Anabaena

Anabaena is a tiny living thing in the water.

It can help plants grow. Some plants live with it. The tiny living thing gives the plant food from the air. This helps the plant grow very fast.

But it can also be bad. It can make a poison. This poison can hurt pets and farm animals.

Scientists study it in a lab. They look at how it sees light. They also look at its tiny parts.

It is a very busy little thing in the water.

Anabaena is a tiny living thing in the water. It lives in long chains. These chains float in the water like plankton.

Anabaena can help plants grow. It lives with a plant called the mosquito fern. The Anabaena takes nitrogen from the air. It turns it into ammonia, which is a type of plant food. It does this in special parts called heterocysts. These parts are like tiny food factories. The plant gets the food from the Anabaena. This helps the plant grow very fast. It can even double its size in less than two days!

But Anabaena can also be dangerous. It can make neurotoxins. These are poisons that can hurt pets and farm animals. This poison might even protect the plant from being eaten by other things.

Scientists study Anabaena in labs. They look at its DNA to learn about life. They also study how it sees light. It has a special protein called sensory rhodopsin. This protein helps the Anabaena sense light. It helps scientists learn how eyes work in larger animals.

Anabaena is a genus of tiny living things called cyanobacteria. These organisms live in long chains called filaments. They float in the water as plankton. Anabaena is very important because it can change nitrogen from the air into a form plants can use. Some species even live inside other living things. This is called a symbiotic relationship. For example, Anabaena lives with the mosquito fern. This partnership helps the fern grow at a huge speed. The fern can even double its size in just 1.9 days.

To help plants, Anabaena uses special parts called heterocysts. These are cells that act like tiny food factories. Inside these cells, a process called nitrogen fixation happens. The heterocysts turn nitrogen into ammonia, which is a type of plant food. To do this, the cells create a thick wall to keep oxygen out. They also use energy from sunlight and sugars to power the work. The regular cells in the chain make sugars like glucose. They send these sugars to the heterocysts. In return, the heterocysts send nitrogen back to the rest of the chain.

Scientists have spent a long time studying these tiny chains. Between 1999 and 2005, the United States Department of Energy started a big project. They wanted to map the complete genome of a specific type called Anabaena variabilis ATCC 29413. A genome is like a complete instruction manual for a living thing. This specific manual is 7.2 million base pairs long. Researchers published a paper about this work in 2014.

Anabaena is also used to learn about how eyes work. Scientists study a protein in Anabaena called sensory rhodopsin. This is a special part of the cell membrane that senses light. By watching how light changes this protein, researchers learn how vision works in much bigger animals. Anabaena can also help farmers. Some species are used in rice paddy fields. They act as a natural fertilizer to help the rice grow.

While Anabaena can be helpful, it can also be dangerous. Some types produce neurotoxins. These are poisons that can harm local wildlife. They can also be bad for pets and farm animals. Scientists think the Anabaena might make these toxins to protect the plants they live with. This stops other animals from eating the plants. Even though they are small, these tiny chains have a huge impact on the world around them.

Anabaena is a genus of filamentous cyanobacteria that exist as plankton. These tiny organisms live in long, chain-like structures called filaments. They are highly significant because of their ability to perform nitrogen fixation. This process allows them to convert atmospheric nitrogen into forms that living things can use. They also form important symbiotic relationships with certain plants. One famous example is the partnership with the mosquito fern, known as Azolla.

The most remarkable feature of Anabaena is its specialized cells called heterocysts. These cells are designed specifically for nitrogen fixation. To make this process work, the heterocyst must create a micro-oxic environment. This means it must keep oxygen levels very low. The cell achieves this by increasing respiration and inactivating photosystem II, which is the part that produces oxygen. It also forms a thickened envelope outside the cell wall to act as a barrier.

Inside these protected heterocysts, an enzyme called nitrogenase performs the chemical work. Nitrogenase transforms dinitrogen from the air into ammonia. This process requires a lot of energy in the form of ATP and reductant. This energy comes from carbohydrate metabolism. In the light, the process is supplemented by the activity of photosystem I. The heterocysts rely on the regular vegetative cells for fuel. The vegetative cells produce carbohydrates, likely in the form of glucose, and move them into the heterocysts. In return, the heterocysts send fixed nitrogen back to the vegetative cells, often as amino acids.

Anabaena also engages in complex symbiotic relationships. The fern Azolla hosts the species Anabaena azollae. This partnership allows the fern to access essential nitrogen from the atmosphere. Because of this, Azolla is often called a "super-plant." It can colonize freshwater areas and grow at an incredible speed. The plant can double its biomass in as little as 1.9 days. However, this growth is usually limited by the availability of phosphorus.

In these relationships, the microorganisms are passed directly from one generation of the plant to the next. This has made Anabaena azollae completely dependent on its host. Some of its genes have even been lost or transferred to the nucleus of the Azolla cells. Beyond helping plants, Anabaena is used by scientists to study vision. They study a light-sensitive membrane protein called sensory rhodopsin. By observing how light changes the shape of these molecules, researchers can learn how vision works in vertebrates.

Scientific research has also focused on the genetic makeup of these organisms. Between 1999 and 2005, the United States Department of Energy conducted a DNA sequencing project. They mapped the complete genome of the model organism Anabaena variabilis ATCC 29413. This genome is 7.2 million base pairs long. A paper detailing this work was published in 2014. Researchers also study how Anabaena repairs its DNA. They have looked at how a protein called RecN helps repair double strand breaks. This repair is active in vegetative cells but absent in mature heterocysts.

While Anabaena is useful for rice paddy fields as a natural fertilizer, it can also be dangerous. Anabaena is one of four genera of cyanobacteria that produce neurotoxins. These toxins can be harmful to local wildlife, farm animals, and pets. Scientists assume the production of these neurotoxins is an input into symbiotic relationships. The toxins likely protect the host plant from grazing pressure by making it undesirable to eat. This shows how even microscopic organisms can deeply affect entire ecosystems.