preparing appropriate dilution of bacteria suspension - (Jun/09/2013 )
A strain suspension in a turbidity test (spectrophotometer) gave 0.2 . I diluted the fresh culture suspension so the spectrop. read which I understand it s equivalent to 10*7 cfu/ml.
From this diluted inoculum suspension I need to inoculate the two fold dilution wells of testing solvent.
However if I add 200 microliters of the 10*7 cfu/ml inoculum to a 200 micro liter of the antibacterial stock in tube (48 well plates) then i may change the strains density, right? if so, shall I take a percentage from the inoculum suspension and how much?? how do i calculate this?
this is new to me and am trying to make the right volume of inoculum suspension to add to wells.
I want to ensure that I have 10^6 cfu/ml in the wells that contain 200 microliters antibacterial testing solution.
Thanks in advance!!!
I may need to post another question being new in this interesting field.
Yes, taking mixing a suspension with an aliquot of medium will change the density and hence the cfu/ml.
To get 10^6 cfu/well is relatively easy: use V=N/C, just like you would for any other solution N=10^6, C=10^7...
However as you have to make doubling dilutions - presumably you don't actually want 10^6 in each well, you probably want 10^6 in the first column, 5x10^5 in the next etc.
Thank you ! therefore i hope I calculated it right:
I have a well of 1000 microliter testing solutions, I inoculate with 100 microliter culture suspension (10^7 cfu/ml). I end up in the first well with 10^6 in that case.
Yes, 100ul of a 10^7 cfu/ml solution would give you 10^6 cfu.