You asked me, so I will respond by saying I agree with Colin (post #3). It is not, as many think, the lack of "food" (ammonia) that kills the nitrifiers; they can live without "food" longer than many realize, by going into what Colin termed a dormant state, or some call hibernation. Whatever the name, the point is the bacteria do not die, unless from the other issues associated with this. I wrote an explanation some years ago that may provide some background, though I will mention that I believe some newer data may be challenging some of this now, but it would take me some time to track this down and study it, so I'll leave it as written. There is another issue, and that is that after the initial period, it is more probably archaea and not bacteria that deal with nitrification. That too is another complex issue which I have not had time to delve into as much as I should, so I will just mention it. Always having live floating plants in my tanks, I have never fussed over bacteria/archaea.
Nitrifying Bacteria
Nitrification is the oxidation of ammonia/ammonium to nitrite and then the subsequent oxidation of nitrite to nitrate; this is performed by two groups of bacteria known collectively as nitrifying bacteria or nitrifiers. True nitrifying bacteria are autotrophs; they use chemosynthesis to manufacture their energy by using oxygen plus nitrogenous waste (ammonia or nitrite) and carbon (from CO2). There are several different bacterium species involved, all in the family Nitrobacteraceae, that carry out this function in soil, and it used to be thought that these, particularly Nitrosomonas europa and Nitrobacter, were the nitrification bacteria in freshwater. But Dr. Timothy Hovanec led the team of scientists that proved this to be a mistaken assumption. Ammonia is converted to nitrite by bacteria of the Nitrosonomas marina-like strain [2] and nitrite is converted to nitrate by bacteria closely related to Nitrospira moscoviensis and Nitrospira marina. [3] With several subsequent scientific studies by other scientists on wastewater nitrifying bacteria this data is now accepted.
Once established, the population of these bacteria in an aquarium will be in direct proportion to the amount of ammonia or nitrite respectively. Nitrifying bacteria require 12-32 hours to multiply, which they do by binary division [each bacterium divides into two bacteria]. Nitrosomonas multiply in less time (12+ hours) while Nitrospira require more time (up to 32 hours). In a new aquarium, it can take up to eight weeks for the bacteria populations to reach a level capable of eliminating ammonia and nitrite.
Scientific studies have also now proven that Nitrospira are inhibited and cannot multiply in water that contains significant concentrations of ammonia, and evidence exists to suggest that existing populations of Nitrospira actually become dormant when ammonia is present in high concentrations. Kim et al. (2006) determined that with an active ammonia [NH3] level of 0.7 mg/l (=ppm) Nitrospira bacteria experienced a decrease of 50% effectiveness, resulting in an accumulation of nitrite. [4]
The pH has a direct effect on nitrifying bacteria. These bacteria operate at close to 100% effectiveness at a pH of 8.3, and this level of efficiency decreases as the pH lowers. At pH 7.0 efficiency is only 50%, at 6.5 only 30%, and at 6.0 only 10%. Below 6.0 the bacteria enter a state of dormancy and cease functioning. [5] Fortunately, in acidic water (pH below 7.0) ammonia automatically ionizes into ammonium which is basically harmless. And since nitrite will not be produced when the ammonia-oxidizing bacteria are in “hibernation,” this decrease in their effectiveness poses no immediate danger to the fish and other life forms.
Temperature also affects the rate of growth of nitrifying bacteria. It will be optimal at a temperature between 25 and 30C/77 and 86F. At a temperature of 18C/64F it will be 50%. Above 35C/95F the bacteria have extreme difficulty. At both 0C/32F (freezing) and 100C/212F (boiling) the bacteria die.
These bacteria cannot survive drying out; without water, they die. Tap water with chlorine may kill these bacteria, depending upon the level of chlorine and the duration of time the bacteria are exposed to it. Some antibacterial medications may negatively impact the nitrifying bacteria to varying degrees.
[Edit today--as mentioned above, there may be contrary evidence on the species, plus the archaea rather than bacteria issue.]
Endnotes:
[2] Paul C. Burrell, Carol M. Phalen, and Timothy A. Hovanec, “Identification of Bacteria Responsible for Ammonia Oxidation in Freshwater Aquaria,” Applied and Environmental Microbiology, December 2001, pp. 5791-5800.
[3] Hovanec, T. A., L. T. Taylor, A. Blakis and E. F. DeLong, “Nitrospira- Like Bacteria Associated with Nitrite Oxidation in Freshwater Aquaria,” Applied and Environmental Microbiology, Vol. 64, No. 1, pp. 258-264.
[4] Kim, D.J., D.I. Lee and J. Keller (2006), “Effect of temperature and free ammonia on nitrification and nitrite accumulation in landfill leachate and analysis of its nitrifying bacterial community by FISH,” Bioresource Technology 97(3), pp. 459-468.
[5] Kmuda, “Aquarium Bacteria and Filtration Manifesto,” Parts 1 and 2, OscarFish website.
) (@Byron , this is your sort of thing) how long I have before I'll have to cycle? 
