Ribosomal DNA sequence analysis, originally conceived as a way to provide a universal phylogeny for life forms, has proven useful in many areas of biological research. Some of the most promising applications of this approach are presently limited by the rate at which sequences can be analyzed. As a step toward overcoming this limitation, we have investigated the use of photolithography chip technology to perform sequence analyses on amplified small-subunit rRNA genes. The GeneChip ( 173-174, 2001). The chip and standard Affymetrix software were able to correctly match small-subunit ribosomal DNA amplicons with the corresponding sequences in the RDP database for 15 of 17 bacterial species grown in pure culture. When bacteria collected from an air sample were tested, the method compared favorably with cloning and sequencing amplicons in determining the presence of phylogenetic groups. However, the method could not resolve the individual sequences comprising a complex mixed sample. Given these results and the potential for future enhancement of this technology, it may become widely useful.

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Aims: A high-volume aerosol collector was developed to efficiently capture airborne bacteria in order to assess levels of diversity in the air. Methods and Results: Particulate matter was collected on a device designed to filter 1AE4 · 10 6 litres of air in a 24 h period on a 1-lm pore size polyester membrane. Methods were optimized for extraction of genomic DNA from the air filter concentrate. Preparation times of 90 s with 0AE5-0AE05 mm diameter zirconia/silica beads yielded the highest concentration genomic DNA that was able to support PCR. A 24-h air sample was taken in Salt Lake City, Utah and the microbial composition was determined by the amplification and sequence analysis of 16S ribosomal DNA fragments. Conclusions: Sequence analysis revealed a large diversity in the type of microbial species present including clones matching the sequence of Clostridium botulinum. The primary components of the aerosol sample included many different spore-forming bacteria as well as more fragile members of the Proteobacteria division. Significance and Impact of the Study: The high-volume air collection and genomic DNA recovery system allows for the rapid detection of both cultivable as well as culture-resistant organisms in the environment.

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