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Dark LB media - (Jul/01/2004 )

I am new to cloning. My overnight culture looks very dark...almost a hint of blue. Is this from contamination or overgrowth. Thank you for educating the clueless.


I have never experienced this. When the overnight culture reaches saturation, the color of the media should not be so dark. It would be thicker and cloudy.

Are you sure your LB is freshly prepared and antibiotics is still working?


Try streaking your overnight culture onto 2 LB plates, with and without antibiotics - contanmination (by anything different from coli) is likely to show up as morphologically different colonies. if you get colonies only in the minus antibiotic plates, then thats the problem with your medium.


Maybe this is the same problem somebody has mentioned before


Very dark and blue? Sure there is no IPTG and X gal in your medium?? blink.gif

-Vincent Delespaux-