Bacteria are single-celled organisms known as prokaryotes. As such simple life forms, do they have any need for genetic information in the form of DNA? Find out more in this lesson, as you learn about chromosomal loops and plasmids.
Definition and Purpose of DNA
Within a family, there are often traits that parents and their kids have in common. You may be told that you have your mother’s nose. A daughter might be born with a head of curls that came from her father. Or perhaps, you were born with red hair, a trait only carried recessively by your parents.
At any rate, all characteristics about a person, from hair color to body type, are determined by genes passed down by their mother and father, and this blueprint of information is found on a very important molecule: DNA.DNA is short for deoxyribonucleic acid. This molecule contains all information for the development of every living thing. Of course, you may say, a being as complex as a human must have this important molecule. However, did you know that even the most simple single-celled life form has DNA?Yes, we are talking about a bacteria. Although fairly rudimentary, bacterial DNA makes it possible for colonies of bacteria to reproduce and spread. And spread they do – often multiplying at a mind-blowing rate.
In this lesson, we will examine bacterial DNA and understand its role in these tiny creatures.
Prokaryotes vs. Eukaryotes
When we talk about bacteria and DNA, are we talking about inherited traits? Not exactly.
Because bacteria reproduce asexually, this is not a situation in which a tiny bacteria family is marveling at what that their little ones got from mom or dad. Like in cloning, bacteria only inherit exactly what the parent cell had. However, just like in humans, DNA is there for replication and reproduction.Before we examine the DNA, we must first address the fact that bacteria are made of a completely different type of cell than organisms such as plants and animals.
Bacteria are prokaryotes, while other living things, like plants and animals, are eukaryotes. What’s the difference?Prokaryotes are a very simple type of cell, often referred to as one of the very first life forms. Inside them, we find nucleic acids (DNA or RNA) and some other macromolecules, such as phospholipids, proteins, and sugars. Eukaryotic cells, on the other hand, are complex cells chock full of organelles designed to do many jobs to keep the cell running smoothly.
DNA in Bacteria
Prokaryotic cells contain DNA that is, as you probably guessed, much simpler than that of our own cells. DNA found in eukaryotes is a complex twisted double helix molecule full of genes that determine everything about a living thing.
In contrast, do bacteria need DNA full of genes that will determine their hair and eye color, skin type, or future as an athlete? Of course not. Accordingly, the DNA is found in two basic forms: a chromosomal loop and ring-like plasmids.The chromosomal loop is literally a looping string of DNA. Since there is no true nucleus in a prokaryotic cell, the DNA is suspended in cytoplasm, or the fluid filling the cell. You can imagine the chromosomal loop as a tangled necklace held in a lovely gelatin mold.
This loop of genetic instructions provides information for that particular type of bacteria so that it can replicate and reproduce. Most bacteria reproduce by simply splitting in half, a process known as binary fission.From a biological standpoint, reproduction is really about passing along genetic information. So before the bacteria splits, it must replicate its DNA to make two identical strands. Once the process happens, each strand heads to opposite poles of the cell, and the cell is cleaved into two. The bacteria ‘child’ will contain the same original DNA as its ‘parent.
The Power of Plasmids
As for the plasmids, these are small circular rings of DNA also suspended in the cytoplasm. They don’t contain as many genes as the chromosomal loop, but have important and unique roles. Plasmids have the ability to turn on, or express, certain traits when needed. These genes are usually linked to their survival. In some cases, this ability is somewhat like having a superpower.
For instance, some plasmids can express a gene that creates resistance to antibiotics at a given time. Like a superhero turning on a force field as defense against the villain, bacteria become immune to the antibiotics that are attempting to destroy them. Although this is extremely beneficial for their survival, it is quite alarming for us.
Every living thing contains genetic information in the form of DNA, which is a molecule that contains all information for the development of every living thing. Although bacteria are very simple life forms, they, too, contain DNA.
Bacteria are prokaryotes, which are a very simple type of cell often referred to as one of the very first life forms, and their DNA is in a much simpler form than that of eukaryotes, which are complex cells chock full of organelles designed to to do many jobs to keep the cell running smoothly.Most bacteria reproduce by simply splitting in half, in a process known as binary fission. However, bacterial DNA is found in two forms: a chromosomal loop and plasmids.
The chromosomal loop is a looping strand of DNA that contains most of the genes and is important in cell division and sits in cytoplasm, the fluid filling a single cell in the absence of a nucleus. The plasmids, which are small, circular rings of DNA, also suspended in the cytoplasm, contain just a few genes and have the ability to express them when needed. It is in this way that bacteria can become resistant to antibiotics.