By Barry C. Fox, M.D., University of Wisconsin
There are roughly 100 trillion cells in the human body, and 90 trillion of them—that is 9 out of 10—are different kinds of bacteria. “Microbes” is a general term that is used for organisms that are too small to be seen by the naked eye. And, in the human body, these include bacteria, viruses, yeast, protozoa that lie in between these categories.
What Is Bacterium?
The term “bacterium” was invented in the 19th century by a German biologist, Ferdinand Cohn, based on the Greek word “bakterion”, meaning small rod. However, there are three shapes of bacteria—rods, spirals, and spheres.
Bacteria are extremely small, usually less than two microns in size, and are found everywhere. Bacteria are single-celled organisms that contain the barest essential components for staying alive and reproducing— chromosome, ribosomes, cytoplasm, and an outer membrane.
A Prokaryote
Bacteria are a simple form of life known as “prokaryotes”. In the center is a genetic code material known as deoxyribonucleic acid, or DNA, which is bundled into a central structure known as a chromosome.
The DNA encodes for a specific sequence of building blocks known as amino acids, and these amino acids are combined into proteins at the ribosomal structure. Proteins are subsequently used to control cellular function. The internal fluid, otherwise known as cytoplasm, is surrounded by an outer membrane, and prokaryotic bacteria hence resemble a water balloon filled with bacteria.
What Are Eukaryotic Cells?
Microorganisms that are more complex than the prokaryotic bacteria contain eukaryotic cells that have a nucleus that contains multiple strands of DNA organized into multiple chromosomes. They also have more complex internal structures such as mitochondria, which produce internal energy.
Eukaryotic cells utilize more formal membrane structures, such as a nucleolar membrane, to contain DNA. The simplest one-cell eukaryote is a protozoan called a “paramecium”. Other examples of multicellular eukaryotes are fungi, plants, and animals.
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DNA Replication
Prokaryotic bacterial reproduction is under the control of the DNA in the chromosome. Bacteria multiply rapidly by a process known as binary fission, but the repeat replication of DNA is prone to errors.
As a result, it can result in genetic mutations that can either lead to a survival advantage or disadvantage. For example, a germ might develop resistance to an antibiotic that is trying to kill it, or the mutation can be unfavorable and lead to the destruction and death of the germ.
DNA replication is controlled by an important enzyme known as “DNA polymerase”. DNA polymerase is a prime antibiotic target since the goal is to halt DNA replication.
Some DNA may not be in the center of the cell, but located in the cytoplasm, forming circles of DNA known as “plasmids”. Plasmid DNA may also be transferred from one bacterium to another through various mechanisms when bacteria touch one another.
Conjugation is one of these means. When this happens, genetic characteristics among bacteria are shared. This is important in the development of bacteria that are resistant to multiple antibiotics, or for other evolutionary traits that support their survival.
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Functions of Enzymes
The synthesis of cellular proteins such as enzymes or toxins is under the control of DNA. It acts through the ribosomes, which combine amino acid building blocks in the cytoplasm. The ribosome is also an excellent target for antibiotics because it can interfere with protein synthesis.
Enzymes play a vital role and are responsible for controlling all the ongoing work in a cell. They are chemical reaction machines, which either break molecules apart or put them together.
Another function of an enzyme is to link amino acid building blocks together to form a protein. A bacterium may have over 1000 different types of enzymes floating around in its cytoplasm at any time.
How Do Bacteria Interact?
For bacteria to interact, there are special structures called fimbriae and pili on the surface that can help them attach to other bacteria or even to human cells.
These interactions can be divided into three general categories. First, some germs are good bacteria and help humans directly, such as assisting in food digestion. There are some germs that are known as “commensal bacteria”. They coexist with other bacteria without causing any harm to humans. And finally, some bacteria are harmful and are known as “pathogenic.”
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How Do Good Bacteria Help Humans?
Bacteria can be beneficial as well as harmful for human beings. However, there are some “good bacteria” that help humans directly.
One of the main jobs of the bacteria in the intestines is to break down nutrients, such as sugars and fats, which humans otherwise cannot digest. Most of these gut bacteria do not like the oxygen in the air and are known as anaerobes.
Besides aiding in digestion, gut bacteria also synthesize certain vitamins and aid the immune system. Specifically, Escherichia coli or E. coli is a common bacterium in the intestine. Unlike others, this germ happens to like oxygen, so it’s known as “an aerobic bacterium.” It synthesizes vitamin K, which is essential for normal blood clotting. W
hen patients receive antibiotics, the antibiotics can kill the good E. coli as innocent bystanders and alter clotting function.
Common Questions About Bacteria
Bacteria are a simple form of life known as “prokaryotes.” The term “bacterium” was invented in the 19th century by a German biologist, Ferdinand Cohn, based on the Greek word “bakterion,” meaning small rod.
Deoxyribonucleic acid or DNA is a genetic code material that is present in the center of prokaryotic bacteria, which is bundled into a central structure known as a chromosome.
One of the main jobs of the bacteria in the intestines is to break down nutrients, such as sugars and fats, which humans otherwise cannot digest.
