Abstract

A systematic investigation on the varieties of culturable airborne bacteria component, concentration and size distribution was conducted in a university campus in Hangzhou, Southeast of China. Results obtained showed that Gram positive bacteria were much more than Gram negative bacteria, contributing to about 84 to 90% of the total number. 22 genera of Gram positive and 12 genera of Gram negative bacteria were identified.Micrococcus, Bacillus, Staphylococcus, and Corynebacterium were dominant in Gram positive bacteria, while Pseudomonas were most common in Gram negative bacteria, and these 5 dominant genus occupied about 60% of the total generally. The mean concentration of culturable bacteria in the university campus was 1224 CFU (Colony Forming Units) /m³. Bacterial concentration in living area was highest (1572 CFU/m³), while the concentration in office area was lowest (651 CFU/m³), obviously lower than other areas in the campus (**P < 0.01). With regard to the bacterial size distribution, there were no significances among different sampling areas and seasons. The percentage of the culturable bacteria was gradually increased from stage 1 (> 8.2 μm) to stage 5 (1.0 to 2.0 μm), and then was dramatically decreased at stage 6 (<1.0 μm) in the sampler. Moreover, airborne bacteria was mostly collected in stage 3 (3.0 to 6.0 μm), stage 4 (2.0 to 3.5 μm) and stage 5 (1.0 to 2.0 μm), and the highest proportions of culturable airborne bacteria were detected at stage 5.

Key words: Airborne bacteria, Micrococcus, Bacillus, size distribution