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pre made nutrient agar plates

How To Make Nutrient Agar Plates At Home?

  1. Buy nutrient agar from Amazon or Ebay. One pack contains 12.5 grams of nutrient agar which is for 500ml water.
  2. Measure 500ml (17 fl. oz.) bottle water (tape water or filtered water will do) with measuring cup and pour it into a clean steel stock pot (you can add up to 550ml, which wouldn’t affect medium solidification).
  3. Dump the nutrient agar into the stock pot and gently stir  with a stainless steel spoon to mix nutrient agar with water.
  4. Slowly heat the stockpot to boil the water and gently stir until the media is completely clear (no visible agar particles). Don’t let agar sit at the bottom of the pot. You will fry the agar. Please keep stirring during heating. You may stop boil and let it sit for 5 min to check if it is clear or not. This step may take longer than 15 minutes. Just be patient. Incompletely dissolved nutrient agar will give you unsolid medium or the medium is fragile. If too much water is evaporated just add some extra water in the pot. You can add a little bit more than 500ml, there is no any problem, but don’t add too much water (over 550ml).
  5. Once the liquid medium is clear pour it into your petri dishes one by one. Just let medium cover the bottom which is enough to grow microorganisms (around 20ml for one 90x15mm petri dish). The medium contains enriched nutrients which are excess for bacteria growth.
  6. Cover each lid immediately after pouring to avoid the bacteria in the air fall into your petri dishes. You can pile up the petri dishes but you have to be very careful since you can flip over the light petri dishes.
  7. After 3 hours (best overnight) the liquid medium should become solid now. If you see excessive condensate water on the lid, gently take off lid and drip water off the lid, and put it back to the dish.
  8. If you don’t use it right away, just pile agar plates up and wrap them with food wrapping film/membrane and store them in your refrigerator (To avoid contamination and water dripping to the medium, please put them upside down (medium on the top)). These agar plates should be used as soon as possible. Bacteria can grow on the plates even you store them at fridge since the medium contains enriched nutrients.

Don’t have time to prepare the LB nutrient agar plates by yourself? You can purchase pre-made nutrient agar plates. For the instruction on how to culture bacteria with premade nutrient agar plates please click here.

Should you have any questions please feel free to contact us at info@greenbioresearch.com. Good luck with your biological science fair project.

prepared agar plates

Culture Microorganisms with Pre-Made Nutrient Agar Plates.

Got an assignment from your teacher to have a science fair project? Are you interested in biological phenomena? Want to conduct a micro biological experiment for your science fair project? Or want to test water contamination in your drinking water, or just for fun? It’s every easy to culture microorganisms and have a lot of fun.  To culture bacteria from your interested stuff all you need is some nutrient agar plates.

Store Nutrient Agar Plates In Refrigerator

You can buy nutrient agar powder and sterile petri dishes, and prepare nutrient agar plates by yourself. But it takes time and kind of messy, and sometimes you can screw up your project. We have premade (or called pre prepared) nutrient agar plates made with sterile petri dishes at very affordable price. These pre-made nutrient agar plates are ready-to use. Since the nutrient agar plates contain enriched nutrients, upon arrival of the package, take the pre-prepared agar plates and the steam sterilized cotton swabs out of the package and store them into refrigerator (NOT the freezer section. Please do NOT freeze). The nutrient agar plates and the steam sterilized cotton swabs are normally packed together in a vacuum bag. Don’t open the vacuum bag until you are ready to conduct your project. Please note, the nutrient agar plates should be stored UPSIDE DOWN (showed in the following picture).

prepared nutrient agar plates

Inoculate Bacteria On The Nutrient Agar Surface

Store agar plates at refrigerator until you are ready to conduct with the experiment. Before you can proceed your experiment please take the agar plates out allow them reach room temperature. Use a scissor to open the vacuum bag, take out the nutrient agar plates and the cotton swab pack.

Use steam sterilized cotton swabs to collect bacteria from whatever you are interested in, touch the swabs containing bacteria on the agar surface gently by draw a “zigzag” pattern. If the  interested surface is too dry you can wet the sterile cotton swab with cooled boiled water, then collect bacteria on the dry surface (don’t use regular water since regular water may contain bacteria which will lead to wrong conclusions).

Place the lid back, and put agar plate upside down. Label the agar plates with a Marker Pen / Sharpie on the bottom of the agar plate (the agar side, not the lid side). Don’t forgot to have a control in your experiment.

Growing Bacteria

Put the nutrient agar plates into a zipper lock bag, and keep the plates upside down and place them in  a warm and dark  place for several days (3 to 7 days depends the incubation temperature). The ideal temperature for growing bacteria is between 70 ~ 98 degrees F (20 ~ 37 degrees C, 37 oC). In winter time, you may place agar plates close to a radiator heater, but don’t place too close since the heat will dry the nutrient agar medium.

Record your results

Record your observations with a notebook, take pictures and keep records of what you see growing in each agar plate. You may see different sized and colored colonies which are different bacteria species. You may notice a smell coming from the dishes containing visible colonies.

Safely Disposing of the Bacteria

Although most of the bacteria growing in your dishes will not be hazardous, large bacteria colonies may pose more of a risk. So you will need to kill all of the bacteria before disposal using household bleach. Open the lids of petri dishes and carefully pour a small amount of bleach on top of the bacteria colonies in each plate. Incubate for 10 min,  then pour the bleach into sink and rinse with tap water. This will destroy the bacteria. Now you can dispose your nutrient agar plates in regular trash bag.

Tips:

  • Always label each plate clearly with a sharpie/marker pen; Always have correct controls;

  • If you have more than 10 interested surfaces you can draw a “+” on the bottom of the petri dish (agar side, not the lid). Thus you can test 4 samples on each petri dish.

  • If interested surface is dry, wet cotton swab with sterile water to collect bacteria.

  • Put the petri dish upside down to culture your bacteria. This trick will prevent any excess condensed water droplets from spreading your samples over the agar. This spreading of the sample could give you inaccurate results if you are using the size of the colonies as a measure of how fast your samples are growing, or contaminate your nutrient agar.

  • Before disposing of dishes in the trash the bacteria should be destroyed. Pour a small amount of household bleach over the colonies while holding dish over sink. Caution – do not allow bleach to touch your skin, eyes or clothes. It will burn!

Good luck to your project!

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