Biodeterioration
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CHAPTER 3.9 no i t aro i re t edo iB
Biodeterioration JI-DONG GU AND RALPH MITCHELL
Introduction Bacteria were the first life-forms to appear on Earth and they have a long history of association with mineral surfaces. Surfaces of clay minerals played an important role in the initial evolutionary processes of bacteria and the diversification of their physiology (Kluyver and van Niel, 1956; Mayr, 1998; Wächtershäuser, 1988; Woese, 1987; Woese, 1990; Woese, 1998; Woese and Olsen, 1986). Bacteria also adapt themselves to a mode of living on physical surfaces and at interfaces (Angles et al., 1993; Bitton, 1980; Brune et al., 2000; Caldwell et al., 1997; Fenchel and Finlay, 1995; Fletcher, 1980; Glagolev, 1984; Hugenholtz et al., 1998; Margulis, 1981; Marshall, 1992; Moat and Foster, 1988; Pace, 1997; Wolfaardt et al., 1994; Zavarzin et al., 1994; Zinder, 1993). In addition, they are capable of degrading a wide range of pollutants (Gibson, 1984; Gu and Berry, 1991; Gu and Berry, 1992a; Gu et al., 1992b; Young and Cerniglia, 1995). It is well recognized that degradation of organic chemicals and nutrient cycling are more rapid on surfaces. Unfortunately, microbial association with surfaces also has a potential negative economic impact, when it accelerates degradation and deterioration of a wide range of materials, including inorganic minerals (Gu et al., 2000b; Mitchell and Gu, 2000), concrete and stone (Gebers and Hirsch, 1978; Gu et al., 2000b; Moosavi et al., 1986; Padival et al., 1995; Piervittori et al., 1994; Prieto et al., 1995); metals (Ford and Mitchell, 1990b; Gu et al., 2000a; Miller, 1970); and natural and synthetic polymers (Gu et al., 2000d; Guezennec et al., 1998; Swift et al., 1979). In all cases, the essential ingredient is the close association between the microflora and the material surface. Under natural conditions, all surfaces are covered with microorganisms except for extremely clean rooms. Biofilm formation is the process by which a complex community of microorganisms becomes established on a surface. Biofilms can exist in many different forms and have many different compositions (Fig. 1). They are ubiquitous on surfaces in soil and aquatic environments (Ford, 1993) and are also present on materials
exposed to humidity, particularly in tropical and subtropical climates. For example, microbial biofilms are common on surfaces of ancient archaeological limestone in Southern Mexico (Fig. 2). This process of biofilm formation is prerequisite to substantial corrosion and/or deterioration of the underlying materials (Arino et al., 1997; Saiz-Jimenez, 1995; Saiz-Jimenez, 1997; Walch, 1992). Biofilms on surfaces are highly structured (Breznak, 1984; Costerton et al., 1978; Costerton et al., 1994; Dalton et al., 1994; Davey and O’Toole, 2000; Kelly-Wintenberg and Montie, 1994; Lappin-Scott et al., 1992; L’Hostis et al., 1997; O’Toole et al., 2000; Wimpenny and Colasanti, 1997). Architectural structure and the organization of microorganisms on a particular surface are generally material specific, dependent o
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