IN THE NEWLY INSTALLED AQUARIUMBy Jim E. Quarles
About three billion years ago, when life was just beginning to
establish itself and evolve here on earth, ammonia was one of the most
common molecules in our atmosphere and oceans. Once primitive plant life
began producing oxygen, Nitrosomonas type bacteria undoubtedly began to
flourish. While plants converted light through the process of
photosynthesis into energy they required for survival, Nitrosomonas type
bacteria developed metabolic pathways to exploit the energy released by
combining ammonia and oxygen.
BIG CHANGES IN THREE BILLION
Fortunately for us, a lot has changed over this long period of time. As
the result of the efforts of Nitrosomonas and other bacteria, ammonia is
no longer a principle constituent of our planet's air and water. But
Nitrosomonas bacteria rely on ammonia as their only food source. This has
become a limited resource for these bacteria under the present conditions
of our air and water.
To survive in such limited conditions with such scarce and
unpredictable sources of ammonia, modern day Nitrosomonas have all
developed a critical life sustaining adaptation. They have evolved the
ability to become dormant. When starved of ammonia for prolonged period of
time, Nitrosomonas began to conserve energy by shutting down the thousands
of metabolic pathways, which characterize their active state.
By the time complete dormancy is achieved, there is only one critical
activity which remains functional. That activity remaining functional is
the ability to detect high concentration of ammonia coming into contact
with the outer cell membrane. Under certain conditions, when a
sufficiently high concentration of ammonia is detected over a sufficiently
long period of time, the ability to transport this ammonia across the cell
membrane also becomes reactivated.
UNDERSTANDING DORMANCY IS
CRITICAL TO THE HOBBYIST!
Entering the dormant state is a major commitment. A significant
expenditure of time and energy is required to systematically shut down
enzymatic activity in the prescribed sequence to ensure long term
survival. Significant amounts of time and energy are also required to
reactivate these metabolic pathways. The dormant Nitrosomonas cannot
afford to be frivolous in its decision to reactivate. If a newly detected
source of ammonia is transient or short lived, a premature or rash
commitment to reactivate could prove deadly. If the ammonia source would
disappear to soon, the organism could be left without enough resources or
time to return to the dormant state and would die.
IDEAL CONDITIONS FOR
Laboratory experiments have demonstrated just how conservative this
reactivation response mechanism is. Dormant Nitrosomonas have been exposed
to various concentrations of ammonia. The length of time required before
reactivation begins was then measured. The ideal concentration required to
obtain reactivation in the shortest period of time is in the area of two
hundred parts per million (200 PPM). But even at this incredibly high
concentration the organisms still require a time lag of two to three days
before reactivation begins.
With the weak concentrations found in new aquariums this time will be
expanded to ten days or even weeks in some cases.
Even when reactivation begins, the commitment is not total. Factors
other than the availability of ammonia influence the rate at which
metabolic activity is restored. When dormant, Nitrosomonas assume a
free-floating form. The ability to move passively with the water currents
increases the likelihood that they will stumble upon a new ammonia source.
When reactivation begins the Nitrosomonas will attempt to become 'fixed'
and adhere to a solid object. Even a new food source, which provides a
high ammonia concentration, is of little value if the organism is soon to
be swept away from it by the currents and left to starve.
A commitment to resume full metabolic activity, therefore, is not made
until the organism adheres to a suitable solid object in ammonia rich
IT WILL BECOME CLEAR WHY
IS OF CRITICAL IMPORTANCE TO THE AQUARIST.
Even small numbers of free floating Nitrosomonas will multiply in
numbers and a new tank will cycle, establishing its own biological
filtration system. Unfortunately this process seems to take forever. While
many species of bacteria can reproduce and double their numbers every 20
minutes, the Nitrosomonas require at least 24 to 36 hours under ideal
laboratory conditions to double their numbers.
Under ideal conditions, Nitrosomonas can survive in its dormant state
for up to about three years but a significant percent of the organisms
will began to die off, however, after more than one year. As with most
adaptations for survival there are trade-offs. While the ability to become
dormant has helped insure Nitrosomonas survival, it has not come without a
price. As metabolic processes are shut down, so too are almost all the
organism's protective mechanisms. While an active cell can respond to and
withstand numerous environmental insults a dormant Nitrosomonas cell is
left extremely vulnerable.
Chemical insults to dormant Nitrosomonas cells are of even greater
significance to the aquarist. Nitrosomonas cells like most other aquatic
organisms, are beasts adapted to an environment with very high water
quality. (A change in concentration of almost any chemical beyond the
level normally found in their natural unpolluted environment, is toxic).
Waste products (except ammonia) from other organisms, water conditioning
agents, and drugs are most common chemical insults of significance to the
Different strains of Nitrosomonas exhibit extreme Variations with
respect to their ability to survive temperature abuse. The outer cell
membrane of these organisms is composed primarily of lipids (fat). When
exposed to high temperatures, this proactive cell coating will actually
melt and the organism will die. All strains will die if the liquid culture
is frozen solid. Unlike most bacteria, Nitrosomonas cannot survive any
drying or freeze-drying process. Even the liquid nitrogen freezing process
In a new aquarium, Nitrosomonas as well as other bacterial reproduction
is often manifested in a bacterial bloom with the obvious turbidity or
cloudiness developing in the water. Although unsightly, this cloudiness is
harmless to other aquarium inhabitants and is actually a good sign,
demonstrating a healthy environment required for the bacterial
populations. This cloudiness will generally disappear within a few days.
While active Nitrosomonas require oxygen, they require much less oxygen
then is generally believed. The natural environment for these bacteria is
beneath the surface of the sediments at the bottom of the oceans or body
of freshwater. This environment is not characterized with an abundance of
dissolved oxygen. While the Nitrosomonas can tolerate oxygen depletion
they cannot tolerate the waste products of anaerobic bacteria such as
hydrogen sulfide. Even a one hour interruptions of air flow to an under
gravel filter, for example, can provide enough time for lethal levels of
these waste products to accumulate. Many aquarium additives are drugs that
are toxic to both dormant and active cells.
Continued in final part