User:Jjmack123/sandbox

Critiquing an Article: Marine bacteriophage

At first glance the article isn't very long despite presenting the fact that "marine bacteriophages play an important part of the marine ecosystem". Citing sources seem to be quite consistent except for the paragraphs under sub-headings "In Sediments" and "Carbon Cycles". Only one citation is used for the entire paragraph. This makes it unclear if all facts are citing that one paragraph or just the last sentence. It seems unclear. However the article seems neutral in its stance, with reputable sources from nature, PLoS other academically-sourced journals. The citations function properly, giving access to the full article and the author does a good job in summarizing their main points. I think the viewpoints under-represented here are the processes that marine bacteriophages undergo. the article mentions the carbon cycle but does not elaborate on its part of the carbon cycle or link the a page that gives more information. I understand that there is a lot of the subject that is unknown, therefore it is understandable that information may be limited. I hope that in the future, with more scientific information available with future studies, this article can expanded on.

= Cyanobiont =

Examples of Symbioses
Cyanobacteria have been documented to form symbioses with a large range of eukaryotes in both marine and terrestrial environments. Cyanobionts are usually of benefit to their hosts through dissolved organic carbon (DOC) production or nitrogen fixation but vary in function depending on their host. Organisms that depend on cyanobacteria often live in Nitrogen-limited, oligotrophic environments and can significantly alter marine composition leading to blooms.

Diatoms
Commonly found in oligotrophic environments, diatoms within the genera Hemiaulus and Rhizosolenia both form a symbiotic association with the filamentous cyanobacteria Richelia intracellularis. As an endophyte of up to 12 species of Rhizosolenia, R. intracellularis provides fixed nitrogen to its host via the terminally-located heterocyst. Richella-Rhizosolenia are abundant within the nitrogen-limited waters of the Central-Pacific Gyre. Several field studies have linked the occurrence of phytoplankton blooms within the gyre to a increase in nitrogen fixation from Richella-Rhizosolenia symbiosis. A dominant organism with warm oligotrophic waters, five species of the genus Hemiaulus receives fixed nitrogen from R. intracellularis. Hemiaulus-Richella symbioses are up to 245 times more abundant than the former with 80%-100% of Hemilalus containing the cyanobiont. Nitrogen fixation from Hemiaulus-Richella is 21 to 45 times greater than Richella-Rhizosolenia within the southwestern Atlantic and Central Pacific Gyre, respectively.

Other genera of diatoms can form symbioses with cyanobacteria, however their relationships are less known. Spheroid cyanobacteria have been found within the diatom Rhopalodia gibba which have been found to posses genes for nitrogen fixation but do not possess the proper pigments for photosynthesis.

Dinoflagellates
Heterotrophic dinoflagellates can form symbioses with cyanobacteria (phaeosomes) most often in tropical, marine environments. The function of the cyanobiont varies depending on its host species. The abundant marine cyanobacteria Synechococcus is a cyanobiont of dinoflagellates in the genus Ornithocercus, Histionesis and Citharistes where it was hypothesized to benefit its host through the provision of fixed nitrogen in oligotrophic, subtropical waters. Increased instances of phaeosome symbiosis have been documented in a stratified, nitrogen-limited environment and living within a host can provide the desired anaerobic environment for fixation to occur. However there is conflicting evidence of this. One study on the phaeosomes of Ornithocercus spp. has provided evidence for carbon rather than nitrogen fixation from Synechococcus, due to the absence of nitrogenase within the cyanobacteria.

Sponges
100 species within the classes Calcarea and Demospongiae form symbioses with cyanobacteria genera Aphanocapsa, Synechocystis, Oscillatoria and Phormidium. Cyanobacteria benefit their host through providing glycerol and organic phosphates through photosynthesis and supply up to half of its required energy and a majority of its carbon budget. Two groups of photosynthetic sponges have been described: "cyanosponges" and "phototrophs". Cyanosponges are mixotrophic and therefore obtain energy through heterotrophic feeding as well as photosynthesis. The latter group receives almost all of their energy requirements through photosynthesis and therefore have a larger surface area in order increase exposure to sunlight. The most common cyanobiont found in sponges is Synechococcus with the species Candidatus Synechococcus spongiarum inhabiting a majority of symbiotic sponges within the Caribbean. Another widely distributed species of cyanobacteria Oscillatoria spongeliae is found within Lamellodysidea herbacea along side ten other species. O. spongeliae benefits their host through providing carbon as well as a variety of chlorinated amino derivatives depending on the host strain.

Lichens
Lichens are the result of a symbiosis between a mycobiont and an autotroph, usually green algae or cyanobacteria. About 8% of lichen species contain a cyanobiont, most commonly Nostoc as well as Calothrix, Scytonema and Fischerella. All cyanobionts inhabiting lichens contain heterocysts to fix Nitrogen and can be distributed throughout their host in specific regions (heteromerous) or randomly throughout the thallus (homoiomerous). Additionally, some lichen species are tripartate, containing both a cyanobacteria and green algal symbiont.

Ascidians
Filamentous cyanobacteria within the genera Synechocystis and Prochloron has been found within the tunic cavity of didemnid sea squirts. The symbiosis is proposed to have originated through the intake of a combination of sand and cyanobacteria which eventually proliferated. The hosts benefit from receiving fixed carbon from the cyanobiont while the cyanobiont may benefit by protection from harsh environments.

Echiuroid Worms
Little is known about the symbiotic relationship between echiuroid worms and cyanobacteria. Unspecified cyanobacteria has been found within the subepidermal connective tissue of Ikedosoma gogoshimense and Bonellia fuliginosa.