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Streaking for Isolation

About microscopic forms of life, including Bacteria, Archea, protozoans, algae and fungi. Topics relating to viruses, viroids and prions also belong here.

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Streaking for Isolation

Postby wesida » Wed Apr 09, 2008 1:08 am

Can anyone tell me a good techinque for streaking that he or she uses to get nice isolated colonies. It seems that i can never get lots of isolated colonies. I usually do the 4 quadrant method.
Help would be greatly appreciated
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Postby canalon » Wed Apr 09, 2008 3:43 pm

I do lot of isolation and use plenty of different techniques. But basically what you want is to significantly decrease the number of bacteria between each streak (or set of streaks). So the simple reliable and quick method I used when I had hundreds of colonies to isolate was to use sterile toothpicks:
1- Pick a colony with a sterile toothpick and make a short streak on the plate
2- with another toothpick make a wavy line crossing the first one at the beginning
3- with yet another toothpick make a third and last line cutting the second on 1 or 2 points and make it wavy across the reamining space.

I could usually isolate easily 6 different culture on 1 plate with a good reliability.
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Postby wesida » Wed Apr 09, 2008 9:57 pm

Humm I see, so just to make sure here is what i got:
1.make a horizontal line across the plate (just one streak right)
2.with another toothpick make a wavy perpendicular like line on the first streak
3with another toothpick make a wavy perpendicular line on the second streak

am i confused or did i get it right?
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Re:

Postby canalon » Thu Apr 10, 2008 6:56 pm

wesida wrote:Humm I see, so just to make sure here is what i got:
1.make a horizontal line across the plate (just one streak right)
2.with another toothpick make a wavy perpendicular like line on the first streak
3with another toothpick make a wavy perpendicular line on the second streak

am i confused or did i get it right?


I attach a poor drawing of what I d. The first streak is in red (it is short), the second in blue, and the third in green.
Attachments
streaks.JPG
streaks.JPG (2.58 KiB) Viewed 8538 times
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Postby wesida » Thu Apr 10, 2008 7:06 pm

Thanks alot canalon i will def try that, What if i use a simpe loop instead of a toothpick (because the sample i will be doing is not a solid colony, but it is diluted in growing broth). by the way how do you make the picture alittle more bigger, can i download it?
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Re: Streaking for Isolation

Postby MichaelXY » Thu Apr 10, 2008 10:11 pm

You can save the image by placing your cursor over the image and right clicking with your mouse and selecting save as. Then use your fav image software to enlarge.
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Postby canalon » Fri Apr 11, 2008 1:15 am

I will post a bigger one, the jpg transformation was not great... and yes you can use a loop, or a straight wire, but sterile toothpicks are faster since you need to sterilize your loop between each streak :) And remeber, the point here is do not put much! you really need little for the first streak
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Re: Streaking for Isolation

Postby MichaelXY » Fri Apr 11, 2008 1:38 am

Pardon my ignorance Can, but wouldn't the nature of wooden toothpicks be moisture magnets, along with that outside bacteria? Not being a wise guy here, just wondering.
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Postby wesida » Fri Apr 11, 2008 3:57 am

Thank you sir! appreciate it :)
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Postby canalon » Fri Apr 11, 2008 2:13 pm

No, toothpicks are good. And cheap. Of course We are not using mint flavored, or worse, wrapped one :-) The point is not to carry over tons of bacteria, rather the opposite, so if you lose some to the toothpick, it's OK, you are even more likely to get isolated colonies.

The new image:
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streaks.GIF
streaks.GIF (1.79 KiB) Viewed 8491 times
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