Limestone biodeterioration: A review on the Portuguese cultural heritage scenario

Abstract Stone, one of the earliest testimonies of human artistic expression, is susceptible to biodeterioration by microorganisms. The most frequent stone colonizing agents are algae, cyanobacteria, bacteria, fungi and lichens, each with their own set of adaptive traits, which allow them to prosper and consequently damage the stone substrate. Limestone is particularly susceptible to biological agents; therefore, in order to act towards the protection and prevention of colonization by microorganisms, it is crucial to understand the microbial communities thriving in limestone heritage buildings. Data regarding the biodiversity and biological activity in Portuguese limestone monuments is, however, still scarce and the scattered knowledge on the subject impairs a full comprehension of the complex and relevant phenomena associated with this particular setting. This review presents and discusses the available studies performed in Portuguese limestone. In addition, the state of the art methodologies to be used, as well as the future studies to be considered, in order to effectively protect such invaluable witnesses of our history, are discussed.