streaking for isolation vs. spread plates (View forum version)



Eternal city

Posted 11 August 2010 - 11:21 AM

Hi guys,

If we do streaking for isolation, instead of spread plates, why is that?

If we do spread plates, we can count colonies which survive in antibiotic plates.

What is good for streaking for isolation?

Thanks,

JA

bob1

Posted 11 August 2010 - 02:21 PM

Streaking is essentially a dilution process - with each streak the cells get diluted out a bit, so that if you have an impure sample eventually you will get single colonies of each component. With spreading you don't get the dilution effect as much so it is not as effective at isolating pure colonies.

Eternal city

Posted 12 August 2010 - 07:06 AM

I got it.
Thanks for the reply

JA

gebirgsziege

Posted 13 August 2010 - 12:22 AM

You are mixing up two different procedures here:

spread plates are used to get CFU counts when you got single colonies on your plates you isloate them with straking which was explained by bob1 already. So spreading is basically to "chatch" bacteria on a plate and get them to grow and then you will streak them to isolate them from other bacteria...am I making sense?