Inactivation of bacteriophage k, Escherichia coli, and Candida albicans by ozone

The effects of ozone (O₃) on three types of microbes were studied. Test suspensions were exposed to 600 ppm O₃ at room temperature. Control experiments were performed under identical conditions using oxygen gas. Bacteriophage λ was completely inactivated at 10 min while Escherichia coli and Candida albicans were only inactivated by factors of 10⁵ and 10⁴ respectively at 40 min. Exposure of a mixed microbial suspension to O₃ for 5 min resulted in 100% killing of bacteriophages while the viability of E. coli remained unchanged. Various body fluids containing phages were exposed to O₃. Compared to buffered solution, the decrease in phage titers was significantly slower in whole blood, plasma, and albumin. Both E. coli and  C. albicans had increased production of thiobarbituric-acid-reactive substances with increased O₃ exposure. ³H-labelled amino acids were incorporated into E. coli. O₃ treatment resulted in a loss of radioactivity, indicating leakage of cytoplasmic contents. The data indicate that microbes are inactivated by O₃ at different rates, possibly related to differential membrane permeability. The milieu in which microbes are present determines the effectiveness and outcome of O₃ treatment. Received: 15 October 1997 / Accepted: 24 February 1998     

Aqueous silicate complexes in wheat, Triticum aestivum L.

The chemical speciation of silicon in xylem exudate from wheat (Triticum aestivum L.) was examined by ²⁹Si NMR spectroscopy. Wheat plants were grown to maturity in silicon‐free nutrient medium, and then transferred to a solution containing 0.02 mm ²⁹Si‐enriched silicic acid. After 30 min the shoots were excised and xylem exudate was collected. Within 10 min the Si concentration of the xylem exudate reached values greatly in excess of that of the starting nutrient solution, eventually reaching levels as high as 8 mm . Silicon‐29 nuclear magnetic resonance spectra indicated the existence of only two Si‐containing species in the xylem exudate, mono and disilicic acid (H₄SiO₄^o and (HO)₃Si(µ‐O)Si(OH)₃^o) in a ratio of approximately 7 : 1. Significantly, there was no evidence of organosilicate complexes. Nevertheless, the efficiency by which the plant concentrates aqueous silicon indicates active mechanisms of silicon transport across root cell membranes.     

Release of a Gonad-Stimulating Substance from the Radial Nerves of the Cushion Star,Asterina pectinifera,in response to Excess Potassium*

The release of a gonad-stimulating substance (GSS) from radial nerves stimulated by a K⁺-rich solution was examined in the cushion star, Asterina pectinifera. The threshold concentration of K⁺necessary for the release of a sufficient amount of GSS to induce shedding of mature oocytes from ovarian fragments was 50 to 75 mM. The minimal amount of fresh nerve required for this release was 3 mg per ml of medium. The time of K⁺stimulation necessary to induce maximal GSS release was about 20 min. Repeated stimulations of radial nerves with 100 mM K⁺caused repeated release of GSS.     

Preparation of Zeaxanthin from Berries of Boxthorn,Lycium chinensis

Purification and properties of a new alkaline protease of rat skeletal muscle have been reported. The purification procedure of the enzyme is as follows: skeletal muscle tissue was extracted successively with Hasselbach-Schneider solution, 5 m urea solution and 2% sodium deoxycholate solution. After then, the enzyme was extracted from the residue with 1.1 m potassium iodide solution. This enzyme solution was treated with n-butanol, and dialyzed against water. The enzyme precipitated during dialysis was collected and dissolved in 1.1 m potassium iodide solution. The enzyme solution was fractionated with acetone, and chromatographed on Sephadex G-200. The final preparation showed over 20,000 times of purity.

The optimum pH range of the enzyme activity is 9.5~10.5, and the maximum reaction rate occurs at 47~57°C. The enzyme is stable below 47°C at pH 7.3. At 37°C, the enzyme is stable during 30 min at least, in the pH range of 5.5~10.0. Below pH 5.0, it is relatively labile. Hg²⁺, Ca²⁺, Mg²⁺, Mn²⁺, Co²⁺, and Zn²⁺ scarcely affect the enzyme activity at the concentration of 1 mm. Ethylenediaminetetraacetate shows little effect on the activity at the concentration of 10 mm, and iodoacetamide, 2,4-dinitrophenol, p-chloromercuribenzoate show the similar effect at the concentration of 1 mm. Diisopropyl-flurophosphate inhibits the enzyme activity. From the results obtained, this enzyme is presumed to be responsible for the activity of autolytic breakdown of rat skeletal muscle proteins in the alkaline pH range.     

Major Ion Chemistry of Soil Solution of Mountainous Soils,Alvand, Hamedan,Western Iran

Soil solution chemistry reflects the most dynamic processes occurring in soils and is responsible for their current status. This study was undertaken to determine the soil solution status in 25 mountainous soils. The major cations in the studied soil solutions are in the decreasing order of Ca²⁺ > Mg²⁺ > Na⁺ > K⁺. The anions are also arranged in decreasing order as HCO^? ₃ > Cl^? > NO^? ₃ > SO ^2? ₄ . Concentrations of NO^? ₃ , P, and K⁺ in soil solutions were in the range of 12–364 mg l^?1, 1.75–34.8 mg l^?1, and 0.78– 198 mg l^?1, respectively. Results suggest that the concentration of P in the soil solutions could be primarily controlled by of the solubility of octacalcium phosphate and ß-tricalcium phosphate. In general, the greater the dissolved P concentration in the soil solution, the closer the solution was to equilibrium with respect to the more soluble Ca²⁺ phosphate minerals. Surface soil accumulations of P, NO^? ₃ , and K⁺ have occurred in these soils to such an extent that loss of these nutrients in surface runoff and the high risk for nutrient transfer into groundwater in concentrations exceeding the groundwater quality standard has become a priority management concern.     

Activity of sodium trimetaphosphate,associated or not with fluoride,on dual-species biofilms

Abstract

A response surface methodology was used to build a model to predict reductions in uropathogenic Escherichia coli biofilms in response to three compounds: cranberry extract [CB] at 3.0–9.0%, and caprylic acid [CAR] and thymol [TM] at 0.01%–0.05%. The predictive model for microbial reduction had a high regression coefficient (R²?=?0.9988), and the accuracy of the model was verified (R²?=?0.9527). Values of CAR, TM, and the quadratic term CAR² were the most significant (P?10 reduction) determined by ridge analysis were 8.3% CB +0.04% CAR +0.04% TM at 37?°C for 1?min. The model could be used to predict the most cost-efficient amounts of antimicrobial agents for anti-urinary tract infection products such as catheter lock solution and antimicrobial coatings for catheters.     

Effect of ouabain,amiloride, and antidiuretic hormone on the sodium-transport pool in isolated epithelia from frog skin (Rana temporaria)

Summary When tracer Na⁺ is added to the solution bathing the apical side of isolated epithelia the observed transepithelial tracer influx increases with time until a steady state is reached. The build-up of the tracer flux follows a single exponential course. The halftime for this build-up under control conditions was 0.92 ±0.06 min, and in the presence of ouabain 4.51±0.7 min. It is shown that the calculated Na⁺-transport pool is located in the cells. The Na⁺-transport pool under control conditions was 35.6 ±3.4 nmol/cm², which corresponds to an intracellular Na⁺ concentration of 7.9mm. Activation of the active Na⁺ transport by addition of antidiuretic hormone resulted in a highly significant increase in the Na⁺ transport pool, and inhibition of the transcellular Na⁺ transport with amiloride resulted in a decrease in the Na⁺-transport pool.Furthermore, the active Na⁺ transport increased along anS-shaped curve with increasing intracellular Na⁺ concentration (Na⁺-transport pool). The Na⁺ pump was found to be half saturated at an intracellular Na⁺ concentration of 12.5mm.     

Salt gland function in the common eider duck (Somateria mollissima)

The function of the supra-orbital salt gland was studied in the common eider duck (Somateria mollissima). The maximum salt-secreting capacity was determined in (1) wild ducks which had been living in a marine environment, (2) ducks reared in captivity on fresh water, and (3) ducks from group 2 adapted to salt water. The maximum secreting capacity was found by infusing a solution of NaCl (1000 mosmol·kg^-1) at increasing rates, from 0.691 to 1.671 mosmol·min^-1. Freshwater-adapted ducks secreted at a maximum rate of 0.785 mosmol·min^-1 (1500 mosmol·kg^-1). Adapted to salt water they increased their capacity, and the best duck secreted at a rate of 1215 mosmol·min^-1 (1600 mosmol·kg^-1). The best wild duck secreted at a rate of 1516 mosmol·min^-1. Ducks in group 3 were used to examine the response to a hyperosmotic or an isoosmotic infusion. The amount of salt (NaCl) given per unit time was the same. Given a hyperosmotic solution their salt glands secreted at a high rate: 30 min after the infusion had stopped the ducks had excreted 94% of the sodium infused, 92.9% via the salt gland. Given an isoosmotic solution they secreted at a rate about half the infusion rate: 30 min after cessation of infusion they had excreted 73% of the sodium, 42.9% via the salt gland and the rest by the kidneys.Abbreviations A II angiotensin II - AV I arginine vasotocin - ED freshwater-adapted ducks - FW fresh water - SD saltwater-adapted ducks - SW sea water - WD wild ducks     

The use of clove oil to induce anaesthesia,and its effects on blood chemistry,in Lates niloticus from Lake Victoria,Uganda

The efficacy of clove oil as an anaesthetic and its effects on blood parameters in Nile perch Lates niloticus were evaluated in 2010. Clove oil concentrations of 49.3, 73.9 and 98.5?mg l^?1 induced anaesthesia in <3?min, while the average recovery time from anaesthesia was 11?min 22 s. The optimal oil clove oil concentration was 49.3?mg l^?1, inducing anaesthesia in 4?min 33 s, with recovery in 3?min 31 s. No stress response was elicited. Clove oil at a concentration of 24.6?mg l^?1 was an effective sedative, whereas a concentration of 49.3?mg l^?1 was sufficient for measuring fish and stripping gametes. A concentration of 73.9?mg l^?1 induced anaesthesia within 4?min and fish recovered in 10?min. Therefore, clove oil was an effective anaesthetic and sedative for the handling of Nile perch within a mass range of 0.4–12?kg fish^?1.     

Removal of heavy metals from aqueous solution by common freshwater filamentous algae

Non-living (dried) biomass of five common filamentous algae belonging to Chlorophyta and Cyanophyta (Cyanobacteria) were screened for their metal ion sorption and removal efficiency in a batch system. A considerably higher magnitude of sorption of Pb²⁺ and Cu²⁺ by all the tested algae suggests the prevalence of Pb²⁺- and Cu²⁺-binding ligands in them. The Langmuir isotherm could more appropriately describe metal sorption by the test algae than the Freundlich isotherm. A 1 g l⁻¹ biomass concentration of Pithophora odeogonia and Spirogyra neglecta, respectively removed 97 and 89% Pb²⁺in 30 min from a solution containing 5 mg l⁻¹ initial concentration of Pb²⁺. Metal ion removal by the test algae decreased with increase in metal concentration in the solution. S. neglecta could remove >70% Pb²⁺ even from a solution containing 75 mg Pb²⁺ l⁻¹. S. neglecta and P. oedogonia could remove more than 75% of Pb²⁺ and Cu²⁺ from a multi-metal solution, and therefore have tremendous potential for removing Pb²⁺and Cu²⁺ from wastewaters containing several metal ions simultaneously. Other test algae, namely, Hydrodictyon reticulatum, Cladophora calliceima and Aulosira fertilissima were relatively less efficient in removing metal ions from solution.     

Ethylene-binding characteristics in Phaseolus,Citrus, and Ligustrum plants

A number of plants were tested for their ability to bind ethylene and the number of binding sites present in each was calculated. Primary leaves of laboratory-grown beans (Phaseolus vulgaris) bound 140 dpm/g fwt (1794 dpm/g dry wt) when exposed to 1.0 Ci/1 of [¹⁴C]ethylene (110 ci/mol). Phytotron-grown leaves were less succulent but only bound 90 dpm/g fwt (1046 dpm/g dry wt). Bean roots bound 30 dpm/g fwt. Citrus and Ligustrum bound 207 and 240 dpm/g fwt, respectively. The time required to achieve equilibrium of leaves with the gas phase was 15 min for bean, 30 min for Citrus, and 30–60 min for Ligustrum. The time for 1/2 of the bound ethylene to diffuse out of the leaves was 20 min for bean, 10 min for Citrus, and 30 min for Ligustrum. The amount of ethylene needed to occupy 1/2 of the binding sites was obtained from Scatchard plots. This value (K_d) was 0.2 l/1 for bean, 0.15 for Citrus, and 0.31 for Ligustrum. The quantity of binding sites in the tissues was 2.0×10^-9 mol of binding sites/kg tissue for bean leaves, 5.7×10^-9 for Citrus leaves, and 6.8×10^-9 for Ligustrum. Pretreatment with indoleacetic acid (IAA), ehtylene, and cycloheximide (1 mg/1) had little effect on the level of ethylene-binding sites in Citrus.Contribution from the Department of Biochemistry, School of Agriculture and Life Sciences and School of Physical and Mathematical Sciences, North Carolina State University. Paper No. 8445 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, North Carolina 27695-7601.North Carolina-Israel exchange Scholar for 1981 at the Department of Biochemistry, North Carolina State University Raleigh, North Carolina, USA     

Evidence for an anion exchanger in the mouse lacrimal gland acinar cell membrane

Summary Anion exchange transport in the mouse lacrimal gland acinar cell membrane was studied by measuring the intracellular H⁺ (pH_i) and Cl^– (aCl_i) activities with double-barreled ion-selective microelectrodes. In a HCO ₃ ^– -free solution of pH 7.4 (HEPES/Tris buffered), pH_i was 7.25 andaCl_i was 33mm. By an exposure to a HCO ₃ ^– (25mm HCO ₃ ^– /5% CO₂, pH 7.4) solution for 15 min,aCl_i was decreased to 25mm and pH_i was transiently decreased to about 7.05 within 1 min, then slowly relaxed to 7.18 in 15 min. Intracellular HCO ₃ ^– concentration [HCO ₃ ^– ]_i, calculated by the Henderson-Hasselbalch's equation, was 11mm at 1 min after the exposure and then slowly increased to 15mm. Readmission of the HCO ₃ ^– -free solution reversed the changes inaCl_i and pH_i. The intracellular buffering power was about 40mm/pH. An addition of DIDS (0.2mm) significantly inhibited the rates of change inaCl_i, pH_i, and [HCO ₃ ^– ]_i caused by admission/withdrawal of the HCO ₃ ^– , solution and decreased the buffer value. Replacement of all Cl^– with gluconate in the HCO ₃ ^– solution increased pH_i, and readmission of Cl^– decreased pH_i. The rates of these changes in pH_i were reduced by DIDS by 32–45% but not by amiloride (0.3mm). In the HCO ₃ ^– solution, a stimulation of intracellular HCO ₃ ^– production by exposing the tissue to 25mm NH ₄ ⁺ increasedaCl_i significantly. While in the HCO ₃ ^– -free solution or in the HCO ₃ ^– , solution containing DIDS, exposure to NH ₄ ⁺ had little effect onaCl_i. All of these findings were consistent with the presence of a reversible, disulfonic stilbene-sensitive Cl^–/HCO ₃ ^– exchanger in the basolateral membrane of the acinar cells. The possibility of anion antiport different from one-for-one Cl^–/HCO ₃ ^– exchange is discussed.     

Rapid, reversible alterations in spinach thylakoid appression upon changes in light intensity

Changes in light quantity and quality cause structural changes within the thylakoid membrane; long‐term responses have been described for so‐called ‘sun’ and ‘shade’ leaves. Many leaves, however, experience changes in irradiance on a time scale of minutes due to self‐shading and sun flecks. In this study, mature, attached spinach leaves were grown at 300 µmol photons m^?2 s^?1 then rapidly switched to a different light treatment. The treatment irradiances were 10, 800 or 1500 µmol m^?2 s^?1 for 10 min, or 10 or 20 min of self‐shading (about 10 µmol m^?2 s^?1). Image analysis of transmission electron micrographs revealed that a 10 min switch to a lower light intensity increased grana size and number per chloroplast profile by 10–20%. Returning the leaves to 300 µmol m^?2 s^?1 for 10 min reversed the phenomenon. Chlorophyll fluorescence measurements of detached, intact leaves at 77 K were suggestive of a transition from state 2 to state 1 upon shading. Diurnal ultrastructural measurements of granal size and number did not reveal a significant net change in ultrastructure over the time scale of hours. It is concluded that spinach chloroplasts can alter the degree of thylakoid appression in response to irradiance changes on a time scale of minutes. These ultrastructural responses are caused by biochemical and biophysical adjustments within the thylakoid membrane that serve to maximize photosynthesis and minimize photo‐inhibition under rapidly fluctuating light environments.     

Dynamics of zinc uptake and accumulation in the hyperaccumulating and non-hyperaccumulating ecotypes of Sedum alfredii Hance

Sedum alfredii Hance has been identified as a Zn-hyperaccumulating plant species native to China. The characteristics of Zn uptake and accumulation in the hyperaccumulating ecotype (HE) and non-hyperaccumulating ecotype (NHE) of S. alfredii were investigated under nutrient solution and soil culture conditions. The growth of HE was normal up to 1000 μM Zn in nutrient solution, and 1600 mg Zn kg⁻¹ soil in a Zn-amended soil. Growth of the NHE was inhibited at Zn levels ≥250 μM in nutrient solution. Zinc concentrations in the leaves and stems increased with increasing Zn supply levels, peaking at 500 and 250 μM Zn in nutrient solution for the HE and the NHE, respectively, and then gradually decreased or leveled off with further increase in solution Zn. Minimal increases in root Zn were noted at Zn levels up to 50 μM; root Zn sharply increased at higher Zn supply. The maximum Zn concentration in the shoots of the HE reached 20,000 and 29,000 mg kg⁻¹ in the nutrient solution and soil experiments, respectively, approximately 20 times greater than those of the NHE. Root Zn concentrations were higher in the NHE than in the HE when plants were grown at Zn levels ≥50 μM. The time-course of Zn uptake and accumulation exhibited a hyperbolic saturation curve: a rapid linear increase during the first 6 days in the long-term and 60 min in the short-term studies; followed by a slower increase or leveling off with time. More than 80% of Zn accumulated in the shoots of the HE at half time (day 16) of the long-term uptake in 500 μM Zn, and also at half time (120 min) of the short-term uptake in 10 μM ⁶⁵Zn²⁺. These results indicate that Zn uptake and accumulation in the shoots of S. alfredii exhibited a down-regulation by internal Zn accumulated in roots or leaves under both nutrient solution and soil conditions. An altered Zn transport system and increased metal sequestration capacity in the shoot tissues, especially in the stems, may be the factors that allow increased Zn accumulation in the hyperaccumulating ecotype of S. alfredii. Section Editor: F. J. Zhao     

Factors Affecting Germination of Oospores of Phytophthora infestans

When oospores from the pairing between A¹ and A² mating types of Phytophthora infestans were treated with 0.25 % KMnO₄ solution for 15 min and incubated at 19 °C under light on a modified S+L medium, germination commenced within 4 days and reached about 70 % after 20 days. Under these conditions, more than 25 % of oospores obtained from a 4-day-old culture germinated. To obtain a high germination rate of P. infestans oospores, light was essential during germination but not during growth and oospore formation. The optimum time for activation of oospores with 0.25 % KMnO₄ was 15 to 30 min and a suitable concentration of KMnO₄ for 15 min activation was 0.25 to 0.45 %.     

Na+-dependent HCO 3 − transport and Na+/H+ exchange regulate pH i in human ciliary muscle cells

Summary We investigated intracellular pH (pH _i ) regulation in cultured human ciliary muscle cells by means of the pH-sensitive absorbance of 5(and 6)-carboxy-4,5-dimethylfluorescein (CDMF). The steady-state pH _i was 7.09±0.04 (n = 12) in CO₂/ HCO ₃ ^– -buffered and 6.86±0.03 (n = 12) in HEPES-buffered solution. Removal of extracellular sodium for 6 min acidified the cells by 1.11±0.06 pH units (n = 12) in the presence of CO₂/ HCO ₃ ^– and by 0.91±0.05 pH units (n = 8) in its absence. Readdition of external sodium resulted in a rapid pH _i recovery, which was almost completely amiloride-sensitive in the absence of CO₂/ HCO ₃ ^– but only slightly influenced by amiloride in its presence. Application of DIDS under steady-state conditions significantly acidified the ciliary muscle cells by 0.25±0.02 (n = 4) in 6 min, while amiloride had no effect. The pH _i recovery after an intracellular acid load was completely dependent on extracellular sodium. In HEPES-buffered solution the pH _i recovery was almost completely mediated by Na⁺/H⁺ exchange, since it was blocked by amiloride (1 mmol/liter). In contrast, a marked amilorideinsensitive pH _i recovery was observed in CO₂/HCO ₃ ^– -buffered solution which was mediated by chloride-independent and chloride-dependent Na⁺ HCO ₃ ^– cotransport. This recovery, inhibited by DIDS (0.2 mmol/liter). was also observed if the cells were preincubated in chloride-free solution for 4 hr. Analysis of the sodium dependence of the pH _i recovery after NH₄Cl prepulse revealed V _max = 0.57 pH units/min, K _m= 39.7 mmol/liter extracellular sodium for the amiloride-sensitive component and V _max = 0.19 pH units/min, K _m= 14.3 mmol/liter extracellular sodium for the arniloride-insensitive component. We conclude that Na⁺/H⁺ exchange and chloride-independent and chloride-dependent Na⁺HCO ₃ ^– cotransport are involved in the pH _i regulation of cultured human ciliary muscle cells.The expert technical assistance of Astrid Krolik is gratefully acknowledged. This work was supported by the Deutsche Forschungsgemeinschaft grant DFG Wi 328/11.     

H+ flux kinetics around plant roots after short-term exposure to low temperature: identifying critical temperatures for plant chilling tolerance

H⁺ flux kinetics were measured in solution around the roots of chilling-tolerant pea (Pisum sativum) and bean (Vicia faba), chilling-sensitive cucumber (Cucumis sativus) and pumpkin (Cucurbita pepo), and intermediate corn (Zea mays) species using a microelectrode technique to measure net flux. As a root warmed to room temperature alter 90 min at 4°C, at which temperature the H⁺ flux was near zero, the flux rose (influx) and then fell. These changes occurred at two apparent critical temperatures, which were higher for the more chilling-sensitive species. The First, lower, apparent critical temperature may represent the start of passive inward H⁺ transport. The higher critical temperature may represent the start of active H⁺ extrusion. From these apparent critical temperatures we have calculated the real critical temperature and the time delay of the chilling signal transduction process. Passive and active H⁺ transporters appear to have the same real critical temperature of chilling sensitivity, about 9°C, but have, respectively, 4 min and 11 min time delays. Measurement of these apparent critical temperatures may provide quick and reliable screening for chilling sensitivity in plant breeding programmes. Future ion flux studies may show the cellular location of chilling stress perception and the signal transduction pathways.     

Absorption characteristics and kinetics of CO2 capture into N-methyldiethanolamine aqueous solution catalyzed by the immobilized carbonic anhydrase

Abstract

Carbonic anhydrase (CA) is the most effective CO₂ hydratase catalyst, but the poor storage stability and repeatability of CA limit its development. Therefore, CA was immobilized on the epoxy magnetic composite microspheres to enhance the CO₂ absorption into N-methyldiethanolamine (MDEA) aqueous solution in this work. In the presence of immobilized CA, the CO₂ absorption rate of MDEA solution (10?wt%) (0.63?mmol·min^?1) was greatly improved by almost 40%, and their reaction equilibrium time was shortened from 150?min to 90?min compared with that into MDEA solution. The results indicated that the absorption of CO₂ into MDEA solution had been significantly enhanced by using CA. After the 7th reuse recycle, the activity of the immobilized CA was still closed to its initial value at 313.15?K. Moreover, enzyme catalytic kinetics of immobilized CA was investigated using the p-nitrophenyl acetate (p-NPA) as substrate. The values of Michaelis–Menten constant (K_m) and the maximum velocity (V_max) of the immobilized CA were calculated to be 27.61?mmol/L and 20.14?×?10^?3?mmol·min^?1·mL^?1, respectively. Besides, the kinetics of CO₂ reaction into MDEA with or without CA were also compared. The results showed that CO₂ absorption into CA/MDEA aqueous solution obeyed the pseudo first order regime and the second order kinetics rate constant (k₂) was calculated to be 929?m³·kmol^?1·s^?1, which was twice higher than that of MDEA aqueous solution without immobilized CA (k₂=414 m³·kmol^?1·s^?1) at 313.15?K.     

Production of constitutive, thermostable, hyper active exo-pectinase from Bacillus GK-8

Summary A new alkalophilic Bacillus GK-8 overproduced three thermostable extracellular pectinases. The temperature optima was 60°C for all the three enzymes which retained full activity for 2 h. They had pH optima 5.4, 7.0 and 10.4 and were designated as PI, PII and PIII respectively. The half life at 80°C of PI, PII and PIII was 18 min., 12 min. and 12 min., respectively. The enzyme activity was stimulated by Mg²⁺, Ca²⁺, Zn²⁺, Co²⁺ and Mn²⁺ ions.     

Administration of the probiotic Lactobacillus rhamnosus IMC 501 as a strategy for the control of Vibrio bacteria in the brine shrimp Artemia

The present study aimed to address the capability of the probiotic bacterium Lactobacillus rhamnosus IMC 501^® to survive in seawater and the ability of Artemia metanauplii to incorporate it, as well as to analyse the potential effect of the probiotic as a control agent for potentially pathogenic Vibrionaceae bacteria in Artemia. The results demonstrate the ability of L. rhamnosus IMC 501^® to survive in seawater for up to 30 h. They also advocate their capability to be efficiently incorporated into Artemia metanauplii at concentrations of 10⁴ CFU per Artemia after 30 min of suspension in probiotic solution, thereby promoting a 1-log reduction in Vibrionaceae levels after 3 h. These low levels of Vibrio bacteria were maintained for about 30 min after transfer into clear seawater, a sufficient time for Artemia to be ingested by aquatic organisms. These results contribute to broaden the knowledge on the suitability of probiotics as sustainable alternatives for the prevention/reduction of diseases in aquaculture facilities.