What are the types of reproduction in microorganisms?
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If you look around you, the surfaces of most things seem clear and empty. You might have even cleaned them recently. But, if you take a closer look under a microscope, there is a world teeming with life crawling on the surface of your table.
These are microorganisms, or living things that can only be seen with a microscope. Most people think of bacteria when they think of a microorganism, but there's actually a variety of kinds. Any organism that you can't see with the naked eye counts, like yeast, parasites, and other protozoans like a paramecium.
For these organisms to carry on their life cycles, they must reproduce. Let's look at four methods microorganisms use.
Binary Fission
Binary fission is the simplest type of reproduction. Bacteria use this strategy to divide one cell into two identical cells. Bacteria have a very basic structure, with a rigid cell wall surrounding a thin plasma membrane to protect the cell. Inside, the DNA (genetic material) floats around in the center.
In the first step of binary fission, the DNA duplicates.
Next, the cell starts to elongate and the DNA is moved to either side of the cell.
Once the cell is long enough, a new cell wall forms in the center and two new cells are made.
Bacteria divide incredibly quickly using this method, sometimes every twenty minutes. This strategy allows pathogenic bacteria, like Streptococcus pyogenes, the cause of strep throat, to quickly colonize a human host.
Budding
Yeast use a more complicated method, as their cell structure is more complicated than bacteria. Yeast are called eukaryotic cells, meaning they have a nucleus holding their DNA and lots of little compartments inside the cell called organelles.
During budding a small outgrowth of the cell appears, like a bud from the main yeast cell. As the bud grows bigger, DNA duplicates inside the nucleus and the nucleus buds as well, creating a new nuclei in the bud. When the process is complete, the bud detaches from the main cell and forms a new cell.
Yeast can be helpful to us, such as Saccharomyces cerevisiae, which is used to make beer and bread. However, some yeast species like Candida albicans can cause illness, like the vaginal yeast infection.
Sexual Reproduction
Although sexual reproduction might sound 'sexy', really it all comes down to combining gametes, (sperm and eggs in humans). Even single celled microbes can do it! During sexual reproduction each gamete has half of the original amount of DNA. When they combine, they make a new organism with the correct total amount of DNA.
An example of this type of reproduction can be seen in the parasite Plasmodium falciparum, which causes malaria. Malaria is transmitted through infected mosquitoes, which, after biting a human, release the parasite into the blood stream.
An adult form of Plasmodium called the sporozoites are injected through the mosquito's salivary glands and travel to the liver. There they create offspring called merozoites. The merozoites then make male and female gametocytes, the sperm and eggs equivalent of Plasmodium. When a mosquito bites an infected person it picks up these gametocytes which then fuse during sexual reproduction, creating new sporozoites and the life cycle begins again.
For Plasmodium to reproduce it must have both mosquito and human hosts. The mosquitoes provide a place for them to combine gametes and make new organisms. Humans continue the life cycle, allowing the Plasmodium to duplicate itself and create new gametes.
Mitosis
Ciliates are single celled microorganisms with two different nuclei. They have smaller micronuclei, which are involved in sexual reproduction, and larger macronuclei that are responsible for daily activities such as producing energy and development. During asexual reproduction, the micronuclei undergo mitosis, or cell division in eukaryotes.
Mitosis can be divided into four steps.
Prophase: the DNA condenses into chromosomes inside the nucleus. In most eukaryotes the nucleus dissolves, releasing the chromosomes into the cell. But, in the ciliates, the nucleus stays intact.
Metaphase: the chromosomes line up in the middle of the cell.
Anaphase: the chromosomes separate to either side of the nucleus.
Telophase: the micronucleus divides into two new nuclei.
Mitosis in the micronuclei of ciliates mitosis.
These are microorganisms, or living things that can only be seen with a microscope. Most people think of bacteria when they think of a microorganism, but there's actually a variety of kinds. Any organism that you can't see with the naked eye counts, like yeast, parasites, and other protozoans like a paramecium.
For these organisms to carry on their life cycles, they must reproduce. Let's look at four methods microorganisms use.
Binary Fission
Binary fission is the simplest type of reproduction. Bacteria use this strategy to divide one cell into two identical cells. Bacteria have a very basic structure, with a rigid cell wall surrounding a thin plasma membrane to protect the cell. Inside, the DNA (genetic material) floats around in the center.
In the first step of binary fission, the DNA duplicates.
Next, the cell starts to elongate and the DNA is moved to either side of the cell.
Once the cell is long enough, a new cell wall forms in the center and two new cells are made.
Bacteria divide incredibly quickly using this method, sometimes every twenty minutes. This strategy allows pathogenic bacteria, like Streptococcus pyogenes, the cause of strep throat, to quickly colonize a human host.
Budding
Yeast use a more complicated method, as their cell structure is more complicated than bacteria. Yeast are called eukaryotic cells, meaning they have a nucleus holding their DNA and lots of little compartments inside the cell called organelles.
During budding a small outgrowth of the cell appears, like a bud from the main yeast cell. As the bud grows bigger, DNA duplicates inside the nucleus and the nucleus buds as well, creating a new nuclei in the bud. When the process is complete, the bud detaches from the main cell and forms a new cell.
Yeast can be helpful to us, such as Saccharomyces cerevisiae, which is used to make beer and bread. However, some yeast species like Candida albicans can cause illness, like the vaginal yeast infection.
Sexual Reproduction
Although sexual reproduction might sound 'sexy', really it all comes down to combining gametes, (sperm and eggs in humans). Even single celled microbes can do it! During sexual reproduction each gamete has half of the original amount of DNA. When they combine, they make a new organism with the correct total amount of DNA.
An example of this type of reproduction can be seen in the parasite Plasmodium falciparum, which causes malaria. Malaria is transmitted through infected mosquitoes, which, after biting a human, release the parasite into the blood stream.
An adult form of Plasmodium called the sporozoites are injected through the mosquito's salivary glands and travel to the liver. There they create offspring called merozoites. The merozoites then make male and female gametocytes, the sperm and eggs equivalent of Plasmodium. When a mosquito bites an infected person it picks up these gametocytes which then fuse during sexual reproduction, creating new sporozoites and the life cycle begins again.
For Plasmodium to reproduce it must have both mosquito and human hosts. The mosquitoes provide a place for them to combine gametes and make new organisms. Humans continue the life cycle, allowing the Plasmodium to duplicate itself and create new gametes.
Mitosis
Ciliates are single celled microorganisms with two different nuclei. They have smaller micronuclei, which are involved in sexual reproduction, and larger macronuclei that are responsible for daily activities such as producing energy and development. During asexual reproduction, the micronuclei undergo mitosis, or cell division in eukaryotes.
Mitosis can be divided into four steps.
Prophase: the DNA condenses into chromosomes inside the nucleus. In most eukaryotes the nucleus dissolves, releasing the chromosomes into the cell. But, in the ciliates, the nucleus stays intact.
Metaphase: the chromosomes line up in the middle of the cell.
Anaphase: the chromosomes separate to either side of the nucleus.
Telophase: the micronucleus divides into two new nuclei.
Mitosis in the micronuclei of ciliates mitosis.
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