Go hand in hand, even bacteria can do it

Imagine such a scene of a race, the class bell rang, and the whole class rushed to the canteen
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Some students are 1.
5 meters tall, and they are struggling to run 1,000 meters.
Some students are 1.
8 meters tall and compete with others in two steps in one step
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Now the whole class set off together, each ran to the cafeteria with their own ability
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Do you think the team will get longer and longer, people will continue to be left behind, and the more they run, the looser they are? Or will the whole class remain basically intact at the moment of running to the cafeteria? Do you think that you will be able to take the lead when you are strong? Do you think that if you rotate your legs like flying, you can throw others two streets away? The answer is that no matter how far you run to the cafeteria, even if no one explicitly asks to maintain the formation, you can still maintain a complete group to reach the end
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(The picture comes from the Internet) Calm down, calm down, I didn't lie to you, this kind of situation really exists, it's just in the group of bacteria
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Recently, researchers from Fu Xiongfei's research group at the Institute of Synthetic Biology, Shenzhen Advanced Institute of the Chinese Academy of Sciences, revealed a mechanism for "bacteria groups to coordinate movement at a steady speed".
The results were published in eLife magazine.
At the same time, the paper was selected as eLife digest scientific digest review report
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(Report link: https://elifesciences.
org/digests/67316/all-together-now article link: https://elifesciences.
org/articles/67316) Research introduction E.
coli is a very common bacteria, although it is A single-celled organism, but there are several long flagella on the surface of the bacteria.
E.
coli can swim in the liquid or roll the body to change the direction of swimming by rotating the flagella
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If you encounter delicious or toxic or harmful substances, bacteria can move in a certain direction by adjusting the frequency of tumbling the body
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Although I look like a drunkard sometimes to the left and sometimes to the right, the movement still has a general direction in the long run
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The structure of Escherichia coli (the picture comes from the Internet) is like some people just clicked and read it and forwarded it to Moments of friends when they saw such an excellent article, while some people were indifferent; a single Escherichia coli is against chemotaxis (we usually think of bacteria Chemical substances with attractive ability are called chemotaxis).
The sensitivity is also different
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Some bacteria are very sensitive and can quickly detect the chemotaxis signal in the environment and determine the direction, and quickly gather to the high concentration area, while some are more numb and arrive slowly
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Schematic diagram of the difference between the abilities of bacteria's random swimming and chemotaxis (painted by Cai Zhuran and Wu Wei) But if a group of bacteria encounters a chemotaxis, must the bacteria that run fast among them always charge forward? How do bacteria that run fast and bacteria that run slowly, respectively? Teacher Fu's team designed a clever experiment to observe this process
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They set up a long and narrow channel in which chemokines (200μM Aspartate Asp, which can be considered a delicacy in the eyes of bacteria) are dispersed throughout the channel, and the cultured bacteria are dripped at one end of the channel
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The bacteria on this end felt the chemokine, and the index finger moved and started to eat
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Slowly, the concentration of chemokine at this end was consumed and the concentration decreased, but the chemokine at the other end had not consumed a higher concentration, and the bacteria began to rush to a table of good dishes at the other end
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Just like when a student rushes from a class without food to a cafeteria with food after class, the bacteria move, and it is natural to distinguish which ones are running fast and which ones are slow
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A moving picture of a single bacterium that is random but directional as a whole (picture source: Fu Xiongfei's research group) But! Bacteria don't get stale in autumn, you can't see it clearly
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Therefore, Mr.
Fu also mixed some bacteria that can emit light (yellow fluorescence) with ordinary bacteria.
The luminescent bacteria are entrained and moved by the rice-grabbing bacteria.
Therefore, the movement path of the luminescent bacteria and ordinary bacteria can be considered to be the same
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This design is wonderful! (The picture comes from the Internet) After researchers track and observe the movement trajectory of each bacteria
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They found that every bacteria reciprocates in the group: when the bacteria fall behind the group, they will swim very hard forward
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However, once they swim to the front of the group, they slowly lose their motivation to move forward, and they will not push forward again until they are overtaken by other bacteria and land at the back of the group
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It seems that there is a big hand at the back of the group, and whenever anyone is left behind, they will urge them, get up, come on! Run! Have you studied? Have you read the literature? Did you plan to complete the last group meeting? When will the results of your experiment come out? Come to my office later.
.
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What is this invisible big hand? To explain this weirdness Teacher Fu’s team established a mathematical model to simulate the trajectory of bacteria, and found that this motivating force for bacteria is likely to come from the concentration gradient produced by the consumption of chemoattractants by the bacterial population! In other words, in the bacterial population, the bacteria that run fast can eat meat, and those who run can only drink the rest of the soup.
The bacteria that drink the soup can learn from pain and work hard, and if they don’t catch up, the food will be cold, and the slower will eat.
Dust it
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And when they swim to the front of the group, because the chemotaxis concentration is almost the same everywhere, the table is full of good food, and the left is to eat and the right is to eat, but they don't know where the "front" is
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In short, the bacteria that solves the warmth problem are full of good things.
It floats and you don’t know the way forward~ This explanation is not only reasonable, but also after comparing the experimental data with the mathematical simulation results, it is one of the two.
It's a coincidence, it's amazing
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So far, the case where strong and weak bacteria in a group reached the end at the same time is solved! In view of your (wo) mathematics level, you certainly can't understand the strict reasoning of Teacher Fu, I will not put the formula.
For details, please refer to "Read the original text".

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Schematic diagram of the characteristics of bacterial movement behavior in different spatial positions in a group (illustrated by Cai Zhuran and Wu Wei).
The significance of the study.
After reading this, you may have to ask, if you are from the perspective of God, will the bacteria that run fast become live Lei Feng? This is not a disguise The slow bacteria waiting to run behind (although it doesn't want to wait for the subjective will of other bacteria)? Of course not
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There are a large number of social creatures living in nature.
In order to find more abundant food and a more suitable environment, they often need to migrate in groups
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However, different individuals will always have differences in their mobility and navigation capabilities.
If they are allowed to move freely, some individuals will inevitably be left alone and fall into a dangerous environment
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For example, the group migration of penguins in the cold wind can reduce heat loss, the group migration of herbivores can reduce the possibility of predation, and bacteria can better protect themselves and expand the population when they exist in complete groups
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Therefore, a robust speed coordination mechanism is essential for a group
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When the bacterial colony migrates, there is such a "pushing force" that is strong at the back and weak at the front, which is a huge benefit for those less sensitive bacteria
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Because whenever they are left behind by their chemotaxis-sensitive companions, they will receive a greater impetus, driving them forward
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However, those individuals who swim in the front lose the direction to continue swimming in the “comfortable” environment with high concentration of chemotaxis
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Of course, it is precisely because of this mechanism that individuals with different abilities can co-exist in the same group in a coordinated manner and move forward at the same average rate, ensuring that individuals with different abilities can migrate to a suitable living environment together.
The "hand in hand" of bacteria
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Schematic diagram of bacteria forming an ordered queue (painted by Chen Qian, Cai Zhuoran and Wu Wei) Intelligent creatures can still use language commands and other methods to transmit information between individuals
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But for single-celled organisms such as bacteria, there is no transmission of information by mouth and ear, and no hands and feet to support it
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Their available information transmission methods are extremely limited, but through evolution, a very simple mechanism has realized the simultaneous migration of bacteria with different abilities
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I have to lament the power of evolution
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Ending: At the end of reading, some smart friends may ask, the bacteria in the culture medium have a driving force where there is a poor chemotactic concentration, so when there is no chemokine in the culture medium, what is the trajectory of the bacteria? In the absence of a concentration gradient, bacteria are also in motion, but there is no directionality and random roaming without a fixed direction.
The speed of simple swimming is not slow, but the overall position is almost unchanged
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Therefore, the main driving force for the movement of bacteria is the "concentration gradient".
The focus is on the gradient rather than the concentration.
Only when there is a concentration difference can there be a direction to move forward.
If there is no concentration difference to guide the direction, there is no direction to move forward, let alone.
The speed is slower
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In general, having a guiding direction is the most important
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Bacteria is the same.
People can move firmly in one direction only when they have a clear goal.
Tomorrow I change my goal and I want to learn painting! The day after tomorrow I changed my target and I still want to learn code! ……Even if you are tired from studying every day, but doing different things every day, it’s hard to say that there is any substantial improvement, isn’t it? Note: All the dry meals, running, complacent, strenuous, etc.
of bacteria in this article are anthropomorphic descriptions.
Bacteria, as single-celled organisms, have no subjective will and are just direct responses based on environmental stimuli
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Anthropomorphic description can increase interest, but the understanding of natural laws should never be accompanied by personified judgments
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References: 1.
Bai, Y.
, He, C.
, Chu, P.
, Long, J.
, Li, X.
, & Fu, X.
(2021).
Spatial modulation of individual behaviors enables an ordered structure of diverse phenotypes during bacterial group migration.
eLife 2021;10:e67316 2.
Dufour, YS, Fu, X.
, Hernandez-Nunez, L.
, & Emonet, T.
(2014).
Limits of Feedback Control in Bacterial Chemotaxis.
PLoS Computational Biology , 10(6).
3.
Fu, X.
, Kato, S.
, Long, J.
, Mattingly, HH, He, C.
, Vural, DC, Zucker, SW, & Emonet, T.
(2018).
Spatial self-organization resolves conflicts between individuality and collective migration.
Nature Communications, 9(1).
Source: Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences