| Haloferax mediterranei | |
|---|---|
 | |
| SEM image of Haloferax mediterranei. | |
Scientific classification  | |
| Domain: | Archaea |
| Kingdom: | Euryarchaeota |
| Class: | Halobacteria |
| Order: | Haloferacales |
| Family: | Haloferacaceae |
| Genus: | Haloferax |
| Species: | H. mediterranei |
| Binomial name | |
| Haloferax mediterranei (Rodriguez-Valera et al. 1983) Torreblanca et al. 1987 [1] | |
| Synonyms | |
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Haloferax mediterranei is a species of archaea in the family Haloferacaceae. [1]
Haloferax mediterranei was discovered in 1983 in marine salterns in the village of Santa Pola, Spain. [2] The species was initially named Halobacterium mediterranei, then renamed Haloferax mediterranei in 1986. [3] Haloferax mediterranei is the fastest-growing known member of the Halobacteriales under optimal laboratory conditions, but it is relatively rare in the environment. [4] The full genome of H. mediterranei was sequenced in 2012. [5]
Haloferax mediterranei is the fastest-growing archaeon in the Halobacteriales family, [4] with generation times as low as 1.2 hours reported under optimal laboratory growth conditions. [6] Haloferax mediterranei is able to use a variety of compounds as carbon and energy sources, [7] and can accumulate materials to serve as a source of carbon and energy, as well as use organic and inorganic nitrogen sources. [4] H. mediterranei is an extremely versatile microorganism that can anaerobically or aerobically, tolerate a wide range of salinities (between 10% and 32.5%), a wide range of pH values (between 5.75 and 8.75) and a wide range of temperatures (between 18 and 55oC). [7] [6] [4] It can also tolerate a variety of high metal concentrations, such as nickel, lithium, cobalt and arsenic, which are toxic to most organisms. [6]
Haloferax mediterranei is an extremely pleomorphic organism, cells are usually flat disks. [4] Like Haloferax volcanii , it performs cell division through the formation of an FtsZ ring. [8]
Haloferax mediterranei produces a mucous exopolysaccharide matrix that accumulates as a top layer in liquid medium. [9] This is a widespread strategy in the microbial world that helps biofilms adhere to surfaces, as well as protects cells from pH and temperature variations and radiation. [10] These exopolysaccharides have been studied as potential emulsifiers for industry. [9] The unshaken biofilms of H. mediterranei in liquid cultures rapidly rearrange into a honeycomb formation pattern upon exposure to air, a phenomenon that has yet to be fully elucidated. [11]
H. mediterranei, when grown under phosphate limitation, [12] produces polyhydroxyalkanoates, a type of biodegradable thermoplastic currently commercially produced using bacteria. [13] It has been suggested that H. mediterranei is a good candidate for industrial production of biodegradable thermoplastics due to its fast growth, low contamination rates and ease of lysis. [14] Deleting the genes responsible for exopolysaccharide synthesis results in a 20% increase in the amount of PHAs in the cell. [13] Increasing the salt concentration of the media also increased the concentration of PHAs produced. [15]
Like some other members of the Halobacteriales group, notably Halobacterium salinarum , Haloferax mediterranei produces gas vesicles, believed to act aiding buoyancy. The production of gas vesicles only occurs in high salt concentrations and once cells have reached stationary phase. [4] By transforming 14 genes from the vac cluster of H. mediterranei into a gas-vesicle deficient archaeon H. volcanii , researchers found that H. volcanii is able to produce functional gas vacuoles. [16] [17]
A halophile is an extremophile that thrives in high salt concentrations. In chemical terms, halophile refers to a Lewis acidic species that has some ability to extract halides from other chemical species.
A biofilm is a syntrophic community of microorganisms in which cells stick to each other and often also to a surface. These adherent cells become embedded within a slimy extracellular matrix that is composed of extracellular polymeric substances (EPSs). The cells within the biofilm produce the EPS components, which are typically a polymeric combination of extracellular polysaccharides, proteins, lipids and DNA. Because they have a three-dimensional structure and represent a community lifestyle for microorganisms, they have been metaphorically described as "cities for microbes".
Halobacterium is a genus in the family Halobacteriaceae.
Burkholderia cenocepacia is a Gram-negative, rod-shaped bacterium that is commonly found in soil and water environments and may also be associated with plants and animals, particularly as a human pathogen. It is one of over 20 species in the Burkholderia cepacia complex (Bcc) and is notable due to its virulence factors and inherent antibiotic resistance that render it a prominent opportunistic pathogen responsible for life-threatening, nosocomial infections in immunocompromised patients, such as those with cystic fibrosis or chronic granulomatous disease. The quorum sensing systems CepIR and CciIR regulate the formation of biofilms and the expression of virulence factors such as siderophores and proteases. Burkholderia cenocepacia may also cause disease in plants, such as in onions and bananas. Additionally, some strains serve as plant growth-promoting rhizobacteria.
Haloferax is a genus of halobacteria in the order Haloferacaceae.
Halocins are bacteriocins produced by halophilic Archaea and a type of archaeocin.
Thermococcus litoralis is a species of Archaea that is found around deep-sea hydrothermal vents as well as shallow submarine thermal springs and oil wells. It is an anaerobic organotroph hyperthermophile that is between 0.5–3.0 μm (20–118 μin) in diameter. Like the other species in the order thermococcales, T. litoralis is an irregular hyperthermophile coccus that grows between 55–100 °C (131–212 °F). Unlike many other thermococci, T. litoralis is non-motile. Its cell wall consists only of a single S-layer that does not form hexagonal lattices. Additionally, while many thermococcales obligately use sulfur as an electron acceptor in metabolism, T. litoralis only needs sulfur to help stimulate growth, and can live without it. T. litoralis has recently been popularized by the scientific community for its ability to produce an alternative DNA polymerase to the commonly used Taq polymerase. The T. litoralis polymerase, dubbed the vent polymerase, has been shown to have a lower error rate than Taq due to its proofreading 3’–5’ exonuclease abilities, but higher than Pfu polymerase.
A prokaryote is a single-celled organism whose cell lacks a nucleus and other membrane-bound organelles. The word prokaryote comes from the Ancient Greek πρό (pró), meaning 'before', and κάρυον (káruon), meaning 'nut' or 'kernel'. In the earlier two-empire system arising from the work of Édouard Chatton, prokaryotes were classified within the empire Prokaryota. However, in the three-domain system, based upon molecular phylogenetics, prokaryotes are divided into two domains: Bacteria and Archaea. A third domain, Eukaryota, consists of organisms with nuclei.
Alteromonas macleodii is a species of widespread marine bacterium found in surface waters across temperate and tropical regions. First discovered in a survey of aerobic bacteria in 1972, A. macleodii has since been placed within the phylum Pseudomonadota and is recognised as a prominent component of surface waters between 0 and 50 metres. Alteromonas macleodii has a single circular DNA chromosome of 4.6 million base pairs. Variable regions in the genome of A. macleodii confer functional diversity to closely related strains and facilitate different lifestyles and strategies. Certain A. macleodii strains are currently being explored for their industrial uses, including in cosmetics, bioethanol production and rare earth mining.
GvpA is a gas vesicle structural protein found in different phyla of bacteria and archaea for example in Halobacterium salinarum or Haloferax mediterranei. Gas vesicles are small, hollow, gas filled protein structures found in several cyanobacterial and archaebacterial microorganisms. They allow the positioning of the bacteria at a favourable depth for growth.
The archaellum is a unique structure on the cell surface of many archaea that allows for swimming motility. The archaellum consists of a rigid helical filament that is attached to the cell membrane by a molecular motor. This molecular motor – composed of cytosolic, membrane, and pseudo-periplasmic proteins – is responsible for the assembly of the filament and, once assembled, for its rotation. The rotation of the filament propels archaeal cells in liquid medium, in a manner similar to the propeller of a boat. The bacterial analog of the archaellum is the flagellum, which is also responsible for their swimming motility and can also be compared to a rotating corkscrew. Although the movement of archaella and flagella is sometimes described as "whip-like", this is incorrect, as only cilia from Eukaryotes move in this manner. Indeed, even "flagellum" is a misnomer, as bacterial flagella also work as propeller-like structures.
Exosortase refers to a family of integral membrane proteins that occur in Gram-negative bacteria that recognizes and cleaves the carboxyl-terminal sorting signal PEP-CTERM. The name derives from a predicted role analogous to sortase, despite the lack of any detectable sequence homology, and a strong association of exosortase genes with exopolysaccharide or extracellular polymeric substance biosynthesis loci. Many archaea have an archaeosortase, homologous to exosortases rather than to sortases. Archaeosortase A recognizes the signal PGF-CTERM, found at the C-terminus of some archaeal S-layer proteins. Following processing by archaeosortase A, the PGF-CTERM region is gone, and a prenyl-derived lipid anchor is present at the C-terminus instead.
An archaeosortase is a protein that occurs in the cell membranes of some archaea. Archaeosortases recognize and remove carboxyl-terminal protein sorting signals about 25 amino acids long from secreted proteins. A genome that encodes one archaeosortase may encode over fifty target proteins. The best characterized archaeosortase target is the Haloferax volcanii S-layer glycoprotein, an extensively modified protein with O-linked glycosylations, N-linked glycosylations, and a large prenyl-derived lipid modification toward the C-terminus. Knockout of the archaeosortase A (artA) gene, or permutation of the motif Pro-Gly-Phe (PGF) to Pro-Phe-Gly in the S-layer glycoprotein, blocks attachment of the lipid moiety as well as blocking removal of the PGF-CTERM protein-sorting domain. Thus archaeosortase appears to be a transpeptidase, like sortase, rather than a simple protease.
Haloferax volcanii is a species of organism in the genus Haloferax in the Archaea.
Haloquadratum walsbyi is a species of Archaea in the genus Haloquadratum, known for its square shape and halophilic nature.
Methanosarcina barkeri is the type species of the genus Methanosarcina, characterized by its wide range of substrates used in methanogenesis. While most known methanogens produce methane from H2 and CO2, M. barkeri can also dismutate methylated compounds such as methanol or methylamines, oxidize acetate, and reduce methylated compounds with H2. This makes M. barkeri one of the few Methanosarcina species capable of utilizing all four known methanogenesis pathways. Even among other Methanosarcinales, which commonly utilize a broad range of substrates, the ability to grow on H2 and CO2 is rare due to the requirement for high H2 partial pressure. Like other Methanosarcina species, M. barkeri has a large genome (4.53 Mbp for the type strain MS, 4.9 Mbp for the Wiesmoor strain, and 4.5 Mbp for the CM2 strain), although it is significantly smaller than the largest archaeal genome of Methanosarcina acetivorans (5.75 Mbp for the type strain C2A). It is also one of the few archaea, particularly among anaerobic species, that is genetically tractable and can be used for genetic studies.
Haloferax larsenii is a gram-negative, aerobic, neutrophilic, extremely halophilic archaeon. It was named in honor of Professor Helge Larsen, who pioneered research on halophiles.
Gas vesicles, also known as gas vacuoles, are nanocompartments in certain prokaryotic organisms, which help in buoyancy. Gas vesicles are composed entirely of protein; no lipids or carbohydrates have been detected.
Shiladitya DasSarma is a molecular biologist well-known for contributions to the biology of halophilic and extremophilic microorganisms. He is a Professor in the University of Maryland Baltimore. He earned a PhD degree in biochemistry from the Massachusetts Institute of Technology and a BS degree in chemistry from Indiana University Bloomington. Prior to taking a faculty position, he conducted research at the Massachusetts General Hospital, Harvard Medical School, and Pasteur Institute, Paris.
Francisco Juan Martínez Mojica is a Spanish molecular biologist and microbiologist at the University of Alicante in Spain. He is known for his discovery of repetitive, functional DNA sequences in bacteria which he named CRISPR. These were later developed into the first widespread genome editing tool, CRISPR-Cas9.