A Microbial Biorealm page on the genus Coccomyxa
Eukaryota; Viridiplantae; Chlorophyta; Trebouxiophyceae; Trebouxiophyceae incertae sedis; Coccomyxaceae
Description and significance
Coccomyxa, typically referred to as green algae, are spherical to oval in shape with a smooth surface and no flagellum. This species appears green under microscope, consisting of photopigments in addition to alloxanthin, diadinoxanthin, and diatoxanthin (3). These autotrophs contain two forms of chlorophyll, and are primarily aquatic. Coccomyxa are often found on wet rocky areas, along shorelines, or in dense films along the surfaces of ponds (4).
Particular species of Coccymyxa have been discovered to infect the gall bladder of marine fish. Polysporous plasmodia form clusters in the bile ducts and gall bladder of the host causing cholestasis, periductular fibrosis, and pericholangitis (2). The species Coccomyxa parasitica have also been discovered to inhabit several components of mussels (Mytilus galloprovincialis) including the mantle and gill filaments (3).
Coccomyxa are valuable for scientific research because this species has GC-rich mitrochondrial and plastid DNA. These GC-rich sequences are studied for phylogenetic analyses. There is also research about species with organelle DNAs biased toward G and C (4).
Green algae has become a promising resource as the world faces oil and energy shortages. Oily substances can be extracted from green algae which can be made into biodiesel. This development will be useful to humans and to the environment because carbon dioxide pollution will be lessened and energy shortage will no longer be a threat (8).
The ptDNA sequence is 175.7 kb in length with 56% noncoding DNA. The mtDNA sequence is 65.4 kb in length with 52% noncoding DNA. Both the mitrochondrial and plastid genome sequences (accession numbers in GenBank are HQ874522 and HQ693844, respectively) are both circular chomosomes. The mtDNA has 59 genes, and the ptDNA has 115 genes. The mitochondrial and plastid DNAs from the trebouxiophyte green alga Coccomyxa is GC-rich (60-70%). The GC-rich nature of the DNA is nonadaptive and is an innate genetic characteristic of the species. The nature of organelle DNAs are currently being researched for this species. The Coccomyxa organelle genomes have ∼500 nt of repeat sequence in common in both mtDNA and ptDNA, an unusual occurrence for eukaryotic species (4).
Cell structure, metabolism & life cycle
There are 75 different Coccymyxa species (1). This organism is a eukaryotic autotroph. Its cell wall ranges from 40-100 nm thick. Approximately 50% of the protoplast volume consists of one cup-shaped chloroplast. Little starch is located between the thylakoids of these cells. Plastoglobuli are frequently located within Coccomyxa. There are often large gelatinous sheaths, or storage bodies, within some of these cells. The cells consist of high quantities of lipids. Each cell has one or a few membrane-bound areas consisting of many vesicles. The plasma membrane appears relatively far from the cell wall (9).
Coccomyxa perform photosynthesis to produce nutrients for defense, nourishment, and environmental interactions using chlorophyll a, the substance that gives the algae their green color. This species also consists of chlorophyll b (10). Green algae display haploid life cycles and generally reproduce asexually (11).
Ecology (including pathogenesis)
Coccomyxa inhabit salt and fresh water environments. The particular species Coccomyxa parasitica have been located off the coast of Newfoundland, Canada, as well as West Kattegat, a bay of the Baltic Sea. This species is a parasite, inhabiting many marine organisms including the gall bladders of fish, and various components of starfish, oysters, heart cockles, and blue mussles. C. parasitica have no flagella, and have a single set of chloroplasts, a mitochondria, a Golgi apparatus, and they reproduce by autosporulation. The parasitic behavior is indicative by deformities of host shells, weight loss, and lowered reproductive rates of the blue mussels. While infections from green algae threaten marine life, blue mussels have indicated some ability to fight the parasite (3).
Green algae species are beneficial to other organisms. Salamander embryos grown in the presence of green algae showed lower mortality and higher growth rates than those grown in the dark with no algae (6). Lichen species often have symbiotic relationships with Coccomyxa species. Lichen-forming fungi have displayed protection for green algae against over exposure to ultraviolet radiation (7).
Coccomyxa hydrodictyon is a unique species of algae which forms a "water net". This species makes a beautiful net-like sack formed by five or six cylindrical cells adjacent to each other. Hydrodictyon inhabits fresh water, and it reproduces very rapidly, growing up to tens of centimeters in length. This species reproduces both asexually and sexually. As a result, each individual cell can develop into a new colony. When Hydrodictyon is present in large amounts, the fish, lakes, and irrigation ditches in the surrounding environment are harmed by these algae. Blooms of Hydrodictyon are problematic for drinking water resources, as this water is difficult to treat (5).
(2) http://www.ncbi.nlm.nih.gov/pubmed/17886740 Diamant, A., Lipshitz, A., and Ucko, M. "Phylogeny of Coccomyxa (Myxosporea: Myxidiidae) spp. with the description of a new species from Bathygobius cyclopterus (Gobiidae) in the northern Red Sea". NCBI.
(3) http://www.ncbi.nlm.nih.gov/pubmed/19686756. Crespo, C., Rodríguez, H., Segade, P., Iglesias, R., and García-Estévez JM. "Coccomyxa sp. (chlorophyta: chlorococcales), a new pathogen in mussels (Mytilus galloprovincialis) of Vigo estuary (Galicia, NW Spain)". NCBI.
(4) http://www.microscopy-uk.org.uk/mag/indexmag.html?http://www.microscopy-uk.org.uk/mag/wimsmall/green.html. Egmond, Wim v. "Green Algae". Microscopy-UK.
(5) http://www.microscopy-uk.org.uk/mag/indexmag.html?http://www.microscopy-uk.org.uk/mag/wimsmall/green.html Parmentier, J. "Water Net". Microscopy-UK.
(6) http://www.jstor.org/pss/1565283 Marco, A., and Blaustein, A. "Symbiosis with Green Algae Affects Survival and Growth of Northwestern Salamander Embryos". Journal of Herpetology. 2000. Volume 34. p. 617-621.
(7) http://resources.metapress.com/pdf-preview.axd?code=dt6hl9kpyp09xrxk&size=largest Gauslaa, Y., Solhaug, K. "Fungal melanins as a sun screen for symbioltic green algae in the lichen Lobaria pulmonaria". 2000.
(8)http://www.castoroil.in/reference/plant_oils/uses/fuel/sources/algae/biodiesel_algae.html "Biodiesel from Algae". CastorOil.
(9)http://www.jstor.org.lucy2.skidmore.edu:2048/stable/2433479?seq=4&Search=yes&searchText=coccomyxa&list=hide&searchUri=%2Faction%2FdoBasicSearch%3FQuery%3Dcoccomyxa%26gw%3Djtx%26acc%3Don%26prq%3Delectron%2Bmicroscopical%2Bstudies%2Bon%2Bthe%2Bphycobiont%2Bcoccomyxa%2Bschmindle%26Search%3DSearch%26hp%3D25%26wc%3Don&prevSearch=&item=1&ttl=188&returnArticleService=showFullText&resultsServiceName=null Peveling, E., and Galun, M. "Electron-Microscopical Studies on the Phycobiont Coccomyxa Schmidle". New Phytologist Trust. Vol. 77, pp. 713-718. 1976.
(10)http://saltaquarium.about.com/cs/algaecontrol/a/aa110900.htm Hauter, S., and Hauter, D. "Algae--The Chlorophyta Phylum".
(11)http://www.ucmp.berkeley.edu/glossary/gloss6/haploid.html "The Haploid Life Cycle".