Garden soil bacteria transiently colonize gardeners' skin after direct soil contact

Abstract

Abstract Urban soils provide a number of ecosystem services and health benefits, yet they are understudied compared with agricultural and wildland soils. Healthy soils host diverse microbiota, exposure to which may be critical for immune development and protection against chronic disorders, such as allergies and asthma. Gardening represents a key pathway for microbiota exposure, yet little is known about microbial community structure of urban garden soils, degree of soil‐to‐skin transfer during gardening, nor ability of soil microbes to persist on human skin. To explore these questions, we recruited 40 volunteers to collect soil samples from their gardens and a series of skin swab samples before and after gardening. Soil and skin bacterial communities were characterized using amplicon (16S) sequencing. Soil samples were also analyzed for chemical/physical characteristics. Soil bacterial communities had more alpha diversity and less beta diversity than skin communities, which varied greatly across individuals and within the same individual across time. The number of bacterial taxa shared between skin and garden soil increased immediately after gardening for most study participants. However, the imprint of garden soil largely disappeared within 12 hours. Despite this lack of persistence, a daily gardening routine with repeated and extended contact with soil likely reinoculates the skin such that soil microbes are often present, holding potential to impact health.