Bacteria form the waveform when there is an effect of oxygen

Each bacterium knows itself so small that it is impossible to act on its own. So bacteria often wait, divide, and then engage in activities that require collective association. There are hundreds of activities in which bacteria participate in group activities. Now Rockefeller University researchers have discovered a previously unknown activity.

In the study results published in the Physical Review Letters on May 12, Albert J. Libchaber, head of the Physical Physics Laboratory and his colleagues, showed that when oxygen approached a group of bacteria Escherichia coli lacks oxygen, this group performs an unprecedented activity in any living organism: they gather and form a unified wave that moves at a stable and unchanging velocity. during.But while the whole block moved, each member of the bacteria did not have any movement.

'It's like a soliton,' Douarche said . 'A solitary wave of self-reliance.'

Unlike ocean waves with undulating shapes, which can be melted or shattered when touching the shore, the soliton is the only waveform, existing on its own and acting as a separate element. For example, when two solitons collide, they merge into one and then split into two elements with the same shape and velocity as before the collision. The first Soliton was recorded by Scott Russell in 1834, in a canal in Scotland. The scientist was very excited with the observable image and chased it many miles on horseback, then he built a 30-foot water tank in his yard and described the soliton's activity successfully. see.

The work began when Douarche and colleagues put E. coli bacteria in a sealed sealed box and measured the volume of oxygen as well as the bacterial density every 2 hours until the bacteria consumed all the initial oxygen.(Unlike humans, the bacteria do not die when oxygen is depleted, but they become inactive, later when they have oxygen they will work again.) Then the researchers open the lid for oxygen to enter.

The ring of immobile E. coli (green) is forming a wave in Libchaber's experiment.

The result: the bacteria in a state of complete silence begin to function; At first, the ones in the outer ring, close to the top of the box, then gradually to the farther. A few hours later, they began to separate in space: a moving group and a group that did not move, then intersected to form a circle in the area between the low oxygen zone and the completely oxygen-free zone. Here they form an independent wave that moves slowly but firmly towards the center of the box and does not change shape during the process.

This effect lasts for 15 consecutive hours and occupies a negligible amount (compared to bacteria). It is impossible to explain why the effect is due to the appearance of protein or increased energy in the system. Instead, the formation of the front of the bacterial mass depends on the dispersion of the active bacteria as well as the time it takes for the oxygen-deficient individuals to completely stop moving (15 minutes).In the above two conditions, the first factor allows the bacteria to move at a constant speed, the second factor that helps the front remain in shape.

However, not only is the front face formed.'To me, the biggest surprise is the bacteria that control the flow of oxygen in the area,' says Libchaber. 'There is a row of bacteria moving, but there is also a row of oxygen moving. And bacteria control this process very precisely with oxygen uptake. '

In theory, oxygen is one of the fastest diffusion molecules, moving from a high density area to a low density area, so that the farther away it is, the faster it will diffuse. But that is not what scientists have observed in this experiment. In contrast, oxygen enters the box very slowly in a straight line. The time and distance traveled by oxygen are proportional to each other.'This is not for biological reasons,' Libchaber said. 'It is because of a certain law of physics. And it is so sophisticatedly arranged that the only thing that is drawn is that we need to study more about bacteria. '

See also: Physical Review Letters 102 (19): 198101 (May 12, 2009); E. coli and oxygen: A motility transition; Carine Douarche, Axel Buguin, Hanna Salman and Albert Libchaber.