Actinobacteria and other heterotrophic bacteria in biofilm samples from Roman catacombs

The heterotrophic microbiota (actinobacteria and other heterotrophic bacteria) of two Roman catacombs was characterised. Microbial isolates were identified using phenotypic methods, ribotyping and partial 16S rDNA sequencing. A total of 15 different actinobacterial and 29 other bacterial species were identified. The dominant micro-organisms were filamentous actinobacteria, mainly Streptomyces species (33%). The most commonly occuring other bacteria belonged to the genera Pseudomonas/Stenotrophomonas (28%), Bacillus (17%) and Staphylococcus (14%). In partial 16S rDNA sequencing the similarities to the until now described species indicated that many of these isolates (30%) are potential members of novel species, e.g. within the genera Amycolatopsis and Nocardia, or even within a new genus. Some species may have the ability to deteriorate mineral surfaces, but these properties of the isolates should be studied further.