Bacteria, also known as prokaryotes, refer to a large class of primitive single-cell organisms whose nuclei are not wrapped in a nuclear membrane and contain only naked DNA called a nucleoid region. It is mainly composed of cell membrane, cytoplasm, ribosomes and other parts, and

bacteria, also known as prokaryotes , refer to a large class of primitive single-cell organisms with nuclei and without a nuclear membrane, and only a naked DNA called the nucleoid region. It is mainly composed of cell membrane, cytoplasm , ribosome and other parts, and the diameter of most bacteria is between 0.5~5μm.

However, according to the official website of the American " Science " magazine, an American research team published an article in the "Science" magazine issued on the 24th, saying that they discovered huge bacteria with a maximum length of 2 centimeters.

In other words, this giant bacterium is 5,000 times larger than most bacteria. This gap is like one person meeting another person who is as high as Mount Everest ! Is really a "discovery" and not an "invention"? Can it be considered a bacterium if it is so big? How did you get so big?

At first glance, the slightly turbid liquid in test tube looks like a spoonful of rainwater, filled with leaves, debris, and even lighter unknown threads. But in fact, in the petri dish , the threads floating above the leaf fragments are individual bacteria visible to the naked eye.

The bacterium itself was discovered in 2009 by Olivier Gros, a professor of marine biology at the University of Guadeloupe Antilles, in a mangrove swamp in the Caribbean. At the time of the discovery, marine biology professor Olivier Gros was searching for bacteria that use sulfur to produce energy.

However, when he poured his swamp water sample into a petri dish, he discovered something very strange. Thin "fan-like" lines visible to the naked eye float above the leaves and soil.

Above: View of a sampling site in the mangroves of Guadeloupe

Over the next few years, researchers used fluorescent tags, After some research on the common organism, they were surprised to find that it was a sulfur-oxidizing prokaryote and named it Thiomargarita magnifica.

Of course, since Sulfothococcus maxima is a prokaryotic organism, it is indeed well-deserved to be called a bacterium. And recently, researchers reported their findings in the magazine Science, revealing the secret that the size of this giant bacterium exceeds the theoretical limit.

Why can Sulfothococcus maxima grow so big?

It is well known that as cells grow older, their volume increases in proportion to their surface area. In this way, when the cell increases to a certain extent, the surface area of ​​the plasma membrane is not suitable for the exchange of internal and external materials of the cell. In order to maintain an optimal survival condition, the cell must maintain an optimal surface area, thus limiting the infinite volume. increase.

At the same time, the copy number of some important molecules in cells is very small. When the cell volume increases, the concentration of these molecules becomes more and more dilute. Some important biochemical reactions require a certain concentration to proceed, so within the cell Molecular concentration has become another factor limiting the unlimited increase in cell size. But Sulfothococcus maxima has its own unique way to solve the above problem of limiting body size.

Generally speaking, bacteria are a type of prokaryotes, and their genetic material floats in the body without being wrapped in a membrane. But the DNA of Thiolobicus maxima is contained in a special membrane, but it is still different from the nucleus of eukaryotic cell . Therefore, S. maxima is still a prokaryotic organism.

The researchers then decided to call these tiny bacterial organelles "pepins" (referring to the small seeds found in fruits such as watermelon or kiwi).

Because S. maxima has more membranes to work with, it can distribute the protein machinery that makes ATP (adenosine triphosphate). ATP is the most direct source of energy in organisms and the "energy currency" for intracellular energy transfer. It is responsible for storing and transmitting chemical energy .

Other bacteria have no membrane inside, so the only place to put the ATP-generating machinery (ATP synthase) is in the cell envelope that surrounds the entire organism.Therefore, it is difficult for other bacteria to transmit energy very far compared to Sulfothococcus maxima, which limits the size of most bacterial cells.

Another factor that limits the size of most bacteria is that they must be able to double in size before they can split in half to reproduce. However, Sulfothococcus maxima only needs to separate a small part of itself to produce daughter cells to reproduce, so its body size is not limited by this factor.

Moreover, the genome of Thiolobia maxima is much richer than that of other bacteria, with 11,788 genes, compared with only 3,935 genes of common prokaryotes.

In short, the discovery of giant bacteria makes us realize that human beings have a bias in their understanding of the size of microorganisms. Maybe there may be other giant bacteria hiding around us, hiding under our noses, and we haven't discovered them yet.

#American scientific research team discovered 2 cm long giant bacteria#