E. coli growth in different water types: Methods

Today I’ll be taking time points of the e. coli growth every hour in LB suspended in DI, DDW, D2O, 30% D2O, and 60% D2O. I’m going to follow my protocol from yesterday, where I blank for the water type, before I measure the absorption for that water type.

  • This morning I recorded the values from the starter cultures
  • Then I diluted 1ml of each culture in 9ml of it’s respective water type (so 1ml of culture from LB-DI goes into 9ml of LB-DI, 1ml of culture from LB-30% D2O goes into 9ml of LB-30% D2O, etc).
  • Next I measured 500ul of each sample in the nanodrop.
    • Blanked for water types DI, DDW, and D2O. The readings for the blank 30% D2O and 60% D2O were pretty close to the reading for 99% D2O, so I used the 99% D2O sample as the blank for these two cultures.
  • Results will be up on figshare later, but I’ll put the starter culture results up now.

I’m not sure what to think about the values for the overnight growth. E. coli grew in 99% D2O, which was rather surprising. Maybe it isn’t. All there needs is to be 1 cell that grows and then there will be a colony. This makes me think that growing e. coli in 99% D2O and switching that colony to DDW wouldn’t reveal too much. I may have to do multiple generations of growth in D2O before I switch growing medium to make sure the colony is fully adapted to life in D2O.

Also that makes me think that my setup from yesterday wasn’t so optimal. Perhaps by growing cells in each water type initially, I’ve just insured that they will all grow at the same rate and there will be nothing to reveal here. Hmmm, I’ll have to think about this. I feel like I’m trying to trick e. coli, but it somehow is outsmarting me.

No sir, I don’t like it…