Who is the "giant" in microorganisms?

Recently, a French scientist has separated from the Plaza of the Caribbean Mangrove Beach. A new type of bacteria called gorgeous sulfuria (huge sulfurflyzaccharides) have a amazing 2 cm size, and it is easy to visible to the naked eye. The bacteria growing to the same size as the worm is indeed staggering.

The contrast between huge sulfur and pearl (white bright line) and coins (picture source: reference 5)

So why do we define gorgeous sulfuria as bacteria? Why does it grow to such a huge size? Is there such a giant in other microorganisms? To answer these questions, we have to start with the classification of creatures and the differences and differences between various microorganisms.

The most mainstream biological classification method -three domains say

The classification of creatures is a very important scientific issue for humans. Only correct classification can better understand and understand different creatures, so as to better use or protect them. At present, in the biological world, the relatively mainstream cognition is divided into three categories: biology, ancient bacteria, and genuine nuclear biological domains. This classification method is based on nuclear glucose RNA sequences, rather than simply depend on anatomy between species. Features, with relatively high scientificity.

Three domains saying schematic diagrams (picture source: reference 2)

It is worth mentioning that the virus does not belong to any of the above categories. This is because the virus does not have the ability to survive separately from cells, and only shows the characteristics of life -like life after infection. Therefore, in the above classification method, the virus often exists as a non -biological supplement.

There are certain similarities between the three domains that the biology of the bacteria and the ancient bacterial domain. Both are single -cell creatures, and the cell types are prokaryotic cells. However, because there are fundamental differences in the aspects of cell membrane lipids and ribosome RNA, bacteria and ancient bacteria have been divided into two domains. In fact, their ancestors have evolved independently from about 2.7 billion years ago. It is two completely different creatures.

It should be noted that although the name of ancient bacteria has the saying "ancient", from the perspective of evolution, ancient bacteria are not "ancient bacteria" or the ancestors of modern bacteria. In fact, the evolution of ancient bacteria is closer to the nuclear creatures, and even widely considered the ancestor of the true nuclear creature.

True cells and primary cell schematic diagrams (picture source: Wikipedia)

Although there is also a very simple single -cell creature in the eukaryotic creatures, in essence, their cells are all kinds of eukaryotic cells, and compared with prokaryotic cells, there is a fundamental difference in structure. True nucleus contains a nucleus, so the name of the true nucleus is obtained. True nucleus also contain other cellular devices, such as mitochondria, chloroplast, golf matrix, etc. Compared to the true nucleus, the nucleus generally does not have an endometrium and the nucleus wrapped without nuclear membranes, the intracellular non -chromosomes, the DNA chain is not spiralized, and it exists in the cytoplasm in the form of free. Cells (such as mitochondria or chloroplasts).

All in all, the structure of true nuclear cells is much more complicated than prokaryotic cells. The various animals and plants we see in our daily life (of course, including humans itself) are composed of real nuclear cells, belonging to the true nucleus.

Various eukaryotes (Picture Source: Wikipedia)

Microbial giant selection, the qualifications are important

After speaking of the classification of creatures, let's take a look at how microorganisms should be classified. Microcat who is difficult to see directly with the naked eye, the general name of the naked eye is that their classification is not recognized, and there is no rigorous biological basis.

At present, the biological community tends to divide microbes into six types. They are algae, native animals, fungi (fungi), bacteria, ancient bacteria, and viruses. The first three of these six microorganisms belong to the real nuclear biological domain, each with bacteria and ancient bacteria, and the virus belongs to non -biological. However, for us ordinary people, everyone has taught the virus. In our daily cognition, the virus has long been the representative of the microorganism.

It must be pointed out that among the three genuine creatures: algae, primary animals, and fungi (fungi), although many members are small creatures that cannot be seen by showing microscopes, there are also many "giants" exist. For example, the representative of fungi -mushrooms, it is easy to grow to an amazing body. For example, Chinese scientists have discovered a mushroom that is known as the largest fungi on the planet in 2018, and its length has reached 12 meters.

However, the existing literature reported that in 1998, scientists of the US Forestry Administration discovered an Armillaria Ostoyae in Oregon. The results of the DNA measurement at different locations, the individual of this fungus covers an area of ​​890 hectares, which may grow in the forest for about 2400 years.

Some people may say that mushrooms are multi -cell fungi, which is not unusual to grow. That's right, but many single -cell algae and single -cell native animals can also grow to the extent that they are microorganisms. For example, the umbrella algae mentioned in the high school biology textbook is a single -cell algae. Its cell core is based on the base, and there are fake roots around the surrounding area. The size of the umbrella algae is actually a huge 2 to 5 cm, and it is not stained with microorganisms. Some more exaggerated single -cell algae and single -cell native animals can reach tens of centimeters or even a few meters long.

Several huge single -cell creatures, from the left are the golf velvet, the leaf fern, and the umbrella algae (picture source: Wikipedia). Generally, there is no more than one nucleus inside the cells. It is a so -called "component" form between multiple cells. The reason why they are single -cell species is because the structure of their bodies is composed of the structure of different cells without cell walls or cell membranes.

In this way, the real microorganisms can only be selected in bacteria, ancient bacteria and viruses.

Microbial giants who subvert cognitive

Looking at bacteria first, before this super giant bacteria was discovered, the world's largest bacteria (volume) in the world was kept by Namibia Sulfia. In 1999, this bacteria was found in the marine sediment of the Namibia continent. Its average diameter is 0.1 to 0.3 mm, and the largest individual even reaches nearly 1 mm. It can be observed with the naked eye. The length of the E. coli that we are very familiar with is only a few microns, and the volume between the two is thousands of times.

The huge sulfuric pearls discovered this time directly refreshed the previous records thousands of times, and their length can reach an exaggerated 2 cm. Not only can it be visible to the naked eye, but also can be easily pinched with mules, which is similar to human eyelashes. If the height of adults is compared with the size of ordinary bacteria, the height of huge sulfuric pearl is Mount Everest, which is more than 5,000 times that of ordinary bacteria.

The size of the huge sulfur and pearl (A/B) and E. coli (picture source: reference: reference 1)

Compared with ordinary bacteria, the DNA size of huge sulfur is greater, and the number of genetic information is about 3 times that of E. coli. As a prokaryotic creature, it does not have a nucleus -like nuclear structure, but inside its cells, it has multiple small cells carrying DNA. Around these DNA "cores", the protein was synthesized in large quantities, thus growing into a huge size. Its discoverers initially never thought that it was a bacteria, but after DNA testing, it confirmed that this behemoth was indeed an independent individual.

Most of the ancient bacteria are polar creatures living in extreme environments, and ordinary people don't know much about them. At present, the largest ancient bacteria, the size is about a dozen microns, and the largest pole -shaped ancient bacteria can reach nearly 100 microns (0.1 mm). However, it may be restricted by the living environment. Human beings have not found the type of ancient bacteria that can be called "huge" so far.

Ancient bacteria is a frequent visitor to deep -sea hot springs (picture source: Wikipedia)

The virus structure is simple, lack of extracellular independent survivability, and is therefore excluded from the three domains. Simple structure means that the size is small. It is for this reason that the virus discovery is hundreds of years later than the bacteria. After the invention of the electronic telescope, humans really observed the virus. Taking the new coronal virus as an example, its size is only 120 nanometers, which is a hundred % of E. coli in volume. However, in recent years, many giant viruses have been discovered one after another, which has also greatly subverted human recognition of the virus before.

In 2003, French scientists discovered Mimivirus, which reached about 400 nanometers in size. Its discovery also marked that huge viruses began to enter human vision. At present, the largest virus discovered by humans is a wide -mouth tank virus reported in 2014. This virus belongs to the double -chain DNA virus and is found in Siberian frozen earth ice core samples, the maximum length is close to 2 microns, and the diameter is 0.5 microns. In terms of appearance, it is very similar to the wide -mouth pot potted in the ancient Roman period, so it is named. The wide -mouth tank virus after thawing has the ability to infect transformers and cause its death. Therefore, in addition to the topicality, people also have unprecedented concerns about the release of unknown pathogenesis after the global warming caused by the thawing of permanent frozen soil.

The size comparison of the size of the wide -mouth tank virus and the new coronary virus (right) (picture source: Wikipedia)

From a certain perspective, microorganisms are the real masters of the earth, and they appear in every corner of the earth. From the fiery deep -sea hot fluid spraying to the permanent frozen soil that was frozen for thousands of years, microorganisms were stubborn and reproduced, and eventually played a key role in the Earth's energy and material cycle. Earth shaped microorganisms, and microorganisms in turn shaped the earth. They are magical diversity in evolution, allowing humans to continue to break through the perception of the concept of "creature". Perhaps there will be a huge microorganism in the future to refresh the microorganism list.

Produced: Popular Science China

Production: Guo Fei (Yantai University)

Producer: China Science Popularization Expo

references

1. A Centimeter-Long Bacterium with DNA Contained in Metabolical Active, Membrane-Bound Organelles

https://www.science.org/doi/10.1126/sclence.abb3634

2. The 30th round of 2.7 billion years ago の "ご Ancestor 様" が バ バ バ バ テ テ テ 込む 込む り 込む 込む

https://gendai.ismedia.jp/articleS//73944

3. Want to observe cells without a microscope?These "giant" single-cell creatures can satisfy your https://tech.sina.com.cn/roll/2020-01-06/doc- IIHNZHA0600724.shtml

4. The world's largest ス イ ル ス "ピソウ イ ル ス" の detailed structure を low -temperature electronic 顕 microscope で analysis

https://www.nips.ac.jp/release/2017/11/post_352.html

5. LARGEST KNOWN BACTERIA in the World Are Visible to the Naked Eye

https://www.newscientist.com/article/2325909- largest-known-bacteria-the-world-Visible-the-naked-Eye/

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