''Alcanivorax borkumensis'' is an

alkane In organic chemistry, an alkane, or paraffin (a historical trivial name that also has other meanings), is an acyclic saturated hydrocarbon. In other words, an alkane consists of hydrogen and carbon atoms arranged in a tree structure in which ...

-degrading

marine bacterium Marine prokaryotes are marine bacteria and marine archaea. They are defined by their habitat as prokaryotes that live in marine environments, that is, in the saltwater of seas or oceans or the brackish water of coastal estuaries. All cellular ...

which naturally propagates and becomes predominant in crude-oil-containing seawater when

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

and

phosphorus Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ear ...

nutrients are supplemented.

Description

''A. borkumensis'' is a rod-shaped bacterium without

flagella A flagellum (; ) is a hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility. Many protists with flagella are termed as flagellates. A microorganism may have f ...

that obtains its energy primarily from consuming alkanes (a type of

hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ex ...

). It is

aerobic Aerobic means "requiring air," in which "air" usually means oxygen. Aerobic may also refer to * Aerobic exercise, prolonged exercise of moderate intensity * Aerobics, a form of aerobic exercise * Aerobic respiration, the aerobic process of cellu ...

, meaning it uses oxygen to gain energy, and it is

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, ...

, meaning it tends to live in environments that contain salt, such as salty ocean water. It is also

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 wall ...

, which essentially means it has a relatively thin cell wall. It is also nonmotile; however, other organisms that appear to be in the same genus are motile through

Discovery

The microorganism was discovered near the island of

Borkum Borkum ( nds, Borkum, Börkum) is an island and a municipality in the Leer District in Lower Saxony, northwestern Germany. It is situated east of Rottumeroog and west of Juist. Geography Borkum is bordered to the west by the Westerems strait ...

(hence the

epithet An epithet (, ), also byname, is a descriptive term (word or phrase) known for accompanying or occurring in place of a name and having entered common usage. It has various shades of meaning when applied to seemingly real or fictitious people, di ...

''borkumensis'') by the Helmholtz Centre for Infection Research and the

Technical University of Braunschweig The Technische Universität Braunschweig (unofficially University of Braunschweig – Institute of Technology), commonly referred to as TU Braunschweig, is the oldest ' (comparable to an institute of technology in the American system) in Germany. ...

and in 2006, them and the

University of Bielefeld Bielefeld University (german: Universität Bielefeld) is a university in Bielefeld, Germany. Founded in 1969, it is one of the country's newer universities, and considers itself a "reform" university, following a different style of organization a ...

identified the Base sequence of the

genome In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding ge ...

of the bacterium.

Genome

The

of ''A. borkumensis'' is a single circular

chromosome A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins are ...

that contains 3,120,143 base pairs. It is highly adapted to degrading

petroleum oil Mineral oil is any of various colorless, odorless, light mixtures of higher alkanes from a mineral source, particularly a distillate of petroleum, as distinct from usually edible vegetable oils. The name 'mineral oil' by itself is imprecise, ...

. For example, a certain sequence on the genome codes for the degradation of a certain range of alkanes. The ''A. borkumensis'' genome has many sequences that each code for a different type of alkane, allowing it to be highly adaptable and versatile. Its genome also contains instructions for the formation of biosurfactants which aid in the process of degradation. To deal with external threats, the ''A. borkumensis'' genome also codes for several defensive mechanisms. Coping with high concentrations of sodium ions (i.e. in ocean water), and protecting against the UV radiation experienced on the surface of the earth are both important for the ''A. borkumensis'' bacteria, and its genome contains ways to solve both of these problems.
Schneiker, Susanne, et al. "Genome Sequence of the Ubiquitous Hydrocarbon-degrading Marine Bacterium ''Alcanivorax borkumensis''." Nature Biotechnology 24.8 (2006): 997-1004.

Ecology

''A. borkumensis'' is found naturally in seawater environments. It is more common in oceanic areas containing

(whether from spills, natural fields, or other sources), although it can be found in small amounts in unpolluted water. It has been found across the world in various locations both in coastal environments and oceanic environments. It also can flourish in areas with heavy tides and other sea related currents/flow. It is found only on or near the surface of water. ''A. borkumensis'' can live in salinities ranging from 1.0-12.5% and in temperatures ranging from 4-35 °C. The abundance of ''A. borkumensis'' in oil-affected environments is because the bacteria use the compounds in oil as a source of energy, thus populations of ''A. borkumensis'' naturally flourish at oil spills or other similar locations. ''A. borkumensis'' outcompetes other species of the ''Alcanivorax''

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

, likely due to its highly flexible DNA and

metabolism Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cell ...

. ''A. borkumensis'' also outcompetes other alkane-degrading organisms such as ''Acinetobacter venetianus''. After a certain period of time, an oily and saline environment containing ''A. borkumensis'' and ''Acinetobacter venetianus'' would eventually become dominated by ''A. borkumensis'' because ''A. borkumensis'' can consume a wider variety of alkanes than other known species.

Metabolism

''A. borkumensis'' primarily uses alkanes as its source of energy/carbon, but it can use a few other

organic compounds In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The s ...

. Unlike most other cells, it cannot consume more common substances such as

sugars Sugar is the generic name for sweet-tasting, soluble carbohydrates, many of which are used in food. Simple sugars, also called monosaccharides, include glucose, fructose, and galactose. Compound sugars, also called disaccharides or double s ...

amino acids Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha am ...

as a source of energy. This is due to the lack of genes that code for active or passive carbohydrate transporters, hence the inability to consume monomeric sugars. In a ''A. borkumensis'', a number of different enzymes are tasked with oxidizing

molecules. The aerobic metabolism of alkanes is carried out through the terminal alkane oxidation pathway, where

monooxygenase Monooxygenases are enzymes that incorporate one hydroxyl group (−OH) into substrates in many metabolic pathways. In this reaction, the two atoms of dioxygen are reduced to one hydroxyl group and one H2O molecule by the concomitant oxidation o ...

s initiate the oxidation of terminal carbons. This sequential pathway first produces alcohols, then alcohol and aldehyde dehydrogenases, and ultimately aldehydes and fatty acids, respectively. Following an oil spill, huge imbalances in the carbon/nitrogen and carbon/phosphorus ratios can be observed. For this, ''A. borkumensis'' have a myriad of transport proteins that allow fast uptake of key nutrients that are limiting in the environment. To increase the growth rate of a population of ''A. borkumensis'' bacteria,

and nitrogenous compounds can be added to the environment. These substances act as a

fertilizer A fertilizer (American English) or fertiliser (British English; see spelling differences) is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from ...

for the bacteria and help them grow at an increased rate.

''A. borkumensis'' and biosurfactants

When ''A. borkumensis'' bacteria use alkanes or pyruvate as their source of energy, each cell forms a

biosurfactant Biosurfactant usually refers to surfactants of microbial origin. Most of the biosurfactants produced by microbes are synthesized extracellularly and many microbes are known to produce biosurfactants in large relative quantities. Some are of commerc ...

. A biosurfactant is an extra layer of material that forms along the cell membrane. The substances that make up the biosurfactant of ''A. borkumensis'' can reduce the

surface tension Surface tension is the tendency of liquid surfaces at rest to shrink into the minimum surface area possible. Surface tension is what allows objects with a higher density than water such as razor blades and insects (e.g. water striders) to f ...

of water, which helps with the degradation of oil. They are also

emulsifiers An emulsion is a mixture of two or more liquids that are normally immiscible (unmixable or unblendable) owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloids. Although ...

, which further serve to create the oil/water emulsion, making oil more soluble. ''A. borkumensis'' forms a

biofilm A biofilm comprises any syntrophic consortium 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 ...

around an oil droplet in seawater and proceeds to use biosurfactants and metabolism to degrade the oil into a water-soluble substance.

Biotechnological applications

Role in oil biodegradation

Petroleum Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crud ...

oil is toxic for most life forms and

pollution Pollution is the introduction of contaminants into the natural environment that cause adverse change. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, the ...

of the

environment Environment most often refers to: __NOTOC__ * Natural environment, all living and non-living things occurring naturally * Biophysical environment, the physical and biological factors along with their chemical interactions that affect an organism or ...

by oil causes major ecological problems. A considerable amount of petroleum oil entering the sea is eliminated by the

microbial biodegradation Microbial biodegradation is the use of bioremediation and biotransformation methods to harness the naturally occurring ability of microbial xenobiotic metabolism to degrade, transform or accumulate environmental pollutants, including hydrocarbons (e ...

activities of microbial communities. As a recently discovered hydrocarbonoclastic, ''A. borkumensis'' is capable of degrading oil in seawater environments. Hydrocarbonoclastic has the root ‘clastic’ meaning it can divide something into parts (in this case

s). Crude oil, or petroleum, is predominantly made up of hydrocarbons, a product that consists of a long chain of carbon atoms attached to hydrogen atoms. Whereas most organisms use sugars or amino acids for their source of carbon/energy, ''A. borkumensis'' uses alkanes, a type of hydrocarbon, in its metabolic process. This diet allows ''A. borkumensis'' to flourish in marine environments that have been affected by

oil spills An oil spill is the release of a liquid petroleum hydrocarbon into the environment, especially the marine ecosystem, due to human activity, and is a form of pollution. The term is usually given to marine oil spills, where oil is released into th ...

. Through its metabolism, ''A. borkumensis'' can break down oil into harmless compounds. This ability makes this particular species a major potential source for bioremediation of oil-polluted marine environments.

Potential as anti-oil spill agent

Oil spills An oil spill is the release of a liquid petroleum hydrocarbon into the environment, especially the marine ecosystem, due to human activity, and is a form of pollution. The term is usually given to marine oil spills, where oil is released into th ...

can occur during transportation of oil or during extraction. Such spills may dump significant quantities of oil into the ocean and pollute the environment, affecting ecosystems near and far. Normally, many years are needed for an ecosystem to recover fully (if at all) from an oil spill, so scientists have been looking into ways to expedite the cleanup of areas affected by an oil spill. Most efforts so far use direct human involvement/labor to physically remove the oil from the environment. However, ''A. borkumensis'' presents a possible alternative. Since ''A. borkumensis'' naturally breaks down oil molecules to a nonpolluting state, it would help ecosystems to quickly recover from an oil spill disaster. The organisms also naturally grow in oil-contaminated seawater, thus are a native species. If the process ''A. borkumensis'' uses to break down oil could be sped up or made more efficient, this would aid recovering ecosystems. Some examples include encouraging the growth of ''A. borkumensis'' (through phosphorus and nitrogen fertilization) so more of them are breaking down oil, or encouraging the metabolism of ''A. borkumensis'' so they metabolize faster and more.

Potential in biopolymer production

By disrupting an acyl-coenzyme A (CoA) thioesterase gene, Sabirova and colleagues were able to mutate the organism to hyper-produce

polyhydroxyalkanoates Polyhydroxyalkanoates or PHAs are polyesters produced in nature by numerous microorganisms, including through bacterial fermentation of sugars or lipids. When produced by bacteria they serve as both a source of energy and as a carbon store. More ...

(PHA). They were then able to recover the large amounts of PHA that were released by mutant ''Alcanivorax'' from the culture mediums with relative ease. Before, costly and environmentally dangerous solvents had to be used in order to retrieve PHA from intracellular granules. This allows for production of environmentally friendly polymers in factories that utilized mutant ''Alcanivorax''.

References

External links

Type strain of ''Alcanivorax borkumensis'' at Bac''Dive'' - the Bacterial Diversity Metadatabase
{{Taxonbar, from=Q143356 Oceanospirillales Biodegradation