''Sporosarcina pasteurii'' formerly known as ''Bacillus pasteurii'' from older taxonomies, is a gram positive

bacterium Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

with the ability to precipitate

calcite Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on ...

and solidify sand given a

calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to ...

source and

urea Urea, also known as carbamide, is an organic compound with chemical formula . This amide has two amino groups (–) joined by a carbonyl functional group (–C(=O)–). It is thus the simplest amide of carbamic acid. Urea serves an important r ...

; through the process of

microbiologically induced calcite precipitation Microbiologically induced calcium carbonate precipitation (MICP) is a bio-geochemical process that induces calcium carbonate precipitation within the soil matrix. Biomineralization in the form of calcium carbonate precipitation can be traced back ...

(MICP) or biological cementation. ''S. pasteurii'' has been proposed to be used as an ecologically sound biological construction material. Researchers studied the bacteria in conjunction with plastic and hard mineral; forming a material stronger than bone. It is a commonly used for MICP since it is non-pathogenic and is able to produce high amounts of the enzyme

urease Ureases (), functionally, belong to the superfamily of amidohydrolases and phosphotriesterases. Ureases are found in numerous bacteria, fungi, algae, plants, and some invertebrates, as well as in soils, as a soil enzyme. They are nickel-containin ...

which hydrolyzes urea to

carbonate A carbonate is a salt of carbonic acid (H2CO3), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word ''carbonate'' may also refer to a carbonate ester, an organic compound containing the carbonate g ...

and

ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous was ...

Physiology

''S. pasteurii'' is a

gram positive In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall. Gram-positive bact ...

bacterium that is rod-like shaped in nature. It has the ability to form

endospore An endospore is a dormant, tough, and non-reproductive structure produced by some bacteria in the phylum Bacillota. The name "endospore" is suggestive of a spore or seed-like form (''endo'' means 'within'), but it is not a true spore (i.e., no ...

s in the right environmental conditions to enhance its survival, which is a characteristic of its

bacillus ''Bacillus'' (Latin "stick") is a genus of Gram-positive, rod-shaped bacteria, a member of the phylum ''Bacillota'', with 266 named species. The term is also used to describe the shape (rod) of other so-shaped bacteria; and the plural ''Bacilli ...

class. It has dimensions of 0.5 to 1.2 microns in width and 1.3 to 4.0 microns in length. Because it is an

alkaliphile Alkaliphiles are a class of extremophilic microbes capable of survival in alkaline ( pH roughly 8.5–11) environments, growing optimally around a pH of 10. These bacteria can be further categorized as obligate alkaliphiles (those that require hig ...

, it thrives in basic environments of pH 9-10. It can survive relatively harsh conditions up to a pH of 11.2.

Metabolism and growth

''S. pasteurii'' are soil-borne

facultative anaerobes A facultative anaerobic organism is an organism that makes ATP by aerobic respiration if oxygen is present, but is capable of switching to fermentation if oxygen is absent. Some examples of facultatively anaerobic bacteria are ''Staphylococcus' ...

that are

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 and require urea and ammonium for growth. The ammonium is utilized in order to allow substrates to cross the

cell membrane The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of all cells from the outside environment ( ...

into the cell. The urea is used as the nitrogen and carbon source for the bacterium. ''S. pasteurii'' are able to induce the

hydrolysis Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution reaction, substitution, elimination reaction, elimination, and solvation reactions in which water ...

of urea and use it as a source of energy by producing and secreting the

enzyme. The enzyme hydrolyzes the urea to form carbonate and ammonia. During this hydrolysis, a few more spontaneous reactions are performed.

Carbamate In organic chemistry, a carbamate is a category of organic compounds with the general formula and structure , which are formally derived from carbamic acid (). The term includes organic compounds (e.g., the ester ethyl carbamate), formally o ...

is hydrolyzed to carbonic acid and ammonia and then further hydrolyzed to ammonium and

bicarbonate In inorganic chemistry, bicarbonate (IUPAC-recommended nomenclature: hydrogencarbonate) is an intermediate form in the deprotonation of carbonic acid. It is a polyatomic anion with the chemical formula . Bicarbonate serves a crucial biochemic ...

. This process causes the pH of the reaction to increase 1-2 pH, making the environment more basic which promotes the conditions that this specific bacterium thrives in. Maintaining a medium with this pH can be expensive for large scale production of this bacterium for biocementation. A wide range of factors can affect the growth rate of ''S. pasteurii.'' This includes finding the optimal temperature, pH, urea concentration, bacterial density, oxygen levels, etc. It has been found that the optimal growing temperature is 30 °C, but this is independent of the other environmental factors present. Since ''S. pasteurii'' are

halotolerant Halotolerance is the adaptation of living organisms to conditions of high salinity. Halotolerant species tend to live in areas such as hypersaline lakes, coastal dunes, saline deserts, salt marshes, and inland salt seas and springs. Halophiles are ...

, they can grow in the presence of low concentrations of aqueous chloride ions that are low enough to not inhibit bacterial cell growth. This shows promising applications for MICP use. ''S. pasteurii'' DSM 33 is described to be

auxotrophic Auxotrophy ( grc, αὐξάνω "to increase"; ''τροφή'' "nourishment") is the inability of an organism to synthesize a particular organic compound required for its growth (as defined by IUPAC). An auxotroph is an organism that displays this ...

for

L-methionine Methionine (symbol Met or M) () is an essential amino acid in humans. As the precursor of other amino acids such as cysteine and taurine, versatile compounds such as SAM-e, and the important antioxidant glutathione, methionine plays a critical rol ...

, L-cystein,

thiamin Thiamine, also known as thiamin and vitamin B1, is a vitamin, an essential micronutrient, that cannot be made in the body. It is found in food and commercially synthesized to be a dietary supplement or medication. Phosphorylated forms of thia ...

e and

nicotinic acid Niacin, also known as nicotinic acid, is an organic compound and a form of vitamin B3, an essential human nutrient. It can be manufactured by plants and animals from the amino acid tryptophan. Niacin is obtained in the diet from a variet ...

Genomic properties

The whole

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 ''S. pasteurii'' NCTC4822 was sequenced and reported unde
NCBI Accession Number: NZ_UGYZ01000000
With a

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 ...

length of 3.3 Mb, it contains 3,036 protein coding

gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...

s and has

GC content In molecular biology and genetics, GC-content (or guanine-cytosine content) is the percentage of nitrogenous bases in a DNA or RNA molecule that are either guanine (G) or cytosine (C). This measure indicates the proportion of G and C bases out o ...

of 39.17% . When the ratio of known functional genes to the unknown genes is calculated, the bacterium shows highest ratios for transport, metabolism, and transcription. The high proportion of these functions allows the conversion of urea to carbonate ions which is necessary for the bio-mineralization process. The bacterium has seven identified genes that are directly related to urease activity and assembly as well, which can be further studied to give insight about maximizing urease production for optimizing use of ''S. pasteurii'' in industrial applications.

Applications with MICP

''S. pasteurii'' have the unique capability of hydrolyzing urea and through a series of reactions, produce carbonate ions. This is done by secreting copious amounts of urease through the

. When the bacterium is placed in a calcite rich environment, the negatively charged carbonate ions react with the positive metal ions like calcium to precipitate calcium carbonate, or bio-cement. The calcium carbonate can then be used as a precipitate or can be crystallized as calcite to cement sand particles together. Therefore when put into a calcium chloride environment, ''S. pasteurii'' are able to survive since they are

and alkaliphiles. Since the bacteria remain intact during harsh mineralization conditions, are robust, and carry a negative

surface charge Surface charge is a two-dimensional surface with non-zero electric charge. These electric charges are constrained on this 2-D surface, and surface charge density, measured in coulombs per square meter (C•m−2), is used to describe the charge di ...

, they serve as good

nucleation site In thermodynamics, nucleation is the first step in the formation of either a new Phase (matter), thermodynamic phase or Crystal structure, structure via self-assembly or self-organization within a substance or mixture. Nucleation is typically def ...

s for MICP. The negatively charged cell wall of the bacterium provides a site of interaction for the positively charged cations to form

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. ( ...

s. The extent of this interaction depends on a variety of factors including the characteristics of the cell surface, amount of

peptidoglycan Peptidoglycan or murein is a unique large macromolecule, a polysaccharide, consisting of sugars and amino acids that forms a mesh-like peptidoglycan layer outside the plasma membrane, the rigid cell wall (murein sacculus) characteristic of most ...

amidation In organic chemistry, an amide, also known as an organic amide or a carboxamide, is a compound with the general formula , where R, R', and R″ represent organic groups or hydrogen atoms. The amide group is called a peptide bond when it is p ...

level of free carboxyl, and availability of

teichoic acid Teichoic acids (''cf.'' Greek τεῖχος, ''teīkhos'', "wall", to be specific a fortification wall, as opposed to τοῖχος, ''toīkhos'', a regular wall) are bacterial copolymers of glycerol phosphate or ribitol phosphate and carbohydr ...

s. ''S. pasteurii'' show a highly negative

which can be shown in its highly negative

zeta potential Zeta potential is the electrical potential at the slipping plane. This plane is the interface which separates mobile fluid from fluid that remains attached to the surface. Zeta potential is a scientific term for electrokinetic potential in coll ...

of -67 mV compared to non-mineralizing bacteria ''E''. ''coli'', ''S''. ''aureus'' and ''B''. ''subtilis'' at -28, -26 and -40.8 mV, respectively. Aside from all of these benefits towards using ''S. pasteurii'' for MICP, there are limitations like undeveloped engineering scale-up, undesired by-products, uncontrolled growth, or dependence on growth conditions like urea or oxygen concentrations.

Current and potential applications

''S. pasteurii'' have a purpose in improving construction material as in

concrete Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most wi ...

or mortar. Concrete is one of the most used materials in the world but it is susceptible to forming cracks which can be costly to fix. One solution is to embed this bacterium in the cracks and once it is activated using MICP. Minerals will form and repair the gap in a permanent environmentally-friendly way. One disadvantage is that this technique is possible only for external surfaces that are reachable. Another application is to use ''S. pasteurii'' in bio self-healing of concrete which involves implementing the bacterium into the

matrix during the concrete preparation to heal micro cracks. This has a benefit of minimal human intervention and yields more durable concrete with higher

compressive strength In mechanics, compressive strength or compression strength is the capacity of a material or structure to withstand loads tending to reduce size (as opposed to tensile strength which withstands loads tending to elongate). In other words, compre ...

. One limitation of using this bacterium for bio-mineralization is that although it is a

facultative anaerobe A facultative anaerobic organism is an organism that makes ATP by aerobic respiration if oxygen is present, but is capable of switching to fermentation if oxygen is absent. Some examples of facultatively anaerobic bacteria are ''Staphylococcus' ...

, in the absence of oxygen, the bacterium is unable to synthesize urease anaerobically. A lack of oxygen also prevents MICP since its initiation relies heavily on oxygen. Therefore, at sites distant from the injection location or at great depths, the likelihood of precipitation decreases. One potential fix is to couple this bacterium in the biocement with oxygen releasing compounds (ORCs) that are typically used for

bioremediation Bioremediation broadly refers to any process wherein a biological system (typically bacteria, microalgae, fungi, and plants), living or dead, is employed for removing environmental pollutants from air, water, soil, flue gasses, industrial effluent ...

and removal of

pollutant A pollutant or novel entity is a substance or energy introduced into the environment that has undesired effects, or adversely affects the usefulness of a resource. These can be both naturally forming (i.e. minerals or extracted compounds like oi ...

s from soil. With this combination, the lack of oxygen can be diminished and the MICP can be optimized with the bacterium. Some specific examples of current applications include: * Architecture student Magnus Larsson won the 2008 Holcim Award "Next Generation" first prize for region Africa Middle East for his project "Dune anti-

desertification Desertification is a type of land degradation in drylands in which biological productivity is lost due to natural processes or induced by human activities whereby fertile areas become increasingly arid. It is the spread of arid areas caused by ...

architecture, Sokoto, Nigeria" and his design of a habitable wall. Larssons also presented the proposal at

TED TED may refer to: Economics and finance * TED spread between U.S. Treasuries and Eurodollar Education * ''Türk Eğitim Derneği'', the Turkish Education Association ** TED Ankara College Foundation Schools, Turkey ** Transvaal Education Depa ...

. *

Ginger Krieg Dosier Ginger Krieg Dosier is an American architect who, in 2010, developed a technique for using microbiologically induced calcite precipitation to manufacture bricks for construction. Dosier's brick-making method consists of filling a rectangular for ...

's unique biotechnology start-up company, bioMason, in Raleigh, NC has developed a method of growing bricks from ''Sporosarcina pasteurii'' and naturally abundant materials. In 2013 this company won the Cradle to Cradle Innovation Challenge (which included a prize of $125,000) and the Dutch Postcode Lottery Green Challenge (which included a prize of 500,000 euros). More potential applications include: * Use bacteria to solidify liquefiable soils in areas prone to

earthquake An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, from ...

s. * Form bio-bricks * Stabilize

marsh A marsh is a wetland that is dominated by herbaceous rather than woody plant species.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p Marshes can often be found at ...

es and

swamp A swamp is a forested wetland.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p. Swamps are considered to be transition zones because both land and water play a role in ...

s * Reduce the settlement rate of buildings * Remove heavy metals from wastewater Considerations of using this bacterium in industrial applications is scale-up potential, economic feasibility, long-term viability of bacteria,

adhesion Adhesion is the tendency of dissimilar particles or surfaces to cling to one another ( cohesion refers to the tendency of similar or identical particles/surfaces to cling to one another). The forces that cause adhesion and cohesion can be ...

behavior of calcium carbonate, and polymorphism.

References

External links

Magnus Larsson: Turning dunes into architecture
- Larsson's talk at TED.
Type strain of ''Sporosarcina pasteurii'' at Bac''Dive'' - the Bacterial Diversity Metadatabase
{{Taxonbar, from=Q7579277 Bacillales Environmental soil science Bacteria described in 2004