Streak Plate of Legionella Public Health Image Library 7925


Streak Plate Technique for Isolating Bacteria
Streaking to Obtain Pure Bacterial Cultures from Clinical Specimen
 




The purpose of streak plating is to spread out a clinical sample on solid growth media, so that individual, isolated bacterial colonies will grow.

Article Summary: Streaking a clinical sample onto a media plate is how specific bacteria are isolated so that the causative agent of a bacterial disease can be identified.
Streak Plate Technique for Isolating Bacteria
Two different styles of streak plate techniques on Blood Agar
Two different styles of streak plate technique on Blood Agar.
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What Is a Bacterial Colony?
A colony is a visible spot on the surface of growing medium that containscontains millions of bacteria that, through cell division, arose from a single parent bacterium. This means that all bacteria in a colony are of the same species.

How to Isolate Bacteria Using Streak Plate Method
By using streak plate technique to spread a clinical sample out on the surface of a solid growth medium individual types of bacteria can be isolated. Here is the basic technique. See the instructional photo that appears with this article.

Supplies needed for streak plating:
  • Petri dish of sterile TSY medium (or a specialized growing medium)
  • Clinical sample (sample obtained from person)

Isolation Streak Plate Technique
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Continued ... 
Final steps to complete 
isolation streak plate + video. 
Go to PAGE 2 >
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Prokaryotic Cell, Mariana Ruiz
​Page last updated: 11/2015
CLASS NOTES 
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What Is Bacterial Growth Media?
Asolid  bacterial growth medium is a gel-like surface made from agar (a seaweed derivative), with an appearance similar to Jell-O. In addition to agar, growing media also contain water, nutrients and buffer to help the bacteria grow. Growth media are made to be sterile until inoculated with a bacterial sample.
Printable Step-by-Step 
Isolation Streak Plate Procedure 
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Streak plate of Micrococcus luteus
Streak plate technique:
  • Streak swab of clinical sample over one quarter of the sterile Petri dish in a back-and-forth "tornado" pattern. This is quadrant #1.
  • Discard swab in biohazard bag.
  • Sterilize loop in flame of Bunsen burner or hub of microincinerator.
  • Allow loop to cool without waving it about.
  • Place loop on next quadrant of Petri dish, next to quadrant #1. Gently drag the loop into quadrant #1 a few times, to obtain just a bit of bacteria from that first sample, then spread that material over quadrant #2, in another tornado pattern.
  • Again sterilize loop in flame of Bunsen burner or hub of microincinerator, and allow loop to cool.
  • Place loop in next quadrant of Petri dish, adjacent to quadrant #2. Gently drag the loop into quadrant #2 a few times, to obtain just a bit of bacteria from that sample, then spread that material over quadrant #3 in a tornado pattern.