Airborne microorganisms in a subterranean archaeological area of the basilica of San Lorenzo in Lucina (Rome)

The basilica of San Lorenzo in Lucina in Rome was built in the fifth century on the foundations of a Roman insula used for dwellings and commercial activities, where the first Christian communities had held their meetings. This archaeological area is still rather isolated since it can only be visited by groups for one/two hours once a month. Such a situation is ideal for studying both the quantity of microorganisms in the air under undisturbed conditions and/or conveyed by visitors. The biodeterioration of subterranean remains is determined by the development of bacteria, cyanobacteria, actinomycetes, algae and fungi. On the walls of this underground archaeological area the main form of alteration is the efflorescence. In order to compare the stone and airborne microflora, the microorganisms living on stone and the airborne ones have been detected. Air samples were taken both during the visits and under non-turbulent conditions utilizing three sampling methods: gravitational, intake by multi-stage impact and intake by single-stage impact. The results have made it possible to determine the microbial content of the air, as well as the sampling schedule required for rarely visited underground environments. Furthermore, a comparison of the three methods used showed that the adoption of one or the other sampling method gave different complementary information on airborne microflora. This revised version was published online in June 2006 with corrections to the Cover Date.