Origin and Control Strategies of Biofilms in the Cultural Heritage
Antimicrobials [Working Title]
Biodeterioration is defined as the undesirable change in the properties of materials caused by the activity of biological agents. This process is complex and involves alterations in the physicochemical and mechanical properties by the action of organisms and depends on the microorganisms involved, type of substrate, and environmental conditions. The biodeterioration of cultural heritage is the physical or chemical damage caused by microorganisms on objects, monuments, or buildings that belong
... dings that belong to the cultural heritage. Among the main materials that can be affected are: stone, metal, ceramic, polymers, and other materials. Among the main undesirable effects to these materials are: discoloration, dissolution, rupture, and efflorescence among others. Biofilms represent the usual form of growth of bacteria and consist of communities of microorganisms that grow attached to an inert surface or a living tissue, surrounded by an extracellular matrix that they themselves synthesize. The importance of biodeterioration by biofilms is mainly related to changes in pH values, ionic concentrations, oxide-reduction reactions in the biofilm thickness, and in the interface with the substrate and enzymatic degradation. This chapter presents evidence of the participation of biofilms and associated mechanisms in biodeterioration as well as the main prevention and control strategies. The tangible heritage is also called material heritage, and there are movable and immovable property such as the objects of the artistic collections such as the collection of religious, ethnographic, technological, historical, artistic, and archeological and artisan objects. The real tangible heritage is made up of archeological sites, engineering works, places, buildings, and architectural ensembles. The intangible cultural heritage includes the wealth of knowledge, also living expressions inherited from our ancestors and transmitted to our descendants, such as language, oral traditions, customs, performing arts, ways of life, rituals, festive events, knowledge, and practices related to nature and the universe, as well as knowledge and techniques linked to traditional crafts  . Cultural heritage is a nonrenewable resource with regard to its past, and that is why it manifests itself tangibly as an untouchable and irreplaceable resource of a people. This heritage is always linked to the human collective, since it is men and women who produce it, and therefore it is what gives identity, origin, and continuity to our people. Hence, it is the responsibility of all its conservation and restoration for which it is essential to know what are its main threats in order to prevent, delay its deterioration and, if necessary, restore this heritage. The alteration of cultural assets is the characteristic of the continuous cycle of disintegration and reconstruction, and it is a natural condition since all matter follows a process of alteration, degradation, or decomposition which means that original physical, chemical, and optical qualities are lost and enter a process of instability promoted by factors or agents of deterioration that are of two types: Intrinsic: it depends on the nature of the material, manufacturing technique, and procedures that were used to perform the work. Extrinsic: It depends on the sources external to the object such as environmental factors (light, relative humidity, temperature, and air pollutants), anthropogenic factors (handling, use, consultation, vandalism, tourism, etc.), biological factors (microorganisms, plants, rodents, and insects), and catastrophic factors (floods, fires, etc.)    . Among the main mechanisms of deterioration, three processes are known: Physical or mechanical processes where the behavior of the material is modified, where several mechanical forces participate (compression, traction, etc.). These change the behavior of a material without modifying its chemical composition. Chemical processes: are those that compromise a chemical reaction that transforms the matter. Biological processes: where living organisms, such as microorganisms, insects, rodents, plants, etc., can chemically attack the material or its mechanical resistance. This process is also known as biodeterioration, which has been defined as "undesirable changes in the properties of materials caused by the vital activity of organisms"  .