Extracellular polymers

Slime layers are a mixture of bacterial secretions called extracellular polymers, other metabolic products, bacteria, gases, detritus, and water. Commonly, 99% of the slime layer is water, although much silt and debris may also become entrapped in it. 

Slime is a network of secreted strands (extracellular polymers) intermixed with bacteria, water, gases, and extraneous matter. Slime layers occlude surfaces—the biological mat tends to form on and stick to surfaces. Surface shielding is further accelerated by the gathering of dirt, silt, sand, and other materials into the layer. Slime layers produce a stagnant zone next to surfaces that retards convective oxygen transport and increases diffusion distances. These properties naturally promote oxygen concentration cell formation. 

Many bacterial polysaccharides contain phosphoric ester groups. There is a limited number of examples of monoesters. More common are phosphoric diesters, connecting an amino alcohol or an alditol to the polysaccharide chain. Another possibility is that oligosaccharide or oligosaccharide-alditol repeating units are connected to a polymer by phosphoric diester linkages. In addition to the intracellular teichoic acids, several bacteria, for example, different types of Streptococcus pneumoniae, elaborate extracellular polymers of this type. These polymers are generally discussed in connection with the bacterial polysaccharides. 

Wolfaardt GM, JR Lawrence, RD Robarts, DE Caldwell (1995) Bioaccumulation of the herbicide diclofop in extracellular polymers and its utilization by a biofilm community during starvation. Appl Environ Microbiol 61 152-158. 

The basic biofilm model149,150 idealizes a biofilm as a homogeneous matrix of bacteria and the extracellular polymers that bind the bacteria together and to the surface. A Monod equation describes substrate use molecular diffusion within the biofilm is described by Fick s second law and mass transfer from the solution to the biofilm surface is modeled with a solute-diffusion layer. Six kinetic parameters (several of which can be estimated from theoretical considerations and others of which must be derived empirically) and the biofilm thickness must be known to calculate the movement of substrate into the biofilm. 

The resident microbes within the mouth readily form biofilms on teeth. A biofilm consists of a population of bacteria coexisting in an orderly structure at the interface of a solid and a liquid [14] and, within a biofilm, bacteria living in colonies encapsulated in a matrix of extracellular polymer. Oral biofilms are known to vary extensively in structure throughout the colony, with regions of densely packed microorganisms surrounded by open water channels. Each type of bacteria exists in reasonably defined environments which are influenced by surrounding cells, distance from the outer surface and local structure, all of which influence availability of nutrients and ambient pH. 

The polarographic method has been used to determine the stability constants and kinetic parameters of ternary complexes of Zn(II) with L-lysine, L-omithine, L-serine, L-phenylglycine, L-phenylalanine, L-glutamic acid, and L-aspartic acid as primary ligands and picoline as secondary ligand at pH 8.5 [103] and also of zinc complexation by extracellular polymers extracted from activated sludge [104]. 

Brown, M. J. Lester, J. N. (1979). Metal removal in activated sludge the role of bacterial extracellular polymers. Water Research, 13, 817-37. 

Chen, J-H., Lion, L. W., Ghiorse, W. C. Shuler. M. L. (1995). Mobilization of adsorbed cadmium and lead in aquifer material by bacterial extracellular polymers. Water Research, 29, 421—30. 

Rudd, T., Sterritt, R. M. Lester, J. N. (1984a). Complexation of heavy metals by extracellular polymers in the activated sludge process. Journal Water Pollution Control Federation, 56, 1260-8. 

Fibrillin-1 microfibrils are highly complex extracellular polymers, and the molecular basis of assembly is not well understood. Studies have focused on defining the role of cells in regulating assembly, the molecular interactions that drive assembly, and the role of microfibril-associated molecules in the assembly process. 

Harvey RW, Luoma SN. 1985. Effect of adherent bacteria and bacterial extracellular polymers upon assimilation by Macoma balthica of sediment-bound cadmium, zinc and silver. Mar Ecol Prog Ser 22 281-289. 

The invaluable comments of the referees are highly acknowledged in improving the quality of this contribution and for encouraging the authors to continue a more detailed experimental study, which will clarify the role of extracellular polymer substances in the mechanism of metal uptake by activated sludge process. 

D.T. Sponza, Investigation of extracellular polymer substances (EPS) and physicochemical properties of different activated sludge floes under steady-state conditions, Enzyme Microb. Technol. 32 (2003) 375-385. 

M.F. Dignac, V. Urbain, D. Rybacki, A. Bruchet, D. Snidaro, R Scribe, Chemical description of extracellular polymers implications on activated sludge floe structure, Water Sci. Technol. 38 (1998) 45-53. 

M.J. Brown, J.N. Lester, Role of bacterial extracellular polymers in metal uptake in pure bacterial culture and activated sludge, Water Res. 16 (1982) 1549-1560. 

Nagaoka, H., Ueda, S. and Miya, A. (1996) Influence of bacterial extracellular polymers on the membrane separation activated sludge process. Water Science Technology, 34 (9), 165-172. 

Schmidt, J.E., and Ahring, B.K. (1994) Extracellular polymers in granular sludge from different upflow anaerobic sludge blanket (UASB) reactors. Appl. Microbiol. Biotechnol. 42, 457-462. 

Smith WO, Carlson CA, Ducklow HW, Hansell DA (1998) Growth dynamics of Phaeocystis antarctica-dominated plankton assemblages from the Ross Sea. Mar Ecol Prog Ser 168 229-244 Solomon CM, Lessard EJ, Keil RG, Foy MS (2003) Characterization of extracellular polymers of Phaeocystis globosa and P. antarctica. Mar Ecol Prog Ser 250 81-89... 

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