Dictyochloropsis

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Dictyochloropsis
Scientific classification OOjs UI icon edit-ltr.svg
Clade: Viridiplantae
Division: Chlorophyta
Class: Trebouxiophyceae
Order: Trebouxiales
Family: Trebouxiaceae
Genus: Dictyochloropsis
Geitler (1966)
Species

Dictyochloropsis is a genus of unicellular green alga of the phylum Chlorophyta. This genus consists of free-living algae which have a reticulate (net-like) chloroplast that varies slightly in morphology between species, [1] [2] [3] and that when mature always lacks a pyrenoid. [3] Dictyochloropsis is asexual and reproduces using autospores. [1]

Contents

Previously, many species of the morphologically similar genus Symbiochloris were incorrectly classified to this taxon. These species were recently reclassified on the basis of molecular DNA analyses. [3]

Dictyochloropsis is found in terrestrial environments all over the world, [2] [4] [5] [6] [7] [8] but can live and grow in freshwater environments as well. [1] [4] Recently, there has been promising research towards growing Dictyocloropsis in culture for the production of biofuels. [4]

Etymology

The name of Dictyochloropsis comes from the Greek language, and references the similar algal genus Dictyochloris . The suffix “-opsis” comes from “ὄψις” or “opsis”, roughly translating to “appearance,” “sight” or “view”. [9] Therefore, “Dictyochloropsis” when translated from its Greek roots means “Dictyochloris-like”. In turn, the prefix “dictyo” is derived from the Greek word “δίκτυο” or “díktyo” meaning “network”, [10] which is in reference to the net-like chloroplast present in this genus and Dictyochloropsis. The medial “-chloro-” is from “χλωρός” or “chloros” meaning “the colour green” [11] [12] because of the green pigment, chlorophyll, which colours the algae.

History of knowledge

Dictyochloropsis was first identified as a genus in 1966 by Lothar Geitler, who defined it as a unicellular green algae with a complex chloroplast that reproduces using autospores. Geitler’s observations were not complete, he was unsure if he had correctly defined the new genus, and he requested supplementary observations from other scientists to attempt at further defining the taxon. [13]

In the early 1980s, Elisabeth Tschermak-Woess used Geitler’s definition to classify several species of lichenized green algae under the same taxon. However, some of these algae reproduce with zoospores or aplanospores, [7] [14] which does not agree with Geitler’s observations. [3] [13]

In 2014, Francesco Dal Grande used microsatellite markers to discover that Dictyochloropsis as previously defined was polyphyletic, forming two distinct clades. The first clade is composed exclusively of free-living algae which reproduce using autospores. [2] The second clade included lichenized as well as free-living algae that reproduce using zoospores or aplanospores. [2] Organisms in both clades have similar morphologies and life cycles, [1] [3] [7] [8] [14]   and this is why they were initially classified in this polyphyletic genus. [3]

In 2016, Pavel Skaloud et al. moved the Dictyochloropsis lichenized species to the genus Symbiochloris based on data from phylogenetic analysis of the 18S rRNA gene. [3] As a result Dictyochloropsis was redefined to its current monophyletic meaning. [3]

Habitat and ecology

Dictyochloropsis is an ecologically important algae [2] most commonly found living as an epiphyte or in soil. Although species in the phylum Chlorophyta mainly live in freshwater habitats, [15] Dictyochloropsis is usually found in terrestrial environments. [1] [2] [3] [4] [7] [8] [13] [14] This algae does not feed, it uses photosynthesis to create its energy, and thus it only lives in habitats with access to light. [15]

Species have been found and cultured from places all over the world, including the Czech Republic, Malaysia, [1] Austria, Germany, Japan, [3] Pakistan, [4] Ukraine [5] and Indonesia. [6] Habitats which Dictyochloropsis has been cultured from include soil, [1] [4] [5] tree bark, [1] [3] [6] and hard surfaces such as rocks and concrete. [3]

Dictyochloropsis is also able to survive and grow in freshwater environments. [4] When isolated, Dictyochloropsis cultures are typically grown in nutrient-rich freshwater environments. [1] [3] [4]

Description

Morphology

Members of Dictyochloropsis are free-living, unicellular green algae. Their cells lack flagella and are globular at all life cycle stages. [3] In this genus, young cells from autospores can be as small as 6 μm in diameter, [1] [3] [4] and the largest species grow up to 50 μm in diameter before reproducing. [3] The cell is often surrounded by a thick envelope of mucilage when mature. Their chloroplast gives Dictyochloropsis cells their characteristic green colour. [3]

Their large, reticulate chloroplast is a key character used to identify this genus. [2] [3] At some ontogenetic stages, the chloroplast forms lobes in a parallel arrangement. [1] [2] [3] When mature, the chloroplast lacks a pyrenoid. [3]   Chloroplast morphology can vary between members of Dictyochloropsis at the same life cycle stage, and is often used to identify specific species within this genus. [3] For example, young D. splendida cells have parietal chloroplasts, while young D. asterochlorodies cells have asteroid chloroplasts. [3]

Dictyochloropsis cells are uninucleate. [1] [2] [3] [4]   Their nucleus is positioned centrally in the cell, and often the chloroplast approaches and surrounds it. [3] As cells grow and produce chlorophyll, the nucleus is often difficult to see through the large chloroplast. Nevertheless, when high portions of the cell lumen fill with clear cytoplasm, the nucleus is revealed. [1] [3]

Life cycle

Dictyochloropsis reproduces asexually exclusively by means of autospores, which largely resemble the parent cell. [1] [2] [3] Different species produce anywhere between 4 and 16 autospores each time they reproduce. [1] [3] Reproduction by autospores is one of the main ways in differentiating Dictyochloropsis from the morphologically similar Symbiochloris taxon. [3]

When Dictyochloropsis cells are preparing to reproduce, the nucleus may first divide intracellularly depending on the number of autospores that will be produced. The number of nuclear divisions prior to cell division dictates the number of spores which will be produced, this can vary even between individuals in the same species. [1] [3] Next, autospores are produced inside the mother cell’s mucilage forming an autosporangium. When the spores are formed, the autosporangium decays by rupturing or dissolving, depending on the species. [3]

As Dictyochloropsis cells prepare to divide, several intracellular changes happen to the chloroplast. [1] The chloroplast's lobes widen, becoming denser and lighter in colour at the edges of the cell, and looser and darker at the center. [1] This change indicates that thylakoids are grouping within the lumen. Lastly, the chloroplast’s lobes fuse into a single, more compact, granular structure surrounding the nucleus and divides into two parts. [1] As the mother cell divides into autospores, several chloroplasts are produced for the resulting cells. [1]

During reproduction, the chloroplast briefly becomes unilayered. As the cell then grows, the chloroplast undergoes longitudinal division producing the characteristic layered lobes. [1]

Practical importance

Culturing algae is one of the most promising fields for generating biofuels, due to their rapid growth rate and minimal nutrition requirements. [4] Dictyochloropsis has been considered as a potential candidate to be farmed for the production of biofuels such as biodiesel, bioethanol and biohydrogen. [4] When cultured under optimal conditions (20-30 °C in BG11 growth medium), Dictyochloropsis produces 21.8% biodiesel per gram of biomass, 175 μmol biohydrogen (mg chl a h−1)−1), and 0.236 g L−1 h−1 bioethanol. [4] Interestingly, Dictyochloropsis produces more biohydrogen when incubated without glucose, rather than with it. [4]

Related Research Articles

<span class="mw-page-title-main">Chlorophyceae</span> Class of green algae

The Chlorophyceae are one of the classes of green algae, distinguished mainly on the basis of ultrastructural morphology. They are usually green due to the dominance of pigments chlorophyll a and chlorophyll b. The chloroplast may be discoid, plate-like, reticulate, cup-shaped, spiral- or ribbon-shaped in different species. Most of the members have one or more storage bodies called pyrenoids located in the chloroplast. Pyrenoids contain protein besides starch. Some green algae may store food in the form of oil droplets. They usually have a cell wall made up of an inner layer of cellulose and outer layer of pectose.

<span class="mw-page-title-main">Chlorophyta</span> Phylum of green algae

Chlorophyta is a division of green algae informally called chlorophytes.

<span class="mw-page-title-main">Green algae</span> Paraphyletic group of eukaryotes

The green algae are a group of chlorophyll-containing autotrophic eukaryotes consisting of the phylum Prasinodermophyta and its unnamed sister group that contains the Chlorophyta and Charophyta/Streptophyta. The land plants (Embryophytes) have emerged deep in the Charophyte alga as a sister of the Zygnematophyceae. Since the realization that the Embryophytes emerged within the green algae, some authors are starting to include them. The completed clade that includes both green algae and embryophytes is monophyletic and is referred to as the clade Viridiplantae and as the kingdom Plantae. The green algae include unicellular and colonial flagellates, most with two flagella per cell, as well as various colonial, coccoid (spherical), and filamentous forms, and macroscopic, multicellular seaweeds. There are about 22,000 species of green algae, many of which live most of their lives as single cells, while other species form coenobia (colonies), long filaments, or highly differentiated macroscopic seaweeds.

<span class="mw-page-title-main">Selenastraceae</span> Family of algae

Selenastraceae is a family of green algae in the order Sphaeropleales. Members of this family are common components of the phytoplankton in freshwater habitats worldwide. A few species have been found in brackish and marine habitats, such as in the Baltic Sea.

Dictyochloris is a genus of green algae in the class Chlorophyceae. It is the sole genus of the family Dictyochloridaceae. It is commonly found in terrestrial and subaerial habitats.

<i>Dictyosphaerium</i> Genus of algae

Dictyosphaerium is a genus of green algae, in the family Chlorellaceae. It occurs in freshwater habitats around the world and is planktonic.

<i>Lagerheimia</i> Genus of algae

Lagerheimia is a genus of green algae in the family Oocystaceae. It is commonly found in freshwater habitats all over the world, although some species are rare and have only been recorded from Europe or the United States.

<i>Monoraphidium</i> Genus of algae

Monoraphidium is a genus of green algae in the family Selenastraceae. Monoraphidium is found free-floating or attached to surfaces in water, or in soils. It is one of the most common types of phytoplankton in freshwater habitats, and has a cosmopolitan distribution.

Pseudomuriella is a genus of green algae, specifically of the class Chlorophyceae. It is the sole genus of the family Pseudomuriellaceae. It is a terrestrial alga that inhabits soils.

<i>Tetraspora</i> Genus of algae

Tetraspora is a genus of green algae in the family Tetrasporaceae of the order Chlamydomonadales, division Chlorophyta. Species of Tetraspora are unicellular green algae that exist in arrangements of four and consist of cells being packaged together in a gelatinous envelope that creates macroscopic colonies. These are primarily freshwater organisms, although there have been few cases where they have been found inhabiting marine environments and even contaminated water bodies. Tetraspora species can be found all around the globe, except in Antarctica. Despite the ubiquitous presence, the greatest growth of the genera's species is seen in the polar climatic zones.

<i>Trebouxia</i> Genus of algae

Trebouxia is a unicellular green alga. It is a photosynthetic organism that can exist in almost all habitats found in polar, tropical, and temperate regions. It can either exist in a symbiotic relationship with fungi in the form of lichen or it can survive independently as a free-living organism alone or in colonies. Trebouxia is the most common photobiont in extant lichens. It is a primary producer of marine, freshwater and terrestrial ecosystems. It uses carotenoids and chlorophyll a and b to harvest energy from the sun and provide nutrients to various animals and insects.

<i>Tetrastrum</i> Genus of algae

Tetrastrum is a genus of green algae (Chlorophyta). It is a common component of the phytoplankton of freshwater habitats, particularly eutrophic and alkaline waters.

<i>Coccomyxa</i> Genus of algae

Coccomyxa is a genus of green algae in the family Coccomyxaceae. This genus is defined by their small, elliptical to spherical shape, and the presence of a simple parietal chloroplast. These features, along with their occurrence in various lifestyles such as free-living, parasitic, or as photobionts, have been used to identify more than 40 species. Using additional morphological features, such as brown akinetes formation, allows for the differentiation between Coccomyxa and the genus Pseudococcomyxa, as they tend to share some morphological characteristics like the general cell shape and one-sided mucilage cap. Recent molecular analysis, however, indicates that the genus Pseudococcomyxa is contained within different Coccomyxa clades, signaling the fact that the two genera are the same. Coccomyxa has often been used as a model organism, and its genome is being completely sequenced. The genus is also an attractive candidate for biofuels.

<i>Chlorokybus</i> Genus of basal green algae

Chlorokybus is a multicellular (sarcinoid) genus of basal green algae or charophyte. It has been classified as the sole member of the family Chlorokybaceae, which is the sole member of the order Chlorokybales, in turn the sole member of the class Chlorokybophyceae. It grows on soil and rock surfaces, and is rare.

Dictyochloropsis reticulata is a species of green alga in the Trebouxiales. It is a known as a photobiont with several lichen species, like Lobaria pulmonaria, but also as a free-living soil alga as well. Phylogenetic analysis of rRNA sequence data revealed that the species shares a sister group relationship with two other green algae that lack motile stages, Chlorella saccharophila and C. luteoviridis.

<span class="mw-page-title-main">Autospore</span>

Autospores are a type of spores that are produced by algae to enable asexual reproduction and spread. They are non-motile and non-flagellated aplanospores that are generated within a parent cell and have the same shape as the parent cell before their release. Autospores are also known as resting spores. Algae primarily use three different types of spores for asexual reproduction - autospores, zoospores, and aplanospores. Autospores occur in several groups of algae, including Eustigmatophyceae, Dinoflagellates, and green algae. One example of a colonial alga that produces autospores is Dichotomococcus. This alga generates two autospores per reproducing cell, and the autospores escape through a slit in the cell wall and remain attached to the mother cell. Some study on autospores and algae in general include looking into its use for biofuel, animal feed, food supplements, nutraceuticals, and pharmaceuticals.

Bracteamorpha is a genus of green algae in the order Sphaeropleales, and is the only genus in the family Bracteamorphaceae. It contains a single species, Bracteamorpha trainorii.

Elisabeth Tschermak-Woess was an Austrian University lecturer, cytologist, and phycologist who worked with lichen photobionts. In 1994, Tschermak-Woess was awarded the Acharius Medal for her lifetime contributions to lichenology. She had a Festschrift dedicated to her in 1988, in the journal Plant Systematics and Evolution. Lichen taxa that have been named after Tschermak-Woess include the genus Woessia and the species Asterochloris woessiae.

Elongatocystis is an autotrophic green alga in the Oocystaceae family that is defined by its elongated type cell. This genus was discovered in a rockpool at Belvedere River, Mpumalanga, South Africa and described by Krienitz and Bock in 2011 along with two other strains of Oocystaceae. Its discovery and genetic analysis determined that Oocystis ecballocystiformis should be removed. In its place, the genus Elongatocystis was proposed to more accurately represent the phylogenetic tree.

Asterochloris is a genus of green algae in the family Trebouxiophyceae. It is a common photobiont in lichen, occurring in the thalli of more than 20 lichen genera worldwide. Asterochloris is distinguishable from the morphologically similar genus Trebouxia, primarily due to its deeply lobed chloroplast, the placement of the chloroplast along the cell's periphery before the initiation of zoospore or aplanospore formation, and its tendency to primarily reproduce asexually through the production of aplanospores.

References

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  4. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Junaid, Sara; Khanna, Namita; Lindblad, Peter; Ahmed, Mehboob (September 2019). "Multifaceted biofuel production by microalgal isolates from Pakistan". Biofuels, Bioproducts and Biorefining. 13 (5): 1187–1201. doi:10.1002/bbb.2009. ISSN   1932-104X. S2CID   149853265.
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  7. 1 2 3 4 Tschermak-Woess, Elisabeth (1980). "Chaenothecopsis consociata ? kein parasitischer oder parasymbiontischer Pilz, sondern lichenisiert mitDictyochloropsis symbiontica, spec. nova". Plant Systematics and Evolution (in German). 136 (3–4): 287–306. doi:10.1007/BF01004633. ISSN   0378-2697. S2CID   26932481.
  8. 1 2 3 Tschermak–Woess, Elisabeth (May 1995). "Dictyochloropsis Splendida (Chlorophyta), the Correct Phycobiont of Phlyctis Argena and the High Degree of Selectivity or Specificity Involved". The Lichenologist. 27 (3): 169–187. doi:10.1016/S0024-2829(95)80016-6. ISSN   0024-2829. S2CID   250349877.
  9. ↑ "Word Information - search results for: -opsis". wordinfo.info. Retrieved 2020-04-29.
  10. ↑ "dictyo- - Word Information". wordinfo.info. Retrieved 2020-04-29.
  11. ↑ "chloro-, chlor- + - Word Information". wordinfo.info. Retrieved 2020-04-29.
  12. ↑ "Chloros Meaning in Bible - New Testament Greek Lexicon - New American Standard". Bible Study Tools. Retrieved 2020-04-29.
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  14. 1 2 3 Tschermak-Woess, Elisabeth (1984). "Über die weite Verbreitung lichenisierter Sippen von Dictyochloropsis und die systematische Stellung von Myrmecia reticulata (Chlorophyta)". Plant Systematics and Evolution. 147 (3–4): 299–322. doi:10.1007/bf00989391. ISSN   0378-2697. S2CID   24675680.
  15. 1 2 Lee, Robert Edward (March 2018). "Chlorophyta". Phycology. pp. 133–230. doi:10.1017/9781316407219.009. ISBN   9781316407219. S2CID   242727609 . Retrieved 2020-04-29.
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