Apologies for a long post.
I never said they did not die. In fact I have said just the opposite in a number of threads on the site. The bacteria most certainly die and they most certainly reproduce. What we have in our tanks is an uncountable number of individual bacteria which all work together. As to how many there will be, that is a function of the availability of ammonia. And there are a variety of strains and lineages and one of the key differences between them is their affinity for ammonia or nitrite. Another way to see that is "how little of these things do they need to thrive?" The strains of bacteria that will dominate are the ones best adapted to the ammonia/nitrite level available.
So, in an established tank with a somewhat constant level of ammonia/there there are numbers of bacteria that can thrive in that level. And regularly individuals will die and when they do,some of the other will reproduce by dividimg. This keep the total numbers fairly constant. What remains constant is the ability of the total colony to oxifize the ammonia and nitrite present.
Inside the bio-film there are other bacteria as well. As the water moves through the bio-film the bacteria take what then need, put back what they do and other bacteria do their thing. As the water moves trough the film, some of it will have all the oxygen removed and will also contain nitrate. And there is a kind of bacteria int he biofilm known as a facultative anaerobe. It can work in water with oxygen or without it. So when the array of bacteria in the biofilm creates place where the O is gone but there is nitrate, the facultative ones use that. We all have a small amount of denitrification happening if we have the cycle established in our tanks. But is not enough to keep the water free of nitrate by any means.
You can see a picture of a Nitrosomas bacteria ( the ammonia oxidizer often in tanks) here. It is 3 microns across in un-magnified size which is 3/25,000 of an inch (3/1,000 mm).
http://commtechlab.msu.edu/sites/dlc-me/zoo/zdrs0232.html I think the image below is enlarged about 39,000 times.
What is going on in our tanks on the mi
https://scholar.google.com/croscopic level is what does all the "dirty" work. We never see it but we can measure certain things to know it is in place. We have to look elsewhere to get information on all the actual details.
Other types of bacteria which form spores when times get tough and they can survive over a long time this way. For the bacteria like the nitrifiers we need, they divide but do not form spores. They have two ways to deal with tough times when what they need disappears. They go dormant, which is basically almost suspended animation. The colony as a whole can remain viable to the extent that if what it needs returns, it will wake up and go back to work. It will hit the same capacity to process ammoina and nitrite as it did when it went dormant.
If the temp is cool enough but not freezing, this will be the case for about year. By then individuals will be dying and they will not be replaced. But considering how many individual are on the colony some can survive for decades as long as they do not exceed freezing or heating to wards 100F and up. If these bacteria did not have a strategy for the species to survive over time they would not have been around for the millions of years they have.
All it takes to create a huge colony of bacteria is one individual able to divide. But what if what they need never returns and a given colony simply dies off completely? The answer gets us to the second method they use to survive. It is not exactly true that there are no free swimming nirtifiers in tank water. Some number of individuals will be motile. Research shows that how many this may be is a function of the nitrogen available where they are. The less there is, the more individuals will be motile. This way they can leave and seek better conditions. If I remember right, the maximum that might be motile is 10%. This would mean it was emergency conditions and not many will likely make it someplace else where they can survive. But again, it only takes a few to re-establish many elsewhere if they make it.
I became curious about all of this about 18 or 19 years ago. I kept reading posts on fish sites about how long the bacteria live pr die awhat they need etc. etc. it was the same stuff everywhere. I simply got curious. I knew there had to be sciece on all this stuff and that was when I discovered Google Scholar.
Google Scholar provides a simple way to broadly search for scholarly literature. From one place, you can search across many disciplines and sources: articles, theses, books, abstracts and court opinions, from academic publishers, professional societies, online repositories, universities and other web sites. Google Scholar helps you find relevant work across the world of scholarly research.
Edited mostly for grammar and spelling and the addition of one line re the denifriers.
