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Thiomargarita namibiensis is a Gram-negative, facultative anaerobic, coccoid bacterium found in the ocean sediments of the continental shelf of Namibia. It is the second largest bacterium ever discovered, 0.1–0.3 mm (100–300 μm) in diameter on average, but sometimes attaining 0.75 mm (750 μm). Cells of Thiomargarita namibiensis are large enough to be visible to the naked eye. The previously largest known bacterium was Epulopiscium fishelsoni, at 0.5mm long. Thiomargarita magnifica, described in 2022, is larger. Thiomargarita namibiensis have large vacuoles for their chemolithotrophic metabolism. The vacuoles contribute to their gigantism, allowing them to store nutrients for asexual reproduction of their complex genome.
Cyanobacteria, also called Cyanobacteriota or Cyanophyta, are a phylum of autotrophic gram-negative bacteria that can obtain biological energy via photosynthesis. The name 'cyanobacteria' refers to their color, which similarly forms the basis of cyanobacteria's common name, blue-green algae, although they are not scientifically classified as algae. They appear to have originated in a freshwater or terrestrial environment.
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.
Chloroflexus aurantiacus is a photosynthetic bacterium isolated from hot springs, belonging to the green non-sulfur bacteria. This organism is thermophilic and can grow at temperatures from 35 °C to 70 °C. Chloroflexus aurantiacus can survive in the dark if oxygen is available. When grown in the dark, Chloroflexus aurantiacus has a dark orange color. When grown in sunlight it is dark green. The individual bacteria tend to form filamentous colonies enclosed in sheaths, which are known as trichomes.
Sulfur-reducing bacteria are microorganisms able to reduce elemental sulfur (S0) to hydrogen sulfide (H2S). These microbes use inorganic sulfur compounds as electron acceptors to sustain several activities such as respiration, conserving energy and growth, in absence of oxygen. The final product of these processes, sulfide, has a considerable influence on the chemistry of the environment and, in addition, is used as electron donor for a large variety of microbial metabolisms. Several types of bacteria and many non-methanogenic archaea can reduce sulfur. Microbial sulfur reduction was already shown in early studies, which highlighted the first proof of S0 reduction in a vibrioid bacterium from mud, with sulfur as electron acceptor and H
2 as electron donor. The first pure cultured species of sulfur-reducing bacteria, Desulfuromonas acetoxidans, was discovered in 1976 and described by Pfennig Norbert and Biebel Hanno as an anaerobic sulfur-reducing and acetate-oxidizing bacterium, not able to reduce sulfate. Only few taxa are true sulfur-reducing bacteria, using sulfur reduction as the only or main catabolic reaction. Normally, they couple this reaction with the oxidation of acetate, succinate or other organic compounds. In general, sulfate-reducing bacteria are able to use both sulfate and elemental sulfur as electron acceptors. Thanks to its abundancy and thermodynamic stability, sulfate is the most studied electron acceptor for anaerobic respiration that involves sulfur compounds. Elemental sulfur, however, is very abundant and important, especially in deep-sea hydrothermal vents, hot springs and other extreme environments, making its isolation more difficult. Some bacteria – such as Proteus, Campylobacter, Pseudomonas and Salmonella – have the ability to reduce sulfur, but can also use oxygen and other terminal electron acceptors.
Beggiatoa is a genus of Gammaproteobacteria belonging to the order Thiotrichales, in the Pseudomonadota phylum. These bacteria form colorless filaments composed of cells that can be up to 200 µm in diameter, and are one of the largest prokaryotes on Earth. Beggiatoa are chemolithotrophic sulfur-oxidizers, using reduced sulfur species as an energy source. They live in sulfur-rich environments such as soil, both marine and freshwater, in the deep sea hydrothermal vents, and in polluted marine environments. In association with other sulfur bacteria, e.g. Thiothrix, they can form biofilms that are visible to the naked eye as mats of long white filaments; the white color is due to sulfur globules stored inside the cells.
Campylobacterota are a phylum of Gram-negative bacteria.. Only a few genera have been characterized, including the curved to spirilloid Wolinella, Helicobacter, and Campylobacter. Until the 2021 revision of bacterial taxonomy by the ICSP, the entire phylum was classified within the Proteobacteria as the Epsilonproteobacteria.
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.
Gammaproteobacteria is a class of bacteria in the phylum Pseudomonadota. It contains about 250 genera, which makes it the most genus-rich taxon of the Prokaryotes. Several medically, ecologically, and scientifically important groups of bacteria belong to this class. All members of this class are Gram-negative. It is the most phylogenetically and physiologically diverse class of the Pseudomonadota.
Thioploca is a genus of filamentous sulphur-oxidizing bacteria, in the order Thiotrichales. They inhabit both marine and freshwater environments, forming vast communities off the Pacific coast of South America and in other areas with a high organic matter sedimentation and bottom waters rich in nitrate and poor in oxygen. Their cells contain large vacuoles that occupy more than 80% of the cellular volume, used to store nitrate to oxidize sulphur for anaerobic respiration in the absence of oxygen, an important characteristic of the genus. With cell diameters ranging from 15-40 µm, they are some of the largest bacteria known. They provide an important link between the nitrogen and sulphur cycles, because they use both sulfur and nitrogen compounds. They secrete a sheath of mucus which they use as a tunnel to travel between sulphide-containing sediment and nitrate-containing sea water.
The Sippewissett microbial mat is a microbial mat in the Sippewissett Salt Marsh located along the lower eastern Buzzards Bay shoreline of Cape Cod, about 5 miles north of Woods Hole and 1 mile southwest of West Falmouth, Massachusetts, in the United States. The marsh has two regions, the Great Sippewisset Marsh to the north and Little Sippewisset Marsh to the south, separated from each other by a narrow tongue of land. The marsh extends into an estuary in which the intertidal zone provides a dynamic environment that supports a diverse ecology, including threatened and endangered species such as the roseate tern. The ecology of the salt marsh is based in and supported by the microbial mats which cover the ground of the marsh.
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.
Chloroflexus aggregans is a thermophilic, filamentous, phototrophic bacterium that forms dense cell aggregates. Its type strain is MD-66.
Thioploca chileae is a marine thioploca from the benthos of the Chilean continental shelf. It is a colonial, multicellular, gliding trichomes of similar diameter enclosed by a shared sheath. It possesses cellular sulfur inclusions located in a thin peripheral cytoplasm surrounding a large, central vacuole. It is a motile organism through gliding. The trichome diameters of Thioploca chileae range from 12 to 20 μm.
Dissimilatory nitrate reduction to ammonium (DNRA), also known as nitrate/nitrite ammonification, is the result of anaerobic respiration by chemoorganoheterotrophic microbes using nitrate (NO3−) as an electron acceptor for respiration. In anaerobic conditions microbes which undertake DNRA oxidise organic matter and use nitrate (rather than oxygen) as an electron acceptor, reducing it to nitrite, then ammonium (NO3−→NO2−→NH4+).
Anaerolineaceae is a family of bacteria from the order of Anaerolineales. Anaerolineaceae bacteria occur in marine sediments. There are a total of twelve genera in this family, most of which only encompass one species. All known members of the family are Gram-negative and non-motile. They also do not form bacterial spores and are either mesophilic or thermophilic obligate anaerobes. It is also known that all species in this family are chemoheterotrophs.
Microbial oxidation of sulfur is the oxidation of sulfur by microorganisms to build their structural components. The oxidation of inorganic compounds is the strategy primarily used by chemolithotrophic microorganisms to obtain energy to survive, grow and reproduce. Some inorganic forms of reduced sulfur, mainly sulfide (H2S/HS−) and elemental sulfur (S0), can be oxidized by chemolithotrophic sulfur-oxidizing prokaryotes, usually coupled to the reduction of oxygen (O2) or nitrate (NO3−). Anaerobic sulfur oxidizers include photolithoautotrophs that obtain their energy from sunlight, hydrogen from sulfide, and carbon from carbon dioxide (CO2).
Roseofilum reptotaenium, also called coral killer, is a filamentous species of cyanobacteria. It is the pathogenic agent responsible for black band disease on Siderastrea siderea coral.
Cyanobacterial morphology refers to the form or shape of cyanobacteria. Cyanobacteria are a large and diverse phylum of bacteria defined by their unique combination of pigments and their ability to perform oxygenic photosynthesis.
Helle Ploug is marine scientist known for her work on particles in seawater. She is a professor at the University of Gothenburg, and was named a fellow of the Association for the Sciences of Limnology and Oceanography in 2017.
References
- ↑ Maier, S.; Gallardo, V. A. (1984). "Thioploca araucae sp. nov. and Thioploca chileae sp. nov". International Journal of Systematic Bacteriology. 34 (4): 414–418. doi: 10.1099/00207713-34-4-414 . ISSN 0020-7713.
