Of all the known bacteria, what percentage can successfully grown in the lab?

I'd have thought all of them, given the right conditions. Do you mean which ones are actually used?

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Edit - turns out I was completely wrong!
http://www.newscientist.com/article/dn7904.html
Apparently many cannot be cultured

Ok to work out the percentage you need to know how many species are known.

Here is what I have found - does any one else have different numbers?
There are approximately 4000 known and recorded bacteria.
However 400 000 is a conservative estamite of how many there actually is
Text Book of Biodiversity - Google Book Search

How many are cultured in labs
I can't find it!

Perhaps you should ask here as well
It an ask a scientist web page
Search Engine & Index Directory

I don't think very many species of bacteria are cultured in labs, basically E. coli and the pathogens that make us sick or that have some economic importance (like bacteria that attack agricultural products). I'd guess something like 100 to 300. The online textbook of bacteriology says there are 3000 named species and estimates that that's about 1% of the true total (so 300,000). So I agree with templelane's numbers. I'd estimate on the order of a tenth of a percent of bacteria have been cultured by someone somewhere. "Can be cultured" is different. A lot of bacteria cannot be cultured, but for most species, nobody has ever tried...

Overview of Bacteriology

It totally depends on the condition of the growth and the straing you are using.
Usaully bacteria are quite resistant creatures can acquire and grow almost in conditions if not very critical.but optimum temperature and humidity is the controlling factor.
Temperature for most is 37C and sterilized conditions are important... only streak or inoculate the pure strain .