Biofilms, consisting of both microorganisms and their extracellular polysaccharides, are highly diverse and variable in both space and time. They are common on all surfaces in both terrestrial and aquatic environments (Caldwell et al., 1997; Fletcher, 1996; Ford et al., 1991; Ford, 1993; Geesey and White, 1990; Gehrke et al., 1998; Neu, 1996). Because virtually all surfaces may act as substrate for bacterial adhesion and bio6lm formation (Busscher et al., 1990; Costerton et al., 1995; Geesey and White, 1990; Geesey et al., 1996; Marshall, 1980), attack of materials by microorganisms can take place either directly or indirectly, depending on the specific microorganisms, chemical and physical properties of the materials, and their environmental conditions (Gu et al., 2000d). Both metal and non-metallic materials immersed in aqueous environments or under high humidity conditions are equally susceptible to biofouling and biodeterioration (Characklis, 1990; Gu and Mitchell, 1995; Gu et al., 1998b, 2000d; Jones-Meehan et al., 1994a, b; Knyazev et al., 1986; Little et al., 1990; Thorp et al., 1994). Speci 6c examples include medical implants (Dobbins et al., 1989; Gu et al., 2001a–c; McLean et al., 1995; Mittelman, 1996), water pipes (Rogers et al., 1994), arti6cial coatings (Edwards et al., 1994; Gu et al., 1998a; Jones-Meehan et al., 1994b; Stern and Howard, 2000; Thorp et al., 1997), rubber (Berekaa et al., 2000), ultrapure systems (Flemming et al., 1994; Mittelman, 1995), porous media (Bouwer, 1992; Cunningham et al., 1990, 1991; Mills and Powelson, 1996; Rittman, 1993; Vandevivere, 1995; Vandevivere and Kirchman, 1993; Williams and Fletcher, 1996), Biodegradability of a Polymer The biodegradability of any polymer depends on its molecular weight, crystallinity and physical forms (Gu etal.,2000). Generally, higher molecular weight results in greater resistance to degradation by microorganisms, whereas monomers, dimmers and oligomers of a polymer’s repeating units are degraded and mineralized more easily. High molecular weights lead to sharply decreased solubility, making the polymer resistant to microbial attack because microorganisms need to assimilate the substrate through their cellular membrane and then degrade the substrate further by means of intracellular enzymes. At least two categories of enzymes, namely extracellular and intracellular depolymerizers, are actively involved in biodegradation of polymers(Doi, 1990; Gu etal.,2000). It is commonly recognized that the closer a polymer’s structure to that of a natural molecule, the more easily it is degraded and mineralized (Gu and Gu, 2005). Polymers such as cellulose,chitin and poly b-hydroxybutyrate (PHB) are all biologically synthesized and can be completely and rapidly biodegraded by heterotrophic microorganisms in a wide range of natural environments (Be´renger etal.,1985; Byrom, 1991; Frazer,1994; Gamerithetal.,1992; Gujer and Zehnder,1983; GunjalaandSulflita,1993; Hamiltonetal.,1995; HespellandO’Bryan-Shah, 1988). It is also known that polymers with carbonated linear chains, such as polyolefins, are unlikely to be attacked by microorganisms. However some research has demonstrated that ligninolytic and cellulolytic fungi can degrade oxidized polymeric chains (Lee etal.,1991; Manzuretal.,1997; Weilandetal.,1994). Several attempts have been made to induce carbon-to- oxygen bonds into the polymeric chain, most of them involving photo-and thermo-oxidative treatment of polyolefins, principally polyethylene (PE); a few of the attempts report the degradation of the polymer after a long period of incubation with selected fungi or in mature compost(ChielliniandCorti,2003; Chiellini et al.,2003; Manzuretal.,2004; Pandey and Singh, 2001; Volke-Sepulvedaetal.,2002). The extracellular polymers produced by microorganisms can act as surfactants that facilitate the exchanges between hydrophilic and hydrophobic phases. These interactions favor the penetration rate of microbial species (Lucas, et al., 2008). Microbes can release active chemicals to facilitate biodegradation and the resulting degradation products can further: Concurrently, the pH inside pores is modified by the degradation products, which normally have some acid–base characteristics (Göpferich, 1996; Lucas, et al., 2008). Organic acids are more efficient than mineral acids to fix cations. They are considered as one of the main causes of biodeterioration (Warscheid and Braams, 2000). Also, some microorganisms as filamentous bacteria and fungi are able to use these organic acids as carbon sources to extend their mycelia framework (cf. § physical way) (Hakkarainen et al., 2000). POLYSTYRENE Some materials considered as recalcitrant polymers (e.g. polyethylene, polystyrene and polyurethane) are nevertheless subject to microbial biodeterioration (Shimao, 2001; Howard, 2002; Szostak-Kotowa, 2004; Shah et al., 2008). The microbial vulnerability of these polymers is attributed to the biosynthesis of lipases, esterases, ureases and proteases (Flemming, 1998; Lugauskas et al., 2003). Enzymes involved in biodeterioration require the presence of cofactors (i.e. cations present into the material matrix and coenzymes synthesised by microorganisms) for the breakdown of specific bonds (Pelmont, 2005). The biodeterioration of thermoplastic polymers could proceed by two different mechanisms, i.e., bulk and surface erosion (von Burkersroda et al., 2002; Pepic et al., 2008). In the case of bulk erosion, fragments are lost from the entire polymer mass and the molecular weight changes due to bond cleavage. This lysis is provoked by chemicals (e.g. H2O, acids, bases, transition metals and radicals) or by radiations but not by enzymes. They are too large to penetrate throughout the matrix framework. While in surface erosion, matter is lost but there is not change in the molecular weight of polymers of the matrix. If the diffusion of chemicals throughout the material is faster than the cleavage of polymer bonds, the polymer undergoes bulk erosion. If the cleavage of bonds is faster than the diffusion of chemicals, the process occurs mainly at the surface of the matrix (von Burkersroda et al., 2002; Pepic et al., 2008; Lucas, et al., 2008). REASONS WHY DEGRADED SILA: Recent studies show that atmospheric pollutants are potential sources of nutrients for some microorganisms (Zanardini et al.,2000; Nuhoglu et al., 2006). Mitchell and Gu (2000) report the deposition of sulphur dioxide, aliphatic and aromatic hydrocarbons from the urban air on several polymer materials. These adsorbed pollutants may also favour the material colonisation by other microbial species. Organic dyes are also potential nutrients for these microorganisms (Tharanathan, 2003; Faÿ et al., 2007; Lucas, et al., 2008). Many fungi reproduce sexually only on occasions, such as the plant pathogens that undergo sexual reproduction once a year after death of their plant hosts. However it must be emphasized that the life cycles of many fungi are so poorly known that some connections between asexual and sexual morphs undoubtedly remain to be made. From a preliminary ecology study on wood colonization and polyethylene colonization, it is evident that these fungi possess some intriguing mechanisms which allow them to rapidly acquire access to a resource and then to exploit it efficiently (Schoeman, 1996). The discovered Xylaria sp. by Cuevas and Manaligod (1997) inhabited plastic along with litter and organic soil. Xylariaceous fungi are often isolated as their anamorphs, like Nodulisporium sp. from soil litter. Most of these xylariaceous litter inhabitants, which grow on litter and organic soil, do not form the teleomorph in culture, thus, have not been identified (Petrini & Rogers, 1986; Rogers, 2000). Many sexually reproducing ascomycetes that we know well usually are seen only as asexual fungi (Alexopoulos, et al., 1996).Thus, fungi cultured in the laboratory are anamorphs, since fungi appear in the asexual stage most of the times, and only rarely in their sexual/teleomorph stage. Hence, there is a consistency between species form as regards to its natural occurrence and when grown in the laboratory. Anamorphs and teleomorphs are not only different sexually, but most likely, physiologically as well. Then perhaps the teleomorph of Xylaria sp., if further tested to reveal its presence or absence, would exhibit a different biodegrading ability for the given pollutants. Fungi reproduce both sexually and asexually, though not necessarily at the same time. Asexual reproduction is more significant for the colonization of the species, because it occurs several times during the season, thereby producing numerous individuals, while the sexual stage of many fungi may occur only once a year. The fact that many species may be found in one stage than the other (i.e. mostly asexual stage), greatly cause difficulties in identification of the species. And it is often impossible to predict if the stage currently at hand would produce another stage. A more common problem encountered is that of fungi with an asexual stage but no known sexual stage. Also, many fungi have no distinctive asexual reproductive stage. It was suggested that water conservation is the initial impetus for colonization of xylariaceous fungi of various hosts and substrates. Thus, diverse lifestyles of Xylaria sp. have developed to save water on occasionally dry sites. (Rogers, 1979; Rogers, 2000). The relationship developed between perithecial stromata to substrate for Xylaria, Hypoxylon, Kretzschmaria, Podosordaria, and others, is to have a massive stromata lacking in conspicuous gelatinous tissue which only develop superficially on the substrate (Rogers, 2000). Most xylariaceous fungi that have been assessed have a strong capacity to degrade cellulose and lignin, causing physiological white rots, and the most efficient of them rival basidiomycetes in substrate degradation (Nilsson et al., 1989; Rogers, 2000).