Some Tips for Using Petri Dishes
Petri dishes are one of the great products in the experiment. And we all know that using Petri dishes requires great care. Here are some tips for avoiding affecting the use of the petri dish.
Some tips for using a petri dish:
1. How to make marks on a Petri dish?
- There are currently no dedicated petri dish markers, stamps, or marking equipment.
- And the use of Petri dishes in the laboratory, each unit generally adopts the following two schemes according to its own situation.
- One is to buy a regular marker at the market and write the relevant information on the bottom surface of the Petri plate.
- The other is to use an engraving pen with a diamond tip that can engrave marks on plastic and relevant information on the underside of a petri dish.
- Since the number of embryo culture droplets is on the bottom of the dish, it is necessary to write on the bottom of the dish when writing or engraving.
- In order to facilitate viewing, when writing on the bottom of the plate, turned upside down the words, so that accurate the number of embryos on the bottom of the plate
- Since the reverse character is not a font that people often use, it takes a lot of time to mark the bottom of the embryo culture dish, which greatly affects work efficiency.
- In addition, due to the different experiences in writing reversed characters, the fonts written are somewhat illegible, which will affect the sequence recording of embryos.
- And in severe cases will cause major medical accidents such as embryo marking errors.
2. Why can’t Petri dishes be exposed for more than 4 hours?
- First of all, because of petri dish chemistry, the “big guy” in the environment will settle down quickly due to the action of gravity.
- And while the “little guy” will take a while to settle down, which can cause many reasons, such as the diffusion caused by the airflow pattern.
- In addition, according to the mathematical model calculated hourly microbial sedimentation rate, we generally believe that 4 hours is the best time for medium exposure, and the sedimentation rate will decay after 4 hours.
- Second, studies showed that after 4 hours, the agar in the cell culture dish will form a surface layer that blocks the passage of microorganisms to obtain moisture, affecting the survival of microorganisms
- In other words, resulting in better detection of live microorganisms than actual results.
- And experiments showed that in the first 4 hours, can pronounce weight loss and then level off.
- Therefore, after accepting a large weight loss, it cannot for further monitored, affecting the growth of microorganisms.
Some tips for counting colonies with Petri dishes:
Growth of bacteria on a petri dish:
- Bacterial concentration: randomly sampled in the air, and the medium was cultured to obtain the number of colonies (CFU), representing the number of planktonic bacteria in the air/m³.
- And obtained colony numbers after culturing a dish with a diameter of 90 mm exposed to the air for 30 minutes. Represents bacteria numbers that can settle in the air.
- Purify the operating room: use Petri dishes with a diameter of 90mm, let them stand for 30 minutes in the room, and then culture the number of colonies in each dish.
- And the placement position and height are consistent with the requirements of ordinary sampling methods.
There are more introduces about how is the petri dish used, how to clean Petri dishes, etc.