Nitrogen cycling activity Bio 114
#1 in a series of activities on bacteria
1. In what important building blocks to macromolecules do you find Nitrogen in bacteria? In
humans? (best to make a table)
2. N2 has a triple bond (N=N). Will this take a large or small amount of energy to break? Defend
your answer.
3. Using the nitrogen
cycle provided, write an
equation for nitrogen
fixation? Is the result usable
by plants and animals yet?
Another way to get NH4 is
by converting amino acids
and nucleotides.
4. Using the nitrogen
cycle provided, write an
equation for nitrification? Is
result in a form that plants
or animals can use?
5. Using the nitrogen cycle provided, write an equation for denitrification? What is the implication
of denitrification?
6. What would you expect to occur if a new virus emerged that killed the bacteria and archaea
that nitrificate NO2– into NO3–?
a. a decrease in ammonia
b. a reduction of nitrite levels in the environment
c. an increase in nitrogen gas in the environment
d. an increase in marine algae and cyanobacteria
e. a decrease in atmospheric N2
7. The proteobacteria Nitrosomonas and Nitrobacter play a critical role in terrestrial ecosystems by
converting atmospheric nitrogen (N2) into nitrite and nitrate. This process generates energy for
the cell and makes nitrogen available for plants. What type of metabolism is this an example
of…?
a. Photoautotrophism
b. Chemolithoautotrophism
c. Photoheterotrophism
d. Chemoheterotorphism
e. None of the above
Semi-random application of the nitrogen cycle: fishtanks
How the Nitrogen Cycle Helps Recycle Metabolic Wastes
In nature, when animals expel their wastes and plants decay, anaerobic bacteria in the
environment break down waste to harmless nitrogen that is released into the air through the
ground and water. If nature did not have some mechanism for using the "waste" material,
eventually, we would run out of good stuff. Luckily, through the participation of bacteria using
these waste substances, harmful materials (to animals) like ammonia are converted into
something harmless and useable again. Two kinds of bacteria participate in this cycle: Nitrite
Bacteria (Nitrosomonas) and Nitrate Bacteria (Nitrobacteria). This process of breaking down
animal wastes is called Nitrification.
In Nitrification, we have: Animal waste (ammonia) is converted by Nitrosomonas → Nitrites is
converted by Nitrobacteria to → Nitrates
What Happens When You Keep Fish In Tanks?
Out of fish waste, the chemical we worry about most in a tank is ammonia since it is most toxic of
the metabolic byproducts to fish. In the tank, without proper filtration, the ammonia level
accumulates in the water, building up to toxic levels eventually killing the fish. Besides the
ammonia level, the actual level of debris would also reach a critical mass rendering the water
unlivable for inhabitants.
How to Improve Your Tank's Nitrogen Cycle
We want to focus on biological filtration equipment as well as limiting waste ending up in the
tank in the first place. Ammonia levels come straight from fish waste, uneaten food, and rotted
plant material.
To cut down ammonia, concentrate your efforts on reducing the sheer bulk of waste in your tank
(feed fish less, keep dead or dying plants out of the water, and improve the mechanical filtration
systems). To help the nitrogen cycle in the tank, consider having as many biological filters as you
can work into your aquarium's design. For saltwater tanks, protein skimming is a must. Help things
out with frequent water changes.
See questions on following page.
8. Draw a revised nitrogen cycle that shows a freshwater aquarium nitrogen cycle.
9. You should have two (maybe more) ways to produce ammonia in your tank (answered in the
reading from above). What are they? Based on this answer, what are two ways you can reduce
the amount of ammonia in the tank?