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Kosmotoga

Introductory text: Kosmotoga is a genus of anaerobic chemo-organotrophs within the order Thermotogales. These bacteria inhabit a myriad of environments including oil reservoirs, marine sediments, and low-temperature bioreactors. They undergo anaerobic fermentation of maltose for energy Kosmotoga present as Gram-stain-negative, non-motile rods or cocci surrounded by sheath-like structures or 'togas' from which they get their name. They are thermophiles, with growth between 20-80 degrees Celsius and an optimal growth temperature of 60-65 degrees Celsius. The organisms are obligate anaerobes that require reduced growth medium, but some species (namely Kosmotoga olearia) are able to grow in the presence of up to 15% oxygen with the addition of cysteine.

Contents: Physiology

Ecology

Special Features

Extremophily

Genome Features

List of Species

Physiology: Kosmotoga undergo anaerobic fermentation of maltose to hydrogen, carbon dioxide, and acetate. They also have been found to make small amounts of ethanol and propionic acid. Fructose, galactose, mannose, raffinose, xylan, casein, and peptone were less preferable fermentation substrates to Kosmotoga. Malate and butanol are toxic. Growth of this bacterium was only observed in media containing yeast extract.

Some members of this genus are able to reduce some forms of sulfur. Kosmotoga shengliensis (formerly known as Thermococcoides shengliensis) is able to reduce elemental sulfur, sulfate, and thiosulfate. Growth can be observed on acetate, methanol, galactose, fructose, xylose, sucrose, maltose, sorbitol, lactose, xylan, arabinose, formate, rhamnose, glycerol, pyruvate, starch, lactate, and n-propyl alcohol. It is unable to grow on H2/CO2, mannose, tartrate, succinate, alpha-ketoglutarate, glutamate, malate, citric acid, fumarate, raffinose, melezitose, salicin, or mannitol.

Kosmotoga pacifica is able to reduce elemental sulfur and L-cystine to H2S but is unable to reduce sulfate or thiosulfate. It can use maltose, yeast extract, peptone, glycerol, tryptone, xylose, glucose, fructose, cellobiose, trehalose, lactate, propionate, or glutamate as growth media. It is unable to use sucrose, ribose, galactose, starch, casamino acids, ethanol, pyruvate, and malate.

Kosmotoga olearia growth is enhanced by the presence of thiosulfate, but not nitrate, nitrite, cystine, sulfite, or elemental sulfur. It also is unable to produce H2S from sulfite and nitrite in the presence of cysteine. Yeast extract was required for growth. Growth occurred with 100 ug kanamycin, ampicillin, carbenicillin, and streptomycin. No growth was observed with 50 ug rifampicin, 10 ug vancomycin, and 10 ug chloramphenicol.

Kosmotoga arenicorallina was able to reduce both sulfur and L-cystine. Growth was inhibited by ampicillin, chloramphenicol, erthromycin, penicillin G, novobiocin, spectinomycin, tetracycline, and rifampicin at 25 ug/ml and by streptomycin, vancomycin at 100 ug/l. Growth was insensitive to kanamycin. Yeast extract was required for growth. Ecology:

Kosmotoga have been discovered in different high temperature habitats around the world including hot springs, oil fields, and marine hydrothermal environments. Kosmotoga arenicorallina was isolated from the Taketomi submarine hot spring hydrothermal field in Yaeyama Archipelago, Japan Kosmotoga olearia was isolated from an oil production fluid. Kosmotoga pacifica was isolated from a hydrothermal sediment on the East Pacific Rise. Kosmotoga shengliensis was isolated from the Shengli Oilfield in China. Special Features:

Extremophily

One special feature of Kosmotoga is the ability to grow from 20-80 degrees Celsius. This is significant because the thermophilic order Thermotogales to which Kosmotoga belongs does not have any other organisms that grow below 30 C. Kosmotoga had a temperature optimum of around 60-65 C. The bacterium was also able to produce non-spore structures that survive temperatures up to 90 C.

Genome Features: The G+C content of the DNA is between 36.4-40.8 mol%. Genomes of Kosmotoga have around two million base pairs (Jiang et al. 2017). Results from genome sequencing of Kosmotoga pacifica indicate the presence of around 1900 protein-encoding genes and 177 RNA genes. The genus Kosmotoga was originally proposed upon discovery of the type species (K. olearia) which was distinguished from other genera of Thermotogales due to the survival of these bacteria in cultures under 30 C. . The organisms in this genus are most closely related to several members of the order Thermotogales which are informally named the 'mesotoga'. List of Species:

Kosmotoga arenicorallina

Kosmotoga olearia (type species)

Kosmotoga pacifica

Kosmotoga shengliensis (Formerly known as Thermococcoides shengliensis)