Your TA gives you an Ecoli culture that has a concentration

Your TA gives you an E.coli culture that has a concentration of 3000cells/ml. He/she tells you to evenly spread 25µl of this culture on an LB agar plate and another 25µl on a GMS plate. Both plates are incubated at 37oC. What do you expect to see the next day and why? Give a detailed explanation!

Solution

LB contains - Peptone, Yeat extract and Nacl.

In overnight culture we canable to see the colonies in LB agar plate.
Peprone rich in aminoacids and peptides. Yeast extract conatins NA, lipids and other nutrients essential for growth.
Here E.coli grow faster - high growth rate (cells in log phase). Nacl used to maintain vell osmolarity.

GMS - Na2HPO4.7H2O, KH2PO4, NH4Cl, NaCl and glucose.

In overnight culture there is no colonies in GMS plate or very small colonies present compare to LB.
Because it only contains glucose for carbon source and Ammonia for nitrogen sources. In lab culture E.coli strain
mostly mutant in of some aminoacids like leucine or isoleucine or nucleotide thiamine. So, with GMS media we have to provide this missing composition for their growth. In LB media the yeast extract has all the necessary
nutrient material for their growth.

If your TA given E.coli culture from LB broth and switch to GMS media it takes very long lag phase before the cells resume growing.