Differences in the aerosolization behavior of microorganisms as revealed through their transport by biogas.

The aerosol microbial diversity of biogas was analyzed in order to examine the aerosolization behavior of microorganisms. Six biogas samples were analyzed: five from mesophilic and thermophilic anaerobic digestors treating different wastes, and one from landfill. Epifluorescent microscopic counts reveal that with 10(6) Prokarya m(-3), only one per one thousand billion were aerosolized from the digestor sludges to the biogas. SSU (Small Sub Unit) ribosomal fingerprinting (Single Strand Conformation Polymorphism) shows that microbial communities in the biogas were not just a rough copy of anaerobic digestor microbial communities and underlines that all microorganisms are not equally convoyed by biogas. To assess the difference occurring in aerosolization, 675 biogas-borne SSU ribosomal DNA were analyzed and compared to published anaerobic digestor microbial diversity. Results show that microorganisms belonging to Archaea, Deltaproteobacteria, Spirochaetes, Thermotogae, Chloroflexi phyla and sulfate-reducing groups were non-aerosolized whereas microorganisms belonging to Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, TM7 phyla as well as strictly aerobic and occasionally pathogenic species presented high levels of aerosolization. Finally, microorganisms belonging to Actinobacteria, Firmicutes and Bacteroidetes phyla represent passively-aerosolized microorganisms with similar frequencies in biogas-borne and anaerobic digestor microbial communities.