| Spirochaeta americana | |
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Scientific classification  | |
| Domain: | Bacteria |
| Phylum: | Spirochaetota |
| Class: | Spirochaetia |
| Order: | Spirochaetales |
| Family: | Spirochaetaceae |
| Genus: | Spirochaeta |
| Species: | S. americana |
| Binomial name | |
| Spirochaeta americana | |
Spirochaeta americana is a single-celled extremophile. [1] This halo alkaliphilic and obligately anaerobic bacterium can be found in the highly alkaline, salty, deep waters of California's Mono Lake. [1] [2]
S. americana has long helically coiled cells, is gram-negative, and is chemotrophic in its metabolism. Spirochaeta also have unique flagella, sometimes called axial filaments, which run lengthwise between the cytoplasmic membrane and outer membrane. These cause a twisting motion which allows the spirochaete to move about. Despite the extreme environment that they require, "their cell walls are very delicate, and it is difficult to keep them alive for long periods in the laboratory," says Dr. Elena Pikuta, one of the discoverers of S. americana.
S. americana thrives in the lake-bottom mud of Lake Mono, a 13 mile wide former monomictic volcanic basin which is fed by numerous small Sierra streams and which has no outflow except evaporation and Californian aqueducts, thereby continually increasing the concentration of salts and other minerals in its waters. Further mineral enrichment of these waters also occur due to the volcanically active area, such as when Negit Island erupted roughly 250 years ago. [3]
Surviving in deep, salty, alkaline lake mud of Lake Mono, the extreme conditions in which S. americana thrive have prompted its discoverers to explore Antarctica's Lake Untersee, hopefully to discover similar species. [4] [5]
S. americana reproduces via transverse binary fission, where the cytoplasm divides transversely between two sets of DNA genomes, forming two dissimilar individuals, as do other Spirochaeta. [6]
This bacterium grows in environments of 10 to 44 degrees Celsius with optimal growth at 37 degrees and prefers a pH balance of 9.5, similar to that of baking soda, hand soap, or a solution of household bleach in water. [7]
S. americana is capable of metabolizing D-glucose, fructose, maltose, sucrose, starch and D-mannitol and has as its waste H2, acetate, ethanol and formate. [1]
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.
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.
In taxonomy, Natrialba is a genus of the Natrialbaceae. The genus consists of many diverse species that can survive extreme environmental niches, especially they are capable to live in the waters saturated or nearly saturated with salt (halophiles). They have certain adaptations to live within their salty environments. For example, their cellular machinery is adapted to high salt concentrations by having charged amino acids on their surfaces, allowing the cell to keep its water molecules around these components. The osmotic pressure and these amino acids help to control the amount of salt within the cell.
Archaea is a domain of single-celled organisms. These microorganisms lack cell nuclei and are therefore prokaryotes. Archaea were initially classified as bacteria, receiving the name archaebacteria, but this term has fallen out of use.
A soda lake or alkaline lake is a lake on the strongly alkaline side of neutrality, typically with a pH value between 9 and 12. They are characterized by high concentrations of carbonate salts, typically sodium carbonate, giving rise to their alkalinity. In addition, many soda lakes also contain high concentrations of sodium chloride and other dissolved salts, making them saline or hypersaline lakes as well. High pH and salinity often coincide, because of how soda lakes develop. The resulting hypersaline and highly alkalic soda lakes are considered some of the most extreme aquatic environments on Earth.
Richard Brice Hoover is a physicist who has authored 33 volumes and 250 papers on astrobiology, extremophiles, diatoms, solar physics, X-ray/EUV optics and meteorites. He holds 11 U.S. patents and was 1992 NASA Inventor of the Year. He was employed at the United States' NASA Marshall Space Flight Center from 1966 to 2012, where he worked on astrophysics and astrobiology. He established the Astrobiology Group there in 1997 and until his retirement in late 2011 he headed their astrobiology research. He conducted research on microbial extremophiles in the Antarctic, microfossils, and chemical biomarkers in precambrian rocks and in carbonaceous chondrite meteorites. Hoover has published claims to have discovered fossilized microorganisms in a collection of select meteorites on multiple occasions.
Shewanella violacea DSS12 is a gram-negative bacterium located in marine sediment in the Ryukyu Trench at a depth of 5,110m. The first description of this organism was published in 1998 by Japanese microbiologists Yuichi Nogi, Chiaki Kato, and Koki Horikoshi, who named the species after its violet appearance when it is grown on Marine Agar 2216 Plates.
Shewanella livingstonensis is a species of bacteria. Its cells are psychrophilic, gram-negative, rod-shaped, facultatively anaerobic and motile by means of a single polar flagellum. Its type strain is LMG 19866T.
Arsenate-reducing bacteria are bacteria which reduce arsenates. Arsenate-reducing bacteria are ubiquitous in arsenic-contaminated groundwater (aqueous environment). Arsenates are salts or esters of arsenic acid (H3AsO4), consisting of the ion AsO43−. They are moderate oxidizers that can be reduced to arsenites and to arsine. Arsenate can serve as a respiratory electron acceptor for oxidation of organic substrates and H2S or H2. Arsenates occur naturally in minerals such as adamite, alarsite, legrandite, and erythrite, and as hydrated or anhydrous arsenates. Arsenates are similar to phosphates since arsenic (As) and phosphorus (P) occur in group 15 (or VA) of the periodic table. Unlike phosphates, arsenates are not readily lost from minerals due to weathering. They are the predominant form of inorganic arsenic in aqueous aerobic environments. On the other hand, arsenite is more common in anaerobic environments, more mobile, and more toxic than arsenate. Arsenite is 25–60 times more toxic and more mobile than arsenate under most environmental conditions. Arsenate can lead to poisoning, since it can replace inorganic phosphate in the glyceraldehyde-3-phosphate --> 1,3-biphosphoglycerate step of glycolysis, producing 1-arseno-3-phosphoglycerate instead. Although glycolysis continues, 1 ATP molecule is lost. Thus, arsenate is toxic due to its ability to uncouple glycolysis. Arsenate can also inhibit pyruvate conversion into acetyl-CoA, thereby blocking the TCA cycle, resulting in additional loss of ATP.
Thioalkalivibrio versutus is an obligately alkaliphilic and obligately chemolithoautotrophic sulfur-oxidizing bacteria. It was first isolated from soda lakes in northern Russia.
Treponema isoptericolens is a spirochaete from the hindgut of the termite Incisitermes tabogae. Its cells are motile, helical in shape, 0.4–0.5 μm in diameter and generally 12–20 μm long; it is obligately anaerobic, with type strain SPIT5T.
Balnearium lithotrophicum is a species of bacterium described in 2003 and classified as belonging to the Aquificota.
Spirochaeta thermophila is a fairly recently discovered free-living, anaerobic, spirochaete that seems to be the most thermophilic of the Spirochaetales order. The type species was discovered in 1992 in Kuril islands, Russia and described in Aksenova, et al. It has been isolated in the sediments and water columns of brackish aquatic habitats of various ponds, lakes, rivers, and oceans. This organism is identified as a new species based on its unique ability to degrade cellulose, xylan, and other α- and β-linked sugars and use them as the sole carbon source by encoding many glycoside hydrolases. It is presumed to secrete cellulases to break down plant-matter around it but there has been little work on the characterization of the enzymes responsible for this.
Thioalkalivibrio is a Gram-negative, mostly halophilic bacterial genus of the family Ectothiorhodospiraceae.
Alkalibacter saccharofermentans is a Gram-positive, obligately anaerobic, alkaliphilic and non-spore-forming bacterium from the genus of Alkalibacter which has been isolated from a soda lake in the Transbaikal regio in Russia.
Methylophaga muralis is a species of Pseudomonadota. It is capable of surviving in saline and alkaline environments and can obtain its carbon from methanol. This species was originally discovered in crumbling marble in the Moscow Kremlin; it has also been found in a soda lake in Buryatia.
Heliorestis acidaminivorans is an obligate anaerobic bacterium from the genus of Heliorestis which has been isolated from lake sediments from the Lake El Hamra from Wadi El Natrun in Egypt.
Natronincola histidinovorans is a moderately haloalkaliphilic, obligately anaerobic, and acetogenic bacterium from the genus of Natronincola which has been isolated from soda deposits from the Lake Magadi.
Tindallia californiensis is a Gram-positive, extremely haloalkaliphilic, strictly anaerobic, acetogenic and motile bacterium from the genus of Tindallia which has been isolated from sediments from the Mono Lake in California.
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