Euglena
Euglena is a genus of single-celled organisms known for exhibiting both plant and animal characteristics, which allows them to adapt to their environments effectively. They belong to the informal group of protists and are typically found in freshwater habitats like ponds and puddles, though they can also inhabit damp soils and brackish waters. The genus name Euglena is derived from Greek, meaning "beautiful eye," referencing their distinctive eyespot that helps them locate light. These organisms are unique in that they can perform photosynthesis like plants, utilizing chloroplasts to convert sunlight into energy, while also being capable of consuming organic material in the absence of light.
Euglena species are characterized by their flexible pellicle, which allows them to change shape, and their flagella, which facilitate movement. They reproduce asexually through mitosis, splitting into two distinct organisms. Recent research has highlighted the potential of Euglena in various applications, including as a source of biofuel, health supplements, and water treatment solutions. Additionally, their ability to absorb nutrients from algae makes them a promising candidate for addressing malnutrition, with the potential to produce valuable compounds like omega-3 fatty acids and antioxidants. Scientists continue to explore the vast genetic makeup of Euglena, which may unlock further beneficial properties for medical and industrial use.
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Euglena
Euglena (pronounced you-GLEEN-nuh) is the name of a genus of single-cell organisms with both plant and animal characteristics. Euglena have the unique ability to adapt to their environment by using methods to eat traditionally associated with either plants or animals depending on what resources are available. Euglena belongs to an informal category of organisms called protists whose defining characteristics are that they are primarily microscopic in size, are composed of a single cell, and have a set of specialized cellular mechanisms called organelles that mimic the functions of organs in multicellular organisms such as human beings. Euglena primarily live in freshwater environments such as ponds and puddles, although they are occasionally seen in damp soils and brackish or saltwater habitats. Due to ongoing studies into their evolutionary status, there is no consensus on how many species may be properly identified as belonging to Euglena, although various estimates place from 138 to more than 1,000 species within the genus.
Background
The name Euglena comes from the Greek words "eu" (meaning "beautiful") and "glena" ("eye"). It was named by German biologist Christian Ehrenberg in 1830, who was the first scientist to identify Euglena's distinctive eyespot. Euglena was initially discovered by Dutch scientist Antonie van Leeuwenhoek in 1675, roughly fifty years after the invention of the compound microscope. Van Leeuwenhoek found the organisms when he placed rainwater from a barrel under a microscope. He believed they were tiny animals and called them "animalcules."
Euglena are often used as a model organism by scientists and in classrooms due to their unusual characteristics, hardiness, well-established biology, and short lifecycles. Melvin Calvin, the winner of the 1961 Nobel Prize in Chemistry, used Euglena in his investigation of how photosynthetic organisms convert carbon dioxide into energy in the Calvin-Benson-Bassham cycle. Euglena species were also employed by NASA during investigations of creating self-sustaining food sources in outer space.
Characteristics
Taxonomy is a system of classification used by scientists to organize all life. As Euglena have such an unusual set of attributes, they have been placed under a number of different taxonomic categories since their initial discovery. In general, Euglena species are placed into the taxonomic domain of Eukarya, which includes a broad spectrum of living creatures such as plants, animals, fungi, amoebas, and other organisms with cells that contain both a nucleus and organelles. The other two taxonomic domains of life (Archaea and Bacteria) are prokaryotic organisms that lack these cellular mechanisms. Within the eukaryotes, Euglena species belong to the phylum of Euglenozoa (in the supergroup Excavata), a category of unicellular organisms that have one or more flagella, which are specialized types of organelles that allow them to move.
Euglena species in particular are defined by a set of traits usually identified only in either animal or plant species. Euglena are both autotrophic (meaning they can manufacture their own food) and heterotrophic (a category of organisms that must consume food). Like plants, Euglena have structures called chloroplasts similar to those found in algae that allow them to transform sunlight into food through photosynthesis. However, like animals, Euglena species are capable of independent movement by virtue of a flagellum. Euglena species have two flagella connected to their cellular body through a round opening called the reservoir. The longer whip-like flagellum is coated in tiny, hair-like appendages on one side and is moved back and forth to allow movement; the second flagellum is located entirely within the reservoir.
The species of Euglena are further characterized by the presence of a red eye-shaped organelle called the stigma that allows them to seek out light sources on which they may feed. They also lack a traditional cell wall; rather, they have a flexible external membrane called a pellicle that enables them to change shape. The inside of the rounded (rather than flat) Euglena cells are filled with cytoplasm, a yellowish fluid. Most of the cell's metabolic functions, such as the conversion of food to energy, occur in the cytoplasm. Euglena species are distinct in that different genes become active when exposed to light and dark conditions. In a lighted environment, Euglena gravitate toward the light and use their chloroplasts to produce energy. In a dark location, the chloroplasts tend to lose their green color, and Euglena resort to the consumption of external materials for food.
Reproduction occurs asexually through mitosis, which occurs when the nucleus of a Euglena splits into two parts. This process is followed by the division of the Euglena cell into two distinct organisms.
Topic Today
Scientists have made several important discoveries regarding the organisms of the Euglena genus in the twenty-first century. A Japanese company that calls itself Euglena has been farming Euglena species for a variety of environmentally friendly commercial uses. The company has discovered methods to cultivate these organisms on a mass scale using carbon dioxide as the primary food source. As of 2015, the company was primarily engaged in the mass production of Euglena-produced algae, which are used as an ingredient in health foods and as a dietary supplement. Some researchers believe that the various Euglena species might have other valuable applications as well, particularly as a source of energy. As Euglena can be fed on carbon dioxide without having to use arable land, they may be a potentially important future source of biofuel that does not contribute to existing carbon dioxide levels in the atmosphere as carbon-based fuels do. Research into developing jet biofuel was in progress in 2022. Euglena may also have applications in water-treatment projects and as a means of reducing emissions from thermal power plants.
In addition, scientists believe that Euglena may be used to help reduce worldwide malnutrition. When fed with algal species, Euglena absorb many of the algae's valuable nutrients. Euglena can then be harvested to produce an easily farmed source of antioxidants, omega-3 fatty acids (like those found in fish oils), and vitamins A, C, and E. Euglena are also known to produce paramylon, a substance that is being studied for its potential link to improved health in humans. Euglena are more easily broken down than algae, which means they are easier and cheaper to farm. Researchers continue to explore growing conditions that would allow for cheap, mass-production of these organisms while retaining the most valuable nutrients.
Biologists attempting to sequence the genetic code of pond algae (Euglena gracilis) found that each organism contained 32,000 active, protein-encoding genes. By comparison, humans only have 21,000 of these same types of genes. Sixty percent of these active genes are new to science, a discovery that may mean that Euglena have other valuable undiscovered properties that can be used in medical treatments and industrial capacities.
Bibliography
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