Scientists explore new window on the origins of life

Feb 12, 2009

(PhysOrg.com) -- The remarkable behaviour of bacteria that have been forced to live without their protective wall has allowed Newcastle University scientists to open a new window on the origins of life on earth.

All living cells on the planet go through the process of division in order to survive and thrive. Cell division, or binary fission, allows one cell to split down the middle to become two cells.

In the work published in Nature, Newcastle University scientists have found that under some conditions, including treatment with antibiotics, common bacteria switch to a whole new way of increasing in number that may have been used by the first cells to evolve on the planet.

Bacteria have been around for more than two billion years and now occupy every corner of the environment. The secret of their success seems to be their tough outer skin or cell wall. This protective barrier can also be a weakness and is the target for many of our best antibiotics, including penicillin.

The Newcastle University scientists have found out how to induce a bacterium to live without a wall. These fragile cells called L-forms, have a wobbly shape with only a thin surface membrane holding them together. What has surprised scientists is that the bacteria seem to be pre-prepared to make this switch to life without a wall.

The scientists believe that the bacteria kept this ability as a way of surviving attacks on their wall that have been happening since the earliest life-form but now happen regularly when patients are treated with antibiotics.

Now that L-forms can be studied more closely the Newcastle University team led by Professor Jeff Errington has found the drug-resistant bacteria are multiplying in a way which has never been seen before.

Instead of dividing in two, the L-form bacterium pulsates and then ‘squirts out babies’, sometimes as many as five new bacteria each time. This was completely unexpected.

In the work the team describe how they made the L-forms and the simple genetic changes that happened in the cells when they adapted themselves to life without a wall.

“What we have uncovered seems to be a primitive mode of growth probably used by the very earliest cells on the planet,” says Professor Errington, Director of the Institute for Cell and Molecular Biosciences at Newcastle University.

“All modern bacteria are used to living inside their wall which is a great sheltered place to be but it’s an engineering feat to be able to expand it, keeping it intact at all times and then pinch it off into two. We now think that before the wall was invented, very early in evolution, cells used this squirting method to increase in number.”

During the research funded by the BBSRC, the scientists for the first time witnessed and were able to video the L-form bacteria multiplying.

The team now intend to work on understanding how the mechanism works that squirts the bacteria out, which might be important for combating some forms of antibiotic resistance, as well as providing powerful new experimental tools for studying the all important cell wall.

More information: Life without a wall or division machine in Bacillus subtilis. M. Leaver, P. Dominguez-Cuevas, J.M. Coxhead, R.A. Daniel and J. Errington. Nature doi:10.1038/nature07742

Provided by Newcastle University

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superhuman
2 / 5 (1) Feb 12, 2009
This division is almost certainly an artifact due to lack of cell wall, cell wall is an essential element of bacteria physiology and plays crucial role in cell division, it's to be expected that bacteria are not dividing in the usual way without it.

There is absolutely no reason to think it has anything to do with how bacterial ancestors divided.
jeffsaunders
5 / 5 (2) Feb 13, 2009
The ancestors had to start somewhere. To decide that that starting point did not include a wall is quite reasonable. To decide that they had to divide and multiply while in the wall-less state is also quite reasonable.

To decide that this division may look something similar to an observed division that has taken place in a wall-less bacterium that exists today is also no great super human leap in brain power.

Having said all that it seems reasonable that the earliest bacteriums may have had multiple births so to speak. This would not involve the central DNA chain breaking in two and then splitting and inhabiting each half one each - although that method may well have been the most common way. It is quite possible that some DNA may have been distributed around the cell in clusters and thus make it easier to have multiple divisions. Likewise the centralist approach may also allow multiple divisions before splitting.

The upshot is that the new versions would be much smaller and perhaps more vulnerable than the larger offspring. Thus perhaps making it easier to increase in numbers in unexploited territory but in already capacity territory the smaller individuals would just end up being a meal for the larger varieties.

This description sounds very much like evolutionary decisions and therefore quite likely to have taken place on more than one occasion. After all - if doesn't work so well now has nothing to do with what would have happened in the early days when a bacterium was the most advanced life form on the planet.
superhuman
not rated yet Feb 13, 2009
The ancestors had to start somewhere. To decide that that starting point did not include a wall is quite reasonable.

It's not "quite reasonable" it is obvious, but obvious conclusions won't make

To decide that they had to divide and multiply while in the wall-less state is also quite reasonable.

"Quite reasonable" that bacteria without wall had to divide in a wall-less state? You seem to think that starting with obvious conclusions will make your other statements more convincing.

To decide that this division may look something similar to an observed division that has taken place in a wall-less bacterium that exists today is also no great super human leap in brain power.

Too bad b.subtilis is not a wall-less bacteria, far from it. It never exist in such state in natural conditions and it takes great pains to achieve it, they have to be grown for generations is special buffers providing osmotic stability and with antibiotics which kill all bacteria reverting to cell wall. It is an extremely unnatural state and therefore it's pure speculation to claim it has any relation to what happens in nature.

Having said all that it seems reasonable that the earliest bacteriums may have had multiple births so to speak. This would not involve the central DNA chain breaking in two and then splitting and inhabiting each half one each - although that method may well have been the most common way. It is quite possible that some DNA may have been distributed around the cell in clusters and thus make it easier to have multiple divisions. Likewise the centralist approach may also allow multiple divisions before splitting.

No, it's far from reasonable.

Each cell has to have a copy of all the DNA and the only reasonable way is to copy the DNA and then divide the cell, even this is quite a feat, especially since cellular organelles have to be divided also. Producing multiple copies of everything and then properly segregating them makes no sense whatsoever when you can just keep dividing in two as many times as needed. Division in two also gives you much better control over the process, division has to be synced with energy levels, it makes more sense to divide in two as soon as the energy level is sufficient then to wait until you can produce more offspring at one go, especially in a competitive bacteria world.

It is reasonable to assume ancestors were simpler, it is NOT reasonable to assume they were more complex, drawing such conclusion because one species of bacteria does something weird in extremely unnatural conditions without and other substantiating evidence is NOT reasonable, it is in fact absurd.

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