Microbially induced deterioration of architectural heritages: routes and mechanisms involved

Abstract

Since ancient time, magnificence and beauty have been the goals of architecture. Artists and architects used high strength, durable and beautiful stones like marble and limestone for the construction of monuments like Taj Mahal, Milan Cathedral, Roman Catacombs and Necropolis in Rome etc. These historic monuments are exposed to open air which allows the invading army of algae, cyanobacteria, fungi etc. to easily access them. The invasion of microorganisms and their subsequent interaction with mineral matrix of the stone substrate under varied environment conditions fosters deterioration of stones by multiple mechanisms resulting in loss of strength, durability, and aesthetic appearance. The review details about the major routes and mechanisms which led to biodeterioration, discusses current remedial methodologies and suggests future directions.

Heteroorganic molecules and bacterial biofilms: Controlling biodeterioration of cultural heritage

“…Through high-throughput screening of a library of marine natural products, Linington and co-workers identified the biofilm-modulatory activity of antibiotic skyllamycins A -C (31-33, Figure 12) in P. aeruginosa biofilms. 180 These same researchers also reported the development of benzo [1,4]oxazines as biofilm inhibitors and dispersal agents against Vibrio cholerae. 245 In this communication, 34 ( Figure 12) was reported as "the first example of a small molecule capable of inducing the dispersal of V. cholerae biofilms" in two hour old biofilms, placing it "among just a handful of compounds capable of inducing the dispersal of mature surface-associated biofilms".…”

“…They do so by modifying substrates and providing through their growth, movement, metabolic processes and cell mass, organic nutrients for successive colonizers such as fungi. 4,5 The proliferation and persistence of these organisms and their potential to cause biodeterioration, either directly or through successive colonization, is the establishment of surface-associated assemblages of microorganisms, known as biofilms which provide enhanced resistance to physical and chemical stress through a multicellular existence. 87 The formation and survival of bacterial biofilms on various surfaces is well documented.…”

“…3 These processes usually begin with bacterial colonisation of a substrate leading to the formation of a biofilm. 4,5 Research suggests that the biofilm mode of bacterial growth modifies the substrate, thereby providing nutrients for successive colonisers such as mould, diatoms, algae and invertebrates. 4,5 The dispersal of singlecelled planktonic bacteria from biofilms is an important mechanism by which the cycle of colonization and infection continues.…”

“…4,5 Research suggests that the biofilm mode of bacterial growth modifies the substrate, thereby providing nutrients for successive colonisers such as mould, diatoms, algae and invertebrates. 4,5 The dispersal of singlecelled planktonic bacteria from biofilms is an important mechanism by which the cycle of colonization and infection continues. 6 Although more motile in the planktonic form, bacteria leaving the physical protection of a biofilm are 1000-times more susceptible to exogenous pressures such as antibiotics and biocides.…”

“…This may involve a bio-corrosion process whereby acidic and pigmented organic and inorganic products are excreted which can etch and stain the object, weakening the matrix of the material, leading to more favourable conditions for further attachment and growth and therefore continuing to add to the degradative process. 4,26 Microorganisms may also secrete chelating agents which form complexes and sequester metallic cations from paint pigments or metallic objects. 25,27 For example, cadmium is known to be accumulated in a large number of microorganisms as cellbound cadmium hydrogen phosphate (CdHPO 4 ).…”