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How big can a free-living, mobile cell be?

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46 Replies

8bit (author)2008-12-18

I wonder what it's biology is like.

Tool Using Animal (author)2008-11-21

Not to sound arrogant, but it does come so naturally to me, the point of this article is not the size, it's the fact that it leaves tracks like a multicellular animals. Frankly "bubble algae", unicellular but sessile can grow larger and you can buy them at any Marine Aquarium store.

bubble algae are single celled... Are they edible? I want to taste a cell... Also they may have done that a long time ago but how do they taste now?

I don't know, some cyanobacteria are toxic, but one shouldn't hurt, I'd bet they taste like seawater. Borrowed the following from the USDA about freshwater cyanobacteria Technical Abstract: The compounds responsible for earthy and musty "off-flavors" in farm-raised channel catfish (Ictalurus punctatus) in the southeastern United States are geosmin and 2-methylisoborneol (MIB), respectively. These compounds are produced by certain species of cyanobacteria (blue-green algae) that grow in the aquaculture ponds. Previous research has focused on the species of cyanobacteria found in catfish ponds in west Mississippi (the leading region of catfish production in the USA) while the species responsible for earthy/musty off-flavors in catfish produced in the Mississippi-Alabama blackland prairie (MABP) region (second greatest region of catfish production) have not been described. In this study, we examined water samples from commercial catfish ponds in both regions to contrast the different types of cyanobacteria and assess the prevalence of geosmin and MIB. Filamentous cyanobacteria were more common in west Mississippi compared to the MABP region. the MIB producing cyanobacterium Oscillatoria perornata was present in catfish ponds in both geographic locations. Geosmin was more prevalent in catfish ponds in the MABP region than in west Mississippi.

Hmm, I suppose saltwater makes sense, mouldy could be a notion if the cells have an element of waste in them, considering that's what seems to change tastes more than their actual presence...

True enough! And, those tracks are morphologically similar to Precambrian trace fossils which have been attributed to "invisible" (i.e. unfossilized) multicellular animals. Seeing these blobs actually moving around (not just drifting, see the Nature writeup) is like something out of an SF novel.

killerjackalope (author)2008-11-20

I wonder what they taste like... I know it seems odd but they're a single cell so it would be interesting... Bits of those articles contradict each other somewhat, unless that is that osmosis or active transport can change their buoyancy.

kelseymh (author)killerjackalope2008-11-20

Hmmmm....shouldn't they taste like chicken?

killerjackalope (author)kelseymh2008-11-21

I would have guessed eggs if that single cell theory is true, chickens a good bet though, one thing it might be very salty too, kind of like sea water if it's a single cell... Does that mean eating the nucleus would let you know what DNA tastes like?

kelseymh (author)killerjackalope2008-11-21

Doesn't everything "taste like chicken"?

Does that mean eating the nucleus would let you know what DNA tastes like?
Funny you should ask], since we just had an I'ble on that topic! (no, it's not mine; I'm a physicist, not a biochemist!)

killerjackalope (author)kelseymh2008-11-21

I knew about that 'ible, I was given how to fossilize you hamster a good while ago, I've been meaning to 'iblize a few of them...

But it's a very interesting question for me, I mean what the hell does a single cell taste like?

I believe this falls in to the same category as my reasons behind my list of things to do.

kelseymh (author)killerjackalope2008-11-21

"What the h*** does a single cell taste like?"

After all of the previous discussion about eggs etc., I think I can answer that -- caviar! Each one is a single, unfertilized fish egg.

killerjackalope (author)kelseymh2008-11-21

Hmm, I have a jar in the house somewhere, I've never tasted it, however I'll open it and compare at the time of capture, I suspect the cell would be healthy food though, the shell would be reasonably calciferous but not inedible, all those nutrients in one place inside and think of the amount of DNA I could produce... I know this seems like such an odd warpath to be on but it's an important thing to think about considering we can potentially grow massive vats of nutritious cells to eat for people, they did it with insulin and biofuel, why not make Kentucky fried cell detritus as a cheap option... Also I'd imagine that these would be nice and easy to digest...

That's a good idea, but I have to say it sounds disgusting...I don't imagine they would taste good at all.

But they could, nobody knows... I mean some food is pretty ugly but pretty tasty...

Dammit no article says anything about how the buggers taste...

I want to know also as such simple organisms are they even organisms? I believe they could be grown at home and farmed easily, you'd need a temperature, a salinity and whatever they eat, then throw some mud in the bottom and see what a cell looks like for real when it divides. Then eat the older one...

guyfrom7up (author)2008-11-20

I'm surprised it can absorb enough nutrients

kelseymh (author)guyfrom7up2008-11-20

I tried to find more information on the Web (actually, via Google Scholar), but there isn't much out there. It looks like the Arabian Sea expedition was the only one to collect samples; maybe they weren't able to keep their specimens alive long enough to figure that out?

Obivously (since they exist :-), they must be able to feed somehow. As you note, it just isn't clear what the mechanism is.

killerjackalope (author)kelseymh2008-11-21

Maybe active transport or osmosis again? They may get nutrients from waste of other animals by simply absorbing it... It all depends on how the cell walls are constructed...

kelseymh (author)killerjackalope2008-11-21

The BBC article (above) describes them as having "mouths all over their surface," presumably the same kind of ingestion vacuoles regular protists have, just much larger. They also apparently move around using pseudopodia, like amoebae do.

killerjackalope (author)kelseymh2008-11-21

I saw that in the newly added article, I suppose that makes sense, I would have though that something along the lines of cilia most likely, I suppose it's a different path for aquatic stuff though. One thing I don't get is how they managed to kill them all, I mean if you bring them up in the water they're caught in and keep it the right temperature they'd live assumably, unless they're extremely sensitive to environment like light and such, maybe pressure too considering they are supposed to be at a certain depth if they're all in a close place on one seabed.

kelseymh (author)2008-11-21

I have added Kiteman's link to the BBC report to the main topic, and I've also modified the title (though not the URL :-) to be more accurate.

TUA's comment below that the main point of the articles I've cited has to do with the tracks (and their link to trace fossils) is correct. I created this topic because I thought the weirdest part was the size of the bloody things!

Kiteman (author)2008-11-20

Isn't a newly-fertilised bird's egg a single cell? I think that would make the ostrich egg the largest cell, no?

kelseymh (author)Kiteman2008-11-21

Hi, Kiteman, Skate, W'burg (ah, that giant apostrophe :-): I found many references making that statement, "an unfertilized ostrich egg is the largest single cell," but most of them seemed to be quoting one another (i.e., identical wording over several sentences).

I also found a references that limited the "cell" part to just the nuclear material, excluding the yolk body, but those didn't have any citations to primary literature either.

I did come across one nice bit of commentary to the effect that, "since the definition of a structure is a human invention, the ambiguity is of our own making, not inherent in nature."

Anyway, I am more than willing to concede the point. Can we agree, however, that a free-living, mobile, single-cell organism that is more than an inch across is awfully freaky?

Kiteman (author)kelseymh2008-11-21
kelseymh (author)Kiteman2008-11-21

Thank you!

xACIDITYx (author)Kiteman2008-11-21

Yeah, I was always taught that...
an unfertilized ostrich egg is the largest known single cell

Lithium Rain (author)Kiteman2008-11-20

[http://en.wikipedia.org/wiki/Egg_(biology) Bingo!]

kelseymh (author)Lithium Rain2008-11-20

I followed that article to the Ostrich, where they claim (without citation), "by extension, the yolk is the largest single cell". But that's not correct. The yolk itself is nutritive material; the embryo grows from the "germinal disc" attached to the yolk membrane, and that's where the actual "cells" are.

Lithium Rain (author)kelseymh2008-11-20

Oh, I didn't see that, I was going by the sentence in the first section "The 1.5 kg ostrich egg contains the largest existing single cell currently known..." But as you say, they give no cite or further explanation. Durn you wikipedia! Giving me false information... (What?? You mean not everything I read on the internet is true?!?!?!) So I guess you're right, and Kiteman and I were wrong. :-)

kelseymh (author)Lithium Rain2008-11-20

I'm not so sure of that, either :-( It is equally possible that I'm misinterpreting or misunderstanding, and you two are correct. As you say, "Durn you wikipedia!" If I could find some definitive statement (like a microscope picture showing a newly-fertilized developing ostrich embryo), I'd be much happier.

killerjackalope (author)kelseymh2008-11-21

Well until it starts growing it could be a single cell, which has cells form an embryo inside it...

kelseymh (author)Kiteman2008-11-20

Umm, but the cell itself is microscopic. Most of any bird's egg is nutrient (yolk) or cushioning (albumen) material, isn't it? ...Time for some research...

http://www.garden-birds.co.uk/information/eggs.htm

Lithium Rain (author)kelseymh2008-11-20

Well, wikipedia says that the ostrich egg contains the largest known existing single cell.

LinuxH4x0r (author)Lithium Rain2008-11-20

Ding!

Weissensteinburg (author)Kiteman2008-11-20

That's what I had always heard.

kelseymh (author)Kiteman2008-11-20

...Man, this stuff is confusing. I've found a source that describes the whole "yolk plus germinal disk" as a single cell, the germinal disk alone as a cell, or the "yolk before the germinal disk forms" as a single cell. In the end, though, they all end up as Hollandaise :-)

Lithium Rain (author)2008-11-20

WOW. This raises an interesting question in my mind-could viruses and bacteria potentially be grown the same size? If so, (assuming they don't give off some kind of toxic substance, like penicillin is to mold), they would be too big to hurt us, wouldn't they?

kelseymh (author)Lithium Rain2008-11-20

I don't think so. Viruses and bacteria don't form tests the way forams do. Bacteria do form spores, but they aren't active (metabolizing) in that state. Without some rigid stabilizing structure, I think an "overgrown" cell would collapse and burst under its own weight. Damn you, square-cubed law!

killerjackalope (author)kelseymh2008-11-21

In a special environment we could grow them under lower and lower pressures to find out... I think the distances would make the cell non-viable though, it wouldn't react to anything with the same speed since the process would be over longer range, kind of like the really tall people that can't feel their feet properly, it would be limited by the chemicals produced, also the nuclear part of the cell may not produce enough chemicals to cause the desired effects, because it would be dissolved in a huge amount of cytoplasm.

Lithium Rain (author)kelseymh2008-11-20

Awww. :-( I wanted to grow a strain of Staph that I could hold in my hand...imagine the instructable...grow your own pet from gunk off the side of a subway toilet! :D

Lithium Rain (author)kelseymh2008-11-20

ROFLOL. I am SO making some of those and ibleizing them!

westfw (author)2008-11-21

Niven hypothesized the single-celled [http://en.wikipedia.org/wiki/Bandersnatch_(Known_Space) Frumious Bandersnatch], genetically engineered with macroscopic (LARGE, in fact) chromosome(s?) so as to be immune to mutation by significant levels of radiation...
Given the degree to which single-celled organisms can have specialization at the sub-cell level (cilia on a paramecium?), I'm not sure I see why you can't have arbitrarily large single cells that include organelles with complex functions...

kelseymh (author)westfw2008-11-21

Even multiple nuclei. Other macroscopic cells (some species of algae) have chromosomal bodies scattered in multiple places within a single continuous cell-wall enclosing cytoplasm. I ran across this trying to find info on "giant" cells.

skunkbait (author)2008-11-21

How big can a cell be? Well, the longer they keep me locked in here, the smaller it seems!