Rapid and Efficient Method for Isolation, Concentration, and/or Cleaning of Diatoms (or other small organisms)?

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SunshineLW
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Rapid and Efficient Method for Isolation, Concentration, and/or Cleaning of Diatoms (or other small organisms)?

#1 Post by SunshineLW » Thu Sep 27, 2018 11:43 am

First off, let me start by saying that the following is essentially "diatom hunting" from an ignorant, parasitologist's perspective. I know almost nothing about diatoms (except for what I have read on www.microbehunter.com). Therefore, my ramblings could be completely irrelevant and/or obvious to the seasoned diatom hunter.

I have read several posts about "cleaning" diatoms. I assume that this is an isolation process, which (at the most complicated level) can involve making dilutions, boiling toxic chemicals, etc. This sounds quite dangerous and complicated, so I have been wondering if it could be done more safely, more efficiently, on a larger scale, and applied in the field while diatom hunting.

I have never "cleaned" diatoms but I do know how to perform a fecal sedimentation. Fecal sedimentation is a diagnostic technique that involves the isolation of small, sinking parasites (ex., ova and oocysts) from the rest of the debris found in a stool sample. IMPORTANT: Sedimentation protocols are intended for isolation of specimens that sink to the bottom of a liquid media. If your specimen(s) float to the top of a liquid media, then you may be more interested in using a fecal flotation protocol (of which there are many).

There are several ways to perform a fecal sedimentation. Simple fecal sedimentation protocols can be performed using only tap water, a beaker, and a coffee filter. There is a specific method for performing a fecal sedimentation, which I believe may be useful for rapid, large-scale, diatom isolation ("cleaning").

The fecal sedimentation protocol that I have in mind involves a device called a "Fluke Finder" (https://www.flukefinder.com). The Fluke Finder is simply a filter with two separate screens positioned one after another (see images below). Using it is as easy as adding water to your sample (making a soup), and running the liquid sample through the paired screens:

1. First, the sample runs through a coarse screen. All of the ova (or diatoms?) pass through this coarse screen, but the larger debris does not. As a result, the larger debris are caught in the coarse screen and are effectively separated from your ova (or diatoms?), which are small enough to have passed through.

2. Then, the sample runs through a fine screen. All of the ova (or diatoms?) are caught in the finer screen, but all of the excess fluid is drained.

After running water through the screens several times, all of your ova (or diatoms?) are caught in the second, finer screen and are ready for observation/ manipulation under the microscope.

The Fluke Finder is made for isolating ova that are around 80-200 micrometers in diameter. Additionally, the Fluke Finder claims that it can isolate Giardia cysts, which are only 8-14 micrometers in diameter. I do not know the mesh sizes of the screens; therefore, I cannot tell you what is the smallest size of diatom that can be caught by the Fluke Finder. Since diatoms can be as small as 1-2 micrometers in length, my bet is that these smaller diatoms would pass through the finer screen, resulting in their loss during the isolation process. However, I'd be curious to see how the Fluke Finder (or a custom Fluke Finder) would function in isolating ("cleaning") diatoms. My hypothesis is that it can be used for isolation and concentration of larger diatoms found in large volumes of diatom soup samples.

Also, because this process involves only the sample and the hand-held Fluke Finder, I believe that it could be applied in the field, allowing for immediate isolation and concentration of samples for rapid identification of an ideal diatom source/ sample.

Let me know what y'all think. I'd be surprised if this technique is not already in regular use for diatom isolation.
Fluke Finder - Complete Apparatus
Fluke Finder - Complete Apparatus
Fluke Finder 1.jpg (113.04 KiB) Viewed 1743 times
Fluke Finder - Fine Screen (left) and Coarse Screen (right)
Fluke Finder - Fine Screen (left) and Coarse Screen (right)
Fluke Finder 2.jpg (155.47 KiB) Viewed 1743 times
Fluke Finder - Fine Screen (left) and Coarse Screen (right)
Fluke Finder - Fine Screen (left) and Coarse Screen (right)
Fluke Finder 3.jpg (181.85 KiB) Viewed 1743 times
Fluke Finder - Fine Screen (left) and Coarse Screen (right)
Fluke Finder - Fine Screen (left) and Coarse Screen (right)
Fluke Finder 4.jpg (208.87 KiB) Viewed 1743 times

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Re: Rapid and Efficient Method for Isolation, Concentration, and/or Cleaning of Diatoms (or other small organisms)?

#2 Post by zzffnn » Thu Sep 27, 2018 1:54 pm

That would be useful for sure. I would probably DIY one out of PVC pipes/joints + filters of 5 different pore sizes.

2 filters of 2 pore sizes may not be enough, if "soup" is not diluted enough. With 5 pore sizes, we can make something like 2mm, then 0.7mm, 0.2mm, 0.05mm (50 micron) and 0.005mm (5 micron), from top to bottom.

The lower 3 filters (0.2, 0.05 and 0.005mm) are for isolating diatoms, while the top 2 filters (2mm and 0.7mm) are mostly for removing debris.

This device does not clean diatoms though (although it will make cleaning easier). We still need to remove their plant fibers, lipids, proteins and starch contents.

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