''Thermotoga neapolitana'' is a hyperthermophilic organism that is a member of the order
Thermotogales.
Discovery
''Thermotoga neapolitana'' was discovered in 1985 in Lucrino,
Italy
Italy ( it, Italia ), officially the Italian Republic, ) or the Republic of Italy, is a country in Southern Europe. It is located in the middle of the Mediterranean Sea, and its territory largely coincides with the homonymous geographical ...
in a
hotspring
A hot spring, hydrothermal spring, or geothermal spring is a spring produced by the emergence of geothermally heated groundwater onto the surface of the Earth. The groundwater is heated either by shallow bodies of magma (molten rock) or by circ ...
environment by Shimshon Belkin, Carl. O Wirsen, and Holger W. Jannasch of the University of California, Berkeley.
Habitat and environmental conditions
''Thermotoga neapolitana'' is considered
thermophilic
A thermophile is an organism—a type of extremophile—that thrives at relatively high temperatures, between . Many thermophiles are archaea, though they can be bacteria or fungi. Thermophilic eubacteria are suggested to have been among the ear ...
with a livable temperature range of 50–95 °C. The optimum temperature was found to be 77 °C, making it nearly
hyperthermophilic
A hyperthermophile is an organism that thrives in extremely hot environments—from 60 °C (140 °F) upwards. An optimal temperature for the existence of hyperthermophiles is often above 80 °C (176 °F). Hyperthermophiles are often within the doma ...
.
[ There is also evidence that it could be found in saline environments, due to its ability to thrive in moderately ]halophilic
The halophiles, named after the Greek word for "salt-loving", are extremophiles that thrive in high salt concentrations. While most halophiles are classified into the domain Archaea, there are also bacterial halophiles and some eukaryotic species, ...
environments.
Physical properties
''Thermotoga neapolitana'' is a rod-shaped, Gram-negative
Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wa ...
bacterium. It is distinguishable by a thick periplasmic cell wall.[ Generally, they are found to be 0.2–5 μm, but they may reach sizes of up to 100 μm. It is non-sporulating - this along with its rod-shape and Gram-negative features are characteristic of the Order Thermotogales.][
]
Thermophilic adaptations
Using a guar-gum based medium, β-mannanase, β-mannosidase, α-galactosidase have been purified. These galactomannan
Galactomannans are polysaccharides consisting of a mannose backbone with galactose side groups, more specifically, a (1-4)-linked beta-D-mannopyranose backbone with branchpoints from their 6-positions linked to alpha-D-galactose, (i.e. 1-6-linked ...
s are associated with allowing an organism to endure harsh environments (through stabilization of the membrane), such as high temperatures. These enzymes help provide simple saccharides to the organism. Polymers similar to those degraded by ''T. neopolitana'' are often used as storage polymers by plants. This may show that as the geothermal environments in which this organism is found have changed and biodiversified, so might the metabolism of this hyperthermophile
A hyperthermophile is an organism that thrives in extremely hot environments—from 60 °C (140 °F) upwards. An optimal temperature for the existence of hyperthermophiles is often above 80 °C (176 °F). Hyperthermophiles are often within the doma ...
.
Growth and metabolic activity
''Thermotoga neapolitana'' is strictly heterotroph
A heterotroph (; ) is an organism that cannot produce its own food, instead taking nutrition from other sources of organic carbon, mainly plant or animal matter. In the food chain, heterotrophs are primary, secondary and tertiary consumers, but ...
ic for its metabolic needs.[ It can also facultatively reduce elemental ]sulfur
Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formul ...
to hydrogen sulfide
Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The und ...
.[ In growth experiments, it was found to multiply rapidly with ]glucose
Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, usi ...
and yeast abstract. After 24 hours of growth, the longest rods divide into two rods, most likely in response to decreases levels of glucose availability.[ ]Glucose
Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, usi ...
, sucrose
Sucrose, a disaccharide, is a sugar composed of glucose and fructose subunits. It is produced naturally in plants and is the main constituent of white sugar. It has the molecular formula .
For human consumption, sucrose is extracted and refi ...
, lactose
Lactose is a disaccharide sugar synthesized by galactose and glucose subunits and has the molecular formula C12H22O11. Lactose makes up around 2–8% of milk (by mass). The name comes from ' (gen. '), the Latin word for milk, plus the suffix ...
, and starch nutrients all support growth when used as a sole source of energy. Low level of growth occurred with exposure to only peptone or tryptone
Tryptone is the assortment of peptides formed by the digestion of casein by the protease trypsin.
Tryptone is commonly used in microbiology to produce lysogeny broth (LB) for the growth of ''E. coli'' and other microorganisms. It provides a ...
. ''Thermotoga neapolitana'' is unable to metabolize acetate
An acetate is a salt formed by the combination of acetic acid with a base (e.g. alkaline, earthy, metallic, nonmetallic or radical base). "Acetate" also describes the conjugate base or ion (specifically, the negatively charged ion called ...
, lactate
Lactate may refer to:
* Lactation, the secretion of milk from the mammary glands
* Lactate, the conjugate base of lactic acid
Lactic acid is an organic acid. It has a molecular formula . It is white in the solid state and it is miscible with ...
, formate
Formate ( IUPAC name: methanoate) is the conjugate base of formic acid. Formate is an anion () or its derivatives such as ester of formic acid. The salts and esters are generally colorless.Werner Reutemann and Heinz Kieczka "Formic Acid" in ...
, pyruvate
Pyruvic acid (CH3COCOOH) is the simplest of the alpha-keto acids, with a carboxylic acid and a ketone functional group. Pyruvate, the conjugate base, CH3COCOO−, is an intermediate in several metabolic pathways throughout the cell.
Pyruvic aci ...
, propionate
Propionic acid (, from the Greek words πρῶτος : ''prōtos'', meaning "first", and πίων : ''píōn'', meaning "fat"; also known as propanoic acid) is a naturally occurring carboxylic acid with chemical formula CH3CH2CO2H. It is a liqu ...
, mannitol
Mannitol is a type of sugar alcohol used as a sweetener and medication. It is used as a low calorie sweetener as it is poorly absorbed by the intestines. As a medication, it is used to decrease pressure in the eyes, as in glaucoma, and to low ...
, ethanol
Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a h ...
, methanol, glycerol
Glycerol (), also called glycerine in British English and glycerin in American English, is a simple triol compound. It is a colorless, odorless, viscous liquid that is sweet-tasting and non-toxic. The glycerol backbone is found in lipids know ...
, glutamate
Glutamic acid (symbol Glu or E; the ionic form is known as glutamate) is an α-amino acid that is used by almost all living beings in the biosynthesis of proteins. It is a non-essential nutrient for humans, meaning that the human body can syn ...
, or glycine
Glycine (symbol Gly or G; ) is an amino acid that has a single hydrogen atom as its side chain. It is the simplest stable amino acid ( carbamic acid is unstable), with the chemical formula NH2‐ CH2‐ COOH. Glycine is one of the proteinog ...
.[ ]Chloramphenicol
Chloramphenicol is an antibiotic
An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting pathogenic bacteria, bacterial infections, and antibiotic medica ...
, vancomycin
Vancomycin is a glycopeptide antibiotic medication used to treat a number of bacterial infections. It is recommended intravenously as a treatment for complicated skin infections, bloodstream infections, endocarditis, bone and joint infection ...
, streptomycin
Streptomycin is an antibiotic medication used to treat a number of bacterial infections, including tuberculosis, ''Mycobacterium avium'' complex, endocarditis, brucellosis, ''Burkholderia'' infection, plague, tularemia, and rat bite fever ...
were all found to completely inhibit growth, though it was resistant to rifampin
Rifampicin, also known as rifampin, is an ansamycin antibiotic used to treat several types of bacterial infections, including tuberculosis (TB), ''Mycobacterium avium'' complex, leprosy, and Legionnaires’ disease. It is almost always used ...
.[ Growth can be found within a 0.25-6% ]NaCl
Sodium chloride , commonly known as salt (although sea salt also contains other chemical salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With molar masses of 22.99 and 35.45 g/ ...
range exclusively, with no survival outside of this limit.[ It was originally thought to be strictly ]anaerobic
Anaerobic means "living, active, occurring, or existing in the absence of free oxygen", as opposed to aerobic which means "living, active, or occurring only in the presence of oxygen." Anaerobic may also refer to:
*Adhesive#Anaerobic, Anaerobic ad ...
, but can also survive under micro-aerophilic environments.
Sulfur usage
''Thermotoga neapolitana'' can facultatively reduce elemental sulfur to hydrogen sulfide
Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The und ...
. This allows for heightened reproductive rates of the organism - up to four-fold with elemental sulfur availability. This process requires the availability of a utilizable carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon makes ...
source. Sulfuric acid and thiosulfate
Thiosulfate ( IUPAC-recommended spelling; sometimes thiosulphate in British English) is an oxyanion of sulfur with the chemical formula . Thiosulfate also refers to the compounds containing this anion, which are the salts of thiosulfuric acid, ...
cannot be used for reduction. The presence of sulfide acts to inhibit growth of the organism. In a concentration of 10 mM, sulfide will inhibit growth by up to 95%.[
]
Hydrogen production
''Thermotoga neapolitana'' shows promise as a useful bacterium due to its hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...
production. It is capable of producing upwards of 25–30% hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...
in the space it occupies when tested. The other notable gas it produces is carbon dioxide
Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is t ...
at a level of 12–15% of the total headspace.[ Despite different levels of hydrogen production under varying conditions, the hydrogen gas to carbon dioxide ratio is approximately 2:1.][ The hydrogen produced is considered extremely clean with a ]carbon monoxide
Carbon monoxide ( chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the si ...
level in the headspace of less than 50 parts per million.[ This may be promising from a bioengineering standpoint as hydrogen gas is commonly sought after as a possible alternative to fossil fuel burning for energy consumption.][ Though originally thought to be strictly anaerobic, ''Thermotoga neapolitana'' is more efficient in its catabolic pathways, especially its hydrogen production, when there are low levels of oxygen available (slightly above 10% total composition) in comparison to ]anoxic
The term anoxia means a total depletion in the level of oxygen, an extreme form of hypoxia or "low oxygen". The terms anoxia and hypoxia are used in various contexts:
* Anoxic waters, sea water, fresh water or groundwater that are depleted of diss ...
environments.[
]
Genomic properties
''Thermotoga neapolitana'' shows a DNA base composition of 41.3% Guanine
Guanine () (symbol G or Gua) is one of the four main nucleobases found in the nucleic acids DNA and RNA, the others being adenine, cytosine, and thymine ( uracil in RNA). In DNA, guanine is paired with cytosine. The guanine nucleoside is c ...
+ Cytosine
Cytosine () (symbol C or Cyt) is one of the four nucleobases found in DNA and RNA, along with adenine, guanine, and thymine ( uracil in RNA). It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attached ...
(and therefore 58.7% Adenine
Adenine () (symbol A or Ade) is a nucleobase (a purine derivative). It is one of the four nucleobases in the nucleic acid of DNA that are represented by the letters G–C–A–T. The three others are guanine, cytosine and thymine. Its derivativ ...
+ Thymine
Thymine () (symbol T or Thy) is one of the four nucleobases in the nucleic acid of DNA that are represented by the letters G–C–A–T. The others are adenine, guanine, and cytosine. Thymine is also known as 5-methyluracil, a pyrimidine n ...
).[ Using DNA-DNA hybridization, ''T. neapolitana'' was found to have a 74% homology with ''Thermotoga thermarum''.][ T. neapolitana is also closely related to '' Thermotoga maritima'', which was also discovered in geothermal environment.][
The ''ino1'' gene is present in ''T. neapolitana''. Most ]eukaryote
Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bact ...
s possess this gene, and it sometimes expressed to produce the rare osmolyte di-miyo-inositol 1,1' phosphate (DIP). This is linked to hyperthermilic tendencies because it protects the organism from high temperatures and salinities. The osmolyte may link ''T. neapolitana'' as well as other members of ''Thermotoga
''Thermotoga'' is a genus of the phylum ''Thermotogota''. Members of ''Thermotoga'' are hyperthermophilic bacteria whose cell is wrapped in a unique sheath-like outer membrane, called a "toga".
The members of the phylum stain Gram-negative as th ...
'' to Archaeans and Aquificales, the only other groups in which it is found.
References
Further reading
*
*
*
*Eriksen, Niels T., et al. "H2 synthesis from pentoses and biomass in Thermotoga spp." Biotechnology letters 33.2 (2011): 293–300.
*Van Ooteghem, Suellen A., Stephen K. Beer, and Paul C. Yue. "Hydrogen production by the thermophilic bacterium Thermotoga neapolitana."Biotechnology for Fuels and Chemicals. Humana Press, 2002. 177–189.
External links
*
Type strain of ''Thermotoga neapolitana'' at Bac''Dive'' - the Bacterial Diversity Metadatabase
{{Taxonbar, from=Q16993092
Gram-negative bacteria
Thermophiles
Thermotogota
Bacteria described in 1986