Novel Sources of Biodiversity and Biomolecules from Bacteria Isolated from a High Middle Ages Soil Sample in Palermo (Sicily, Italy)

The urban plan of Palermo (Sicily, Italy) has evolved throughout Punic,Roman, Byzantine, Arab, and Norman ages until it stabilized within the borders thatcorrespond to the current historic center. During the 2012 to 2013 excavation cam-paign, new remains of the Arab settlement, directly implanted above the structures ofthe Roman age, were found. The materials investigated in this study derived from theso-called Survey No 3, which consists of a rock cavity of subcylindrical shape coveredwith calcarenite blocks: it was probably used to dispose of garbage during the Arabicage and its content, derived from daily activities, included grape seeds, scales andbones offish, small animal bones, and charcoals. Radiocarbon dating confirmed themedieval origin of this site. The composition of the bacterial community was character-ized through a culture-dependent and a culture-independent approach. Culturablebacteria were isolated under aerobic and anaerobic conditions and the total bacterialcommunity was characterized through metagenomic sequencing. Bacterial isolateswere tested for the production of compounds with antibiotic activity: aStreptomycesstrain, whose genome was sequenced, was of particular interest because of its inhibi-tory activity, which was due to the Type I polyketide aureothin. Moreover, all strainswere tested for the production of secreted proteases, with those belonging to the ge-nusNocardioideshaving the most active enzymes. Finally, protocols commonly usedfor ancient DNA studies were applied to evaluate the antiquity of isolated bacterialstrains. Altogether these results show how paleomicrobiology might represent an inno-vative and unexplored source of novel biodiversity and new biotechnological tools.