page_title: Streaking (microbiology)
section_title: Growth medium
hierarchical_section_title: Streaking (microbiology) / Growth medium
caption_attribution_description: العربية: يُضاف دم الغَنم إلى المستنبت بَهدف تحسين العناصر الغذائية اللازمة للنمو البكتيري، حيثُ يَقوم علماء المُختبر بزرع وتنمية أنواع بكتيرية مُختلفة على هذا المستنبت وغيره من المستنبتات بغرض المُساعدة في تقييم العدوى البشرية والحيوانية. تُظهر الصُورة اليُمنى نمو البكتيريا العقدية حالة الدم-بيتا، حيثُ تقوم بإنتاج مُركب حال يعمل على تَحليل كريات الدم الحمراء المُحيطة بكل مُستعمرة. المستنبت مبقع كما ينبغي للحصول على مستعمرات بكتيرية معزولة. أما الصُورة اليُسرى تُظهر نمو أنواع المكورات العنقودية، فالمستنبت مُبقع بشكلٍ كثيف بالتالي لا يُمكن الحصول على مستعمرات بكتيرية معزولة. English: Sheep blood is added to growth media to enhance the nutrients available for bacterial growth. Laboratory scientists grow various bacteria on this medium as well as numerous other media, in order to help assess infections in humans and animals. The image on the right shows growth of a beta-hemolytic streptococcus. The bacterium has produced a hemolytic compound that has lysed the red blood cells surrounding each colony. The plate was properly streaked to attain isolated colonies. The plate on the left is growing a Staphylococcus species. The plate was streaked too heavily, so isolated colonies were not attained.
context_page_description: In microbiology, streaking is a technique used to isolate a pure strain from a single species of microorganism, often bacteria. Samples can then be taken from the resulting colonies and a microbiological culture can be grown on a new plate so that the organism can be identified, studied, or tested.
  The modern streak plate method has progressed from the efforts of Robert Koch and other microbiologists to obtain microbiological cultures of bacteria in order to study them. The dilution or isolation by streaking method was first developed by Loeffler and Gaffky in Koch's laboratory, which involves the dilution of bacteria by systematically streaking them over the exterior of the agar in a Petri dish to obtain isolated colonies which will then grow into quantity of cells, or isolated colonies. If the agar surface grows microorganisms which are all genetically same, the culture is then considered as a microbiological culture.
context_section_description: The sample is spread across one quadrant of a Petri dish containing a growth medium. Bacteria need different nutrients to grow. This includes water, a source of energy, sources of carbon, sulfur, nitrogen, phosphorus, certain minerals, and other vitamins and growth factors. A very common type of media used in microbiology labs is known as agar, a gelatinous substance derived from seaweed. The nutrient agar  has a lot of ingredients with unknown amounts of nutrients in them. On one hand, this can be a very selective media to use because as mentioned bacteria are particular. If there is a certain nutrient in the media the bacteria could most certainly not grow and could die. On the other hand, this media is very complex. Complex media is important because it allows for a wide range of microbial growth. The bacteria growth can be supported by this media greatly due in part to the high amounts of nutrients.   Choice of which growth medium is used depends on which microorganism is being cultured, or selected for.
caption: Different labs have different standards as to the direction and style of the streaking.
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