Chlamydomonas globosa - 400x (13263097835)

''Chlamydomonas'' is a genus of

green algae The green algae (singular: green alga) are a group consisting of the Prasinodermophyta and its unnamed sister which contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ( Embryophytes) have emerged deep in the Charophyte alg ...

consisting of about 150 speciesSmith, G.M. 1955 ''Cryptogamic Botany Volume 1. Algae and Fungi'' McGraw-Hill Book Company Inc of unicellular

flagellate A flagellate is a cell or organism with one or more whip-like appendages called flagella. The word ''flagellate'' also describes a particular construction (or level of organization) characteristic of many prokaryotes and eukaryotes and the ...

s, found in stagnant water and on damp soil, in freshwater, seawater, and even in snow as "snow algae". ''Chlamydomonas'' is used as a model organism for

molecular biology Molecular biology is the branch of biology that seeks to understand the molecular basis of biological activity in and between cells, including biomolecular synthesis, modification, mechanisms, and interactions. The study of chemical and phys ...

, especially studies of

flagellar A flagellum (; ) is a hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility. Many protists with flagella are termed as flagellates. A microorganism may have fro ...

motility and

chloroplast A chloroplast () is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant and algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, and stores it ...

dynamics, biogenesis, and genetics. One of the many striking features of ''Chlamydomonas'' is that it contains

ion channel Ion channels are pore-forming membrane proteins that allow ions to pass through the channel pore. Their functions include establishing a resting membrane potential, shaping action potentials and other electrical signals by gating the flow of ...

s ( channelrhodopsins) that are directly activated by light. Some regulatory systems of ''Chlamydomonas'' are more complex than their homologs in Gymnosperms, with evolutionarily related regulatory proteins being larger and containing additional domains.

Molecular phylogeny Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...

studies indicated that the traditional genus ''Chlamydomonas'' as defined using morphological data was

polyphyletic A polyphyletic group is an assemblage of organisms or other evolving elements that is of mixed evolutionary origin. The term is often applied to groups that share similar features known as homoplasies, which are explained as a result of conver ...

within Volvocales. Many species were subsequently reclassified (e.g., in '' Oogamochlamys, Lobochlamys''), and many other "''Chlamydomonas''" s.l. lineages are still to be reclassified.

Description

All ''Chlamydomonas'' are unicellular organisms, spherical or slightly cylindrical, and a papilla may be present or absent. Chloroplasts are green and usually cup-shaped. Guiry, M.D., John, D.M. Rindi, F. and McCarthy, T.K. (ed) ''2007 New Survey of Clare Island Volume 6: The Freshwater and Terrestrial Algae''. Royal Irish Academy. A key feature of the genus is its two anterior flagella, each as long as the other. The flagellar microtubules may each be disassembled by the cell to provide spare material to rebuild the other's microtubules if they are damaged.

Species

*''Chlamydomonas acidophila'' * ''Chlamydomonas caudata'' Wille * ''Chlamydomonas ehrenbergii'' Gorozhankin * '' Chlamydomonas elegans'' G.S.West 1915 * ''Chlamydomonas moewusii'' * '' Chlamydomonas nivalis'' * ''Chlamydomonas ovoidae'' * '' Chlamydomonas reinhardtii''

Ecology

''Chlamydomonas'' is widely distributed in freshwater or damp soil. It is generally found in a habitat rich in ammonium salt. It possesses red eye spots for photosensitivity and reproduces both asexually and sexually. ''Chlamydomonass asexual reproduction occurs by zoospores, aplanospores, hypnospores, or a palmella stage, while its sexual reproduction is through

isogamy Isogamy is a form of sexual reproduction that involves gametes of the same morphology (indistinguishable in shape and size), found in most unicellular eukaryotes. Because both gametes look alike, they generally cannot be classified as male or ...

, anisogamy or

oogamy Oogamy is an extreme form of anisogamy where the gametes differ in both size and form. In oogamy the large female gamete (also known as ovum) is immobile, while the small male gamete (also known as sperm) is mobile. Oogamy is a common form o ...

Nutrition

Most species are obligate

phototroph Phototrophs () are organisms that carry out photon capture to produce complex organic compounds (e.g. carbohydrates) and acquire energy. They use the energy from light to carry out various cellular metabolic processes. It is a common misconce ...

s but '' C. reinhardtii'' and ''C. dysostosis'' are facultative heterotrophs that can grow in the dark in the presence of acetate as a carbon source.

Morphology

* Motile unicellular algae. * Generally oval and/or circular. * Cell wall is made up of a glycoprotein and non-cellulosic polysaccharides instead of cellulose. * Two anteriorly inserted whiplash flagella. Each flagellum originates from a basal granule in the anterior papillate or non-papillate region of the cytoplasm. Each flagellum shows a typical 9+2 arrangement of the component fibrils. * Contractile vacuoles are near the bases of flagella. * Prominent cup or bowl-shaped chloroplast is present. The chloroplast contains bands composed of a variable number of the photosynthetic thylakoids which are not organised into grana-like structures. * The nucleus is enclosed in a cup-shaped chloroplast, which has a single large pyrenoid where starch is formed from photosynthetic products. Pyrenoid with starch sheath is present in the posterior end of the chloroplast. * Eye spot present in the anterior portion of the chloroplast. It consists of two or three, more or less parallel rows of linearly arranged fat droplets.

Uses

Some ''Chlamydomonas'' are edible.

References

External links

''Chlamydomonas'' Center

''Chlamydomonas reinhardtii'' Transcription Factor Database

3D electron microscopy structures of Chlamydomonas-related proteins at the EM Data Bank(EMDB)

The Seaweed Site

Ancient gene family protects algae from salt and cold in an Antarctic lake
on: EurekAlert!, 20-Aug-2020, on species UWO241 and in Lake Bonney (Antarctica) {{Taxonbar, from=Q133008 Chlamydomonadales genera Chlamydomonadaceae Taxa named by Christian Gottfried Ehrenberg