Model Building: Phase shift curve model of Moina-Bacteria in bottle

Model Building: Phase shift curve model of Moina-Bacteria in bottle

Phase shifted curve model of reproduction of moina with bacteria in a bottle, causerie and model building by Pratit, Old school cubist of 2012



Please tell us more about the phase shift in moina culture of moina bacteria

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In Moina Bottle cultures, there is a pattern of growth of Moina, as well as of Bacteria.
When Moina increases, number of bacteria will be decreasing, as moina feeds on bacteria.
Vice versa, when number of bacteria increases, moina numbers could be decreasing as bacteria will use up the oxygen.

Thus moina growth pattern and bacterial growth pattern can be inversely proportional to eachother for a period of time in bottle cultures, hence there is a phase shift model of curve.

This modeling of moina-bacteria reproduction kinetics is being discussed with an old cubist Pratit, of 2012 batch who was with us and who is currently in his junior college.

Pratit is likely to join the site, and will be replying more in this thread.


In a system of moina culture stored in a bottle if you observe there is mainly a single variable.

  1. The oxygen available for the organisms inside the bottle

Depending on this variable there are other interdependent multiple variables i.e.

  1. The number of Moina’s inside the bottle
  2. The number of bacterias or other micro organisms inside the bottle.
  3. The amount of waste generated inside the bottle.
  4. The rate at which waste is generated inside the bottle.

The above mentioned variables also affect the first one which is the amount of oxygen available for the organisms.

The relationship can be deduced using deduction.

  1. As you can deduct that there is obviously a relation between the amount of Moina inside the bottle and the available oxygen for each one of them. Since there will be a limit to the oxygen that can maximum be dissolved inside the water. So at some point our Moina will start generating excess of hemoglobin to meet there oxygen needs in a hypoxic environment. Then when there numbers further increase and they reach a maxima. After that there numbers start falling until there is enough oxygen for each one of them. That’s represented by the green wavy line in the bottom right graph.

  2. You can also deduce that there is a similar relationship between the number of bacterias in the bottle and the oxygen available for them. But the wavy curve plotted will be a bit phase shifted which will be because there is also an inverse relationship between the bacteria and the moina populations. As you might know that Moina eat bacteria.

  1. There is also a relationship between the amount of waste inside the bottle and the Moina population. As one can observe the waste products are harmful for Moina. Therfore there is an inverse relationship between waste and moina population. Due to which the wavy curve plotted for Moina will not be parallel to the x axis but instead will start dipping downwards after the waste increases more than what moina can handle.
    This will go on till extension of the moina population.
  1. The bacterial population unlike Moina will continue to maintain population as depicted by the wave function until all moina die. Once that happens there will be boost in the bacterias population since there are no moina to feed on them which will increase until there are enough to cause hypoxia by using excess of oxygen. Then they will continue the wave function forever if nothing changes except for oxygen and the amount of waste. Since there will be excess of waste by then the bacteria found will mostly be the ones decomposing the waste. Hence different from the ones we had in the beginning.

  2. The waste growth will be exponential with a few changes in the rate of increase caused by the varing number of organisms that would create the waste. Which can be depicted by a exponentially increasing graph with steps in between where the change (increase) of amount of waste will vary

All this is just the hypothesis which is yet to be tested.


Welcome Pratit…

Great explanation of modeling design for studying dynamics of moina-bacteria cultures in bottle.

Can you send a good picture of your graph, so that this hypothesis is emphasized with all moina groups in cube and tried for testing.

Please also explain how are you planning to test role of bacteria and role of waste in your bottle cultures?
How are you planning to study this kinetics?
Please explain your design.

Also what do mean by waste? What waste would be generated in moina bottle cultures? Which chemicals? Can they be tested?

Brilliant entry point in chemistry…

Eagerly looking forward to… @pratittodkar

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The waste here refers to the excretory products produced by all the organisms that will be present inside the system. This waste includes but is not limited to

  1. The waste created by Moina
  2. The Nitrates, Nitrites, Ammonia that could be produced by the decomposition of any organic matter by bacteria
  3. Dead remains of organisms after completion of there life span.
  4. Urea that could be a excretory product created by Moina or other organisms.
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Image of the graph

Black represents growth of waste.
Green represents growth of Moina.
Red represents growth of Bacteria.

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I currently haven’t worked out the way of quantifying and estimating the growth of Bacteria and plan on doing so as soon as possible. I am also open to suggestions. You all can also try some things that might help.

For the waste we can see that waste mostly consists of chemicals and after a discussion with @jaikishan sir and @Arunan sir as they suggested we can do chemical testing to check the concentration of specific chemicals like nitrates and urea.

After we have a large enough data from all the experiments that the whole CUBE collective can do together we can generate a computer model of such data to predict how various factors can affect Moina

Welcome @pratittodkar after 6 years!

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As pointed out by one of the CUBIST bacteria can switch to anaerobic form of respiration. Which means there would be exponential growth of Bacteria and instead of any kind of wave it would look like a graph of an exponential function and that also means that Moina population would come to extinction faster than thought.

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