The ESENCYA project_Environmental SENsory perception in CYAnobacterial biofilms : understanding biodeterioration of outdoor stone materials in a changing environment

Many of the world’s most precious artworks are made of stone. Their irreversible deterioration due to biological attack is a worldwide concern. Cyanobacteria colonize outdoor lithic surfaces and develop into biofilms at the interface solid/air (subaerial biofilms, SABs), which, in turn might cause aesthetic, chemical and physical decay. The fragile character of the stone heritage material is further exacerbated by the unpredictable nature of impacts from environmental changes, posing challenges for conservation management. Although it has been estimated that at least 99% of the world's microbial biomass exists in biofilms, the role and behavior of cyanobacteria within the biofilm matrix and their complex interactions with the external environment is still unknown. ESENCYA project provides a pioneering, interdisciplinary and multidisciplinary research to investigate perception of environmental changing in cyanobacteria within the biofilm matrix for sorting out time-spatial relationships and to elucidate microorganism-EPS, inter-organism, biofilm-atmosphere and biofilm-stone interactions. As never before there is the urgent need to advance our knowledge on this complex phenomenon in order to comprehend the molecular program embraced by SABs to sense the changes in the environment and respond accordingly, laying the basis for novel preventive conservation strategies. In addition, with the advent of global warming, there is growing interest in processes that couple CO2 captures to chemical synthesis through the use of photosynthetic microorganisms. In this contest, the knowledge acquired from the ESENCYA project on cyanobacterial biofilms will promote future works involving cyanobacteria in biotechnological applications. The project spans sophisticated molecular, chemical, physical and data modeling techniques and it is approached from two complementary angles: i) Lab-scale study to examine the sensory machinery of cyanobacterial biofilms by analyzing the cell’s capacity to sense different chemical and physical properties of the biofilm matrix, to integrate the incoming signals and to respond to them, triggering specific biodecay activities; ii) Real heritage case studies to investigate the ecological landscape of cyanobacteria within subaerial biofilms. A light apparatus system has been created to host an elegant bioreactor and control the growth of the phototrophic microrganism. Cyanobacterial SABs has been grown in a modified drip flow reactor that provides a very low shear and high gas transfer environment for growing biofilms on microscope-slide shaped stone coupons. The configuration of the modify drip flow reactor allows to simulate different environmental conditions like acid rain, drought, increase in salinity, rainfall events etc. Several media and system configurations have been developed and tested to ensure and improve the growth of SABs. In addition, a protocol to reproduce a multi-species SAB has been successfully obtained. The artificial consortium system consisted of two of the major functional guilds found on stoneworks including a photoautotrophic cyanobacterium and a chemoheterotroph. Investigations of the SAB dynamic, 3-D architecture and behavior have been carried out. The findings demonstrated the capability of the developed systems and methodologies to successfully reproduce complex sub-aerial biofilms at the laboratory-scale, opening new exciting research opportunity and new exploitation of the developed methodologies. Explorative investigations of outdoor artifacts located in the northeast regions of the USA have been performed in order to understand the nature of the alterations present on the stoneworks, and to create a map of the most interesting area to analyze deeply. Finally, modeling work is in progress to incorporate data on microbial community ecology and function into computational biofilm models that will predict biofilm-induced chemistry and its effect on stone (or other) substrata. The findings obtained so far will contribute to better understand the complexity of all the interactions encountered within SAB communities, and how these interactions may influence the biofilm outcome and behavior and the biodeterioration of the stone materials under different environmental conditions.