Prokaryotes

Today it is widely known that one of the smallest and most abundant living organisms on earth go by the name, “prokaryotes.” These microorganisms have been the center of much scientific investigation. The more biologists understand these creatures, the more they grow in fascination of them and the things they can do to help us advance in medicine, technology, and further scientific investigation.

Prokaryotes are normally unicellular organisms and are well known in how they differ from eukaryotes. However, here you will not learn about the differences between eukaryotes and prokaryotes, but about the importance prokaryotes have in biology and for future human development and understanding.

Prokaryotes are the oldest, most abundant, and most adaptive organisms on earth. They can handle extreme conditions, such as lethal radiation and metal-dissolving acidity.  A handful of soil could contain more prokaryotes than the total number of human beings that have ever lived. Yes, they are astonishing. These tiny little organisms come in a variation of shapes like spherical (cocci or coccus), rod-shaped (bacillus or bacilli), and spiral-shaped. In order to better study these creatures, the prokaryotic domain has been divided into two well differentiated ones, bacteria and archaea.

Archaea are considered to be the oldest living things on earth that adapted to the planet’s early and “extreme” conditions. For that reason archaea are also referred to as extremophiles. Because they have been found in the most impossible places to sustain life on earth, some research has taken scientists to hypothesize in the fact that these organisms might also be found in other planets. If this is correct, then micro-extraterrestrial life might pretty well exist in other planets. Archaea also consume 300 billion kilograms of methane per year, reducing the greenhouse effect! To add to your knowledge, know that archaea have structures similar to those of bacteria and contain a DNA structure that also resembles the one of eukaryotes.

Bacteria are more abundant than archaea. Even though much popular belief toward bacteria is that they are harmful, much of bacteria are beneficial to the environment and ultimately to human beings. To fight and destroy harmful bacteria, we have developed drugs denominated, “antibiotics”. Bacteria have a cell wall that is made out of a substance called peptidoglycan. What some antibiotics basically do is destroy the peptidoglycan to penetrate the microbe and eliminate it. We are told that humans have no peptidoglycan, and this is why antibiotics supposedly have little to no effect in us.

There are bacteria that contain a thick layer of peptidoglycan within them and others that have a thin layer “sandwiched” between two plasma membranes. Bacteria with a thick layer of peptidoglycan are called, Gram Positive Bacteria, and those that have a thin layer are known as Gram Negative Bacteria. How do we know which are positive or negative?  Through a process known as Gram staining. Here people in a laboratory use a substance to analyze the cell wall of the bacteria. If the bacteria turn violet, it is positive. If the bacteria turn pink, it is negative.  Gram- negative bacteria tend to be harmful.

We know that about 50% of prokaryotes are capable of taxis or movement towards and away from stimulus using a complex structure called a flagellum. The flagellum is made of 42 different proteins and looks like a tale that can function like a propeller and in many other ways to move the prokaryotes around. The velocity of a prokaryote can exceed 50 times its body length per second, this is equivalent to a human running as fast as 190 miles per hour.

Now let’s deepen our understanding; the word prokaryote literally means “before a nucleus”. Therefore, the question arises of “where or how do they contain their DNA?” Well, the answer is that prokaryotic DNA is in a ring-shaped chromosome that is supercoiled together by specialized proteins inside the cell (this is not applicable to the Archean domain).

For a longtime, the manner in which prokaryotes reproduce was fairly unknown. However, it has currently been understood that prokaryotes reproduce through a process similar to that one of mitosis known as “Binary Fission”. In this process, prokaryotes can reproduce very rapidly and double their population size in an hour. This rapid reproduction enables frequent genetic mutations within the cells, creating diversity in their genes or DNA. Their genetic diversity can be maintained by the transformation, transduction, and conjugation of genes.

In transformation the cells pick up or “download” genetic material from the environment, ultimately altering their own DNA. Different from transformation, is transduction, where special viruses called “phages” insert genetic material in prokaryotes. These survive the “invasion”, assimilate the new genes and change their original structures. Finally, in conjugation, two bacteria “conjugate” or join together to transfer genes from one to the other. This process is also known as “horizontal gene transfer”.

Certain types of prokaryotes provide ecosystems and eukaryotic cells with usable nitrogen. These prokaryotes are like the ones of cyanobacteria and methanogens. They carry out nitrogen fixation and convert atmospheric N2 (nitrogen) into ammonia (NH3). Cyanobacteria only need light, carbon dioxide, nitrogen and some other minerals to survive in a variety of habitats. Cyanobacteria are perhaps the most successful microorganisms on earth.

Some prokaryotic cells live in colonies or filaments. In colonies, prokaryotes cooperate with each other, divide labor and share resources between them to satisfy each other’s needs. Then, these colonies might form biofilms, which are micro structures of cells that stick together on living or nonliving surfaces.

Finally, prokaryotes are extremely important for the ecology within our planet, business, and even for the correct functioning of our bodies. Prokaryotes are decomposers and unlock many valuable nutrients in the tissues of dead organisms to make them for other species to consume them. One of these nutrients is nitrogen, which is unlocked through the process of nitrogen fixation that some prokaryotes undergo.

There are about 150 sorts of bacteria living on our skin. You can find about 10 million of them in every square centimeter of our dermis (skin), but don’t worry, they usually don’t harm us. However, that is not all, but nearly 1,000 beneficial species of bacteria live in our intestines. One of the most studied ones is Escherichia Coli. Bacteria living in our intestines help us in our digestion, like in the processing of proteins and carbohydrates to produce vitamins that enable us to be healthy. Some intestinal bacteria emit signals to human intestine cells, inducing the production of blood vessels, useful proteins, and etcetera. Research has also suggested that having an abundance of bacteria with us improves our emotional well-being. Yes, we are never lonely.

Technology, has found the hand of prokaryotes as well. Yogurt and cheese, for example, need prokaryotes for their making. Gene cloning, transgenic crops, the synthesis of PHA for biodegradable plastics, the decomposing in sewages, the breaking down of petroleum and other pollutants, the precipitation of uranium out of groundwater, the production of certain vitamins and drugs, the synthesis of ethanol and fuel, and many more, are some of the examples of the benefits that tiny microorganisms, as prokaryotes, can do for humanity and planet earth. As scientific research advances, biologists grow in greater awe of them.

 

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