Dictyostelium discoideum

Tiny cells live in the soil.

They like to eat small bits of food. When their food is gone, they need to find more. The cells send out a signal to find friends.

They bump into each other and stick together. This makes a small, moving slug. The slug moves toward light and heat. Soon, the slug grows into a tall stem.

This stem holds new seeds to start again. It is a very busy life!

Dictyostelium discoideum is a tiny amoeba. It lives in moist soil and leaves.

These single cells eat bacteria to grow. When food runs out, they must change.

First, the cells start to gather. They use a signal called cAMP. This chemical lets out a call to neighbors. The cells move toward the signal. They bump into each other and stick.

Next, they form a moving slug. This slug is 2 to 4 mm long. It can have 100,000 cells. The slug moves toward heat and light. It leaves a slimy trail behind it.

Then, the slug settles in one spot. It forms a shape like a Mexican hat.

The cells move to make a stalk and spores. The spores are like tiny seeds. The stalk holds them high in the air. After 8 to 10 hours, the fruiting body is ready. It lets out new spores to start again. Scientists study these cells to learn about human health.

Dictyostelium discoideum is a tiny living thing found in moist soil and leaf litter. It is a type of amoeba that belongs to a group called the slime molds. This name comes from how it changes throughout its life. Sometimes it lives as single cells, but other times it works as a group. These cells eat bacteria like Escherichia coli to grow and stay healthy.

This ability to switch between being single and being a group makes it very special to study.

The life cycle begins when spores hatch into tiny cells called myxamoebae. These cells eat bacteria until their food supply runs out. When they are hungry, they start a process called aggregation. They release a chemical signal called cyclic AMP to call to their neighbors. The cells move toward this signal and stick together using glycoproteins. Soon, they form a moving group called a slug.

This slug is 2 to 4 mm long and can have 100,000 cells.

Moving as a slug is a very organized thing that happens. The slug moves in one direction toward light, heat, or moisture. It makes a cellulose sheath to help it move across the ground. As it travels, it leaves a slimy trail behind it. Inside the slug, cells begin to change into different types. Some become prestalk cells and others become prespore cells.

This change is called differentiation, which means cells become specialized for a job.

Once the slug finds a good spot, it enters the culmination stage. The slug settles and forms a shape that looks like a Mexican hat. The cells then move to build a fruiting body. The anterior cells form a cellulose tube to create a stalk. The posterior cells move up the tube to form spores on top. This whole process takes about 8 to 10 hours to finish.

After this, the mature fruiting body releases new spores to start over.

Scientists use Dictyostelium discoideum as a model organism to learn many things. A model organism is a living thing used to study how other things work. This amoeba has many genes that are similar to human genes. It helps researchers study how cells move and how they grow. It can also help us understand human health issues like asthma or arthritis. By watching these tiny cells, we can learn about the secrets of life.

Dictyostelium discoideum is a species of soil-dwelling amoeba. It belongs to the phylum Amoebozoa and the infraphylum Mycetozoa. This organism is part of a group called the slime molds. This name describes how it switches between single-celled and multicellular forms. It is a eukaryote with a unique asexual life cycle. This cycle consists of four distinct stages: vegetative, aggregation, migration, and culmination. Because of its simple life cycle, scientists use it as a model organism. It helps researchers study genetic, cellular, and biochemical processes in many other organisms.

The life cycle begins when spores are released from a mature sorocarp. A sorocarp is a type of fruiting body. Under warm and moist conditions, myxamoebae hatch from these spores. During the vegetative stage, these myxamoebae divide by mitosis to grow. They feed on bacteria like Escherichia coli found in decaying organic matter. The bacteria actually secrete folic acid, which attracts the myxamoebae to their food. This stage continues as long as the bacteria are plentiful.

When the bacteria supply runs out, the amoebae enter the aggregation stage. Starvation triggers the production of specific protein compounds. One important protein is adenylyl cyclase, which creates a chemical called cyclic AMP. The amoebae secrete this cyclic AMP to attract neighboring cells. This process is known as chemotaxis, which is movement toward a chemical signal. As cells move toward the signal, they bump into each other. They use glycoproteins, which are adhesion molecules, to stick together.

Once the cells form a tight aggregate, the migration stage begins. The mound of cells tips over and lies flat on the ground. The amoebae now work together as a single motile pseudoplasmodium, also called a slug. This slug is about 2 to 4 mm long. It can be composed of up to 100,000 individual cells. The slug moves in a forward-only direction toward light, heat, or humidity. It produces a cellulose sheath in its anterior cells to help it move. As it travels, the slug leaves a slimy trail behind it.

Inside the slug, cells begin to undergo differentiation. Differentiation is the process where cells become specialized for specific roles. Cyclic AMP and a differentiation-inducing factor help form different cell types. The slug divides into prestalk cells and prespore cells. The prestalk cells move to the anterior, or front, end. The prespore cells move to the posterior, or back, end. Recently, scientists also discovered anterior-like cells in the posterior region. These cells help form the very bottom of the fruiting body and the spore caps.

The culmination stage starts once the slug finds a suitable environment. The slug settles and the ends spread out to look like a "Mexican hat." During this stage, the prestalk and prespore cells switch positions. The anterior end forms a cellulose tube to create a stalk. This tube allows the posterior cells to move up the outside. The prestalk cells move down to form the base. This rearrangement takes about 8 to 10 hours to complete. The final fruiting body is 1 to 2 mm tall.

While asexual reproduction is common, Dictyostelium can also reproduce sexually. This occurs when specific mating types meet in dark, wet environments. There are three different mating types, identified by specific genes like MatA, MatS, and MatT. Successful mating results in the formation of a diploid zygote. In some cases, this forms a macrocyst, which is a thick, protective structure. Inside the macrocyst, the cell undergoes meiosis and mitosis to produce new amoebae. This recombination is very important for natural populations of the species.

Scientists value Dictyostelium because it is a powerful model organism. Many of its genes are homologous, or similar, to human genes. It is used to study cell differentiation, chemotaxis, and apoptosis. It also helps researchers understand cell sorting and signal transduction. Studying its chemotaxis can provide insights into human conditions like asthma and arthritis. Because it is closely related to higher metazoans, it is an excellent tool for biology. It allows us to observe the evolution from single cells to multicellular life.