Bacterial population in Russian space station "Mir".

We had the opportunity to investigate the bacterial population in air samples, condensation water, and inner wall swabs from the Russian space station Mir. From the first and second air samples during the mission, 29 and 7 bacterial colonies were collected, respectively. The values were equivalent to 16.8 and 4.0 cfu/100 liter air, respectively. Condensation water was collected from three different sites. The total viable bacterial counts were 2.1 x 10(6), 5.2 x 10(2), and 3.0 x 10(1) cfu/ml. The phylogenetic position of each isolate was determined by total 16S rDNA sequencing. Bacteria from air samples were mainly Gram-positive (35/36 colonies), and staphylococci occupied dominant specifically (23/36 colonies). On the other hand, Gram-negative bacteria were mainly isolated from condensation water samples. Most strains were thought to be opportunistic pathogens or environmental bacteria (such as those that inhabit soil, water, or air) found on earth. However, 6 of 23 isolates were suspected to be new species according to phylogenetic analysis and quantitative DNA-DNA hybridization data. The isolation of the other levels 3 and 2 bacteria, using specific selective media, was unsuccessful because all samples were heavily contaminated with fungi. To overcome this situation, PCR methods were applied to survey most levels 3 and 2 pathogenic bacteria in the condensation water samples. Up to 380 different primers for bacterial pathogens were used in this study. Only Mycobacterium avium 16S DNA sequences, however, could be amplified from the three water samples. The average bacteria count was estimated to be about 10(4) organisms/ml water.