Identification of bacterial diversity in the indoor air environment

indoor air samples of two dwellings were investigated quantitatively and qualitatively for the presence and genus allocation of culturable bacteria. Glycerol-arginine-agar and a mineral-agar according to Gauze, both described as selective media for Actinomycetes were used. By impaction to agar surfaces, the bacteria were collected from both living rooms and kitchens of each dwelling. Reference samples were collected from outdoor air. Concentrations of airborne bacteria in the dwellings and outdoor ranged between 20 and 328 CFU m(-3). In total, 294 bacterial isolates were obtained. The isolates could be assigned to 30 different genera of the phyla Actinobacteria, Proteobacteria, Firmicutes and Bacteroidetes by 16S rRNA-gene sequence analyses. Only 60% of them belong to the order Actinomycetales indicating the limited selectivity of used culture media. The comparison of the compositions of indoor and outdoor bacterial communities revealed pronounced differences, although concentrations of culturable bacteria were quite similar. Some of the isolates from the order Actinomycetes could be assigned to the genera Nocardiopsis and Streptomyces which contain also species of medical importance. Further isolates were identified to the genera Rhodococcus, Aeromicrobium, Arthrobacter, Dietzia and Kocuria. Isolates belonging to the Proteobacteria, Firmicutes and Bacteroidetes were also present, among them representatives of the genera Methylobacterium, Bacillus, Paenibacillus and Spirosoma.