Silicate Medium Research Articles

Enhancing growth and Cadmium remediation in red alga, Gracilaria edulis through silicate intervention

This study investigates the potential of silicate to alleviate cadmium (Cd) toxicity in Gracilaria edulis, an agarophyte. Under various culture conditions spanning 21 days, alga was grown in control, Silicate (Si) medium, and different Cd concentrations (100, 200, and 300 µM) with or without Si100 µM and the effect was measured by photosynthesis O2 evolution, relative growth rate (RGR), biomass, biochemical compositions such as chlorophyll a, phycobilipigments (phycocyanin, allophycocyanin, and phycoerythrin), carbohydrate, protein, lipid peroxidation and Cd accumulation. Cd, a toxic heavy metal, negatively impacts plant and algal growth and metabolism. In contrast, traditionally considered non-essential, Si has growth-promoting properties under various stress conditions. The present study reveals that Si significantly enhances photosynthesis except for Cd300. In Cd100, the photosynthetic O2 evolution was 0.08 nM s−1, whereas in Cd100 + Si, it increased to 0.09 nM s−1. The Cd300 + Si treatment exhibited a rate of 0.07 nM s−1, but in Cd300, it was 0.05 nM s-1 on the 9th day of culture, and the rate was proportionately high on the 18th day of culture. The RGR and biomass significantly improved, particularly when Cd100 was combined with Si. Alga shows a decrease in the chlorophyll a, phycobilin pigments, carbohydrate, and protein content when grown at Cd300 concentration but significantly increased when combined with Si treatment. Alga showed less carbohydrate content (0.30 ± 0.02) at Cd300 µM exposure, of which was increased by adding Si (Cd300 + Si) to 0.34 ± 0.02 mg g−1 alga fresh wt. Cd uptake by the alga is high at Cd300 but considerably low at Cd100 + Si and Cd200 + Si concentrations. Malondialdehyde (MDA) level indicating lipid peroxidation-induced oxidative damage was significantly reduced in Si-treated Cd concentrations compared to heavy metal treatment alone. This study demonstrates that silicate can potentially mitigate the adverse effects of Cd on G. edulis by creating a favorable environment for its growth. Thus, it exhibits promise in alleviating Cd toxicity in G. edulis.

Elucidating the relationship between PFOA and PFOS destruction, particle size and electron generation in amended media commonly found in soils

Ball milling has emerged as a promising destructive technique for treating per- and polyfluoroalkyl substances (PFAS)-impacted soils. Environmental media properties such as reactive species generated upon ball milling and particle size are postulated to influence the effectiveness of the technology. In this study, four media types amended with perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) were planetary ball milled to investigate destruction, fluoride recovery without additional co-milling reagents and the relationship between PFOA and PFOS destruction, particle size during milling, and electron generation. Silica sand, nepheline syenite sand, calcite and marble were sieved to achieve similar initial particle sizes (6/35 distribution), amended with PFOA and PFOS, and milled for 4 h. Particle size analysis was conducted throughout milling and 2,2-diphenyl-1-picrylhydrazyl (DPPH•) was used as a radical scavenger to assess electron generation from the four media types. Particle size reduction was observed to be positively correlated to PFOA and PFOS destruction and DPPH• neutralization (demonstrating electron generation by milling) in silica sand and nepheline syenite sand. Milling of a fine fraction (< 500 μm) of silica sand revealed less destruction compared to the 6/35 distribution suggesting the ability to fracture grains in silicate media is integral to PFOA and PFOS destruction. DPPH• neutralization was demonstrated in all four amended media types, confirming silicate sands and calcium carbonates generate electrons as a reactive species during ball milling. Fluoride loss as a function of milling time was observed in all amended media types. A sodium fluoride (NaF) spiked was used to quantify fluoride loss in the media independent of PFAS. A method was developed using the NaF-amended media fluoride concentrations to estimate the total fluorine liberated from PFOA and PFOS by ball milling. Estimates produced suggest complete recovery of theoretical fluorine yield is obtained. Data from this study was used to propose a reductive destruction mechanism for PFOA and PFOS.

Interaction of carbonates with peridotite containing iron metal: Implications for carbon speciation in the upper mantle

Due to the significantly reduced conditions in the mantle below ~250 km, carbonates transported by the subducting oceanic plates will inevitably interact with Fe-saturated mantle peridotites to form diamonds or other reduced carbon species. In this study, we present the reaction experiments at 6 and 10 GPa, and 1100–1400°С between carbonates and peridotite with iron to model the behaviors of subducted carbonates in the reduced mantle. Magnesiowüstite (Mws), ferropericlase, metastable graphite, or diamond crystallization showed the occurrence of the redox reactions. The reactions in Ca‑carbonate and dolomite-containing systems were accompanied by the appearance of carbonate melt already at 1100 and 1200 °C. Formation of the melt at such a low temperature in the studied systems shows that the redox gradient between iron-containing mantle peridotites and carbonate-containing subduction lithologies could trigger deep mantle melting at the hot subduction zone conditions, even in the anhydrous and alkali-free systems. Carbonate melts, and oxides, formed in the redox reactions, would further interact with olivine, pyroxenes , and garnet with the formation of merwinite , Ca-rich garnet, and Fe-rich olivine. Here we confirm that merwinite could be an indicator of the mantle metasomatism and may originate via interaction of Ca-rich carbonate melt with peridotite. The kinetic calculations reflect that, in natural systems where carbonates and iron are separated by silicate media, the redox reactions are limited due to slow chemical diffusion rates in silicates and will not have any significant effect on the preservation of carbonates in the anhydrous and melt free environment. On the contrary, the presence of carbonate melt during the reaction between carbonate and metallic Fe will lead to significant consumption of carbonates. • We studied the carbonate-iron reactions in the complex peridotite systems at 6,10 GPa • We observed formation of magnesiowüstite, diamond, graphite and carbonate melt • The redox gradient between mantle peridotites and subduction lithologies could trigger deep mantle melting. • Merwinite in diamond inclusions is linked to the carbonate metasomatic activity in the ultramafic assemblages.

Plant-Growth-Promoting Potential of PGPE Isolated from Dactylis glomerata L.

Plant-growth-promoting endophytes (PGPE) are a kind of beneficial microorganisms which could inhabit plant tissues to antagonize certain plant pathogens and promote the host plant’s growth and development. At present, many studies have confirmed the mutualistic effect of endophytes with plants, but there are few systematic studies on beneficial roles between endophytes and Dactylis glomerata, especially on the PGPE characteristics of the forage and environmental restoration plant. This study aimed to isolate PGPE from D. glomerata, evaluate their effects on plant growth, and ultimately acquire desirable microbial inoculants for agricultural use. First, endophytes were isolated from D. glomerata by plant re-inoculation experiment, and identified by morphological and molecular analyses. Fixation medium and methods were carried out to assess the nitrogen fixation ability of the strains. Then, the ability to dissolve phosphorus was determined by the Olsen and silicate medium methods; secretory IAA was measured by Salkowski colorimetric method; and the inhibitive effects on phytopathogen were observed by confrontation culture. Twenty-one strains were isolated from four varieties of D. glomerata, among which 14 strains with plant-growth-promoting characteristics were obtained by re-inoculation experiments, including seven endophytic bacteria and seven endophytic fungi. Further evaluation of three selected strains with the most significant PGP attributes were performed by using the pot re-inoculation experiment which revealed that TG2-B derived from Myroides odoratimimus was the most effective plant-growth-promoting agent due to its ability to produce high levels of IAA; the strain Bacillus cereus exhibited the most robust ability in dissolving inorganic phosphorus; and Trichoderma harzianum manifested a conspicuously antagonistic effect against a variety of plant pathogens. For the first time, this study reports the identification of D. glomerata endophytes that were able to promote plant growth and have a considerable antagonistic effects on plant pathogens, which could be considered as microbial inoculants for using in improving crop production and plant disease control.

Preservation conditions of CLIPPIR diamonds in the earth’s mantle in a heterogeneous metal–sulphide–silicate medium (experimental modeling)

The genesis of CLIPPIR diamonds (Cullinan–like, large, inclusion–poor, pure, irregular, and resorbed) have attracted much interest due to their possible crystallization from metal melt in deep horizons of the earth’s mantle. These diamonds usually show a pronounced resorption and irregular morphology. The present paper reports new experimental data on the dissolution of diamond crystals at high P–T parameters in Fe–S melt containing large amounts of silicate components (5–20 wt%). The experiments were performed using a split–sphere multi–anvil apparatus (BARS) at a pressure of 4 GPa and a temperature of 1450 °C. The samples consisted of natural diamond crystals placed in mixtures of Fe, S, and kimberlite. Wide variations in dissolution rates of diamond crystals were obtained. The absence of diamond dissolution in a heterogeneous medium indicates that the amount of solid silicate phases present in metal melt plays a role in the preservation of diamonds. This study demonstrated how diamonds can be stored in natural environments due to the heterogeneity of the medium composition which could insulate diamonds from the metal–sulphide melt. The obtained results improve our understanding of processes that lead to preservation of CLIPPIR diamonds in the deep mantle.

Combined artificial high-silicate medium and LED illumination promote carotenoid accumulation in the marine diatom Phaeodactylum tricornutum

BackgroundDiatoms, which can accumulate large amounts of carotenoids, are a major group of microalgae and the dominant primary producer in marine environments. Phaeodactylum tricornutum, a model diatom species, acquires little silicon for its growth although silicon is known to contribute to gene regulation and play an important role in diatom intracellular metabolism. In this study, we explored the effects of artificial high-silicate medium (i.e. 3.0 mM sodium metasilicate) and LED illumination conditions on the growth rate and pigment accumulation in P. tricornutum, which is the only known species so far that can grow without silicate. It’s well known that light-emitting diodes (LEDs) as novel illuminants are emerging to be superior monochromatic light sources for algal cultivation with defined and efficient red and blue lights.ResultsFirstly, we cultivated P. tricornutum in a synthetic medium supplemented with either 0.3 mM or 3.0 mM silicate. The morphology and size of diatom cells were examined: the proportion of the oval and triradiate cells decreased while the fusiform cells increased with more silicate addition in high-silicate medium; the average length of fusiform cells also slightly changed from 14.33 µm in 0.3 mM silicate medium to 12.20 µm in 3.0 mM silicate medium. Then we cultivated P. tricornutum under various intensities of red light in combination with the two different levels of silicate in the medium. Higher biomass productivity also achieved in 3.0 mM silicate medium than in 0.3 mM silicate medium under red LED light irradiation at 128 μmol/m2/s or higher light intensity. Increasing silicate reversed the down-regulation of fucoxanthin and chlorophyll a under high red-light illumination (i.e. 255 μmol/m2/s). When doubling the light intensity, fucoxanthin content decreased under red light but increased under combined red and blue (50:50) lights while chlorophyll a content reduced under both conditions. Fucoxanthin accumulation and biomass productivity increased with enhanced red and blue (50:50) lights.ConclusionHigh-silicate medium and blue light increased biomass and fucoxanthin production in P. tricornutum under high light conditions and this strategy may be beneficial for large-scale production of fucoxanthin in diatoms.

Evaluation of isolation and field effect of ginseng disease resistance and growth-promoting bacteria

This study was aimed to isolate the strains with both disease resistance and growth-promoting, and clarify the field application effects of the strain for laying the further application foundation. The strains with good antagonistic effect were isolated from the 298 strains in Panax ginseng and the soil by plate confrontation method. The nitrogen fixation potential was verified by Ashby medium. The Salkowski method was used to determine the ability of producing IAA. Silicate medium screening and flame spectrophotometry was used to determine the ability of dissolving potassium. CAS method was applied to detect the ability of producing siderophores to determine its growth characteristics. The morphological, physiological and biochemical and 16S rRNA sequences were used to identify the species. The method of root irrigation was used to determine the effects of its disease control and growth-promoting on ginseng. A strain TY15 with broad spectrum of antimicrobial effect, nitrogen fixation, potassium-dissolving and the capacity of producing IAA and siderophores was obtained by screening. And the strain TY15 was identified as Pantoea agglomerans. The control effect of TY15 on the disease of ginseng in the field was 68.02%, which was equivalent to 68.94% of 30 billion per gram of beneficial microecological bacterium agent. The fresh weight of P. ginseng treated with TY15 strain was increased by 22.73% compared with the control group treated with water. And finally a strain TY15 with good application prospects was obtained.

Antagonistic Effect of Plant Growth Promoting Rhizobacteria (PGPR ) as Biocontrol of Plants Damping-Off.

In the rhizosphere can be found that different groups of plant growth promoting rhizobacteria (PGPR). These bacteria including variety genera of nitrogen fixation and potassium silicate minerals solubilization in soils which can promote the growth of plant. In the present work, nine cotton and sugar beet rhizospheric soil samples were collected from two governorates in Egypt.Twenty three bacteria were isolated and screening for antagonism to soil borne fungi i.e.,Fusarium oxysporum and growth on potassium- silicate medium, indole acetic acid (IAA) , ammonia productions , cyanid hydrogen (HCN),catalase as biofertilizers and bioagents to soil borne fungi. Four bacterial isolates showed highly antagonistic effects for pathogenic fungus (F.oxysporum) and three of them were positive for growth on potassium-silicat medium . IAA production was shown by all the bacterial isolates. Three isolates were positive for ammonia production. Two isolates were positive for HCN production and all isolates were found to be catalase positive. These bacterial isolates as maximum antagonistic for pathogen and growth promotion for plants were identified on the basis colonies morphology on silicate medium, Gram staining , spore formation , capsule forms and biochemical tests as Bacillus spp. (B.subtilis, B.amyloliquefaciens, B.weihensteephanensis and B.pseudomycodies). As PGPR and bioagents are environmental friendly to increase production of crops and health. Therefore, these isolates can be utilized for biofertilizer and biological control under agroclimatic conditions of Egypt.

Screening and identification of indoleacetic acid producing endophytic bacterium in Panax ginseng

Endophytic bacteria which was producing indoleacetic acid was screened from Panax ginseng by using the Salkowski method. The active strain was also tested for its ability of nitrogen fixation by using the Ashby agar plates, the PKV plates and quantitative analysis of Mo-Sb-Ascrobiology acid colorimetry was used to measure its ability of phosphate solubilization, for its ability of potassium solubilization the silicate medium and flame spectrophotometry was used, for its ability of producing siderophores the method detecting CAS was used, for its ability of producing ACC deaminase the Alpha ketone butyric acid method was applied. And the effect on promoting growth of seed by active strain was tested. The results showed that the indoleacetic acid producing strain of JJ5-2 was obtained from 118 endophytes, which the content of indoleacetic acid was 10.2 mg x L(-1). The JJ5-2 strain also had characteristics of phosphate and potassium solubilization, nitrogen fixation, producing siderophores traits, and the promoting germination of ginseng seeds. The JJ5-2 strain was identified as Bacillus thuringiensis by analyzing morphology, physiological and biochemical properties and 16S rRNA gene sequences.

Persian turquoise glazed bodies: reproduction and optical properties

Ancient turquoise Persian glazed ceramics, which are well known as Khar-Mohreh, belonged to several centuries ago. In this research, reproduction of ancient glazed bodies was performed, and the products were studied by different techniques. Experimental evaluations were focused on elemental, structural, morphological, and colorimetric characteristics. SEM micrographs illustrated a thin (10 μm) uniform composite glazed layer on a porous composite thicker layer (500 μm). The layers consist of microneedle-shaped and nanospherical particles of copper oxide distributed in an amorphous silicate medium. Modeling of this architecture was used for determination of the visual aspect of the ceramic via the reflectance coefficient. Structural and colorimetric results showed that the shape and distribution of copper oxide particles do not play a crucial role on the color of these ceramics.

Вивчення властивостей композитів на основі модифікованого силікату натрію

The research in the field of interaction between inorganic binder (sodium silicate) and organic hardeners (dicarboxylic acid esters) has been conducted. The kinetics of saponification of several dicarboxylic acid esters in a sodium silicate medium has been studied. In this case, the kinetics of saponification is described by the pseudo-first order equation. The results of kinetic researches allow predicting the selection of dicarboxylic acid esters aimed at decreasing or increasing the prolonged action of esters depending on their structure and nature during organic-silicate composites structurization. Interrelation of structural properties of organic-inorganic composites components and physicochemical properties of coatings based on them has been shown. The hardeners effect on the properties of paint and adhesive composites has been verified. The improvement of operation properties when using the hardeners in organic-inorganic composites has been shown, namely increased paint coating water resistance and adhesive joint strength in adhesive composites. It is shown that the compounds containing ester groups can be used as hardeners of organic-inorganic composites.

Initial stages of AZ91 Mg alloy micro-arc anodizing: Growth mechanisms and effect on the corrosion resistance

In the framework of the new ecological regulations, micro-arc oxidation (MAO) appears as an alternative to usual processes in the field of corrosion protection of Mg alloys. In this work, the initial stages of anodic layer growth in KOH-based electrolytes are studied up to and beyond the initiation of the micro-arc regime.The properties of the first anodized film preceding the occurrence of the dielectric breakdown (corresponding to the start of the micro-arc regime) are mainly determined by the incorporation of additives (fluorides or silicates) in the film, as shown by in situ electrochemical measurements. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and micro-Raman spectroscopy reveal both the change of morphology and chemical state of silicate and fluoride in the anodized layer before and after the micro-arc regime. In terms of electrochemical behaviour, investigated by stationary methods and electrochemical impedance spectroscopy (EIS) in reference corrosive water, the anodic film grown in the silicate medium provides the best corrosion resistance thanks to a thick layer containing Mg2SiO4, whose degradation products seal the porosities of the coating.

茅苍术叶片可培养内生细菌多样性及其促生潜力

Atractylodes lancea is a medicinal plant grown in Jiangsu Province,China.The diversity of the endophytic bacteria culturable from the leaves of A.lancea and their plant growth-promoting potential,including nitrogen fixation,phosphorus solubilization,potassium solubilization and indole acetic acid(IAA) production were investigated.According to morphological characteristics of bacterial colonies,52 endophytic bacterial strains were obtained and 45 could be subcultured normally in vitro and subjected to amplified ribosomal DNA restriction analysis(ARDRA).Based on the ARDRA fingerprints,the 45 subculturable endophytic bacterial strains could be classified into 14 clusters.The 16S rDNA fragments of representative strains from different clusters were sequenced and deduced by a BLAST search to identify similar strains.The results showed that the isolated endophytic bacteria most likely belong to Pantoea sp.,Microbacterium sp.,Curtobacterium sp.,Agrobacterium sp.,Pseudomonas sp.,or Bacillus sp.Among them,the Pseudomonas sp.was the most dominant genera.BOX-PCR was then used to study the diversity of the endophytic bacteria in the main ARDRA clusters.The BOX-PCR fingerprints showed that the endophytic bacteria in the same cluster were not similar,indicating a broad genetic diversity within the same genera.Ten of the 45 subculturable endophytic bacteria could grow normally on Burk′s medium,which indicates their potential to fix nitrogen.We also amplified the nifH genes in these strains and all strains generated a band of the expected size except for ALEB 33.Among all subculturable endophytic bacteria,19 and 15 strains could dissolve insoluble calcium phosphate and lecithin,respectively,and then release dissociative phosphorus into the medium.ALEB 43 could dissolve the largest amount of phosphorous from calcium phosphate,reaching(251.43±6.55) mg/L.Furthermore,ALEB 4A could dissolve the largest amount of phosphorous from lecithin,reaching(23.63±1.46) mg/L.After comparing the amount of phosphorous dissolved from calcium phosphate by the endophytic bacteria and the pH of the bacterial inoculum,we deduced that some phosphate-solubilizing bacteria dissolve insoluble calcium phosphate by secreting certain types of acids.However,the pH of the fermentation solution of endophytic bacteria capable of dissolving lecithin was not related to the release of dissociative phosphorus.There were 24 strains that could grow on silicate medium,indicating these strains had the potential to dissolve insoluble potassium feldspar and release dissociative potassium,which was available to plants.Forty three endophytic bacterial strains could produce and release IAA into the medium.The amount of IAA released by ALEB 44 was the highest,reaching(268.44±10.12) μg/mL.These endophytic bacteria could promote the growth of host plants by increasing the amounts of available nutrients or phytohormones.This paper is the first to reveal the diversity of endophytic bacteria in A.lancea and their plant growth-promoting potential.Continued research will be needed to clarify the interactions between A.lancea and its endophytes.

Ultrasonic propagation in molten lithium, sodium and potassium silicates

Velocity and attenuation of ultrasonic wave in molten alkaline silicates of lithium, sodium and potassium were measured at a temperature range between their liquidus and ∼200 K higher than their liquidus. Measurements were carried out by the pulse transmission method using a couple of ultrasonic pulse generator and receiver. Composition of the silicate sample was selected for covering the enough temperature range and for getting the correct knowledge of composition dependence of alkaline silicate. Measured velocity of ultrasound decreases with the increase in temperature in all samples. Composition dependence were similar between sodium and potassium silicates but little different in lithium silicate. Absorption of ultrasound depends both on the sound frequencies and temperatures. It suggests that there is some dispersion of sound waves propagating in the silicate medium. Since the lithium silicate melt behaves in a dissimilar way from those of other alkaline silicates, the authors tried the additional measurement on the pseudobinary system of lithium and sodium disilicate system. The results are discussed from the structural aspect comparing with the previous work on Ni ion colour indicator.

Growth and characterization of antimony sulphobromide single crystals

Antimony sulphobromide, ASB, single crystals were grown in sodium meta silicate medium at ambient temperature. The grown crystals were identified by chemical analysis, EDAX and X-ray diffraction techniques. The single crystal X-ray diffraction technique was used to determine the cell parameters and the space group. ASB crystallizes in the monoclinic system with space group C 3 2. Dielectric properties, dielectric constant, dielectric loss and ac conductivity of ASB crystals are presented. The refractive indices of the crystal were obtained for the wavelength 5893 Å.

The effects of silicate depletion and subsequent replenishment on the cytoplasmic fine structure of the silica-secreting testate amoeba Netzelia tuberculata in laboratory culture.

In the absence of silicate in the growth medium, Netzelia tuberculata cells withdraw their feeding lobopodia, become quiescent, and cease to divide. Upon replenishment of silicate, growth resumes within 18-24 hours. Cytoplasmic changes produced by a low silicate medium result in a zonal arrangement, with siliceous particles at the outer periphery of the cytoplasm in a region rich in Golgi bodies (Region A), a more centrally located layer containing endoplasmic reticulum, lipid reserves, and finely granular cytoplasm (Region B), and a region of partially digested food and waste material fringed by fine rhizopodia extending into the central space of the test (Region C). The reserve siliceous particles in the outer peripheral cytoplasm are foreign particles that contain a fragile deposit of silica and appear to be incomplet. This may be a mechanism for conserving silica in the low-silicate medium by coating particles instead of making particles of solid silica de novo. Upon addition of silicate to the growth medium, new siliceous particles are synthesized within vacuoles in the region of the Golgi apparatus within 2-18 hours. Vacuoles containing fine silica deposits, characteristic of new particle production, are surrounded by Golgi-derived vesicles previously shown to be a source of membrane for the silica-secreting vacuoles. The newly synthesized particles are solid silica as is characteristic of de novo secreted test particles, in contrast to the numerous silica-coated foreign bodies found in quiescent cells produced in low-silicate medium.

A Coating with Antifouling Properties from the Reaction between Cuprous Oxide and Sodium Silicate

FILMS prepared from dispersions of zinc dust in sodium silica media of a high silica ratio of about Na2O : SiO2/1 : 3.8 by weight (Pass, A., and Meason, M. J. F., private communication) have been reported to become substantially insoluble in water within a few hours without the aid of curing agents previously needed to produce satisfactory air-drying zinc silicate paints1. The mechanism of the formation of these films is only partially understood, and in the course of work undertaken to elucidate it, changes in viscosity occurring when zinc and other pigments are dispersed in silicate media are being examined.

A new silicate medium, a useful substitute for agar-agar

Two silicate media are described which in comparison with agar-agar media have only slight disadvantages. They are very cheap.

Effect of Silica on the Growth of the Tubercle Bacillus.

In silicosis, silica in some form or in some way seems to increase the pathogenic effects of the tubercle bacillus. It therefore suggested itself that silica might have a stimulating effect on the growth of the tubercle bacillus in vitro. Accordingly, I carried out a number of cultural experiments, by adding 1 cc. of sodium silicate or silicic acid, each standardized to contain 1 mg. of the silica used in the preparation per cubic centimeter, to every 100 cc. of Dorset's egg medium, modified by replacing the distilled water by a beef infusion free from added peptone, or sodium chloride, and adjusted to a pH of 7.6. The results obtained in these preliminary studies have been consistently uniform, and indicated a definite stimulating effect of the added substances, even though the estimated quantity of silica is 0.001 mg. per cc. of medium. This is shown by a lessening of the latent period, and a greater luxuriance of growth. The stimulating effect appeared to be continuous throughout the period of growth. I was thus able to produce readily visible colonies in initial cultures from guinea pigs, and directly from human sources, such as pus, urine and ascitic fluid, in a much shorter time than with other media. In one instance, a primary culture was isolated from ascitic fluid on sodium silicate medium, whereas we failed to obtain any growth on the control tubes of our Dorset's egg medium, with or without glycerine. Colonies became visible in about 6 days, growth continued rapidly, and could be considered luxuriant within 3 weeks. These observations now cover 20 primary cultures, 17 of which were isolated through guinea pig inoculation, and the remaining 3 directly from human materials.