Bacteria without cell walls?

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Bacteria without cell walls?

Postby Jorpho » Fri Aug 15, 2008 2:29 pm UTC

I happened to be reading about ureaplasma recently. Many sources state that it lacks a cell wall, but unfamiliar with microbiology as I am, I can't seem to find out how it lives without a cell wall. Wikipedia does suggest that some bacteria might have really primitive cell walls, which I suppose might be the case for ureaplasma, except then I would expect sources to say that it has a really primitive cell wall rather than no cell wall.

Is anyone here familiar with how these bacteria work? How exactly can a cell function without a cell wall?
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Re: Bacteria without cell walls?

Postby Klotz » Fri Aug 15, 2008 2:44 pm UTC

There is a difference between a cell wall and a cell membrane. A cell wall is rigid and made of cellulose; plant cells have them. A cell membrane is fluid and permeable and is made of fats. Animals cells have a membrane but no wall; bacteria can have either.
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Re: Bacteria without cell walls?

Postby thoughtfully » Fri Aug 15, 2008 3:53 pm UTC

They can't have either. Cell membranes are obligatory, walls are optional. For bacteria. I'm pretty sure they are obligatory for plants, however. Membranes are obligatory for everybody. The cell wall, if present, is on the outside, and the membrane is inside.
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Re: Bacteria without cell walls?

Postby Jorpho » Fri Aug 15, 2008 4:29 pm UTC

Ah, but of course. A silly thing to forget.

(Crikey, it suddenly occurs to me that it's been nine years since my last biology course! I'm kind of glad I remember as much as I do.)
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Re: Bacteria without cell walls?

Postby Yakk » Fri Aug 15, 2008 7:27 pm UTC

I believe they have found a virus that grows a cell-wall like structure only after it enters a cell and starts pumping out copies of itself. And another virus that infects that cell-like sub-structure and hijacks it to produce copies of itself instead of the first virus!
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Re: Bacteria without cell walls?

Postby tantalum » Fri Aug 15, 2008 7:52 pm UTC

If there were no plasma membrane, there would be nothing from preventing you from falling apart into a goopy, watery mess, kind of like in movies :P Your body is a huge collection of miniature soap bubbles with reinforced walls - the fact that they're so tiny also improves their surface area/volume ratio, strengthening the bubbles further.
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Re: Bacteria without cell walls?

Postby HistidineTheCat » Sat Aug 16, 2008 3:34 am UTC

It's a fun subject! Cell walls come in all sorts of shapes and forms, with all sorts of different compositions. Some bacteria even make a layer of wax around themselves! Diatoms are pretty cool in that they form glass shells around themselves. Diatoms are some of the coolest-looking critters on earth: http://www.bio.miami.edu/dana/pix/diatoms.jpg.

Meteorswarm's post above is a pretty good summary of cell walls. Gram negative bacteria tend to have really thin walls, since they're sandwiched between the membranes. Gram positives have really thick cell walls that aren't covalently held. The outer layer constantly flakes away, while the cell continually adds new layers from the inside. It's like a giant layer of cheap legos.

Archaea cell walls are probably even more varied, given they have to survive a wide array of different environments.
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Re: Bacteria without cell walls?

Postby justaman » Mon Aug 18, 2008 12:44 am UTC

check out mycoplasma for bacteria that don't have a cell wall. To survive without a cell wall, all that is required is a system of conforming to the osmolality of the solution surrounding the bacterium, usually this is done through ion transport channels maintaining a balance of ions inside the cell.

Edit: what the hell??? my url doesn't seem to be working

Edit again: Fixed
Felstaff wrote:"deglove"? I think you may have just conjured the sickest image within my mind since I heard the term "testicle pop".
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Re: Bacteria without cell walls?

Postby Jorpho » Mon Aug 18, 2008 4:50 am UTC

justaman wrote:check out mycoplasma for bacteria that don't have a cell wall. To survive without a cell wall, all that is required is a system of conforming to the osmolality of the solution surrounding the bacterium, usually this is done through ion transport channels maintaining a balance of ions inside the cell.


Now, see, that would have helped, but for some reason the ureaplasma article only links to Mycoplasmataceae, a stub that is no help whatsoever. And the cell wall article doesn't link there at all!

(Someone who knows what he's doing ought to rearrange the links.)
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Re: Bacteria without cell walls?

Postby Creigon Quall » Mon May 25, 2009 3:28 am UTC

Yakk wrote:I believe they have found a virus that grows a cell-wall like structure only after it enters a cell and starts pumping out copies of itself. And another virus that infects that cell-like sub-structure and hijacks it to produce copies of itself instead of the first virus!


HAHA! I just took an AP test, and I assure you there is never a cell wall on any virus. They have an casing called a capsid that is made of a bunch of proteins.

I stumbled across this because my dad offered another one of his $3 questions. He asks these science questions and wants an authoritative source. I got all I needed from the first post. Thanks!
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Re: Bacteria without cell walls?

Postby alexh123456789 » Mon May 25, 2009 3:46 am UTC

Creigon Quall wrote:HAHA! I just took an AP test, and I assure you there is never a cell wall on any virus. They have an casing called a capsid that is made of a bunch of proteins.

I stumbled across this because my dad offered another one of his $3 questions. He asks these science questions and wants an authoritative source. I got all I needed from the first post. Thanks!


Just because something is generally true doesn't mean there aren't exceptions or variations. Also, he never said that it was floating around with a fully made cell wall; just that, when it enters a cell, it forms something like a cell wall.
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Re: Bacteria without cell walls?

Postby Yakk » Mon May 25, 2009 6:38 am UTC

I think the thing I was remembering was a vacuole. But it was a long time ago, in another country -- and besides, the virus is dead.
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Re: Bacteria without cell walls?

Postby Creigon Quall » Mon May 25, 2009 10:21 pm UTC

A vacuole would make more sense, but alexh, in order for a cell wall to exist, there has to be a cell membrane. And even if that wasn't the case, it would be impossible to have a 'cell wall' on a virus because cells are considered life, and viruses are not. A virus and a cell are two totally different things. If there was a casing around the virus LIKE a cell wall, it would be called an envolope or something of that sort, but not a 'cell wall'. In order for something to have a cell wall, then it has to be classified in the domain for eukarya, prokarya or some other type of cell that I know nothing about. A bacterium are prokaryiotic cells.
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Re: Bacteria without cell walls?

Postby justaman » Tue May 26, 2009 4:55 am UTC

Creigon Quall wrote:A vacuole would make more sense, but alexh, in order for a cell wall to exist, there has to be a cell membrane. And even if that wasn't the case, it would be impossible to have a 'cell wall' on a virus because cells are considered life, and viruses are not. A virus and a cell are two totally different things. If there was a casing around the virus LIKE a cell wall, it would be called an envolope or something of that sort, but not a 'cell wall'. In order for something to have a cell wall, then it has to be classified in the domain for eukarya, prokarya or some other type of cell that I know nothing about. A bacterium are prokaryiotic cells.

Archaea - cyanobacteria have cell walls as well. Viruses have capsids, which typically incorporates a wall like structure and a bi-layer membrane.
Felstaff wrote:"deglove"? I think you may have just conjured the sickest image within my mind since I heard the term "testicle pop".
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Re: Bacteria without cell walls?

Postby Karantalsis » Thu May 28, 2009 12:58 pm UTC

Just thought I'd add my comments to this as its something I actually feel qualified to comment on for once :).

Bacteria can have cell walls, but don't neccessarily have them, if they do they typically fall into the gram positive or gram negative style as shown in someones post above. All bacterial cell walls are composed of, primarily, peptidoglycan, which is a really cool polymer. The outer most surface of the cell, whether it has a cell wall or not, is generally the S-layer a glycoprotein coat that has lots of wierd and wonderful things in it.

Of these components (Membrane, Wall and S-Layer) only the Membrane is always present. In Bacteria this membrane is made of ester linked phospholipids in a bilayer. Without a membrane there is no cell, it defines the cells outer limit and is essential for the life of the organism.

Eukarya; Animals, Fungi, Plants and Protozoa are all largely similar with ester linked phospholipid bilayer mebranes similar to those of bacteria. They can have cell walls, in the case of Fungi, Plants and some Protozoa. These cell walls are typically made of either cellulose or chitin.

Archaea, a domain of prokaryotes distinct from bacteria, can have cell walls, but most don't. Instead archaea commonly have a particularly well defined S-layer which acts to give structure to the cell. They also have phospholipid bilayers, however, unlike those of Bacteria and Eukarya they are ether linked, which leads to archaeal membranes having many properties dissimilar to the other two Domains.

Viruses come in various forms, the parts common to all are the nucleic acid (which can be RNA or DNA) and the capsid, a protenaecous coat that covers the nucleic acid. Some viruses co-opt cell membranes from their hosts to form an envelope, but this is not a true cell membrane nor cell wall.

On a side note Prokarya is not a domain. The Domains are Eukarya, Bacteria and Archaea.
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Re: Bacteria without cell walls?

Postby Creigon Quall » Sat May 30, 2009 6:33 pm UTC

:D You used a textbook didn't you?:D You used a textbook didn't you?
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Re: Bacteria without cell walls?

Postby Karantalsis » Mon Jun 08, 2009 4:02 pm UTC

Nope. This question just happened to land neatly in my field, and I just happen to talk in this manner most of the time. :).
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