======Observing Yogurt Bacteria======


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**Alternative titles:** Observing Probiotic Bacteria
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====Summary====                   
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====Procedure====  
  - Place a clean glass slide on your work surface.
  - Use a toothpick to collect a tiny drop of yogurt and smear it thinly across the slide.
  - (Optional) Add a drop of methylene blue solution to improve visibility of bacteria; if used, wear gloves and handle carefully.
  - Gently lower a cover slip over the sample, avoiding air bubbles.
  - Blot excess liquid from the edges of the cover slip with a tissue or paper towel.
  - View under a compound microscope, starting at 4x or 10x magnification before moving to higher power.
  - Look for different bacterial arrangements: single cells, pairs (diplo), chains (strepto), and clusters.



====Links==== 
Yogurt Microscope Experiment - Sci Files: 
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Yogurt Under the Microscope - Sci- Inspi: 
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📄 Yoghurt bacteria - MRC Laboratory of Molecular Biology: [[https://www2.mrc-lmb.cam.ac.uk/microscopes4schools/yoghurt.php]]\\


====Variations====
  * Compare different yogurt brands or types (Greek, natural, flavored, probiotic drinks).
  * Try viewing without stain versus with methylene blue to see differences in contrast.
  * Compare yogurt with “live cultures” versus sterilized or pasteurized dairy products.
  * Examine other fermented foods (kefir, sauerkraut, kimchi) for bacterial diversity.



====Safety Precautions====
  * Use gloves if handling methylene blue; it is a mild irritant and stains skin and clothing.
  * Do not ingest microscope samples.
  * Wash hands thoroughly after preparing and observing slides.
  * Supervise children closely when using stains or glass slides.




====Questions to Consider====
  * Which bacterial shapes are visible in the yogurt sample? (Rod-shaped bacilli, spherical cocci, chains, or clusters.)
  * Why is methylene blue sometimes used when viewing bacteria? (It stains cells, increasing contrast under the microscope.)
  * How do bacteria transform milk into yogurt? (They ferment lactose into lactic acid, which curdles proteins and gives yogurt its tangy flavor.)
  * What are some examples of probiotic bacteria commonly found in yogurt? (Lactobacillus bulgaricus, L. acidophilus, Streptococcus thermophilus, Bifidobacterium bifidus.)
  * How does the presence of beneficial bacteria in yogurt relate to human gut health? (They support digestion and contribute to a healthy microbiome.)