Petri plates

Dropkin, V.H. and Halbrendt, J.M. (1986) Inbreeding and hybridizing soybean cyst nematodes on pruned soybeans in petri plates. Journal of Nematology 18, 200. 

Procedure Purslane seeds were collected from crop fields near Naples. Five hundred seeds were sown in 10 Petri dishes (0 =90 mm), containing 5 layers of Whatman filter paper impregnated with 7 ml of water (control) or 7 ml rue infusion/chromatographic fractions or isolated compounds as per treatment. Thereafter, daily 3 ml water was added to each Petri plate. Germination conditions were 30 1°C with a continuous light of 25 4,E/m2/... 

The tissue of interest should be removed from the animals using equipment that has been treated to ensure that it is RNase-free. The surface hair of the animals can be soaked in 70% ethanol to minimize the inclusion of hair or dander in the isolated tissues. A sterile disposable Petri plate, placed on top of a bed of crushed ice, is a suitable RNase-free surface for microdissection. Immediately after isolation from the animal, individual samples of tissue can be flash frozen by immersion in liquid nitrogen and stored in cryovials in liquid nitrogen or at -70°C until all samples from an experimental set have been obtained. RNA extraction and preparation of single-stranded cDNA can then be performed simultaneously on all samples. This will minimize differences between RNA populations that result from differences in sample preparation. 

Figure 1. The "spot test. Each petri plate contains, in a thin overlay of top agar, the tester strain TA98 and, in the cases of plates C and D, a liver microsomal activation system (S-9 Mix). Mutagens were applied to 6-mm filter-paper discs which were then placed in the center of each plate (A) spontaneous revertants (B) furyl-furamide (AF-2) (1 fig) (C) aflotoxin Bi(l fig) (D) 2-aminofluorene (10 fig). Mutagen-induced revertants appear as a ring of colonies around each disc (3).

An antibiotic inhibition zone often appears around Trichoderma spp. interacting with other fungi. The genus contains many species which produce secondary metabolites. Claydon et al. (23) have identified an antibiotic from T. harzianum as a volatile, 6-n-pentyl-2H-pyran-2-one this was recently shown to be an active antibiotic from T. koningii (24). The volatile appeared to be the factor responsible for the coconut smell of some biocontrol-effective strains of T. harzianum (25). However, in a Petri-plate assay, it can be difficult to be certain that antibiosis is involved. As well as competitive growth, lytic enzymes could also contribute to the action and Trichoderma has been shown to produce / -l,3-glucanase and chitinase (26-29). 

Standards and Controls. In all experiments, the 85 g standard patties were made from freshly ground top round steaks (excess fat trimmed) and immediately frozen in covered glass petri plates until the day of the assay. The fat content was routinely from 4-5%, determined by the method of Koniecko (57). The standards generally had relatively low values for hexanal, total volatiles (TV) and TEARS, and low intensity values for painty (PTY), cardboardy (CED), sour (SUR) and bitter (ETR). These results indicated the absence of lipid oxidation and no formation of off-flavors. As expected, the desirable flavor notes, cooked beef/brothy (CEE), beefy/meaty (EM), brothy (ERO), browned/caramel (ERC) and sweet (SWT) had high intensity values. 

Poured, sterile soybean casein digest agar (SCDA) petri plates Poured, sterile potato dextrose agar (PDA)... 

Infection of bacteria and colony growth on petri plate... 

Evolutionary experiments can be done in tubes, on petri plates, or in various continuous culture devices. Each type of culture provides different environmental conditions and different advantages and disadvantages.7 Although there are many different kinds of continuous culturing devices,8 most evolutionary experiments have been carried out in chemostats. Chemostats are designed to provide a constant, homogeneous environment in which the cells grow at a constant rate. 

Fig. 33.23. AZCL-polysaccharide hydrolysis in (a) Petri plates and (b) microtiter plates.The dark particulates are the AZCL-/3-Glucan (a) and AZCL-galactan (b). Soluble blue dye is released upon hydrolysis.

Minimal medium agar Petri plates supplemented with 50 /ug/ml tryptophan ... 

The following procedures require sterile technique that is, use of sterilized glassware, pipettes, Petri plates, and other equipment. Do not use equipment that has lost a covering cap and consequently has been exposed to the air for long periods. If you are unfamiliar with sterile techniques for transferring bacterial cultures, consult your instructor for details of the techniques required in this experiment. 

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-... 

Analysis of the transformation performed in this experiment requires agar plating to determine the number of transformed cells (Trp+ cells) in each of the six tubes of the experiment. The Petri plates used in this determination obviously do not contain tryptophan in the growth medium. In a separate experiment, you will determine the total number of cells (Trp+ plus Trp- cells) in the transformation mixture by plating a diluted sample of known volume and known dilution on a Petri plate in which the agar growth medium does contain tryptophan. The number of transformants (Trp+) cells divided by the total number of cells (Trp+ plus Trp-) is the efficiency of that transformation experiment. 

Immediately after placing each 0.1-ml sample of culture on a Petri plate, spread the sample uniformly over the surface of the plate with a sterile bent glass rod (see Fig. 20-1). Be sure that you sterilize the glass rod between spreadings... 

Allow all the plated samples to diffuse into the agar for 5 to 10 min. Then, invert each Petri plate (agar side up), write your name or initials on each, combine the plates in stacks held by masking tape, and incubate all plates for 48 to 72 hr at 37°C. Count the colonies on each plate. 

Culture shaker with test tube racks at 37°C Petri plates (disposable, plastic)... 

Minimal medium agar Petri plate (see section on transformation below)—1 required. 

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