Chlamydomonas reinhardtii
Scientific classification
Kingdom: Protista Division: Chlorophyta Class: Chlorophyceae Order: Volvocales Family: Chlamydomonadaceae Genus: Chlamydomonas Species: C. Protists (ˈproʊtɨst are a diverse group of eukaryotic Microorganisms Historically protists were treated as the kingdom Protista but this Chlorophyta, a division of Green algae, of mostly aquatic Photosynthetic Eukaryotic organisms The Chlorophyceae are one of the classes of Green algae distinguished mainly on the basis of ultrastructural morphology In taxonomy, the Volvocales are an order of Flagellate or pseudociliate Green algae, specifically of the Chlorophyceae. In taxonomy, the Chlamydomonadaceae are a family of Algae, specifically of the Chlamydomonadales. Chlamydomonas is a genus of Green alga. They are unicellular Flagellates Chlamydomonas is used as a Model organism for Molecular reinhardtii
Binomial name
Chlamydomonas reinhardtii P. A. Dang.

Chlamydomonas reinhardtii is a motile single celled green alga about 10 micrometres in diameter that swims with two flagella. A microorganism (also spelled micro organism or micro-organism and also called a microbe) is an Organism that is Microscopic (usually The green algae (singular green alga) are the large group of Algae from which the Embryophytes (higher plants emerged A micrometre ( American spelling: micrometer; symbol µm) is one millionth of a Metre, or equivalently one thousandth of a Millimetre A flagellum ( plural flagella) is a tail-like structure that projects from the Cell body of certain Prokaryotic and Eukaryotic cells and it See Chlamydomonas. Chlamydomonas is a genus of Green alga. They are unicellular Flagellates Chlamydomonas is used as a Model organism for Molecular

These algae are commonly found in soil and fresh water. They have a cell wall made of hydroxyproline-rich glycoproteins, a large cup-shaped chloroplast, a large pyrenoid, and an "eyespot" that senses light. A cell wall is a tough flexible and sometimes fairly rigid layer surrounding a cell, located external to the Cell membrane, which provides the cell with structural Chloroplasts are Organelles found in Plant cells and eukaryotic Algae that conduct Photosynthesis. In Cell biology, pyrenoids are centers of carbon dioxide fixation within the Chloroplasts of Algae and Hornworts Pyrenoids are not Normal Chlamydomonas can grow on a simple medium of inorganic salts in the light, using photosynthesis to provide energy. Photosynthesis is a Metabolic pathway that converts Light Energy into Chemical energy. They can also grow in total darkness if acetate is provided as a carbon source for catabolism. Acetic acid, also known as ethanoic acid, is an organic chemical compound, giving Vinegar its sour taste For the related metabolic process see Anabolism. Catabolism is the set of Metabolic pathways which break down molecules into

The C. reinhardtii wild type laboratory strain c137 (mt+) originates from an isolate made near Amherst, Massachusetts, in 1945.

C. reinhardtii as a model organism

Schematic drawing of a Chlamydomonas cell

Chlamydomonas is used as a model organism for research on fundamental questions in cell and molecular biology such as:

• How do cells move?
• How do cells respond to light?
• How do cells recognize one another?
• How do cells regulate their proteome to control flagellar length?
• How do cells respond to changes in mineral nutrition? (nitrogen, sulfur etc. A model organism is a Species that is extensively studied to understand particular biological Phenomena, with the expectation that discoveries made The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called Molecular biology is the study of Biology at a molecular level A flagellum ( plural flagella) is a tail-like structure that projects from the Cell body of certain Prokaryotic and Eukaryotic cells and it )

There are many known mutants of C. reinhardtii. These mutants are useful tools for studying a variety of biological processes, including flagellar motility, photosynthesis or protein synthesis. Photosynthesis is a Metabolic pathway that converts Light Energy into Chemical energy. Protein synthesis is the creation of proteins using DNA and' RNA'. Since Chlamydomonas species are normally haploid, the effects of mutations are seen immediately without further crosses.

In 2007, the complete nuclear genome sequence of C. reinhardtii was published. ^[1]

Reproduction

Vegetative cells of the reinhardtii species are haploid with 17 small chromosomes. "Haplo" redirects here For the fictional character see The Death Gate Cycle. A chromosome is an organized structure of DNA and Protein that is found in cells. Under nitrogen starvation, haploid gametes develop. Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 A gamete (from Ancient Greek γαμέτης; translated gamete = wife gametes = husband is a cell that fuses with another gamete There are two mating types, identical in appearance and known as mt(+) and mt(-), which can fuse to form a diploid zygote. Mating types occur in Eukaryotes that undergo Sexual reproduction via Isogamy. "Haplo" redirects here For the fictional character see The Death Gate Cycle. For other meanings see Zygote (disambiguation. A zygote (from Greek ζυγωτός zugōtos "joined" or "yoked" The zygote is not flagellated, and it serves as a dormant form of the species in the soil. In the light the zygote undergoes meiosis and releases four flagellated haploid cells that resume the vegetative life cycle. In Biology or life science meiosis (pronounced my-oh-sis is a process of reductional division in which the number of chromosomes per cell is cut in half

Curious fact: Under ideal growth conditions, cells may undergo two or three rounds of mitosis before the daughter cells are released from the old cell wall into the medium. Mitosis is the process in which a Eukaryotic cell separates the Chromosomes in its Cell nucleus, into two identical sets in two daughter nuclei Thus, a single growth step may result in 4 or 8 daughter cells per mother cell.

The cell cycle of this unicellular green algae can be synchronized by alternating periods of light and dark. The growth phase is dependent on light, whereas, after a point designated as the transition or commitment point, processes are light-independent. ^[2]

Genetics

The attractiveness of the alga as a model organism has recently increased with the release of several genomic resources to the public domain. The current draft (Chlre3) of the Chlamydomonas nuclear genome sequence prepared by Joint Genome Institute of the U. S. Dept of Energy comprises 1557 scaffolds totaling 120 Mb. Roughly half of the genome is contained in 24 scaffolds all at least 1. 6 Mb in length. The sequences of all three C. reinhardtii genomes are available.

The ~15. 8 Kb mitochondrial genome (database accession: NC_ 001638) is available online at the NCBI database. [1] The complete >200 Kb chloroplast genome is available online. [2] The current assembly of the nuclear genome is available online at. [3]

In addition to genomic sequence data there is a large supply of expression sequence data available as cDNA libraries and expressed sequence tags (ESTs). Seven cDNA libraries are available online [4]. A BAC library can be purchased from the Clemson University Genomics Institute [5]. There are also two databases of >50 000 [6] and >160 000 [7] ESTs available online.

C. reinhardtii DNA transformation techniques

Gene transformation occurs mainly by homologous recombination in the chloroplast and heterologous recombination in the nucleus. The C. reinhardtii chloroplast genome can be transformed using microprojectile particle bombardment and the nuclear genome has been transformed with both glass bead agitation and electroporation. The biolistic procedure appears to be the most efficient way of introducing DNA into the chloroplast genome. This is probably because the chloroplast occupies over half of the volume of the cell providing the microprojectile with a large target. Electroporation has been shown to be the most efficient way of introducing DNA into the nuclear genome with maximum transformation frequencies two orders of magnitude higher than obtained using glass bead method.

C. reinhardtii as a clean source of hydrogen production

In 1939 the German researcher Hans Gaffron (1902-1979), who was at that time attached to the University of Chicago, discovered the hydrogen metabolism of unicellular green algae. Chlamydomonas reinhardtii and some other green algae can, under specified circumstances, stop producing oxygen and convert instead to the production of hydrogen. This reaction by hydrogenase, an enzyme only active in the absence of oxygen, is short-lived. A hydrogenase is an Enzyme that catalyses the reversible oxidation of molecular Hydrogen (H2 Enzymes are Biomolecules that catalyze ( ie increase the rates of Chemical reactions Almost all enzymes are Proteins Over the next thirty years Gaffron and his team worked out the basic mechanics of this photosynthetic hydrogen production by algae. ^[3]

Such a production of hydrogen would only need water, sunlight and green algae. There is no need for electricity, nor is there any release of greenhouse gases. Greenhouse gases are gaseous constituents of the atmosphere bothnatural and anthropogenic that absorb and emit radiation at specific wavelengths within the spectrum of thermal infrared In other words, this is truly clean energy.

This hydrogen production cannot take place in the presence of oxygen. Under anaerobiotic circumstances however, the hydrogenase enzyme can produce briefly, during only a few minutes, light-mediated photosynthetic hydrogen. An anaerobic organism is any Organism that does not require Oxygen for growth and may even die in its presence Photosynthesis is a Metabolic pathway that converts Light Energy into Chemical energy. This reaction acts as a safety valve, dissipating the surplus of electrons created during a critical phase in the production of sugars in the chloroplast. Carbohydrates (from ' Hydrates of Carbon ' or saccharides ( Greek σάκχαρον meaning " Sugar " are the most Chloroplasts are Organelles found in Plant cells and eukaryotic Algae that conduct Photosynthesis. This critical phase emerges because the reactions, transferring the electrons, happen immediately under the effect of light, while the synthesis of sugars gets going at a slower rate. Through this pumping of electrons into the production of hydrogen, the hydrogenase avoids choking the system. This reaction is gradually stopped after a few minutes by the oxygen emerging through the reactions producing the sugars.

To increase the production of hydrogen, two tracks are being followed by the researchers.

• The first track is decoupling hydrogenase from photosynthesis. This way, oxygen accumulation can no longer inhibit the production of hydrogen. And, if one goes one step further by changing the structure of the enzyme hydrogenase, it becomes possible to render hydrogenase insensitive to oxygen. This makes a continuous production of hydrogen possible. The flux of electrons needed for this production comes, in this case, no longer from the production of sugars, but is drawn from the breakdown of its own stock of starch. Starch, CAS # 9005-25-8 Chemical formula (C6H10O5n is a Polysaccharide ^[4]
• A second track is to interrupt temporarily, through genetic manipulation of hydrogenase, the photosynthesis process. Genetic engineering, Recombinant DNA technology, genetic modification/manipulation (GM and gene splicing are terms that apply to the direct This inhibits oxygen reaching a level where it is able to stop the production of hydrogen. ^[5]

Both tracks are very promising and the practical implications to the energy supply of the world could be enormous. But industrial production of hydrogen by green algae is not yet for the very near future. At this moment the yield of the first prototypes fluctuates between 0. 5 and 3 %, while 10 % could be the maximum yield of this biological process.

Notes

External links

• Chlamydomonas genome sequenced published in Science, October 12, 2007
• Chlamydomonas reinhardtii resources at the Joint Genome Institute
• Chlamydomonas frequently asked questions
• The Chlamydomonas Center provides access to Chlamydomonas genomic, genetic and bibliographic information, the Chlamydomonas culture collection, and other resources for the Chlamydomonas community.
• The Chlamydomonas Teaching Center offers information on how to use Chlamydomonas in teaching and student research projects
• Chlamydomonas reinhardtii. AlgaeBase. AlgaeBase is a global Species Database of information on all groups of Algae   as well as one group of Flowering plants the sea-grasses National University of Ireland, Galway. The National University of Ireland Galway ( NUI Galway) ( Irish Ollscoil na hÉireann Gaillimh or OÉ Gaillimh) is a tertiary-level