Extracellular polymeric substances (EPSs) are natural polymers of high molecular weight secreted by

microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...

s into their environment. EPSs establish the functional and structural integrity of

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 ...

s, and are considered the fundamental component that determines the physicochemical properties of a biofilm. EPS in the matrix of biofilms provides compositional support and protection of microbial communities from the harsh environments. Components of EPS can be of different classes of polysaccharides, lipids, nucleic acids, proteins, Lipopolysaccharides, and minerals.

Components

EPSs are mostly composed of

polysaccharide Polysaccharides (), or polycarbohydrates, are the most abundant carbohydrates found in food. They are long chain polymeric carbohydrates composed of monosaccharide units bound together by glycosidic linkages. This carbohydrate can react with wa ...

s (exopolysaccharides) and

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

s, but include other macromolecules such as DNA,

lipid Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include ...

s and

humic Humic substances (HS) are organic compounds that are important components of humus, the major organic fraction of soil, peat, and coal (and also a constituent of many upland streams, dystrophic lakes, and ocean water). For a long era in the 19th an ...

substances. EPSs are the construction material of bacterial settlements and either remain attached to the cell's outer surface, or are secreted into its

growth medium A growth medium or culture medium is a solid, liquid, or semi-solid designed to support the growth of a population of microorganisms or cells via the process of cell proliferation or small plants like the moss ''Physcomitrella patens''. Differen ...

. These compounds are important in biofilm formation and cells' attachment to surfaces. EPSs constitute 50% to 90% of a biofilm's total

organic matter Organic matter, organic material, or natural organic matter refers to the large source of carbon-based compounds found within natural and engineered, terrestrial, and aquatic environments. It is matter composed of organic compounds that have c ...

. Exopolysaccharides (also sometimes abbreviated EPSs; EPS sugars thereafter) are the sugar-based parts of EPS. Microorganisms synthesize a wide spectrum of multifunctional

s including

intracellular This glossary of biology terms is a list of definitions of fundamental terms and concepts used in biology, the study of life and of living organisms. It is intended as introductory material for novices; for more specific and technical definitions ...

polysaccharides, structural polysaccharides and

extracellular This glossary of biology terms is a list of definitions of fundamental terms and concepts used in biology, the study of life and of living organisms. It is intended as introductory material for novices; for more specific and technical definitions ...

polysaccharides or exopolysaccharides. Exopolysaccharides generally consist of

monosaccharide Monosaccharides (from Greek ''monos'': single, '' sacchar'': sugar), also called simple sugars, are the simplest forms of sugar and the most basic units (monomers) from which all carbohydrates are built. They are usually colorless, water-solub ...

s and some non-

carbohydrate In organic chemistry, a carbohydrate () is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula (where ''m'' may or ma ...

substituents (such as acetate, pyruvate,

succinate Succinic acid () is a dicarboxylic acid with the chemical formula (CH2)2(CO2H)2. The name derives from Latin ''succinum'', meaning amber. In living organisms, succinic acid takes the form of an anion, succinate, which has multiple biological ro ...

, and

phosphate In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphoric acid . The phosphate or orthophosphate ion is derived from phospho ...

). Owing to the wide diversity in composition, exopolysaccharides have found diverse applications in various food and pharmaceutical industries. Many microbial EPS sugars provide properties that are almost identical to the gums currently in use. With innovative approaches, efforts are underway to supersede the traditionally used plant and algal gums by their microbial counterparts. Moreover, considerable progress has been made in discovering and developing new microbial EPS sugars that possess novel industrial applications. Levan produced by ''

Pantoea agglomerans ''Pantoea agglomerans'' is a Gram-negative bacterium that belongs to the family Erwiniaceae. It was formerly called ''Enterobacter agglomerans'', or ''Erwinia herbicola'' and is a ubiquitous bacterium commonly isolated from plant surfaces, seed ...

'' ZMR7 was reported to decrease the viability of

rhabdomyosarcoma Rhabdomyosarcoma (RMS) is a highly aggressive form of cancer that develops from mesenchymal cells that have failed to fully differentiate into myocytes of skeletal muscle. Cells of the tumor are identified as rhabdomyoblasts. There are four subt ...

(RD) and

breast cancer Breast cancer is cancer that develops from breast tissue. Signs of breast cancer may include a lump in the breast, a change in breast shape, dimpling of the skin, milk rejection, fluid coming from the nipple, a newly inverted nipple, or a re ...

(MDA) cells compared with untreated

cancer cell Cancer cells are cells that divide continually, forming solid tumors or flooding the blood with abnormal cells. Cell division is a normal process used by the body for growth and repair. A parent cell divides to form two daughter cells, and these d ...

s. In addition, it has high

antiparasitic Antiparasitics are a class of medications which are indicated for the treatment of parasitic diseases, such as those caused by helminths, amoeba, ectoparasites, parasitic fungi, and protozoa, among others. Antiparasitics target the parasitic agent ...

activity against the

promastigote Trypanosomatida is a group of kinetoplastid excavates distinguished by having only a single flagellum. The name is derived from the Greek ''trypano'' (borer) and ''soma'' (body) because of the corkscrew-like motion of some trypanosomatid species. ...

of ''

Leishmania tropica ''Leishmania tropica'' is a flagellate parasite and the cause of anthroponotic cutaneous leishmaniasis in humans. This parasite is restricted to Afro-Eurasia and is a common cause of infection in Afghanistan, Iran, Syria, Yemen, Algeria, M ...

.'' In the1960s and 1970s, the presence of exopolysaccharides in the matrix of plaques associated with tooth decay was investigated. In the field of paleomicrobiology, dental biofilms and their EPS components provide scientists with information about the composition of ancient microbial and host biomolecules as well as the diet of the host. The minerals, results of biomineralization processes regulated by the environment or bacteria, are also essential components of the EPS. They provide structural integrity to biofilm matrix and act as a scaffold to protect bacterial cells from shear forces and antimicrobial chemicals. The minerals in EPS were found to contribute to morphogenesis of bacteria and the structural integrity of the matrix. For example, in ''Bacillus. subtilis, Mycobacterium smegmatis, and Pseudomonas aeruginosa'' biofilms calcite (CaCO3) contributes to the integrity of the matrix. The minerals also associate with medical conditions. In the biofilms of ''Proteus mirabilis, Proteus vulgaris, and Providencia rettgeri,'' the minerals calcium and magnesium cause catheter encrustation.

EPS and Biofilm

Biofilm Formation

The first step in the formation of Biofilms is adhesion. The initial bacterial adhesion to surfaces involves the adhesin–receptor interactions. Certain polysaccharides, lipids and proteins in the matrix function as the adhesive agents. EPS also promotes cell–cell cohesion (including interspecies recognition) to facilitate microbial aggregation and biofilm formation. In general, the EPS-based matrix mediates biofilm assembly as follows. First, the EPS formation takes place at the site of adhesion, it will be either produced on bacterial surfaces or secreted on the surface of attachment, and form an initial polymeric matrix promoting microbial colonization and cell clustering. Next, continuous production of EPS further expands the matrix in 3 dimensions while forming a core of bacterial cells. The bacterial core provides a supporting framework, and facilitates the development of 3D clusters and aggregation of microcolonies. Studies on ''P. aeruginosa, B. subtilis'', ''V. cholerae'', and ''S. mutans'' suggested that the transition from initial cell clustering to microcolony appears to be conserved among different biofilm-forming model organisms. As an example, ''S. mutans'' produces an exoenzymes, called glucosyltransferases (Gtfs), which synthesize

glucans A glucan is a polysaccharide derived from D-glucose, linked by glycosidic bonds. Glucans are noted in two forms: alpha glucans and beta glucans. Many beta-glucans are medically important. They represent a drug target for antifungal medications of ...

''in situ'' using host diet sugars as substrates. Gtfs even bind to the bacteria that do not synthesize Gtfs, and therefore, facilitate interspecies and interkingdom coadhesion.

Significance of EPS in Biofilms

Afterwards, as biofilm becomes established, EPS provides physical stability and resistance to mechanical removal, antimicrobials, and host immunity. Exopolysaccharides and environmental DNA (eDNA) contribute to viscoelasticity of mature biofilms so that detachment of biofilm from the substratum will be challenging even under sustained fluid shear stress or high mechanical pressure. In addition to mechanical resistance, EPS also promotes protection against antimicrobials and enhanced drug tolerance. Antimicrobials cannot diffuse through the EPS barrier, resulting in limited drug access into the deeper layers of the biofilm. Moreover, positively charged agents will bind to negatively charged EPS contributing to the antimicrobial tolerance of biofilms, and enabling inactivation or degradation of antimicrobials by enzymes present in biofilm matrix. EPS also functions as local nutrient reservoir of various biomolecules, such as fermentable polysaccharides. A study on ''V. cholerae'' in 2017 suggested that due to osmotic pressure differences in ''V. cholerae'' biofilms, the microbial colonies physically swell, therefore maximizing their contact with nutritious surfaces and thus, nutrient uptake.

Function

Capsular exopolysaccharides can protect

pathogenic bacteria Pathogenic bacteria are bacteria that can cause disease. This article focuses on the bacteria that are pathogenic to humans. Most species of bacteria are harmless and are often Probiotic, beneficial but others can cause infectious diseases. The n ...

against

desiccation Desiccation () is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic (attracts and holds water) substance that induces or sustains such a state in its local vicinity in a moderately sealed container. ...

and

predation Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill the ...

, and contribute to their

pathogen In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...

icity.

Sessile Sessility, or sessile, may refer to: * Sessility (motility), organisms which are not able to move about * Sessility (botany), flowers or leaves that grow directly from the stem or peduncle of a plant * Sessility (medicine), tumors and polyps that ...

bacteria fixed and aggregated in

s are less vulnerable compared to drifting

plankton Plankton are the diverse collection of organisms found in Hydrosphere, water (or atmosphere, air) that are unable to propel themselves against a Ocean current, current (or wind). The individual organisms constituting plankton are called plankt ...

ic bacteria, as the EPS matrix is able to act as a protective diffusion barrier. The physical and chemical characteristics of bacterial cells can be affected by EPS composition, influencing factors such as cellular recognition, aggregation, and

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 ...

in their natural environments. Furthermore, the EPS layer acts as a nutrient trap, facilitating

bacterial growth 250px, Growth is shown as ''L'' = log(numbers) where numbers is the number of colony forming units per ml, versus ''T'' (time.) Bacterial growth is proliferation of bacterium into two daughter cells, in a process called binary fission. Providing ...

. The exopolysaccharides of some strains of

lactic acid bacteria Lactobacillales are an order of gram-positive, low-GC, acid-tolerant, generally nonsporulating, nonrespiring, either rod-shaped (bacilli) or spherical (cocci) bacteria that share common metabolic and physiological characteristics. These bacte ...

, e.g.,

Lactococcus lactis ''Lactococcus lactis'' is a Gram-positive bacterium used extensively in the production of buttermilk and cheese, but has also become famous as the first genetically modified organism to be used alive for the treatment of human disease. ''L. lact ...

subsp. cremoris, contribute a gelatinous texture to

fermented milk products Fermented milk products or fermented dairy products, also known as cultured dairy foods, cultured dairy products, or cultured milk products, are dairy foods that have been fermented with lactic acid bacteria such as ''Lactobacillus'', ''Lactococcu ...

(e.g.,

Viili Viili (Finnish) is a mesophilic fermented milk product found in the Nordic countries, particularly Finland. Viili is similar to yoghurt or kefir, but when left unmixed, its texture is malleable, or "long". The metabolism of the bacteria used in ...

), and these polysaccharides are also digestible. An example of the industrial use of exopolysaccharides is the application of

dextran Dextran is a complex branched glucan ( polysaccharide derived from the condensation of glucose), originally derived from wine. IUPAC defines dextrans as "Branched poly-α-d-glucosides of microbial origin having glycosidic bonds predominantly C-1 ...

panettone Panettone (, ; lmo, label= Milanese, panetton ) is an Italian type of sweet bread, and fruitcake, originally from Milan, usually prepared and enjoyed for Christmas and New Year in Western, Southern, and Southeastern Europe as well as in South ...

and other breads in the bakery industry. Apart from negative contributions of EPS in biofilms, EPS can also contribute to some beneficial functions. For example, ''B. subtilis'' has gained interest for its probiotic properties due to its biofilm which allows it to effectively maintain ''a favorable microenvironmnet in the gastrointestinal tract. In order to survive the passage through the upper gastrointestinal tract'', ''B. subtilis'' produces an extracellular matrix that protects it from stressful environments such as the highly acidic environment in the stomach. In ''B. subtilis'', the protein matrix component, TasA, and the exopolysaccharide have both been shown to be essential for effective plant-root colonization in ''Arabidopsis'' and tomato plants. It was also suggested that TasA plays an important role in mediating interspecies aggregation with streptococci.

Ecology

Exopolysaccharides can facilitate the attachment of

nitrogen-fixing bacteria Nitrogen fixation is a chemical process by which molecular nitrogen (), with a strong triple covalent bond, in the air is converted into ammonia () or related nitrogenous compounds, typically in soil or aquatic systems but also in industry. Atmo ...

to plant roots and soil particles, which mediates a

symbiotic Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or parasit ...

relationship. This is important for colonization of roots and the

rhizosphere The rhizosphere is the narrow region of soil or substrate that is directly influenced by root secretions and associated soil microorganisms known as the root microbiome. Soil pores in the rhizosphere can contain many bacteria and other microor ...

, which is a key component of soil

food web A food web is the natural interconnection of food chains and a graphical representation of what-eats-what in an ecological community. Another name for food web is consumer-resource system. Ecologists can broadly lump all life forms into one o ...

s and

nutrient cycling A nutrient cycle (or ecological recycling) is the movement and exchange of inorganic and organic matter back into the production of matter. Energy flow is a unidirectional and noncyclic pathway, whereas the movement of mineral nutrients is cycli ...

ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...

s. It also allows for successful invasion and

infection An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable dise ...

of the

host plant In biology and medicine, a host is a larger organism that harbours a smaller organism; whether a parasitic, a mutualistic, or a commensalist ''guest'' ( symbiont). The guest is typically provided with nourishment and shelter. Examples include ...

. Bacterial extracellular polymeric substances can aid in

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 ...

heavy metals upright=1.2, Crystals of osmium, a heavy metal nearly twice as dense as lead">lead.html" ;"title="osmium, a heavy metal nearly twice as dense as lead">osmium, a heavy metal nearly twice as dense as lead Heavy metals are generally defined as ...

as they have the capacity to adsorb metal cations, among other dissolved substances. This can be useful in the treatment of

wastewater Wastewater is water generated after the use of freshwater, raw water, drinking water or saline water in a variety of deliberate applications or processes. Another definition of wastewater is "Used water from any combination of domestic, industr ...

systems, as biofilms are able to bind to and remove metals such as

copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...

lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...

nickel Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow to ...

, and

cadmium Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Like zinc, it demonstrates oxidation state +2 in most of ...

. The

binding affinity In biochemistry and pharmacology, a ligand is a substance that forms a complex with a biomolecule to serve a biological purpose. The etymology stems from ''ligare'', which means 'to bind'. In protein-ligand binding, the ligand is usually a m ...

and metal specificity of EPSs varies, depending on polymer composition as well as factors such as

concentration In chemistry, concentration is the abundance of a constituent divided by the total volume of a mixture. Several types of mathematical description can be distinguished: '' mass concentration'', ''molar concentration'', ''number concentration'', an ...

and pH. In a geomicrobiological context, EPSs have been observed to affect

precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. ...

of minerals, particularly

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 ...

s. EPS may also bind to and trap particles in biofilm suspensions, which can restrict dispersion and element cycling.

Sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand an ...

stability can be increased by EPS, as it influences cohesion, permeability, and

erosion Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is distin ...

of the sediment. There is evidence that the

and metal-binding ability of EPS affects mineral

leaching Leaching is the loss or extraction of certain materials from a carrier into a liquid (usually, but not always a solvent). and may refer to: * Leaching (agriculture), the loss of water-soluble plant nutrients from the soil; or applying a small amou ...

rates in both environmental and industrial contexts. These interactions between EPS and the

abiotic In biology and ecology, abiotic components or abiotic factors are non-living chemical and physical parts of the environment that affect living organisms and the functioning of ecosystems. Abiotic factors and the phenomena associated with them under ...

environment allow for EPS to have a large impact on

biogeochemical cycling A biogeochemical cycle (or more generally a cycle of matter) is the pathway by which a chemical substance cycles (is turned over or moves through) the biotic and the abiotic compartments of Earth. The biotic compartment is the biosphere and the ...

Predator-prey Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill the ...

interactions between biofilms and

bacterivore A bacterivore is an organism which obtains energy and nutrients primarily or entirely from the consumption of bacteria. The term is most commonly used to describe free-living, heterotrophic, microscopic organisms such as nematodes as well as many s ...

s, such as the soil-dwelling

nematode The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant-Parasitism, parasitic nematodes also known as eelworms. They are a diverse animal phylum inhab ...

Caenorhabditis elegans, had been extensively studied. Via the production of sticky matrix and formation of aggregates,

Yersinia pestis ''Yersinia pestis'' (''Y. pestis''; formerly '' Pasteurella pestis'') is a gram-negative, non-motile, coccobacillus bacterium without spores that is related to both ''Yersinia pseudotuberculosis'' and ''Yersinia enterocolitica''. It is a facult ...

biofilms can prevent feeding by obstructing the mouth of C. elegans. Moreover,

Pseudomonas aeruginosa ''Pseudomonas aeruginosa'' is a common encapsulated, gram-negative, aerobic–facultatively anaerobic, rod-shaped bacterium that can cause disease in plants and animals, including humans. A species of considerable medical importance, ''P. aerugi ...

biofilms can impede the slithering motility of C. elegans, termed as 'quagmire

phenotype In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology or physical form and structure, its developmental processes, its biochemical and physiological proper ...

', resulting in trapping of C. elegans within the biofilms and preventing the exploration of nematodes to feed on susceptible biofilms. This significantly reduced the ability of predator to feed and reproduce, thereby promoting the survival of biofilms.

Novel Industrial Use

Due to the growing need to find a more efficient and environmentally friendly alternative to conventional waste removal methods, industries are paying more attention to the function of bacteria and their EPS sugars in

. Researchers found that adding EPS sugars from

cyanobacteria Cyanobacteria (), also known as Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's common name, blu ...

s removes heavy metals such as

and

. EPS sugars alone can physically interact with these heavy metals and take them in through

biosorption Biosorption is a physiochemical process that occurs naturally in certain biomass which allows it to passively concentrate and bind contaminants onto its cellular structure. Biosorption can be defined as the ability of biological materials to accumu ...

. The efficiency of removal can be optimized by treating the EPS sugars with different

acid In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a sequ ...

s or bases before adding them to wastewater. Some contaminated soils contain high levels of

polycyclic aromatic hydrocarbon A polycyclic aromatic hydrocarbon (PAH) is a class of organic compounds that is composed of multiple aromatic rings. The simplest representative is naphthalene, having two aromatic rings and the three-ring compounds anthracene and phenanthrene. ...

s (PAHs); EPSs from the bacterium ''Zoogloea'' sp. and the

fungus A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from th ...

Aspergillus niger ''Aspergillus niger'' is a mold classified within the ''Nigri'' section of the ''Aspergillus'' genus. The ''Aspergillus'' genus consists of common molds found throughout the environment within soil and water, on vegetation, in fecal matter, on de ...

'', are efficient at removing these toxic compounds. EPSs contain

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...

s such as

oxidoreductase In biochemistry, an oxidoreductase is an enzyme that catalyzes the transfer of electrons from one molecule, the reductant, also called the electron donor, to another, the oxidant, also called the electron acceptor. This group of enzymes usually u ...

and

hydrolase Hydrolase is a class of enzyme that commonly perform as biochemical catalysts that use water to break a chemical bond, which typically results in dividing a larger molecule into smaller molecules. Some common examples of hydrolase enzymes are este ...

, which are capable of degrading PAHs. The amount of PAH degradation depends on the concentration of EPSs added to the soil. This method proves to be low cost and highly efficient. In recent years, EPS sugars from

marine bacteria 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 ...

have been found to speed up the cleanup of oil spills. During the

Deepwater Horizon oil spill The ''Deepwater Horizon'' oil spill (also referred to as the "BP oil spill") was an industrial disaster that began on 20 April 2010 off of the coast of the United States in the Gulf of Mexico on the BP-operated Macondo Prospect, considere ...

in 2010, these EPS-producing bacteria were able to grow and multiply rapidly. It was later found that their EPS sugars dissolved the oil and formed oil aggregates on the ocean surface, which sped up the cleaning process. These oil aggregates also provided a valuable source of nutrients for other marine microbial communities. This let scientists modify and optimize the use of EPS sugars to clean up

oil spill 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 ...

List of Extracellular polymeric substances

* acetan (''Acetobacter xylinum'') *

alginate Alginic acid, also called algin, is a naturally occurring, edible polysaccharide found in brown algae. It is hydrophilic and forms a viscous gum when hydrated. With metals such as sodium and calcium, its salts are known as alginates. Its colour ...

(''Azotobacter vinelandii'') *

cellulose Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose is an important structural component of the primary cell wall ...

(''Acetobacter xylinum'') *

chitosan Chitosan is a linear polysaccharide composed of randomly distributed β-(1→4)-linked D-glucosamine (deacetylated unit) and ''N''-acetyl-D-glucosamine (acetylated unit). It is made by treating the chitin shells of shrimp and other crustacean ...

(''Mucorales spp.'') *

curdlan Curdlan is a water-insoluble linear beta-1,3-glucan, a high-molecular-weight polymer of glucose. Curdlan consists of β-(1,3)-linked glucose residues and forms elastic gels upon heating in aqueous suspension. It was reported to be produced by '' ...

(''Alcaligenes faecalis'' var. ''myxogenes'') * cyclosophorans (''Agrobacterium'' spp., ''Rhizobium'' spp. and ''Xanthomonas'' spp.) *

(''Leuconostoc mesenteroides'', ''Leuconostoc dextranicum'' and ''Lactobacillus hilgardii'') * emulsan (''Acinetobacter calcoaceticus'') * galactoglucopolysaccharides (''Achromobacter'' spp., ''Agrobacterium radiobacter'', ''Pseudomonas marginalis'', ''Rhizobium'' spp. and ''Zooglea' spp.) * galactosaminogalactan (''Aspergillus spp.'') *

gellan Gellan gum is a water-soluble anionic polysaccharide produced by the bacterium ''Sphingomonas elodea'' (formerly ''Pseudomonas elodea'' based on the taxonomic classification at the time of its discovery). The gellan-producing bacterium was disco ...

(''Aureomonas elodea'' and ''Sphingomonas paucimobilis'') * glucuronan (''Sinorhizobium meliloti'') *

N-acetylglucosamine ''N''-Acetylglucosamine (GlcNAc) is an amide derivative of the monosaccharide glucose. It is a secondary amide between glucosamine and acetic acid. It is significant in several biological systems. It is part of a biopolymer in the bacterial ...

(''Staphylococcus epidermidis'') * N-acetyl-heparosan (''Escherichia coli'') *

hyaluronic acid Hyaluronic acid (; abbreviated HA; conjugate base hyaluronate), also called hyaluronan, is an anionic, nonsulfated glycosaminoglycan distributed widely throughout connective, epithelial, and neural tissues. It is unique among glycosaminoglycans ...

(''Streptococcus equi'') *

indican Indican is a colourless organic compound, soluble in water, naturally occurring in ''Indigofera'' plants. It is a precursor of indigo dye. Chemical reactions Common and significant reactions involving indican are as follows: *Indican is a glyco ...

(''Beijerinckia indica'') *

kefiran Kefir ( ; also spelled as kephir or kefier; ; ; ) is a fermented milk drink similar to a thin yogurt or ayran that is made from kefir grains, a specific type of mesophilic symbiotic culture. The drink originated in the North Caucasus, in p ...

(''Lactobacillus hilgardii'') *

lentinan Lentinan is a polysaccharide isolated from the fruit body of shiitake mushroom (''Lentinula edodes'' mycelium). Chemistry Lentinan is a β-1,3 beta-glucan with β-1,6 branching. It has a molecular weight of 500,000 Da and specific rotation of +1 ...

(''Lentinus elodes'') * levan (''Alcaligenes viscosus'', ''Zymomonas mobilis'', ''Bacillus subtilis'') *

pullulan Pullulan is a polysaccharide polymer consisting of maltotriose units, also known as α-1,4- ;α-1,6- glucan'. Three glucose units in maltotriose are connected by an α-1,4 glycosidic bond, whereas consecutive maltotriose units are connected to e ...

(''Aureobasidium pullulans'') * scleroglucan (''Sclerotium rolfsii'', ''Sclerotium delfinii'' and ''Sclerotium glucanicum'') *

schizophyllan Schizophyllan (Sonifilan, SPG) is a neutral extracellular polysaccharide produced by the fungus ''Schizophyllum commune''. Schizophyllan is a β-1,3 beta-glucan with β-1,6 branching. Schizophyllan is also known as sizofiran. Schizophyllan has a ...

(''Schizophylum commune'') * stewartan (''Pantoea stewartii subsp. stewartii'') * succinoglycan (''Alcaligenes faecalis'' var. ''myxogenes'', ''

Sinorhizobium meliloti ''Ensifer meliloti'' (formerly ''Rhizobium meliloti'' and ''Sinorhizobium meliloti'') are an aerobic, Gram-negative, and diazotrophic species of bacteria. ''S. meliloti'' are motile and possess a cluster of peritrichous flagella. ''S. meliloti'' ...

'') *

xanthan Xanthan gum () is a polysaccharide with many industrial uses, including as a common food additive. It is an effective thickening agent, emulsifier, and stabilizer that prevents ingredients from separating. It can be produced from simple sugar ...

(''Xanthomonas campestris'') *

welan Welan gum is an exopolysaccharide used as a rheology modifier in industrial applications such as cement manufacturing. It is produced by fermentation of sugar by bacteria of the genus ''Alcaligenes ''Alcaligenes'' is a genus of Gram-negative, ...

(''Alcaligenes'' spp.)

New Approaches to Target Biofilms

The application of Nanoparticles (NPs) are one of novel promising techniques to target biofilms due to their high surface-area-to-volume ratio, their ability to penetrate to the deeper layers of biofilms and the capacity to releasing antimicrobial agents in a controlled way. Studying NP-EPS interactions could provide deeper understanding on how to develop more effective nanoparticles. "smart release" nanocarriers that can penetrate biofilms and be triggered by pathogenic microenvironments to deliver drugs or multifunctional compounds, such as catalytic nanoparticles to aptamers, dendrimers, and bioactive peptides) have been developed to disrupt the EPS and the viability or metabolic activity of the embedded bacteria. Some factors that would alter the potentials of the NP to transport antimicrobial agents into the biofilm include physicochemical interactions of the NPs with EPS components, the characteristics of the water spaces (pores) within the EPS matrix and the EPS matrix viscosity. Size and surface properties (charge and functional groups) of the NPs are the major determinants of the penetration in and the interaction with the EPS. Another potential antibiofilm strategy is phage therapy. Bacteriophages, viruses that invade specific bacterial host cells, were suggested to be effective agents in penetrating biofilms. In order to reach the maximum efficacy to eradicate biofilms, therapeutic strategies need to target both the biofilm matrix components as well as the embedded microorganisms to target the complex biofilm microenvironment.

EPS in Microalgal Biofilms

EPS is found in the matrix of other microbial biofilms such as microalgal biofilms. The formation of biofilm and structure of EPS share a lot of similarities with bacterial ones. The formation of Biofilm starts with reversible absorption of floating cells to the surface. Followed by production of EPS, the adsorption will get irreversible. EPS will colonize the cells at the surface with hydrogen bonding. Replication of early colonizers will be facilitated by the presence of organic molecules in the matrix which will provide nutrients to the algal cells . As the colonizers are reproducing, the biofilm grows and becomes a 3-dimensional structure. Microalgal biofilms consist of 90% EPS and 10% algal cells. Agal EPS has similar components to the bacterial one; it is made up of proteins, phospholipids, polysaccharides, nucleic acids, humic substances, uronic acids and some functional groups, such as phosphoric, carboxylic, hydroxyl and amino groups. Algal cells consume EPS as their source of energy and carbon. Furthermore, EPS protects them from dehydration and reinforces the adhesion of the cells to the surface. In algal biofilms, EPS has two sub-categories; soluble EPS (sEPS) and the bounded EPS (bEPS) with former being distributed in the medium and the latter being attached to the algal cells. Bounded EPS can be further subdivided to tightly bounded EPS (TB-EPS) and loosely bounded EPS (LB-EPS). Several factors contribute to the composition of EPS including species, substrate type, nutrient availability, temperature, pH and light intensity.

References

External links

EPS, BioMineWiki
{{Webarchive, url=https://web.archive.org/web/20210108130147/http://wiki.biomine.skelleftea.se/wiki/index.php/Extracellular_polysaccharide , date=2021-01-08 Microbiology terms Bacteria Bacteriology Environmental soil science Membrane biology Biological matter Microbiology Biomolecules Polymers Water treatment