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The mystery of prokaryotes: Why don't they have a nucleus?
Under the vast starry sky of life, prokaryotes are like a shining pearl, allowing our biological knowledge to bloom anew. These simple single-celled organisms, with their unique structure and ability to reproduce, challenge our understanding of the nature of life. Why, after all, do prokaryotes lack a nucleus? This question has triggered in-depth exploration and discussion among scientists.
Prokaryotes are single-celled organisms that lack a nucleus and other membrane-enclosed organelles.
Prokaryotes can be divided into two major categories: bacteria and archaea. Because of their early appearance on the evolutionary tree, scientists believe that prokaryotes predate the emergence of eukaryotes, making prokaryotes a crucial role in the evolution of life. The simple structure of prokaryotes enables them to survive in a variety of extreme environments, including areas of high temperature, high salt, and low oxygen.
Prokaryotes’ structure
The cell structure of prokaryotes is relatively simple. Unlike eukaryotic organisms, their internal cellular components are not surrounded by membranes. In prokaryotes, DNA is free in the cytoplasm in the form of a circular chromosome. This structure is called a ribosome and is not surrounded by a nuclear membrane.
In prokaryotes, the genome is protected by a DNA/protein complex, forming a structure called a ribosome in the cytoplasm.
In addition, there are many different structures inside prokaryotes that, although not surrounded by membranes, have basic functions. For example, bacteria can possess tiny rudimentary skeletal structures that provide the ability to move and carry out important biochemical reactions.
Reproduction and Gene Transfer
Prokaryotes usually reproduce asexually, the most common method being binary fission. However, horizontal gene transfer is one of the important ways for its survival and evolution. This means that gene conversion can be carried out between different bacteria through various means such as virus-mediated transduction, conjugation and natural transformation, thereby promoting genome diversity.
In bacteria, gene transfer can occur in three ways: virus-mediated transduction, conjugation, and natural transformation.
The gene transfer mechanism of archaea is relatively unique. For example, some archaea can form cytoplasmic bridges between cells and directly transfer DNA, which makes scientists rethink the way genes are transferred and its impact on genetic evolution.
Biofilms and communities
Although prokaryotes are single-celled organisms, many prokaryotes can form stable communities called biofilms. These biofilms can exist on solid surfaces or at the interface between liquid and air. They are usually composed of multiple tiny colonies, and water flows between these colonies to maintain the life activities of the biofilm.Bacterial biofilms are often resistant to antibiotics and can make them difficult to remove from surfaces where they have colonized.
The complex structure of biofilms and the interactions between cells make the lifestyle of prokaryotes close to that of multicellular organisms, so their behavior, signal transmission and even self-death phenomena undoubtedly increase their ecological importance. .
Prokaryotes in the Ecological Environment
Prokaryotes are not limited to a specific environment on Earth; they can be found in a wide range of environments, from the icy soil of Antarctica to deep-sea hydrothermal vents. The diversity of prokaryotes enables them to adapt to a variety of environments, including extreme conditions such as very high temperatures and salinity.
Prokaryotes have a more diverse metabolism than eukaryotes, which allows them to have unique survival strategies.
The resilience of these adaptations makes them play an indispensable role in nature, especially in maintaining balance and producing organic matter in different ecosystems, prokaryotes are the most basic participants.
The significance of evolution
The origin of prokaryotes may be traced back to about 3.5 billion years ago, when they were the earliest life forms on Earth. Regarding the evolution of prokaryotes, some scientists have proposed that they may have evolved from primitive cells, with eukaryotes being the result of later evolution. All of this has triggered in-depth thinking in the scientific community about the origin and evolution of life. The oldest fossil evidence shows that prokaryotes existed shortly after the formation of the Earth, while eukaryotes appeared about 1.7 billion years ago.
From the evolution of prokaryotes, we have seen a series of interesting changes and adaptations. So, how can the life forms of prokaryotes inspire us to think about life again?
