All these Biology lesson are giving me headache... All I know and keep in mind is, Ammonia and Nitrite zero.. Can stock liao...
As for the bacteria population in the tank, bacteria reproduce and die in the tank... It is not possible that all the bacteria will die leaving your tank "bacterialess". As long as there are living things in the tank(Even bacteria) the bacteria population is there but whether it can handle more bioload from your fishes.. So stocking slow is the key, the bacteria can slowly grow in population and handle the new amount of waste...