Repository of exotic diatoms?

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75RR
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Repository of exotic diatoms?

#1 Post by 75RR » Mon Apr 06, 2020 10:03 am

.
Was looking at the label of this recently bought pineapple, it says Costa Rica.

Got me wondering if it might have some hitch-hikers on board. It is a Bromeliaceae after all and tends to accumulate water between the leaves.

So ... rinse and brush the leaves once I have decapitated it?

Not sure if there will be any, but if they are and I am to find them, I think I need to use as little water a possible so that they are more concentrated.
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Hobbyst46
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Re: Repository of exotic diatoms?

#2 Post by Hobbyst46 » Mon Apr 06, 2020 10:07 am

Perhaps wipe with moist Q-tips or a tiny piece of lens tissue, then press the moist tip onto the slide?
If they are, they would probably hide between the dense leaf bottoms.
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75RR
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Re: Repository of exotic diatoms?

#3 Post by 75RR » Mon Apr 06, 2020 10:10 am

Perhaps wipe with moist Q-tips or a tiny piece of lens tissue, then press the moist tip onto the slide?
If they are, they would probably hide between the dense leaf bottoms.
That sounds more sensible than my idea. Thanks :)

As an aside - anyone have a hand centrifuge and have they found it practical/useful?
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Re: Repository of exotic diatoms?

#4 Post by daruosha » Mon Apr 06, 2020 11:24 am

75RR wrote:
Mon Apr 06, 2020 10:10 am
As an aside - anyone have a hand centrifuge and have they found it practical/useful?
I have this model and I found it to be OK, not the best, but it does the job:
Image
https://www.amazon.com/Eisco-Crank-Cent ... B00UUBN2HM

Later on I bought a proper bench top centrifuge (it's safer, faster and results are more repeatable).
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Re: Repository of exotic diatoms?

#5 Post by 75RR » Mon Apr 06, 2020 11:52 am

Thanks daruosha

Life size image?
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Re: Repository of exotic diatoms?

#6 Post by MicroBob » Mon Apr 06, 2020 12:03 pm

Hi Glen,
I have a hand centrifuge that looks very similar to Daruosh's but is a couple of decades old. They are better for the diatomist than electric centrifuges for the tiny Eppendorf tubes because the glass tubes hold 15ml of fluid. For some diatom cleaning methods it is necessary to remove a chemical quickly and there is no time to just let the diatoms settle by themselves. I'm very happy with my centrifuge. Mine has two tubes and both have to be filled to roughly the same level. The fluid is filled in special glass tubes with a nearly pointed bottom. With used ones it is important that the vertical rotor shaft is straight. They can be bent from using unbalanced rotors or being dropped.

The other thing I use to concentrate diatom suspensions is a 25µ stainless steel sieve. The material is cheap to buy and can be welded onto a piece of plastic tube.

Bob

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Re: Repository of exotic diatoms?

#7 Post by 75RR » Mon Apr 06, 2020 12:38 pm

Thanks MicroBob,

Found this one but I think the postage is too high: https://www.ebay.co.uk/itm/Vintage-Hand ... k#viTabs_0
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Re: Repository of exotic diatoms?

#8 Post by MicroBob » Mon Apr 06, 2020 1:19 pm

Enclosed a picture of my centrifuge. The rotor shaft is supported right up to the top and the tolerances are tight. This is no rocket science but good traditional workmanship is needed for good performance. The ukranian model won't really work properly.

"Hettich" would be a good brand: https://www.ebay.de/itm/Hettich-Handzen ... 4662574835
My one has cost me below 30€ incl. shipping but prices seem to have gone up on german ebay.
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Re: Repository of exotic diatoms?

#9 Post by daruosha » Mon Apr 06, 2020 2:08 pm

Here's mine next to a 600ml beaker

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Re: Repository of exotic diatoms?

#10 Post by daruosha » Mon Apr 06, 2020 2:21 pm

MicroBob wrote:
Mon Apr 06, 2020 12:03 pm
They are better for the diatomist than electric centrifuges for the tiny Eppendorf tubes because the glass tubes hold 15ml of fluid. For some diatom cleaning methods it is necessary to remove a chemical quickly and there is no time to just let the diatoms settle by themselves.
Hi Bob,

My bench top unit accepts 8 15ml/10ml tubes.
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Daruosh.

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Re: Repository of exotic diatoms?

#11 Post by Hobbyst46 » Mon Apr 06, 2020 2:49 pm

1. Manual centrifuges are really obsolete, they were used 60 years ago in basic science lab classes, and the maximum capacity of 4 sample tubes x15ml is small.
2. Yet, for diatom separation, low speed (say, <1000 rpm) and short-term centrifugations (< 10min) are adequate. I have seen some video clips showing diatom separation by means of a short-term centrifugation, maybe with hand centrifuges.
3. Manual centrifuges are more compact than electrical ones.
4. Yet, manual cranking, even for 5 min, is really boring.

If at all, I would prefer a used electrical low-speed, 6-8 tubes capacity, centrifuge. The main problem is bench space.
Some centrifuges are equipped with receptacles for 50ml tubes, and spacer-adapters that enables the insertion of 15ml tubes as well (not inter-mixing of 15 and 50ml, though).
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Re: Repository of exotic diatoms?

#12 Post by MicroBob » Mon Apr 06, 2020 5:43 pm

Hi Daroush and Doron,
I have no background in laboratory work and never searched for a used electric centrifuge due to the space problem. Our group has one that is intended for quite small Eppendorf tubes. So my market overview is full of bling spots. But the centrifuges you have and describe would for sure be useful for diatom cleaning. For some diatoms (like the ones from northern atlantic I showed recently) the centrifuging forces might already be too brutal but testing this in detail would be a lot of work. A slow speed electic centrifuge might just be fine, as one doesn't have to crank one could let it run for a wile longer. When I use the centrifuge for diatom cleaning I only have to crank for a minute or so and the strain on the arm is not that high. One disadvantage of the manual centrifuges is that there is no housing around so it is easy to hit something with the spinning tubes. Also one has to accelerate quickly to avoid beeing hit on the hand by the tubes when the crank points upwards.

Bob

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Re: Repository of exotic diatoms?

#13 Post by dtsh » Mon Apr 06, 2020 6:26 pm

I have one of the uiquitous cheap import centrifuges often labelled only as 800-1. It's cheap in both price and assembly quality, but aside from a few minor repairs it has been reliable thus far. I wouldn't trust it in a professional lab environment where it would see heavy use, but in my home lab it's operated mostly reliably (some early issues with wiring aside) for about a year of occasional use. It's intended for 20ml tubes, but it was trivial to make an adapter for the various tubes I use on projects. It takes up about as much space as a 4 liter/1gallon sauce pan. I'd rather a smaller unit to hold perhaps 4 tubes, but for the money this one has been functional.

I have seen a number micro centrifuges, commercial and 3D printed, intended for 1.5ml and 2ml tubes which don't take up much space, but 2ml isn't a lot of volume either.

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Re: Repository of exotic diatoms?

#14 Post by jmp » Mon Apr 06, 2020 6:51 pm

If you have access to a 3D printer and 1.5ml tubes this might be of use: dremelfuge. You can use it with a regular drill. Just be aware that running it at full tilt it might 1) generate more than 50kG's of centrifugal force and 2) in the event of a failure plastic pieces flying around can cause injuries (so wear at least eye protection, I would also run the contraption within an empty tin can or plastic bucket to contain pieces if that happens). This version is for 15ml tubes and this version for 1.5ml tubes does not even need a drill and can be safely spun using a cord.

And this paper might give you some idea of what diatom species you might find hitching a ride. The Tárcoles river drains most of the Central Valley of Costa Rica, including farmland, and pineapple plantations.
Last edited by jmp on Mon Apr 06, 2020 7:52 pm, edited 1 time in total.

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Re: Repository of exotic diatoms?

#15 Post by MicroBob » Mon Apr 06, 2020 7:30 pm

If I were even lazier I would just put the rotor of my hand centrifuge in a bench drill and use it that way. My main machine in the workshop is powered over a frequency converter and can be regulated from zero up. My first centrifuge was home built and I used it in a strong steel construction drill in a big drill stand. Today I use my hand centrifuge in the kitchen with sink and water in reach and never looked back. But diatoms are quick to centrifuge, I wouldn't like to use it on something that really needs to be spun for a while.

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Re: Repository of exotic diatoms?

#16 Post by 75RR » Mon Apr 06, 2020 9:08 pm

Update:

An initial look using cotton swabs on the base of some leaves I pulled out did not reveal any diatoms.

Will have another go soon.

Thanks to everyone
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