followed that increase.Abbreviations APW artificial pond water     

(Ca + Mg)-stimulated ATPase activity of a rat brain microsomal preparation.

ATPase activity of freshly prepared brain microsomes was stimulated 20% when 0.1 mm CaCl₂ was added in the presence of a “saturating” concentration of MgCl₂ (4 mm). This (Ca + Mg)-stimulated activity declined rapidly on storage. Treatment of the microsomes with 0.12% deoxycholate in 0.15 m KCl, followed by centrifugation and resuspension in sucrose, produced a preparation both stable on storage at ?15 °C and with an increased stimulation in the presence of CaCl₂. SrCl₂ was more effective than CaCl₂, but BaCl₂ was a poor activator. KCl and NaCl stimulated the (Ca + Mg)-ATPase activity by reducing substrate (ATP) inhibition. The K_m for ATP was 0.1 mm, a third that of the Mg-ATPase. CTP, ITP, and GTP could not substitute for ATP, although they were fair substrates for the Mg-ATPase. The energy of activation of the (Ca + Mg)-ATPase was 21 kcal, nearly twice that of the Mg-ATPase. After sucrose density-gradient centrifugation of the microsomal preparation, the (Ca + Mg)-ATPase activity was distributed with the (Na + K)-ATPase and not with the mitochondrial marker succinic dehydrogenase. Studies with ouabain, oligomycin, and azide distinguished the (Ca + Mg)-stimulated ATPase from (Na + K)- and mitochondrial ATPases. Sensitivity to ruthenium red suggested a link to Ca transport, although the microsomal ⁴⁵Ca accumulating system was much more sensitive to the inhibitor than was this ATPase activity.     

EFFECTS OF GUAIACOL AND HEXYLRESORCINOL IN THE PRESENCE OF BARIUM AND CALCIUM

Guaiacol was applied at two spots on the same cell of Nitella. At one spot it was dissolved in 0.01 M NaCl, at the other in 0.01 M CaCl₂ or BaCl₂. The effect was practically the same in all cases, i.e. a similar change of P.D. in a negative direction, involving a more or less complete loss of P.D. (depolarization). When hexylresorcinol was used in place of guaiacol the result was similar. That Ca⁺⁺ and Ba⁺⁺ do not inhibit the effect of these organic depolarizing substances may be due to a lack of penetration of Ca⁺⁺ and Ba⁺⁺. The organic substances penetrate more rapidly and their effect is chiefly on the inner protoplasmic surface which is the principal seat of the P.D.     

ELECTROKINETICS : XVII. SURFACE CHARGE AND ION ANTAGONISM

1. The question of the critical pore diameter for streaming potential is discussed. 2. The surface charge is calculated for cellulose in contact with solutions of K₃PO₄, K₂CO₃, K₂SO₄, KCl, and ThCl₄. 3. The surface charge of cellulose in contact with a solution of 2 x 10^–4 N NaCl is calculated as a function of temperature and is found to show a sharp break at 39°. This is interpreted in terms of the change of the specific heat of water. 4. A marked ion antagonism is found in NaCl:KCl, KCl:MgCl₂, NaCl:MgCl₂, NaCl:CaCl₂, KCl:CaCl₂, CaCl₂:MgCl₂ mixtures when the surface charge is calculated as a function of concentration.     

Studies on the permeability of living cells

Summary The penetration of the dye, dahlia, into the sap ofNitella has been determined in the presence of NaCl, KCl, MgCl₂ and CaCl₂ at various concentrations.NaCl is the least effective and MgCl₂ was the most effective in preventing penetration of the dye.It was found that NaCl antagonizes the action of CaCl₂ in certain proportions to a small degree but not sufficiently to permit the dye to penetrate at a normal rate.Published by permission of the Surgeon General.     

Chloride channels in human platelets: Evidence for activation by internal calcium

Summary Whole-cell patch-clamp recordings were made from freshly isolated human platelets. The pipette contained a high concentration of divalent cations, which permitted easy disruption of cell-attached membrane patches by suction. Single-channel currents were measured when the pipette contained isotonic BaCl₂ or MgCl₂ saline; over 30 sec –5 min an increasing number of channels appeared until conductance steps through individual channels could no longer be distinguished. The current-voltage relationship was curvilinear; chord conductance at –35 mV was 25 pS increasing to 45 to 52 pS at +45 mV. Ion substitution experiments showed the current to be primarily carried by Cl^–.E _rev was shifted 30 mV/10-fold change in external Cl^– (replaced by gluconate), was similar with BaCl₂ or MgCl₂ in the pipette and was not significantly shifted by replacing external Na⁺ with K⁺. Addition of 1mm BAPTA to the MgCl₂ pipette saline prevented activation of Cl^– currents; with isotonic CaCl₂ internal saline, current appeared immediately upon patch rupture, suggesting that the Cl^– channels are dependent on internal Ca²⁺, 5-nitro-2-(3-phenylpropylamino)-benzoate, reported to block a Cl^– conductance in studies of rat epithelial cells, caused a potent flickery block and may be a useful tool with which to investigate the physiological role of Cl^– currents in human platelets.     

Electrical properties of Paramecium caudatum: all-or-none electrogenesis

Summary Specimens of Paramecium immersed in solutions of CaCl₂ show graded electrogenesis in response to imposed transmembrane current. However, when BaCl₂ in a final concentration of 0.25 mM is added to a 1 mM CaCl₂ solution, an outward current pulse of 10^-10 amp or greater elicits an all-or-none transient reversal in membrane potential having a duration of about 40 msec. An increase of [Ba⁺⁺] results in (a) lower resting potential, (b) positive shift in critical firing level, (c) increased overshoot of the action potential, (d) decreased hyperpolarizing afterpotential, and (e) increased duration of the action potential (a.p.). If [Ca⁺⁺] is increased along with [Ba⁺⁺] so as to keep the ratio [Ba⁺⁺]/[Ca⁺⁺] constant, the same results are obtained except that the duration of the a. p. remains unaltered. Thus, effects a-d appear to be related to [Ba⁺⁺] and not to [Ca⁺⁺] or [Cl^-]. The degree of overshoot in 1 mM Ca is linearly related to log [Ba⁺⁺] with a slope of approximately 22 mv. With the ratio [Ba⁺⁺]/[Ca⁺⁺] constant, the slope closely approaches the ideal value of 29 mv. The evidence indicates that prolongation of the action potential is due to a delayed onset of Ba inactivation, and that this in turn is a function of surface-bound Ba. Other features of the action potential are absolute refractoriness during its rising and plateau phases, relative refractoriness lasting several seconds, and repetitive firing in response to steady current depolarization. The response is unaffected by TTX and TEA. Mn prolongs the action potential. Sr has an action similar to Ba, whereas the addition of K, Na, Rb, or Mg to the basic calcium medium is unaccompanied by all-or-none electrogenesis.On leave of absence from the Zoological Institute, Faculty of Science, University of Tokyo.Support came from National Science Foundation grant GB-5752x, U.S.P.H.S. grant NB-03664, and in part from Office of Naval Research grant Nonr 4785(00) administered by the Marine Biological Laboratory, Woods Hole.     

LUMIMESCENCE IN PELAGIA NOCTILUCA

1. Ca and K condition the irritability of Pelagia both in regard to rhythmical contractions and general luminescence. If either ion is omitted from the solution conduction of stimuli for pulsations and luminescence does not occur, although local responses still persist. 2. When Mg is omitted from the solution, Pelagia shows hyper-irritability with respect to rhythmical contraction and general luminescence. This is referable to the unantagonized action of K and Ca ions. 3. Exposure to the carbon arc suppresses general luminescence, the effect depending upon the quantity of light i.e. intensity x time of exposure. 4. The luminescent material secreted by Pelagia is inactive in sea water, but when put into salt solutions is activated by some of them. The efficiency of the salts, measured by brightness of light, is in the following order: MgSO₄, K₂SO₄, Na₃ citrate, KCl, BaCl₂, SrCl₂, CaCl₂, and LiCl while NaCl and MgCl₂ act as inhibitors. 5. Acidity inhibits the reaction, alkalinity promotes it. NH₄OH in concentrations 0.27 N to 0.9 N causes luminescence for 10 minutes at 20°. 6. The average temperature coefficient for the reaction of the luminescent substance when activated by ammonia or MgSO₄ is 2.18 for a temperature interval of 10°C. 7. The luminescence reaction cannot be the result of cytolysis, because (a) raising the temperature of sea water in which luminous material is immersed does not cause luminescence, although sufficient to produce cytolysis. (b) The salt solutions used in our experiments to cause luminescence, do not act cytolytically on cells in general.     

EFFECT OF SALINITY ON POLLEN I. POLLEN VIABILITY AS ALTERED BY INCREASING OSMOTIC PRESSURE WITH NaCl,MgCl2, and CaCl2

Petunia (Petunia hybrida Vilm. cv. ‘Snowstorm') plants were grown in saline solution (NaCl, MgCl₂, and/or CaCl₂) of 0, 1, 2, and 3 bars osmotic pressures. Pollen viability was tested by tetrazolium chloride staining and by germination (by the hanging drop method, using 15 % sucrose and 0.01 % boric acid as the nutrient medium, at 27 ± 1 C). Pollen viability decreased with increased salinity. Pollen from plants grown in single salt solutions of NaCl, MgCl₂, and CaCl₂ (each at 0, 1, 2, or 3 bars osmotic pressure) was germinated in base culture medium. Pollen viability decreased more with NaCl than with MgCl₂ or CaCl₂. In vitro studies of the effects of three salts, viz., NaCl, MgCl₂, and CaCl₂, on pollen germination and tube growth showed that NaCl inhibited germination and pollen tube growth more than did MgCl₂ or CaCl₂. MgCl₂ was least injurious, and even promoted tube growth at 0.5 and 0.75 bars osmotic pressure. Adding low concentrations of MgCl₂ reduced the toxic effect of NaCl and increased the percentage of germination. CaCl₂ reduced the effect of NaCl less than did MgCl₂. We conclude that specific ion effects were more important than osmotic pressure.     

Effects of morphine tolerance and dependence on Mg++ dependent ATPase activity of synaptic vesicles.

The effect of morphine on ATPase of synaptic plasma membranes (SPM) and synaptic vesicles isolated from the mouse brain was studied. The activity of synaptic vesicle Mg⁺⁺-dependent ATPase from mice rendered morphine tolerant and dependent by pellet implantation was 40% higher than that from placebo implanted mice. However, the activities of Mg⁺⁺-dependent ATPase and Na⁺, K⁺ activated ATPase of SPM of tolerant and nontolerant mice were not significantly different. The activity of synaptic vesicular Mg⁺⁺-dependet ATPase was dependent on the concentration of Mg⁺⁺ but not of Ca⁺⁺; maximum activity was obtained with 2 mM MgCl₂. On the other hand, Mg⁺⁺-dependent ATPase activity of SPM was dependent on both Mg⁺⁺ and Ca⁺⁺, activity being maximum using 2 mM MgCl₂ and 10^?5 M CaCl₂. It is suggested that this stimulation of ATPase activity may alter synaptic transmission and may thus be involved in some aspects of morphine tolerance and dependence.     

Role of calcium ion in the excitability and electrogenic pump activity of theChara corallina membrane: I. Effects of La3+, verapamil,EGTA, W-7, and TFP on the action potential

Summary The cytoplasmic streaming of the normal internodal cell of giant algaChara stops transiently at about the peak of action potential. Application of La³⁺ or verapamil (a calcium channel blocker) or removal of external Ca²⁺ by EGTA caused a partial depolarization of the resting potential, partial decrease of the membrane conductance and a marked decrease of the amplitude of action potential. Under these conditions, the conductance at the peak of action potential reduced markedly and the streaming of cytoplasm did not cease during action potential (excitation-cessation (EC) uncoupling). The effects of Ca²⁺ channel blockers could not be removed by addition of CaCl₂ to the external medium. In contrast, the effect of EGTA on the excitability could be removed to a greater extent and the cytoplasmic streaming ceased at about the peak of action potential by the addition of Ca²⁺ externally. Application of calmodulin antagonists W-7 or TFP caused similar effects on the action potential and on the cytoplasmic streaming.     

CaCl2-induced germination and peptidase secretion inAphanomyces astaci

Divalent cations were found to cause a specific release of peptidase from mechanically encysted zoospores of the fungusAphanomyces astaci, whereas germination could be induced only by CaCl₂, SrCl₂, and MgCl₂ with CaCl₂ being most efficient. It is concluded that peptidase secretion is a prerequisite to enable the cysts to become capable of germination, but that germination is not a consequence of peptidase release. Following this conclusion it is suggested that CaCl₂, SrCl₂, and MgCl₂ in themselves are unable to elicit germination and that other unknown processes in the cell are triggered which allow germination to take place. These processes are short-lived and can be elicited only in young encysted spores, whereas 15-min-old mechanically encysted zoospores did respond to CaCl₂ by the release of peptidase but did not germinate. The mechanism by which divalent cations caused the release of peptidases could not be elucidated, since drugs known to affect exocytosis in animal cells lysed the cysts even at very low concentrations.     

HYPERPOLARIZING RESPONSE IN NITELLA INTERNODES

The ionic aspect of the hyperpolarizing response in the internodalcell of Nitella is reported in some detail. The response wasobserved by passing a large inward current through the Nitellamembrane, the resistance of which had been decreased by a concentratedalkali metal ion. It was not possible to demonstrate the responsein a concentrated solution of CaCl₂, MgCl₂, BaCl₂, ZnCl₂ orAlCl₂ or AlCl₃. After hundreds of the spontaneous repetitiveaction potentials, which occurred in a single solution of concentratedNaCl or LiCl or caused by an application of 1–2 mM EDTAin the artificial pond water, the Nitella cell showed the hyperpolarizingresponse. Almost the same size of the response was observedfor change in pH of the external KC1 solution from 6.7 to 10.0,but it decreased markedly for pH lower than 4.7. It seems tobe an essential condition for the response to remove the divalentcations from the cell surface, having a concentrated monovalentcation in the external medium. (Received April 22, 1966; )     

CaCO3 and SrCO3 bioprecipitation by fungi isolated from calcareous soil

The urease‐positive fungi Pestalotiopsis sp. and Myrothecium gramineum, isolated from calcareous soil, were examined for their properties of CaCO₃ and SrCO₃ biomineralization. After incubation in media amended with urea and CaCl₂ and/or SrCl₂, calcite (CaCO₃), strontianite (SrCO₃), vaterite in different forms [CaCO₃, (Ca_xSr_1?x)CO₃] and olekminskite [Sr(Sr,Ca)(CO₃)₂] were precipitated, and fungal ‘footprints’ were observed on mineral surfaces. The amorphous precipitate mediated by Pestalotiopsis sp. grown with urea and equivalent concentrations of CaCl₂ and SrCl₂ was identified as hydrated Ca and Sr carbonates by Fourier transform infrared spectroscopy. Liquid media experiments showed M. gramineum possessed the highest Sr²⁺ removal ability, and ～ 49% of supplied Sr²⁺ was removed from solution when grown in media amended with urea and 50 mM SrCl₂. Furthermore, this organism could also precipitate 56% of the available Ca²⁺ and 28% of the Sr²⁺ in the form of CaCO₃, SrCO₃ and (Ca_xSr_1?x)CO₃ when incubated in urea‐amended media and equivalent CaCl₂ and SrCl₂ concentrations. This is the first report of biomineralization of olekminskite and coprecipitation of Sr into vaterite mediated by fungi. These findings suggest that urease‐positive fungi could play an important role in the environmental fate, bioremediation or biorecovery of Sr or other metals and radionuclides that form insoluble carbonates.