Culturing ciliates: The Hay Infusion, Day 8

My pond culture has reached its 100th day and I seem to have hit upon a wonderful ecological equilibrium. Yet, there is a certain impatience to see more, which is why I thought I’d make a hay infusion. The hay infusion is a wonderful concept. Making it is rather trivial (see Figure 1): Cut some hay (I use Timothy hay available at a pet store) into 1-3 inch pieces, boil it in water for 10 minutes and you have a hay infusion. I used bottled water but would recommend the same pond water; tap water might also be fine.  I made up the lost volume (due to boiling) with more water and let it cool. I then took about 5 ml of the pond water, avoiding the duckweed and invertebrates in the pond water (as much as I could see) and inoculated the hay infusion.

Figure 1: Making the hay infusion

The idea is to inoculate a hay infusion with pond water. First the fast growing bacteria will try to win the race by consuming the rich medium. Once the bacteria reach a sufficient density, predators of the bacteria, if present, will grow in numbers, and there their predators will grow and what you get is a grand symphony of successions. It is a wonderful way to teach ecological concepts such as R- and K-selection. It is also a great way to enrich ciliates.

Post-inoculation, I actually forgot about it in the hustle and bustle of daily life. Last night, which was the 8th day post inoculation, I saw a biofilm on the surface (Figure 2) and decided to investigate it by making a slide with bits of the biofilm itself.

Figure 2: The biofilm
  1. An unknown ciliate/flagellate appears: At 140x magnification it was pretty hard to see the individual bacteria, but surrounding the film there were these little and very busy cells mostly of a single type. What I found fascinating was the way they would rest and then take off, so you have very active ones, others that slowly rotate in one spot and stationary ones– try looking for this pattern.

At 430x magnification, the tiny bacteria can now be seen, although just barely, but the other cells comes into view a bit more clearly. They seem to be a eukaryotic flagellate and they have a depression like the flagellate that showed synchronous disaggregation. I suspect they are the same type. I will be on the lookout for a repeat show of synchronous disaggregation, but I think I am already seeing the symptoms in these.

I am planning to play with this culture a bit more. Have a ton of experiments to try out.  Look out for more on this. For those interested in culturing ciliates and bacteria in a home lab setting, I would high recommend Richard Howey’s article on the same. Click here to access it.

6 Comments Add yours

  1. Manu Prakash says:

    @Laks: this is incredible. I am going to buy Hay tomorrow 🙂 To be able to keep things alive for long in pond cultures really brings life to being able to image them for a long time.

    I can clearly see the three modes of swimming you describe. I have been reading some articles that have been written on “ethology” of swimming organisms.. So it fits this description very well. My sense is that a “rotating” mode could be a stuck cilia on the surface (since they don’t see glass surface often – and thus it rotates.

    On seeing the flagella; I have been able to image the flagella before – so my sense is by playing with your illumination – you would get some contrast from the same. Remember our discussion on this long time ago:


  2. laksiyer says:

    Oh @Manu I didnt think of the organisms being stuck to the surface. Will investigate this further. Yes that discussion is a good reminder that I need to use the nail polish idea to confine the organism. I was talking to Tom about oblique illumination, need to try it on this too. I have plans to play with stains and also India ink.. Lots of experiments to do.

  3. Saad Bhamla says:

    @Laks – fantastic post!
    I have just started my own ciliates culture (inspired by you and Manu 🙂 and will try the hay infusion.
    I was reading online that I had to also use wheat for paramecium (which in turn are food for didinium).. I guess I am slowly venturing into this new microscopic world and have to properly feed the pets 🙂

    Thanks again for the hay infusion post!

  4. Saad Bhamla says:

    @Laks – I’m actually curious as to why you used bottled water instead of tap water?
    Can you share reasons if any?


  5. laksiyer says:

    Hi @Saad. Its just that Tap water might be toxic to some ciliates. I usually worry about dissolved chlorine. The Hay infusion is boiled and so any dissolved chlorine will be boiled away, but given that tap water also contains other uncontrollables (e.g. antibiotics), I prefer to either use the filtered pond water itself (that has the advantage of the optimal ratio of dissolved salts) or bottled water.

  6. Saad bhamla says:

    I see. Makes sense.
    I was just curious 🙂


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