Nannochloropsis and USO's

pwnell · Post by **pwnell** » Mon Oct 03, 2011 6:56 pm

I have just started my Nannochloropsis culture from a disk I got from Florida Aqua Farms. I followed all their instructions to sterilise the water and everything I use to manipulate the cells.

I just took a sample from the newly rehydrated cells and saw weird, tiny things swimming in the sample. The Nannochloropsis cells are about 6um in length and are clearly visible, the swimming things (bacteria?) can be made out as ghostly outlines generally wriggling upwards in the two videos I have attached (darkfield and phase contrast as they are not visible at all under brightfield).

Can anyone tell me what it is and whether I should be concerned? Warning: Each video is about 110MB. Oh - it was taken with a 40x objective.

Darkfield

Phase Contrast

pwnell · Post by **pwnell** » Mon Oct 03, 2011 7:31 pm

Here is an example of what I was referring to. The red arrow is obviously the Nannochloropsis cells, the blue arrow is the unknown swimming things.

Cactusdave · Post by **Cactusdave** » Tue Oct 04, 2011 12:25 am

Yes those are bacteria. Whether they are harmful or not depends on what you intended to use your culture for. It's difficult to avoid contamination like this unless you are working under lab conditions with laminar air flow hoods etc.

phytoplankton · Post by **phytoplankton** » Tue Oct 04, 2011 2:02 am

Yep, bacteria. I would also carefully observe several different samples and make sure it is unialgal. Especially look out for Isochrysis or Tetraselmis. Florida Aqua Farms disks are famous for cross contamination. Which can be a plus if you want to culture several different species of algae and have the means to isolate them. But not as convenient otherwise.

Is this for aquaculture, or a feed supplement, etc?

René · Post by **René** » Tue Oct 04, 2011 3:10 am

Bacteria are difficult to get out of cultures. Pure such cultures would be called 'axenic'. Sometimes, things grow quicker with them, or not at all without them. Most researchers don't bother getting rid of them.

But be careful for parasitic fungi and such, they can take over your culture in no time.

Best wishes, René

pwnell · Post by **pwnell** » Tue Oct 04, 2011 8:36 am

phytoplankton wrote:Yep, bacteria. I would also carefully observe several different samples and make sure it is unialgal. Especially look out for Isochrysis or Tetraselmis. Florida Aqua Farms disks are famous for cross contamination. Which can be a plus if you want to culture several different species of algae and have the means to isolate them. But not as convenient otherwise.

Is this for aquaculture, or a feed supplement, etc?

Ha and here I thought by buying from them I will avoid cross contamination. It is for feed supplementation for my reef aquarium but I want to sustain the culture from this one disk, i.e. I want to start new cultures every so often from this culture.

phytoplankton · Post by **phytoplankton** » Tue Oct 04, 2011 12:38 pm

pwnell wrote:Ha and here I thought by buying from them I will avoid cross contamination. It is for feed supplementation for my reef aquarium but I want to sustain the culture from this one disk, i.e. I want to start new cultures every so often from this culture.

It sounds like you have the right idea. Culturing in batches, where you use a portion of the old culture to inoculate the next batch, is a good cheap and easy way to do it.

Frankly, I wouldn't worry about the disks being cross contaminated too much. Both Tet and Iso are more nutritious than Nanno anyway. Outward signs of a different species taking over could be indicated by the culture changing color or smelling different. But since you have a microscope it's easy to find out what's going on in a culture.