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How much slower does E coli grow in M9 vs LB?


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#1 donny

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Posted 29 March 2011 - 11:06 PM

I'm working on an E coli strain that grew from OD 0.05 to 5 in ~8h. However, when I inoculated a colony of the strain in M9 (no other supplements), I got no growth after 16h! Is this normal for cell growth in M9? I'm switching to M9 because the residual lactose in E coli is giving me leaky expression. Would replacing tryptone with casamino acid in LB help? (I've tried adding 0.5% glucose but need further repression)

#2 protolder

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Posted 29 March 2011 - 11:55 PM

I'm working on an E coli strain that grew from OD 0.05 to 5 in ~8h. However, when I inoculated a colony of the strain in M9 (no other supplements), I got no growth after 16h! Is this normal for cell growth in M9? I'm switching to M9 because the residual lactose in E coli is giving me leaky expression. Would replacing tryptone with casamino acid in LB help? (I've tried adding 0.5% glucose but need further repression)

Hola, you think that you have lactose in LB because tryptone could have traces of it; but if you add glucose to the LB you could repress in the same way that in minimal medium, because I think one of the problem is de cAMP level, (high in any medium without glucose). Moreover if you use a lacY minus strain or lacIq+ you could repress better. Buena suerte

#3 phage434

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Posted 30 March 2011 - 01:27 AM

M9 medium needs a carbon source added, and often strains require thiamine (see the genotype). As was mentioned, glucose would be a good carbon source, to inhibit Lac promoter expression.




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