Agar Plate Test Research Articles

Interactions between Bioactive Glass and Periodontal Pathogens

Bioactive glasses have been used in periodontal applications such as grafting infrabony periodontal lesions. We studied a bioactive glass S53P4 for its possible antibacterial effects on the periodontal pathogens Porphyromonas gingivalis, Prevotella intermedia and Actinobacillus actinomycetemcomitans using agar plate tests. Also the colonisation of the bioactive glass with these microorganisms was studied by incubating bacterial suspensions with glass granules. Two precorrosion procedures were used to create chemically differing surfaces on the bioactive glass.The bioactive glass did not alter the growth properties of any of the tested microorganisms. P. intermedia and A. actinomycetemcomitans showed adherence both to the untreated and precorroded bioactive glasses. However, P. gingivalis adhered only to the precorroded glasses and was agglutinated in the presence of the untreated glass. Coating the untreated glass with serum or Actinomyces viscosus cells did not eliminate the agglutination. Thus, even though the bioactive glas S53P4 did not alter the growth properties of the studied microorganisms it may in vivo beneficially modify the microbiota of periodontal lesions by agglutinating P. gingivalis.

Ecotoxicity assessment of the aquatic environment around Lake Kojima, Japan

To reduce the impact of chemical substances on the aquatic ecosystem, it is essential to understand their ecotoxicological properties in the natural aquatic environment. Consequently, we conducted an ecotoxicological study on the aquatic environment around Lake Kojima, a man-made lake located in the southwest of Japan. Lake Kojima receives its chemical inputs mainly from two rivers that flow through various agricultural and industrial areas. For ecotoxicity screening, surface water and sediment samples were collected 4 times in 1993 from 16 preselected sites. Then, the solutes in the filtered surface water were concentrated by ODS resin, and the organic chemicals in the suspended solids (SS) and sediments were extracted by acetone. A battery of five ecotoxicity tests (agar plate test using bacteria and yeast, algal growth inhibition test, Daphnia magna immobilization test, and root elongation test using lettuce seeds) was used to assess these extracts. The results show that the surface water extracts had a lethal effect on D. magna, the SS extracts suppressed algal growth, and the sediment extracts were inhibitory to the growth of yeast. A significant inhibitory effect by the sediment extracts from 4 lake sites and 3 river sites was detected by these ecotoxicity tests. Attempts also were made to identify the putative ecotoxic chemicals in the collected samples. Elementary sulfur was identified as one of the major toxicants in the sediment extracts that were inhibitory to the yeast growth. Moreover, samples of surface water around Lake Kojima, collected weekly from June to September in 1994, were found to contain three pesticides and were toxic to D. magna. But the concentration of the pesticides detected was too low to cause daphnia immobilization. It is believed that the toxicity of the water extracts was mainly due to the combined toxic effect of natural and man-made components. © 1996 by John Wiley & Sons, Inc.

Durability of Angiosperm Heartwood: The Importance of Extractives

Analysis of osage orange (Maclura pomifera) heartwood extractives showed that two compounds were present at much higher levels than previously reported, the flavanonol dihydromorin (2.51%) and the stilbene oxyresveratrol (2.65%). All compounds present in osage orange heartwood that were tested had low activity against wood-decaying fungi. The agar plate test showed no synergistic effect, but the soil block test usinh white-rot fungi suggested synergism. The high durability of osage orange heartwood may be due to the large amounts of oxyresveratrol and dihydromorin. High levels of one or two monomeric compounds may also explain the exceptionally good durability of black locust and red mulberry heartwood

A rapid evaluation plate-test for the biodegradability of plastics

Solid-media agar-plate tests were investigated for their potential to evaluate the biodegradation of polymeric particles by certain strains of microorganisms. A reliable test was developed. Stable suspensions of 1-μm globules of two poly(3-hydroxyalkanoates) were prepared. These were mixed with liquified agar-agar to form turbid plates. Inoculation was carried out by plate puncturing. Seven strains isolated from sewage sludge formed clear zones. These zones were distinct, circular, and reproducible in outlook and growth. The maximal duration of single experiments was 192 h. A growth rate was defined. It allowed the classification of the polymers, and of the microorganisms used. Poly(3-hydroxybutyrate-co-valerate) was degraded faster by all the strains used than was the homopolyester poly(3-hydroxybutyrate). Strains achieving high zone growth rates generally did so on both of the polymers. This led to the assumption of similar enzymatic processes being active. Zone formation was concluded to be dependent on the amount of enzyme production plus the enzyme activity. The technique provides a means of either distinguishing the degradation abilities of a microorganisms, or the degradability of materials.

Effect of Flutriafol on Saprophytic Survival and Growth of Rhizoctonia Solani (Ag-8).

The effect of flutriafol (a sterol-inhibiting triazole fungicide) on saprophytic survival and growth of Rhizoctonia solani (AG-8, causal agent of rhizoctonia root rot of wheat) in vitro and in soil was investigated with agar plate tests, a soilsandwich experiment and soil bioassays. At a concentration of 25 μg/mL agar, flutriafol reduced the growth of R. solani in vitro, but at 2.5 μg/mL it reduced growth of only two of the three isolates tested. Mycelium from plugs removed from plates of agar containing inhibitory concentrations of flutriafol retained pathogenicity to wheat seedlings. Flutriafol reduced growth of the fungus in unsterilised and autoclaved soil when applied at 190 μg/100 g, but not at 19 μg/100 g. Less fungal growth occurred in unsterilised than autoclaved soil at all concentrations of flutriafol. Bioassays of fungal mycelium placed in soil treated with flutriafol showed that pathogen survival was unaffected by the fungicide. Flutriafol appears to have a negligible effect on saprophytic survival and growth of R. solani (AG-8) at rates which could be considered commercially acceptable in the field.

Use of Petal Infestation to Forecast Sclerotinia Stem Rot of Canola: The Influence of Inoculum Variation over the Flowering Period and Canopy Density

The relationship in canola (oilseed rape) between the percentage of petals infested with Sclerotinia sclerotiorum and the incidence of Sclerotinia stem rot was investigated relative to changes in petal infestation during flowering and to canopy density. Using an agar-plate test, percent petal infestation was assessed in commercial crops of Brassica napes and B. rapa (=B. campestris) in various regions of Saskatchewan. Crop height, stem thickness, percent light penetration of the canopy, leaf area index, and the number of plants per square meter also were assessed at some locations. The incidence of stem rot was determined before harvest. Substantial changes in petal infestation were observed between early and late bloom. Most changes were increases; in 1989, however, infestation generally decreased [...]

Assessment of in vivo screening systems for potential biocontrol agents of Gaeumannomyces graminis

A screening programme was used to search for biocontrol agents against Gaeumannomyces graminis causing take‐all disease of wheat. Of the 1800 rhizosphere microorganisms tested, 10% controlled the disease in a secondary screen. The 30 most effective isolates were further investigated for mode of action. Although 72% of the sites sampled for antagonistic microbes were planted to continuous cereals, they yielded only 23% of the most effective isolates. Of all the isolates selected, 63% belonged to the genera Bacillus, Pseudomonas and Penicillium; Beauveria and Rhodococcus were also antagonistic. Fluorescent pseudomonads, all producing siderophores in low‐iron medium, accounted for 23% of the isolates. Over 50% of strains produced β‐glucanases and chitinases. Less than 50% of the strains selected by the in vivo screen inhibited G. graminis in agar plate tests. In the gnotobiotic system used, the Pseudomonas strains were faster in colonizing the wheat roots than the majority of the Bacillus and fungal strains.

New method for detecting rhamnolipids excreted byPseudomonas species during growth on mineral agar

A new semi-quantitative agar plate test for the detection of extracellular rhamnolipids has been developed. These biological anionic tensides (biosurfactants) form an insoluble ion pair with the cationic tenside cetyltrimethylammonium bromide and the basic dye methylene blue which was included in mineral agar plates. On the light blue agar, productive colonies ofPseudomonas spec. were surrounded by dark blue halos. The test is specific for anionic biosurfactants and can be applied to other glycolipid producing microorganims.

Oxidative coupling of 2,6-dimethoxyphenol by fungi and bacteria

An agar plate test was used to screen bacteria and fungi for their ability to oxidatively couple 2,6-dimethoxyphenol. Positive reactions were demonstrated by the production of purple, needle-shaped crystals within the medium. Trametes versicolor and Pseudomonas lemonnieri were found to be the most efficient organisms to catalyse the coupling reaction. These organisms also produced crystals in liquid culture. The coupling reaction was spontaneous at high pH values. A purple product was isolated using TLC and identified as 3,5,3′,5′-tetramethoxydiphenoquinone by mass spectroscopy.

Biological mode of action of soil-applied flutriafol in controlling take-all of wheat

The mode of action of flutriafol (a sterol-inhibiting, triazole fungicide) against Gaeumannomyces graminis var. tritici (causal agent of take-all of wheat) was investigated with agar plate tests, soil sandwich experiments and pot experiments to determine the effect of the fungicide on growth of the fungus on agar, in soil and on disease, respectively. All fungicide concentrations generally reduced growth of G. graminis on agar but pathogenicity remained unaffected. Flutriafol reduced saprophytic growth of the fungus through unsterilised soil at concentrations equivalent to 200 and 2000g a.i. ha −1, but only at 2000g a.i. ha −1 in autoclavcd soil. At 200 g a.i. ha −1 it also reduced survival of the fungus in colonised oat grains. Take-all was reduced by all fungicide concentrations in unsterilised soil. but only by 2000 g a.i. ha −1 in autoclaved soiland excluding this concentration, < 1μ g −1 flutriafol was detected in the plant roots. Control of take-all with flutriafol appears to be achieved by a protective effect, the fungicide reducing saprophytic survival and growth of G. graminis and not by a therapeutic effect resulting from uptake of the fungicide by the host.

Comparison of the fungicidal activities of ( E)-4-hydroxylated stilbenes and related bibenzyls

The fungicidal activities of ( E)-4-hydroxylated stilbenes and related bibenzyls were measured by the agar plate procedure and selected active compounds by the soil block method. In the agar plate test, stilbenes with 3′-substituents were all active against two brown-rot ( G. trabeum and P. placenta) fungi, with the activity having a parabolic hydrophobic relationship. A highly fungitoxic monomer was used to synthesize a dehydrogenative dimer which showed no brown-rot activity. No stilbene was active against the white-rot fungi C. versicolor while three bibenzyls had white-rot activity. Most bibenzyls had moderate brown-rot fungicidal activity. No structural requirement was apparent for bibenzyl brown-rot activity in contrast to the stilbenes. No synergism was observed when various combinations of stilbenes and bibenzyls were tested by the agar plate procedure. Similarities were observed between the agar plate activity and soil block results, although the soil block required higher levels of the stilbene/bibenzyl. No synergism was observed in the soil block results for stilbene and/or bibenzyl combinations. Stilbenes and/or bibenzyls in combination with didecyldimethylammonium chloride, however, showed some synergism.

Control of potato gangrene by thiabendazole in relation to time of harvest after haulm destruction and site of production

SUMMARYThe efficiency of thiabendazole in controlling gangrene on potato tubers harvested on different dates was assessed over two years in Scotland (East Craigs) and England (Rothamsted). At East Craigs the incidence of gangrene on wounded and cold‐stored tubers was greater than on those tubers kept at ambient store temperatures and graded in January, but the assessments were correlated. The incidence of gangrene increased with delay in harvest after haulm destruction although the pattern differed with year and site. Dipping tubers in thiabendazole or sodium hypochlorite almost eliminated gangrene on all harvest dates at Rothamsted but at East Craigs the incidence of gangrene on dipped tubers was much greater and tended to increase the longer the interval between haulm destruction and harvest. Furthermore, dipping tubers in thiabendazole was much more effective than spraying even though the fungicide residues were twice as large with the latter treatment. All 43 isolates of Phoma foveata collected in Scotland were sensitive to thiabendazole in agar plate tests. The results are discussed in relation to disease development at each of the sites.

Use of the ATP bioassay to assess toxic effects in marsh treatment systems

AbstractA firefly luciferase bioluminescent assay of bacterial adenosine triphosphate (ATP) was used to measure the toxic effects of metal ions on six bacterial genera isolated from two geographically different marsh treatment systems. The toxicity of eleven different metals, as well as metal mixtures, was monitored using the agar plate test and the resazurin reduction test in addition to measurement of intracellular ATP. All the organisms surveyed tended to be sensitive to much lower concentrations of metals when the metals were present in mixtures. Isolates from a marsh system constructed on normal soil exhibited lower metal resistance patterns than organisms isolated from a marsh built on mine tailings. The intracellular ATP assay appeared to be the most sensitive method of determining the viability of bacterial cells following metal treatment.

Cellulose bound chlorophenols II: Preparation and characterization of phenyloxycarbonylpentanoyl celluloses dependence of substitution on chlorophenol structure

AbstractNew types of polymeric phenols (including the fungicide PCP) are prepared by linking phenol and different chlorophenols to cellulose via ester bonds using adipic acid as bridging molecule. Monophenylesteracid chlorides of adipic acid are prepared as intermediates. The yield of esterification of cellulose with these compounds depends in a complicated manner on size and chlorosubstitution pattern of the phenolic substituents. It is tentatively assumed that hydrogen bonding between chlorophenol and cellulose is an important factor. The polymeric PCP ester showed fungicidal activity in an agar plate test.

Pentachlorophenylcellulose preparation and investigation on its applicability as a controlled release fungicide

AbstractPentachlorophenylethers (PCP‐ethers) of cellulose are prepared using cellulosetosylates as intermediates. The products release no measurable quantities of PCP into buffered solutions (pH 4, 7, and 9, resp.). However, the modified cellulose shows no fungicidal effect in agar plate tests with the usually cellulose‐metabolizing fungus, Trichoderma viride. The lack of biological activity is attributed to the stability of the cellulose pentachlorophenyl ether bond.

Genetic activity of 2-aminofluorene in the Salmonella/erythrocyte mutagenicity assay

In a previous study, we demonstrated the activation of cyclophosphamide by mouse erythrocytes in a yeast test using the D 7 strain of Saccharomyces cerevisiae. The present study provides further information on the ability of washed red blood cells from mice to activate 2-aminofluorene (2-AF) detected as an increase in mutation frequency of the tester strain, TA1538 (frameshift mutation) of Salmonella typhimurium. The 2-AF was tested at different concentrations (1–8 μg/plate) using both the liquid-suspension test and the agarplate test. For comparison, the bioactivation of 2-AF by the hepatic postmitochondrial supernatant (S9 fraction) from Aroclor-1254-induced rats was studied. 2-AF was only found to be clearly mutagenic in the agarplate test with both activation systems. The genetic response obtained with the erythrocytes appeared to be related to the number of cells/plate. At the lowest dose, slight differences are observed when genotoxic effects were compared to those with the S9 fraction.

Keimzahlbestimmung in Bakteriensuspensionen mit Hilfe der Laser-Nephelometrie im Vergleich mit der Photometrie und der Plattenzählmethode

We determined the number of bacteria in suspensions of three bacterial species ( S. aureus ATCC 25923, E. coli ATCC 25922, P. aeruginosa ATCC 27853) in liquid medium using two optical methods — laser-nephelometry and photometry. These results were compared with the CFU/ml determined by the agar plate test in each suspension. Further we defined the applicable range of measurement of both optical methods. The calculated factor of correlation (r = 0,99) attested the very good conformity of the results obtained by both optical methods. The determination of the number of bacteria in suspensions by laser-nephelometry is a simple though very sensitive method. The results can well be reproduced. A further advantage of this method is the immediate information about the number of bacteria in suspension. All these facts recommend laser-nephelometry as a method useful in any bacteriological routine laboratory for determination of the number of bacteria in suspensions.

Treatments to control Phoma and Alternaria infections of brassica seeds

The screening of chemicals using agar plate tests for activity against cultures of Phoma lingam, Alternaria brassicicola and A. brassicae is described. Most fungicides which were inhibitory to growth at 20 μg/ml or less showed eradicant activity when used as seed treatments. Selected on this basis, thiabendazole, applied as a slurry at 2–5 g a.i./kg seed, showed excellent eradicant activity against seed‐borne Phoma but not Alternaria when tested under laboratory, glasshouse and field conditions. Triarimol, tridemorph and azepine‐A2151, nuarimol, fenarimol and imaza‐lil although effective in agar plate tests against Alternaria and Phoma were phytotoxic when applied to seeds at rates sufficient to eliminate these fungi, Iprodione and fenpropimorph inhi bited the growth of the fungi at concentrations of 0.625 to 4 μg/ml and subsequent treatment of infected seeds at 1.25–2.5 g a.i. fungicide/kg seed with these fungicides proved effective against all three pathogens. Neither chemical adversely affected germination or emergence.

Fungicidal activity of 2‐[2‐(arylthio)ethyl] pyrrolidine derivatives

Abstract Nineteen new compounds from the title group were prepared and their fungicidal activity was investigated. One compound showed moderate activity against Rhizoctonia solani, Fusarium culmorum and Aspergillus niger in the agar plate test. Two others were moderately active against Botrytis cinerea in the slide germination test and moderately or slightly active against Rhizoctonia solani in the agar plate test. All other compounds showed little or no fungicidal activity against Erysiphe graminis in the greenhouse test.

Differential sensitivity of Pyrenophom teres to organomercury formulations

SUMMARYIn agar plate tests, all 45 isolates ol Pyrenophora teres Drechsler tested were less sensitive to methoxyethyl mercury acetate (MEMA) as ‘Panogen M’ than to phenyl mercury acetate (PMA) as‘Agrosan D’, In further tests with eight isolates selected at random, mean ED50 values (p.p.m. Hg) for inhibition of mycelial growth at 17°C were 0.620 for MEMA, 0.098 for PMA, 0.070 for ethyl mercury phosphate and 0.060 for phenyl mercury chloride.In field trials on spring barley in 1980 at seven different sites throughout England and one in Scotland, mean seedling infection of 5.8 percent was reduced to 1.2 per cent by PMA and to 1.9 per cent by MEMA.