Dynamics of Primary Succession in Airborne Microbial Communities on Urban Masonry

Microbial succession on urban masonry surfaces is a critical yet understudied aspect of environmental microbiology, with implications for public health within the One Health framework. This study investigated how building age, orientation, and vegetative cover influence microbial diversity on masonry, metal, and glass substrates at the University of La Verne, California. Biophysical characterizations were conducted, and microbial communities were analyzed using morphospecies richness and DNA sequencing. Significant variation in microbial species richness (χ2 = 20.3882, p = 0.0011) and diversity (Fisher’s LSD, p < 0.05) was observed. Masonry surfaces exhibited the highest microbial diversity, with a mean richness of 23 morphospecies compared to 14 on metal and 12 on glass. Penicillium fungi dominated masonry sites, comprising 45% of colonies, while Pseudomonas and Klebsiella were more prevalent on metal and glass surfaces (35% and 28%, respectively). Microbial succession did not follow a linear progression but showed non-sequential shifts influenced by local conditions. The abundance of Penicillium, known for antibiotic production, raises concerns about spreading antibiotic resistance genes. Opportunistic pathogens further highlight potential health risks. These findings underscore the importance of understanding primary successional processes in urban environments to manage microbial communities and mitigate public health risks.