Smartphones as an Ecological Niche of Microorganisms: Microbial Activities, Assembly, and Opportunistic Pathogens.

Smartphone usage and contact frequency are unprecedentedly high in this era, and they affect humans mentally and physically. However, the characteristics of the microorganisms associated with smartphones and smartphone hygiene habits remain unclear. In this study, using various culture-independent techniques, including high-throughput sequencing, real-time quantitative PCR (RT-qPCR), the ATP bioluminescence system, and electron microscopy, we investigated the structure, assembly, quantity, and dynamic metabolic activity of the bacterial community on smartphone surfaces and the user's dominant and nondominant hands. We found that smartphone microbiotas are more similar to the nondominant hand microbiotas than the dominant hand microbiotas and show significantly decreased phylogenetic diversity and stronger deterministic processes than the hand microbiota. Significant interindividual microbiota differences were observed, contributing to an average owner identification accuracy of 70.6% using smartphone microbiota. Furthermore, it is estimated that approximately 1.75 × 106 bacteria (2.24 × 104/cm2) exist on the touchscreen of a single smartphone, and microbial activities remain stable for at least 48 h. Scanning electron microscopy detected large fragments harboring microorganisms, suggesting that smartphone microbiotas live on the secreta or other substances, e.g., human cell debris and food debris. Fortunately, simple smartphone cleaning/hygiene could significantly reduce the bacterial load. Taken together, our results demonstrate that smartphone surfaces not only are a reservoir of microbes but also provide an ecological niche in which microbiotas, particularly opportunistic pathogens, can survive, be active, and even grow. IMPORTANCE Currently, people spend an average of 4.2 h per day on their smartphones. Due to the COVID-19 pandemic, this figure may still be increasing. The high frequency of smartphone usage may allow microbes, particularly pathogens, to attach to-and even survive on-phone surfaces, potentially causing adverse effects on humans. We employed various culture-independent techniques in this study to evaluate the microbiological features and hygiene of smartphones, including community assembly, bacterial load, and activity. Our data showed that deterministic processes drive smartphone microbiota assembly and that approximately 1.75 × 106 bacteria exist on a single smartphone touchscreen, with activities being stable for at least 48 h. Fortunately, simple smartphone cleaning/hygiene could significantly reduce the bacterial load. This work expands our understanding of the microbial ecology of smartphone surfaces and might facilitate the development of electronic device cleaning/hygiene guidelines to support public health.

Linking aerosol characteristics of size distributions, core potential pathogens and toxic metal(loid)s to wastewater treatment process.

Wastewater treatment plants (WWTPs) play important roles in water purification but are also important source of aerosols. However, the relationship between aerosol characteristics and wastewater treatment process remains poorly understood. In this study, aerosols were collected over a 24-month period from a WWTP using a modified anaerobic-anoxic-oxic process. The aerated tank (AerT) was characterized by the highest respiratory fraction (RF) concentrations (861-1525 CFU/m3) and proportions (50.76%-65.96%) of aerosol particles. Fourteen core potential pathogens and 15 toxic metal(loid)s were identified in aerosols. Mycobacterium was the genus that aerosolized most easily in fine grid, pre-anoxic tank, and AerT. High wastewater treatment efficiency may increase the emission of RF and core potential pathogens. The median size of activated sludge, richness of core potential pathogens in wastewater, and total suspended particulates were the most influential factors directly related to the RF proportions, core community of potential pathogens, and composition of toxic metal(loid)s in WWTP aerosols, respectively. Relative humidity, temperature, input and removal of biochemical oxygen demand, dissolved oxygen, and mixed liquor suspended solids could also directly or indirectly affect the aerosol characteristics. This study enhances the mechanistic understanding of linking aerosol characteristics to treatment processes and has important implications for targeted manipulation.