Streak plate

Pick a single colony from a freshly streaked plate and inoculate 5 mL LB containing ampicillin into a test tube. Culture overnight at 37°C. 

The color of a mineral sample cannot be used to definitively identify the mineral because of impurities that may be present, however, the color can narrow down the identity of a mineral to a few choices. The streak of a mineral is the color of its powdered form. Rubbing the mineral across an unglazed porcelain square, called a streak plate, can best show streak color. A mineral will have a characteristic streak color, although more than one mineral may have the same color. Therefore, streak is not a definitive identification tool, although it may be used to verify the identity of a mineral of suspected composition. 

Scratch tests are a common method used to identify mineral hardness relative to Mohs scale. Streak tests are often carried out on streak plates. Mineral hardness is a fundamental property of minerals and can be used to identify unknown minerals, hi the absence of comparative minerals, geologists often resort to common objects with a relatively well-established Mohs hardness number. In addition to glass (5.5), copper pennies measure 3.5, and the average human fingernail averages a Mohs hardness of 2.5. 

Several laboratory methods are used to quantify bacteria present in the urine. The most accurate method is the pour-plate technique. This method is unsuitable for a high-volume laboratory because it is expensive and time-consuming. The streak-plate method is an alternative that involves using a calibrated-loop technique to streak a fixed amount of mine on an agar plate. This method is used most commonly in diagnostic laboratories because it is simple to perform and less costly. 

Incubate the streaked plate upside down (to avoid condensation of water on the agar) overnight at 37°C. 

Figure 1 Colonies of microorganisms on agar plates after incubation (A) close-up of bacteria pour plate, plate count agar (B) close-up of mold surface plate, oxytetracycline glucose yeast extract agar (C) Salmonella species streak plate, xylose lysine decarboxylase agar.

Flame and cool transfer loop. Collect a well-isolated colony from a previously streaked plate or from a sample (i.e., refermenting wine) containing suspect yeast. 

Streak plate method Method used to prepare pure cultures in which bacterial are lightly spread over the surface of agar plates, resulting in isolated colonies. 

Black-like Black like a black mirror, next to the assay dark gray crystals indicates As Black similar to As, transferred to a streak plate and rubbed it turns red indicates HgS Black fusible globules indicates Se or Te, small globules of Se transmit a reddish light... 

Two conditions cause thin and streaked plates. First, the slurry may not have been mixed thoroughly before the dipping operation the adsorbent might then have settled to the bottom of the jar, and Figure 20.1 slurry at the top would not have coated... 

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. 

Procedure. The sample is drawn over unglazed porcelain (streak plate or the unglazed bottom of an evaporation dish). The scratch is held for 2-3 minutes over bromine water and then spotted with alkali stannite solution. When bismuth is present, the scratch becomes dark and the metal deposited remains in place when washed with water. 

The test described on page 388 may be applied for the rapid detection of phosphates in rocks and minerals. A few milligrams of the powdered rock or a splinter of the solid are placed on filter paper, moistened with a drop of ammonium molybdate solution, and held over a flame for a short time. A drop of benzidine acetate solution is added and the moist fleck held over ammonia. A brilliant blue forms on the paper either at or near the position of the sample, sometimes in continuous patches, and wherever traces of ammonium phosphomolybdate have been formed. A useful procedure is to carry out the test on a streak plate. The reagents are applied to the streak. 

Procedure. The sample is drawn over a piece of unglazed porcelain (streak plate). The hair-fine scratch on the porcelain is treated with dilute nitric acid, applied with a fine glass rod, and the plate is held over a small flame until the acid has evaporated. Filter paper (S S 589g), moistened with dilute nitric acid, is pressed against the warm plate. After one minute, the paper is spotted with a saturated solution of />-dimethylaminobenzylidenerhodanine in acetone. A red violet streak appears if silver is present and remains unaltered after the paper has been bathed in acetone to remove the excess reagent. 

This procedure can be conducted so as to obviate any interference from mercury, when amalgamated surfaces are under examination. The mercury can be volatilized by igniting the scratch on the streak plate or by heating the evaporation residue from a drop of the test solution. The silver nitrate will remain for the subsequent nitric acid treatment and is easily identified by the />-dimethylaminobenzylidenerhodanine test. 

Jagessar, RC Mars, A Gomes, G. Selective antimicrobial properties of Phylanthus acidus leaf extract against Candida albicans, Eschericia coli and Staphylococcus aureus using Disk diffusion, Well diffusion. Streak plate and a Dilution method. Nature and Science, 2008, 6(2) 24-38. 

Cultures from a freshly streaked plate of yeast will typically be ready within 12-16 h. However, cultures from plates that are more than 1 month old may take as long as 24 h to reach an OD, of0.5. 

The media used in the two types of t. sts an different and may, thereby, modify the action of the antibacterial substances. The influon c of alkalinity, salts, and phosphate concentration on the activity of streptothricin (73) can be cited as an example of the effect of composition of medium on activity. Several different media were used in the serial dilution methods. The kinds of media used in testing (when given in the original publications) are as follows Streak-plate method (104,115,145,146,160,162, 164,166,170). Serial dilution method in (a) beef extract, small inocula (96,102), and large inocula (158) (6) beef heart broth (119,122), small inocula (112,177), and large inocula (50,71,113) (c) beef heart dextrose (123), small inocula (132) (d) nutrient broth (107,158,165) (e) nutrient broth dextrose (57,118,158) (/) 1% tryptone broth, small inocula (134). 

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