What is plate spreader?
usually is a cylindrical rod
as a hand tool that is used in biology and related fields for smoothly spreading cells and bacteria on culture plates, such as Petri dishes. Cell spreader
is a basic tool for spreading technique in microbiology
Types of plate spreader
L shaped rod
The L-shaped plate spreader
is designed to minimize the damage to the culture medium with its inwardly curved end.
T shaped plate spreader
T-shaped plate spreader allows for uniform dispersion of the medium and rapid and smooth dispersal of cells.
Sterile disposable plate spreader
Sterile disposable plate spreaders are sterile packaging, single-use, with safe and efficient features.
Plastic cell spreader / plastic spreader
Steel stick spreader
Advantages of plate spreader
a. High-quality materials, including but not limited to Medical-grade ABS, PP, stainless steel, etc.
b. With the features of easy-using, complete specifications, clean and hygienic, ergonomic, etc.
c. Reasonable design with high precision mold.
d. Customization support. Support different sizes of pipette tips and deep-well plates, PCR plates, etc.
Use of plate spreader
Spreader plate is a nice hand tool that helps to distribute bacterial cells evenly across the surface of an agar plate. By using it, bacterial cells suspended in a small drop of liquid can be distributed quickly and smoothly. If the concentration of bacteria is low, the spreading process will result in individual colonies. If the bacterial concentration is too high, a confluent "lawn" of bacteria will form and individual colonies will be indistinguishable.
Steps of making a spread plate
a. Use a marker to mark the bottom of the spread plate with the date, your initials, and the type of bacteria you are spreading. Always keep the lid on the agar plate until you are ready to finish spreading. By doing this, you can minimize the risk of contamination.
b. It is important to use a sterile spread plate
when spreading your plates. Your spreaders
may be individually wrapped or in a bag and they should be opened just before use. If the spreaders are individually packaged, open them at the handle end. If the spreaders are packaged in bulk, one person should distribute the spreaders to others when they are ready to use them. When using an L-shaped spread plate
, remember that the L-shaped end should not touch anything except the liquid sample and agar.
c. Place 20 µl of the diluted bacterial culture in the center of the agar plate by using a cell culture pipette
, without touching the agar.
d. You should then use a sterile spread plate
to gently rub across the agar surface while rotating the plate with the other hand. Be careful that do not to allow the spreader to dig into the agar. Spreading the sample over the entire agar plate is important as this makes counting colonies easier. You should keep spreading until the liquid is absorbed by the agar.
e. It is obvious that most bacterial samples will not be colored during the operation. You will not be able to see the bacteria you spread on the plate until after they have grown.
f. After completing the spread, decontaminate the spreader with alcohol or bleach and disinfect the spreader with alcohol or bleach and discard it in a spent beaker. Put the lid on the plate and seal its edges with Parafilm or tape. Turn the culture plate
upside down. During incubation, you may find condensation. If it drips onto the agar, all the colonies will run together. If it stays on the lid, it will not do any harm. Check bacterial growth on the plates after 2-3 days if you incubate at room temperature. Colonies form more quickly if the plates are incubated at 37℃.
g. Once your colonies have grown, take some time to analyze your results. Be very careful that do not to open the lid and count your colonies. Look closely at the shape, size, and texture of your colonies. Compared to the characteristics of the ancestral colonies, individual colony differences in shape, texture, size, or outline are indicative of genetic changes in the bacteria giving rise to that colony. When finished with the operation, you should decontaminate the plate with bleach and dispose of your sealed plate in an appropriate waste container.
Plating bacteria on agar plates
Plating bacteria on agar plates is a standard technique in biology. However, care must be taken when plating cells because an open flame and ethanol are used to maintain a sterile environment and equipment. A well-thought-out lab bench design is a must: make sure the alcohol is not too close to the open flame, and that the open flame is positioned to limit your hand's proximity to the fire. Knowing how to use all fire prevention equipment and its location in the lab is also critical: this includes emergency showers and fire extinguishers.
a. Work area preparation
a) Put on personal protective equipment (PPE) like hair ties, goggles, close-toed shoes, flame-retardant lab coats, and any other equipment that is required. Meanwhile, you should remove any clothing or
personal items that may pose a specific threat. For example, loose and dangling clothes or jewelry or
any synthetic fabrics that could melt or
burn in a fire and cause an accident. This is because the presence of latex could greatly increase the severity of accidental burns, just
like the melting of synthetic fabrics. You should simply wash your hands with
warm soap and water
to remove possible contaminants.
b) Clean your workbench
and remove Items not related to the experiment from the immediate work area, especially flammable items and chemicals.
c) When having ethanol cell culture, you should pour the ethanol into a secondary container made of glass or metal that is wide enough to dip the spreader
into (dip spreaders). Plastic is not suitable since it would melt if the alcohol ignited, preventing fire containment. The container should have an easily replaceable lid so that any fire can be snuffed out if the alcohol ignites. Only a small amount of ethanol is needed, 1 cm or less deep. In a standard container, the volume should be less than 10 ml.
d) Wipe off any ethanol that spills when pouring from the storage bottle into the above container.
e) Arrange the liquid culture racks, culture dishes, alcohol containers, Bunsen burner, and other materials needed for plating the cells. The alcohol container should be kept as far
away as possible from the Bunsen burner. Liquid cultures and Petri dishes should be kept at a reasonable distance, but not so close as to risk burns to the hands when handling plates and test tubes. Placing cultures and plates near a flame will aid in maintaining a sterile environment by utilizing the updraft of air created by the Bunsen burner to reduce the risk of spores falling into Petri-dished or test tubes.
b. Plating cells
a) Ignite the Bunsen Burner of a 3‐5 cm flame (a 3‐5 cm flame is sufficient enough).
b) Remove the desired culture from the test tube and place it on an agar
c) Dip the glass spreader into alcohol, allow excess to drip off, and return the lid to the ethanol container.
d) Touch the spreader to the flame, ignite the alcohol, and remove it. Slowly rotating the spreader will prevent burning water droplets from falling when the alcohol burns.
e) Spread the culture around the plate and recover the Petri dish.
f) Repeat steps 2-6 if necessary.
g) When finished, immediately turn off the flame and then proceed with clean-up of other materials.
Cell lab sterilization
A. Formaldehyde fumigation
Formaldehyde is a chemical sterilant. It has the features of being non-flammable, non-explosive, and non-corrosive to metals. It can combine with amino acids in proteins to denature proteins and make the enzyme activity disappear. Therefore, it can be used for cell lab sterilization. It is generally used for thorough sterilization of intercellular disinfection. However, there are some disadvantages that we should pay attention to:
1) Formaldehyde is a harmful substance to our body.
2) Air circulation in cell culture laboratories is usually very poor, and the excretion of formaldehyde is very slow and needs one week or more.
3) If you want to use the cell lab in an emergency, you can neutralize the formaldehyde in the air with an equal amount of ammonia after sterilizing.
B. Air Filtration
This is one of the safest and most effective methods of cell lab sterilization, but it charges high.
C. Germicidal UVC lamp
UV sterilization is carried out by irradiation with UV tubes. UV light acts on cellular DNA, causing adjacent pyrimidine bases on the DNA strand to form pyrimidine dimers, which inhibit DNA replication. In addition, air under ultraviolet radiation can produce ozone, which also has a certain sterilization effect.
D. Electronic sterilizer
The electronic sterilizer is also known as ozone sterilization. With the function of the high-voltage electric field, intense electron bombardment occurs at the inner and outer electrodes of the electron tube, which ionizes the air and converts the oxygen in the air into ozone. Ozone has an unstable molecular structure at room temperature and pressure. They will soon decompose into oxygen (O2) and individual oxygen atoms (O); the latter is very active and can carry out oxidative decomposition reactions with bacterial cell membranes and enzyme protein hydrogen-sulfur groups, thus achieving the purpose of sterilization by diffuse diffusion of oxygen atoms, with no dead space for disinfection. After disinfection, the residual excess oxygen atoms in the space will only need 30-40min to recombine themselves into ordinary oxygen atoms (O2) without any toxic residue, so it is called a non-polluting disinfectant.
E. Hydrogen peroxide silver ion disinfectant
Hydrogen peroxide silver ion disinfectant is food contactable, colorless, and odorless. Due to its unique principle of sterilization, it can kill all types of microorganisms including budding spores, bacterial spores, fungal spores, radioactive bacteria, branching bacilli, yeasts, molds, and viruses. The sterilization principle of silver ion is based on monovalent silver ion through covalent and ligand bonding to firmly bond with bacterial proteins, thereby passivating or precipitating bacteria. It is a kind of high-efficiency bactericide that can be used to quickly kill a variety of microorganisms or inhibit microbial reproduction of laboratory equipment, and cell room disinfection. It has been very widely used in the disinfection of various laboratory instruments and equipment.
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