Molecular mechanisms and environmental determinants controlling the propagation of pathogenic and non-pathogenic bacteria in built environments

People in Hong Kong can spend over 80% of time indoors. Indoor environments are not only occupied by people, who built the environment for their use and comfort but also many invisible microorganisms. With the support from ARCPE, we revealed a strong correlation between microbial communities and activities and urine-like odour production in air-cooling units. This urine-like smell has caused many complaints in HKBU campus. The result of this study was accepted for publication in an international peer-reviewed journal. Our new discoveries also lead to more research questions about the role of different organisms and their metabolites in odour production. In the past months, we further investigated the ability of different microbes to use skin squames to produce ammonia and volatile short-chain fatty acids (VFAs), which are also common sources of odour complaints in indoor environments. In addition, we have sampled more air-cooling units and extracted their microbial communities for metagenomic analysis. Metagenomic analysis is a molecular approach using DNA information to determine the microbial communities in an environment. So far our results demonstrated that many microbes inhabiting in air-cooling units can produce ammonia and VFAs. Bacteria, which release keratinase enzymes to break down keratins have the highest potential to emit the odours. We also examined several microbial control strategies to reduce or even eliminate the odour emission problems. For instance, our studies showed that strong odour-producing bacteria are more sensitive to the moisture level, relative humidity (RH) in the air. Furthermore, by controlling the input of skin squames into the air-cooling units, we can effectively reduce the microbial activities by cutting the nutrient supply. The below publication is accepted from this research study.

Lai, K.M., Sung, Y.H. and Ma, K.K. 2017. Viable airborne microbial counts from air-cooling units with and without complaints of urine and body odors. Aerobiologia. [DOI: 10.1007/s10453-016-9466-y; ISSN: 15733025].