Dilution plate method

To the fully grown culture of Aspergillus niger (obtained from soil using dilution plate method), taken in different conical flasks, 150 mg of each of the compounds were added separately and incubated on rotary shaker for a period of 72 hours at room temperatoe. Control was also maintained under the same conditions. At the end of the period, fungal medium was filtered and the mycelium discarded. The filtrate was extracted with chloroform, diethyl ether and ethyl acetate, in the same order. The extracts were dried over anhydrous sodium sulfate and the solvent was removed under reduced pressure conditions to yield a pasty mass for each of the substrates. 

Table 8.2. Numbers of microorganisms of the major groups present in various horizons, determined by the dilution plate method [1]...

The level of B. moniliforme present in SD and NSD kernels direct plated kernels was compared to the level of moniliforme in corn determined by the dilution plate method developed at North Carolina State in Ralegh, NC, by P. Hamilton (personal communication). This later method is as follows ... 

Whereas we could detect jF. moniliforme in 10% or less of NSD corn samples its occurrence in SD corn ranged from 44 to 61% which indicates that as a surface saprophytic contaminating fungus, F. moniliforme is not as prevelant as A. flavus and A. glaucus but as an internal parasitic fungus of corn, F. moniloifome was the predominant fungus found in Maryland corn. The use of the dilution plate method (see Materials and Methods) to detect F. monilifome verified these results as well. 

Two standard methods were used in the determination of the mold flora of the marihuana samples. These were the serial dilution method for the plant material and the direct plating techniques for marihuana seeds (Mislivec and Stack, 198A). In the serial dilution plating method, 10 g of finely ground plant material were taken from each of the 25 marihuana samples, and used in the study. This test portion was... 

The LB film depositions were performed using a Joyce-Loebl Langmuir Trough IV equipped with a microbalance for measurement of the surface pressure by the Wilhelmy plate method. Filtered deionized water with a pH of 7 was used for the subphase. For the electron beam lithography study, PMMA was spread on the water surface from a dilute benzene solution ( 10 mg PMMA in 20 ml benzene). The novolac/PAC mixtures were spread from solutions ( 20 mg solids in 10 ml solvent) of isopropyl acetate. For the fluorescence studies, the PMMA/PDA mixture was spread on fee water surface from a dilute benzene solution (1.75 mg PDA and 8.33 mg PMMA in 20 ml benzene). Prior to compression, a 20 min interval was allowed for solvent evaporation. The Langmuir film was compressed to the desired transfer pressure at a rate of 50 cm2/min, followed by a 20 minute equilibration period. The Cr-coated silicon wafers and quartz wafers were immersed into fee subphase before... 

You will determine the number of cells in each bacterial suspension by use of the agar plating method. In this method, you spread a small sample of known volume (or a known dilution of such a sample) over the surface of a sterile Petri plate containing an agar-stabilized growth medium (Fig. 20-1). The sample dif-... 

Pour plate method. An aliquot of the neat or diluted sample is added to a sterile Petri dish and mixed with the selected molten agar medium. When the agar has solidified, the plates are incubated for a predetermined time at the specified temperature. Surface or subsurface colonies will develop in some of the agar plates, which can be counted to provide a quantitative value for the bacterial density of the original sample. They can also be picked for further qualitative study. 

Spread plate method. A pre-selected small volume of the neat or diluted sample is inoculated onto a solid selective or non-selective medium. It is spread uniformly over the surface by mechanical or manual methods e.g. by holding a sterile stick at a set... 

The agar plate method was used to determine the minimum inhibition concentration (MIC) of CM, Q, and CMQ as follows the samples were prepared at a concentration of 1% (w/v) and then autoclaved at 121°C for 25 min. Duplicate twofold serial dilutions of each sample were added to nutrient broth (beef extract 5 g, peptone 10 g to 1000 mL distilled water, pH 7.0) for final concentration of 0.1%, 0.05%, 0.025%, 0.0125%, 0.00625%, and 0.00313%. Some samples were prepared and diluted by the same way except for a final concentration of 0.00065% and 0.00033%. The culture of each bacterium was diluted by sterile distilled water to 105-106 CPU mL. A loop of each suspension was inoculated on nutrient medium with sample or control added. After inoculation, the plates were incubated at 37°C for 72 h, the colonies were counted, and the MIC values were obtained. The MIC was considered to be the lowest concentration that completely inhibited against on agar plates comparing, disregarding a single colony or a faint haze caused by the inoculum (Speciale et al. 2002). 

The SimPlate is a method that resembles a plating method in its setup but individual colonies are not enumerated. It can be viewed as an MPN method that uses special plates rather than tubes. The special plates contain 84 or 198 wells and a diluted sample is added to a single plate. Broth is then added and distributed evenly into the wells with excess medium being decanted. After incubation for 24 h, plates are exposed to ultraviolet light and the fluorescent wells are coimted. Special MPN tables are used to... 

Both previous methods suffer from the requirement of initially small sample volumes. In the case of pour plates, the volume of inoculum must be limited, lest the agar not become sufficiently solid, whereas in the spread-plate method, excess surface moisture permits spreading and coalescence of colonies. Because of this, it is necessary to plate a range of dilutions in order to have countable plates. 

Pour plate method Method used to prepare pure cultures using serial dilutions, each of which is mixed with melted agar and poured into a sterile Petri plate. 

Spread plate method A technique used to prepare pure cultures by placing a diluted sample of cells on the surface of an agar plate and then spreading the sample evenly over the surface. 

Three methods may be used for the enumeration membrane filtration, plate count, and most probable number (MPN) method. The advantages of the membrane filter method are its low limit of detection (LOD) of < 1 CFU/g or mL and the efficient separation of the micro-organisms from components of the product, particularly antimicrobial agents. For the pour-plate method, the sample is generally 1 10 dissolved in the diluent, and 1 mL of the dilution is mixed with the agar. This corresponds to a LOD of 10 CFU/g or mL. The LOD is sometimes higher (e.g. 100 CFU/g or mL) if the product needs to be further diluted due to microbial inhibition, or lower in case of products with low microbial acceptance criteria. If the spread plate count technique is used the LOD is a factor of ten higher (>100 CFU/g or mL), because only 0.1 mL of the... 

The surface tension was calculated from the maximum force measured by the Wilhelmy plate method using a 2.0-cm-wide and 0.2-mm-thick platinum plate. The purification of the solutions and the dilution were made in a cylindrical cell of 8-cm diameter. The measurements were performed at 25.00 0.05 °C. The concentrations of the solutions were determined from electrical conductivity measurements by means of a calibration curve. Five parallel measurements were made at each concentration and between the consecutive measurements the solution surface was sucked off to form a fresh surface and to eliminate the possible effect of contamination from the environment. The measurements were performed 1-2 min after the fresh surface had formed. Time dependence was not observed in the concentration range of the decyl sulfate solutions investigated. The reproducibility of the maximum force was 2x10 N (which corresponds to 0.05 mN/m surface tension). 

Table 14.1. Estimating sample dilutions needed when enumerating microoi anisms using plating methods.

Fuel emulsification. Emulsify 1 ml of fuel in 9 ml of Ringer s solution with Tween 80. Prepare serial dilutions of the emulsion in sterile phosphate buffer and pour or streak plate the dilutions. If the fuel is viscous, 0.1ml of fuel can be added to 0.2 ml of the emulsifying agent. Then add 9.7 ml sterile deionized water to make a 1 100 dilution. Plate this solution directly or prepare dilutions for plating on or with agar media. This method has a lower level of detection compared to the filtration method. 

A variety of techniques have been used to estimate microbial biomass in natural habitats. Visual measurements of cell volume are laborious, and subject to a variety of errors when converted to dry-weight equivalents (Jones Mollison 1948 Carroll et al. 1980). Hydrolysis of fluorescein diacetate has been shown to be correlated to microbial biomass, especially for epiphytic fungi (Swisher Carroll 1980). Other methods of sampling include dilution plating of tissue homogenates or surface wash fluids, incubation of leaves or other biological... 

The antibacterial activity of the nanocomposites was investigated by modified Kirby-Bauer diffusion plate method against gram negative Escherichia coli (E. coli) and gram positive Staphylococcus aureus (S. aureus). An equal quantity of the nanocomposites with different Ag-NPs concentrations was pressed into pellets of diameters about 13 mm and thickness of 1-2 mm and incubated with the bacteria at 37 °C. Zone of inhibition was measured after 24 h of incubation. Broth dilution method was employed to determine the values of MIC (Minimum Inhibitory Concentration) of PPy-NTs Ag-NPs nanocomposites against E. coli and 5. aureus. 

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