Extracellular slime

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. 

Selective plugging of highly permeable zones by injecting slime-forming bacteria followed by sucrose solution that turns on the production of extracellular slimes... 

Extracellular material of a slimy or gelatinous nature is formed by many bacteria, especially those producing mucoid growths. This material may remain firmly adherent as a discrete covering layer on each cell, or it may part freely from the cells. In the former case it is known as a capsule in the latter, as free slime or gum. 

All types of sewer biofilms are produced at surfaces exposed to the water phase and also, to some extent, at the sewer air surfaces where aerosols are present and the humidity is high. Biofilms in sewers are often referred to as slimes and consist mainly of microorganisms, extracellular polymeric substances (EPS) produced by the microorganisms and adsorbed organic and inorganic compounds from the wastewater. 

Microbes are ubiquitous in the subsurface environment and as such may play an important role in groundwater solute behavior. Microbes in the subsurface can influence pollutants by solubility enhancement, precipitation, or transformation (biodegradation) of the pollutant species. Microbes in the groundwater can act as colloids or participate in the processes of colloid formation. Bacterial attachment to granular media can be reversible or irreversible and it has been suggested that extracellular enzymes are present in the system. Extracellular exudates (slimes) can be sloughed-off and act to transport sorbed materials [122]. The stimulation of bacterial growth in the subsurface maybe considered as in situ formation of colloids. 

Most slime-forming bacteria are aerobic. Species such as Pseudomonas produce an extracellular, gel-like, polysaccharide capsule which acts to protect and shield the organism. When in combination with other metabolic by-products, bacteria... 

Exocellular polysaccharides, which are produced by strains of both Gram-positive and Gram-negative bacteria. They include capsular and extracellular (slime) polysaccharides. 

These bacterial polysaccharides have been considered to be slimes they are often in reality loose capsules that are produced extracellularly by the bacteria. It was found that low molecular weight L. mesenteroides NRRL B-512F dextran could be used as a blood plasma extender and was produced on a relatively large scale during the cold war , but also found uses as a gel-filtration material when cross-linked by epichlorohydrin to give a family of cross-linked dextrans [41]. 

Microorganisms can produce extracellular materials, such as slimes of polysaccharides and mucilages, which may help to maintain attachment to the solid substrate, provide a source of nutrients if the nutrient availability declines for any reason, or enhance protection of the cells. 

Aerobic slime formers (eg., Pseudomonas) Aerobic Produce extracellular polymers referred to as "slime. Slime can prevent oxygen from reaching the material surface. 02 (lower)... 

The ability of the stone-colonizing microflora to cover and even penetrate material surface layers by the excretion of organic extracellular polymeric substances (EPS) leads to the formation of complex slimes, or biofilms, in which the microbial cells are embedded. Phototrophic organisms usually initiate colonisation by establishing a visible, nutrient-rich biofilm on new stone from which they can penetrate the material below to seek protection from high light intensities or desiccation. Stone EPS trap aerosols, dust and nutrients, minerals,... 

Stabilisation by climate control. The most desirable method to prevent damage induced by the repeated cycles of crystallisation and hydration would probably be environmental control. However, neither the selection nor the maintenance of such an ideal environment is possible if looked at realistically. Predictions of salt crystallisation and hydration from mixed salt solutions are more or less impossible, taking into account all the different parameters that influence the process. Sawdy provides a brilliant overview of the subject and considers relative humidity, temperature, air movement, type and structure of the porous support, salt mixture composition and salt concentration. It is necessary to consider not only consolidation treatments of the plaster or the paint layer, which as such may influence the transition behaviour of the salts, but also the influence of microbial extracellular slimes on the porosity of the system. 

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