Effects of biocide treatments on the biofilm community in Domitilla's catacombs in Rome.

Different types of biofilms are widespread on lithic faces of the Catacombs of Domitilla (Rome, Italy) due to the favorable microclimatic conditions (temperature, high RH% and low irradiance). The biofilm, once established, becomes particularly dangerous due to the coverage of valuable surfaces causing spoilage, softening of materials and mineral precipitation. It is common practice to treat these surfaceswith biocides in order to eradicate the microorganisms present. The aim of the present research was to compare the changes occurring to the microbial community present in the biofilm in one site of the Catacombs of Domitilla (CD15) before and after a biocide treatment (a mixture of quaternary ammonium compounds and octylisothiazolone, OIT), applied for a one month period. A multistep approach was followed, based on microscopy, cultural methods and molecular techniques (f-ITS and 16S rDNA sequencing), for the phenotypic and genetic analysis of the culturable microbial population. Our results highlighted that the biocide treatments had little effect against cyanobacteria, while the bacterial population increased in numbers but changed drastically in terms of diversity. In fact, some bacteria proliferate at the expense of the organic matter released by dead microorganisms as demonstrated by laboratory tests. Further, our data describe howthe microbial interaction can have different responses depending on the favorable conditions for one kind of microorganism in respect to the others. This study exemplifies the real risks of applying biocide treatments on complex microbial communities and pinpoints the necessity of subjecting treatments to monitoring and reassessment. Moreover, the work showed the potential of bacteria isolated after the treatment for use, under controlled conditions, in combatting unwanted microbial growth in that they possess a positive tropismtoward stressed microorganisms and high hydrolytic enzymatic activity against cell components (e.g. cellulose, chitin and pectin). A tentative protocol is proposed

Complex bacterial diversity in the white biofilms of the Catacombs of St. Callixtus in Rome evidenced by different investigation strategies

Roman Catacombs are affected by different kinds of biofilms that were extensively investigated in the last 14 years. In particular, the areas far from the lamps are often covered by white biofilms of different extension, consistency and nature.The aim of this paper is to describe the profile of the microbial community present in two areas of the Ocean's Cubiculum (CSC13), characterized by similar alterations described as white biofilms, by using a multistep approach that included direct microscopy observations, culture-dependent and culture-independent methodologies through the extraction of DNA and RNA directly from the sampled areas. In addition to this, we extracted the DNA directly from the Petri dishes containing R2A and B4 media after incubation and growth of bacteria.Our results evidenced that a complex bacterial community (mainly constituted by filamentous Actinobacteria, as well as Firmicutes and Proteobacteria) colonizes the two different white biofilms and its detection, quantitative and qualitative, could be revealed only by different approaches, each method gave different information that only partially overlap

Complex bacterial diversity in the white biofilms of the Catacombs of St. Callixtus in Rome evidenced by different investigation strategies

Roman Catacombs are affected by different kinds of biofilms that were extensively investigated in the last 14 years. In particular, the areas far from the lamps are often covered by white biofilms of different extension, consistency and nature.The aim of this paper is to describe the profile of the microbial community present in two areas of the Ocean's Cubiculum (CSC13), characterized by similar alterations described as white biofilms, by using a multistep approach that included direct microscopy observations, culture-dependent and culture-independent methodologies through the extraction of DNA and RNA directly from the sampled areas. In addition to this, we extracted the DNA directly from the Petri dishes containing R2A and B4 media after incubation and growth of bacteria.Our results evidenced that a complex bacterial community (mainly constituted by filamentous Actinobacteria, as well as Firmicutes and Proteobacteria) colonizes the two different white biofilms and its detection, quantitative and qualitative, could be revealed only by different approaches, each method gave different information that only partially overlap