Mucilage extracellular

S. V. Fareed and E. Percival, The presence of rhamnose and 3-O-methylxylose in the extracellular mucilage from the red alga Rhodella maculata, Carbohydr. Res., 53 (1977) 276-277. 

Fig. 2.2. Mycelium of Hebeloma crustuliniforme after colonization of a potassium feldspar surface for seven months. The sample was prepared by fixation and critical point drying followed by gold coating and analysis by scanning electron microscopy. Hyphae (H) and bacteria (B) are visible. Scale bar = 10 pm. The hyphal surface contact is mediated by a fdm of extracellular mucilage (arrow) and bacteria are seen in the mucilage.

The significance of adhesion to fungal survival and spread, as well as the chemistry of adhesives and extracellular mucilages have been discussed extensively in recent reviews (2, , 5.). Perhaps the most important aspect of fungal adhesion, regardless of the mechanism by which it occurs, is the prevention... 

The time at which release of extracellular matrices by conidia or germlings occurs is also important to understanding their involvement in disease development. In some cases extracellular mucilages or matrices are released upon hydration... 

Figure 3. Scanning electron micrographs of CollfitQtrlchum graunlnlcola. A) Fully developed acervulus of the fungus on a corn leaf showing conidia (c) interspersed with sterile setae (st). Bar represents 10 Jim. B) The cut surface of an acervular mass of conidia. The cut surfaces of conidia (c) are visible and demonstrate that conidia are embedded within an extracellular mucilage (em). Bar represents 10 Jim. Fig. 3A reproduced with permission from Ref. 69. Copyright 1989 Academic Press, Inc.

The following 0-methylaldoses have been isolated from, or identified as constituents of, natural products 3-0-methylxylose (in the extracellular mucilage from the red alga Rhodella maculata), 3-0-methyl-L-xylose (together with L-xylose and L-rhamnose from the lipopolysaccharide of Pseudomonas maltophilia), 3-0-methy]-D-ribose (from the extracellular polysaccharide of a Cowpea strain of slow-growing Rhizobium, strain CB 756), 2-0-methyl- and 2,4-di-O-methyl-L-rhamnose (in the antibiotics steffimycin and steffimycin B produced by Strepto-myces steffisburgensis), and 3-0-methyl-galactose and -mannose (from the haemocyanin of snails). ... 

Rhamnose and 3-0-methylxylose have been identified (by g.l.c. and g.l.c.-m.s., respectively) as components of the extracellular mucilage from the red alga Rhodella maculata. The principal polysaccharide extracted from both Vrospora... 

It is sometimes claimed that mucilage and similar gels may help to maintain hydraulic conductivity between root and. soil (52). However, the hydraulic conductivity of soils is often substantially decreased when soils are irrigated with waste water. Apart from the inducement of sodicity, which is real in many cases, the decreases in hydraulic conductivity are attributed largely to the production of microbial biomass, particularly extracellular polysaccharides (e.g.. Ref. 53). These extracellular polysaccharides form gels that may store large quantities of water and allow water and ions to diffu.se through them at rates not much less than those of free water, but they could be expected to restrict mass flow of water and thus nutrients, to roots (54). 

Transmission electron microscopy of immunogold labelled sections has shown that the extracellular lignin-degrading enzymes lignin-peroxidase and laccase were localized within the cell wall and mucilage of the hyphae of C. versicolor. Laccase was present in the cell wall layer whereas lignin-... 

Gums and mucilages may be found either in the intracellular pans of plants or as extracellular exudates. Those found within plant cells represent storage material in seeds and roots. They also serve as a water reservoir and as protection for germinating seed. The polysaccharides found as extracellular exudates of higher plants appear to be produced as a result of injury caused by mechanical means or by insects. It has not been well established whether the exudates are formed at the site of the injury. 

The extracellular plant gums and mucilages (gum arabic, karaya gum. and tragacanlh, for example) generally have a more complex structure... 

Mucilage has protective functions for the root meristem and improves root-soil contact by inclusion and aggregation of soil particles. It may also contribute to P desorption and to the exclusion of toxic elements (Al, Cd, Pb) by complexation with galacturonates, mainly in exchange with Ca2+ (Neumann and Romheld, 2002). Secreted enzymes contribute to the extracellular enzyme pool it has been shown that the activity of extracellular enzymes, such as phophatases, proteases, and aryl-sulfatases, exhibit more activity in the rhizosphere relative to the bulk soil and may have a dramatic effect on the cycling of nutrients such as P, N, and S (Badalucco and Nannipieri, 2007). 

Extracellular polysaccharides are produced by some species of the genus Rhodella, but their composition seems to be even more complex than that of Porphyridium. In addition to monosaccharide components just mentioned, rhamnose and 3-O-methyl-xylose were found in the mucilage of R. maculata.723 724 An extremely complex proteoglycan was shown to be produced by Rhodella grisea.725... 

Fig. 11.1. Fungal microcolonies and associated extracellular pol3uneric substances (EPS). (A) On the surface of marble in Greece (Athens). The EPS network around black fungal colonies is stained red (on the photo -light grey) by periodic acid - Schiff s reagent stain (PAS). (B) Cryo-scanning electron microscope image of a fungal microcolony with its inherent mucilage. This colony of strain A49 was cultured in subaerial conditions with some additional supply of nutrients from the substrate.

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. 

In addition to the cell wall, micro-organisms can display other extracellular layers such as slimes and mucilages which, for some organisms, are used to help attach to a substrate. 

Fig. 10.1. Terms used in this chapter to describe possible enzyme location. In the case of mucilage external to the wall, it is recommended to state in each case whether it is treated as surface or extracellular. ...

Table 8. Monosaccharide composition (%) and content of polyanionic sulfate in extracellular polysaccharides and a mucilage sample from the Adriatic... 

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