| Zoothamnium niveum | |
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| Species: | Z. niveum |
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| Zoothamnium niveum | |
Zoothamnium niveum is a species of ciliate protozoan which forms feather-shaped colonies in marine coastal environments. The ciliates form a symbiosis with sulfur-oxidizing chemosynthetic bacteria of the species " Candidatus Thiobios zoothamnicoli", which live on the surface of the colonies and give them their unusual white color.
The conspicuously white and feather-shaped colonies are composed of individual bell-shaped cells known as zooids. The stalks of individual cells grow from a single central stalk. Colonies can reach a length of up to 15 mm, formed from hundreds of single zooids, each with a length of only 120 µm. An entire colony can contract into a ball-shaped bunch through the contraction of myonemes in their stalks. [2] [3]
The white color is produced by chemolithoautotrophic sulfur-oxidizing bacteria, which cover the entire surface of the Z. niveum colony. [4] In most other species of Zoothamnium, bacteria are only known to cover the stalks. The bacteria contain elemental sulfur, which appear white. Z. niveum appears colorless when the bacteria are absent. [3]
Like in other ciliates, a contractile vacuole maintains osmotic balance for the cell, and allows it to survive the salt concentrations in both marine and brackish water. The vacuole is located in Z. niveum directly below the lip of the peristome. [2]
Most ciliates live as single-celled organisms in aquatic environments, and the single cell carries out all functions of life, such as nutrition, metabolism, and reproduction. Colonies of Z. niveum are composed of numerous individual cells that form a feather-like colonial unit, with several different cell types. Old branches of the colony illustrate the polymorphism of the zooids when viewed under the microscope. Three different forms of the individual ciliate cells are present, which are distinct in both form and function. The large macrozooids can transform into swarmers and leave the colony. They settle on suitable surfaces and develop into new colonies. The microzooids are small cells specialized for feeding, which the colony does by consumption of their symbiotic bacteria and other organic particles. At the terminal ends of the colony are specialized zooids that can elongate and facilitate the asexual reproduction of the colony. [2]
The bacteria on different parts of a host have different shapes despite belonging to the same species (polymorphism). Those on the stalks are shaped like rods, but those in the region of the ciliated oral apparatus of the microzooids are shaped like small spheres (coccoid). Intermediate forms are also found in between. [4]
The sessile colonies of Z. niveum were first described from the shallow waters of the Red Sea. [5] They were later also found in the Florida Keys in the Gulf of Mexico, and at the Belize Barrier Reef in the Caribbean Sea. [3]
The colonies settle in environments that contain sulfide. Hydrogen sulfide, sulfide, and related sulfur-containing compounds like thiosulfate are produced during the decomposition and remineralization of organic material. For example, plant material like the torn-off leaves of Posidonia oceanica in seagrass meadows of the Mediterranean accumulate in depressions of rocky ledges and decompose. In mangrove forests of the Caribbean, organic material can form peat and release sulfide. [6] Hydrogen sulfide can also originate from geological phenomena such as at underwater hydrothermal vents, e.g. off the Canary Islands.
Extreme ecological conditions prevail at these sources of sulfide close to which colonies of Z. niveum settle. Because there is little water current under mangrove roots and at seagrass deposits under rock ledges, these decomposition hot-spots are extremely poor in oxygen and rich in sulfide. In mangrove forests off the coast of Belize, they have been found around small holes in the mangrove peat which form when the mangrove rootlets decompose. [6] These openings have been called sulfide "microvent[s]", [7] because they resemble in miniature the hydrothermal vents of the deep sea, the so-called black smokers, although the temperatures in shallow waters are much lower (28 °C in the Caribbean, 21 °C-25 °C in the Mediterranean (summer)), compared to the gradient between >300 °C and 2 °C in the deep sea because of volcanic activity. The Zoothamnium colonies do not settle directly over the decomposing material, but nearby e.g. on overhanging rocks, leaves of seagrass or seaweed, or mangrove roots. [3]
The symbiotic benefits provided by the colonies of Z. niveum for its attached ectosymbiotic bacteria Candidatus Thiobios zoothamnicoli (a member of the Gammaproteobacteria [4] ), which are vertically transmitted to its host, [8] are its active alternation between oxygen-rich and sulfide-rich conditions. This alternation can occur through the regular contraction and extension of the colonies and through the water currents set up by the beating of the cilia in the region of the oral opening of the ciliates. [9]
The rapid contraction and slow re-extension of the colonies causes a flow of both sulfide-rich water for the feeding of the bacteria and normal oxygenated seawater for the respiration of Z. niveum. Through the beating of its cilia at the oral apparatus of Zoothamnium is the mixing regulated. When there is a low supply of sulfur compounds, the bacteria use the sulfur that is stored inside their cells. They eventually appear pale and transparent after four hours because the stored sulfur has been consumed. However, if the sulfide concentration is too high, it can be toxic to the Zoothamnium colonies and kill the ciliates despite the bacteria. [9]
Bacteria close to the oral end of the microzooids have a coccoid form, a larger volume, and a higher division rate than the rod-shaped bacteria on the stalks, despite both belonging to the same species. This is because the mixing of water by the beating of the oral cilia result in a more optimal concentration of both oxygen and sulfide in the water there. [9] The bacteria at the oral region can thus be used as a food source and are swirled into the mouth (cytostome) of the ciliate and digested.
Bryozoa are a phylum of simple, aquatic invertebrate animals, nearly all living in sedentary colonies. Typically about 0.5 millimetres long, they have a special feeding structure called a lophophore, a "crown" of tentacles used for filter feeding. Most marine bryozoans live in tropical waters, but a few are found in oceanic trenches and polar waters. The bryozoans are classified as the marine bryozoans (Stenolaemata), freshwater bryozoans (Phylactolaemata), and mostly-marine bryozoans (Gymnolaemata), a few members of which prefer brackish water. 5,869 living species are known. At least two genera are solitary ; the rest are colonial.
Thiomargarita is a genus which includes the vacuolate sulfur bacteria species Thiomargarita namibiensis, Candidatus Thiomargarita nelsonii, and Ca. Thiomargarita joergensii. In 2022, scientists working in a Caribbean mangrove discovered an extremely large member of the genus, provisionally named T. magnifica, whose cells are easily visible to the naked eye at up to 2 centimetres (0.79 in) long.
Riftia pachyptila, commonly known as the giant tube worm and less commonly known as the giant beardworm, is a marine invertebrate in the phylum Annelida related to tube worms commonly found in the intertidal and pelagic zones. R. pachyptila lives on the floor of the Pacific Ocean near hydrothermal vents. The vents provide a natural ambient temperature in their environment ranging from 2 to 30 °C, and this organism can tolerate extremely high hydrogen sulfide levels. These worms can reach a length of 3 m, and their tubular bodies have a diameter of 4 cm (1.6 in).
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Vorticella is a genus of bell-shaped ciliates that have stalks to attach themselves to substrates. The stalks have contractile myonemes, allowing them to pull the cell body against substrates. The formation of the stalk happens after the free-swimming stage.
Beggiatoa is a genus of Gammaproteobacteria belonging to the order Thiotrichales, in the Pseudomonadota phylum. This genus was one of the first bacteria discovered by Ukrainian botanist Sergei Winogradsky. During his research in Anton de Bary's laboratory of botany in 1887, he found that Beggiatoa oxidized hydrogen sulfide (H2S) as an energy source, forming intracellular sulfur droplets, with oxygen as the terminal electron acceptor and CO2 used as a carbon source. Winogradsky named it in honor of the Italian doctor and botanist Francesco Secondo Beggiato (1806 - 1883), from Venice. Winogradsky referred to this form of metabolism as "inorgoxidation" (oxidation of inorganic compounds), today called chemolithotrophy. These organisms live in sulfur-rich environments such as soil, both marine and freshwater, in the deep sea hydrothermal vents and in polluted marine environments. The finding represented the first discovery of lithotrophy. Two species of Beggiatoa have been formally described: the type species Beggiatoa alba and Beggiatoa leptomitoformis, the latter of which was only published in 2017. This colorless and filamentous bacterium, sometimes in association with other sulfur bacteria (for example the genus Thiothrix), can be arranged in biofilm visible to the naked eye formed by a very long white filamentous mat, the white color is due to the stored sulfur. Species of Beggiatoa have cells up to 200 µm in diameter and they are one of the largest prokaryotes on Earth.
Thiothrix is a genus of filamentous sulfur-oxidizing bacteria, related to the genera Beggiatoa and Thioploca. They are usually Gram-negative and rod-shaped. They form ensheathed multicellular filaments that are attached at the base, and form gonidia at their free end. The apical gonidia have gliding motility. Rosettes of the filaments are not always formed but are typical. Sulfur is deposited in invaginations within the cell membrane.
Lucinidae, common name hatchet shells, is a family of saltwater clams, marine bivalve molluscs.
Phylactolaemata is a class of the phylum Bryozoa whose members live only in freshwater environments. Like all bryozoans, they filter feed by means of an extensible "crown" of ciliated tentacles called a lophophore, and like nearly all bryozoans, they live in colonies, each of which consists of clones of the founding member. Unlike those of some marine bryozoans, phylactolaemate colonies consist of only one type of zooid, the feeding forms known as autozooids. These are supported by an unmineralized "exoskeleton" made of gelatinous material or protein, secreted by the zooids. The class contains only one extant order, Plumatellida.
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Epixenosomes, also known as Candidatus Epixenosoma, are a genus of bacteria in the phylum Verrucomicrobiota that form a symbiosis with marine ciliates of the genus Euplotidium, where they help to defend their ciliate hosts against predators. It is a monospecific genus, containing only the species Ca. Epixenosoma ejectans.
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Solemya velum, the Atlantic awning clam, is a species of marine bivalve mollusc in the family Solemyidae, the awning clams. This species is found along the eastern coast of North America, from Nova Scotia to Florida and inhabits subtidal sediments with high organic matter (OM) content and low Oxygen, such as salt ponds, salt marshes, and sewage outfalls.
Sulfurimonas is a bacterial genus within the class of Campylobacterota, known for reducing nitrate, oxidizing both sulfur and hydrogen, and containing Group IV hydrogenases. This genus consists of four species: Sulfurimonas autorophica, Sulfurimonas denitrificans, Sulfurimonas gotlandica, and Sulfurimonas paralvinellae. The genus' name is derived from "sulfur" in Latin and "monas" from Greek, together meaning a “sulfur-oxidizing rod”. The size of the bacteria varies between about 1.5-2.5 μm in length and 0.5-1.0 μm in width. Members of the genus Sulfurimonas are found in a variety of different environments which include deep sea-vents, marine sediments, and terrestrial habitats. Their ability to survive in extreme conditions is attributed to multiple copies of one enzyme. Phylogenetic analysis suggests that members of the genus Sulfurimonas have limited dispersal ability and its speciation was affected by geographical isolation rather than hydrothermal composition. Deep ocean currents affect the dispersal of Sulfurimonas spp., influencing its speciation. As shown in the MLSA report of deep-sea hydrothermal vents Campylobacterota, Sulfurimonas has a higher dispersal capability compared with deep sea hydrothermal vent thermophiles, indicating allopatric speciation.
Paracatenula is a genus of millimeter sized free-living marine gutless catenulid flatworms.
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Zoothamnium is a genus of ciliate protozoan.
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