Microbio cell growth dilution question. Please show all steps! Thank you. You ha

Question

Microbio cell growth dilution question. Please show all steps! Thank you.

You have a sample of bacteria and perform the following dilution set:

Take 1 ml of original sample and add to 9 ml of diluent (tube A).

From tube A remove 1 ml and add to 9 ml of diluent (tube B).        

From tube B remove 1 ml and add to 9 ml of diluent (tube C)

From tube C remove 1 ml and add to 9 ml of diluent (tube D)

From tube D remove 1 ml and plate the entire sample on tryptic soy agar.

If 145 colonies grow on the plate, what was the concentration of bacteria in the original sample?

Explanation / Answer

Ans. On agar plate you found 145 colonies indicate 145 individual bacterian initially. you have taken 1 ml from tube D. so tube D conatians 10 ml. now multuply 145 colonies with 10 ml. that means each ml of D contains 145 bacterian.

Calcu;ation:

1 mL of tube D =145 colonies. that means 145 bacterian. so 10 ml of tube D conatins 1450 bacteria( 145X10)

1mL of Tube C =1450 bacterian. total 10mL of tube C=14500 bacterian(1450X10)

1mL of tube B=14500 bacterian. total 10 mL of tube B=145000 bacterian (14500X10)

1ml of tube A =145000 bacterian. total 10mL of tube A= 1450000 (14500X10)

initially you have taken 1mL original sample and diluted into 10 mL by adding 9mL which does not contains any bacterian.

Finally your 1 mL of original sample contains 1450000 bacterian.,

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