This issue provides a both a primer and advanced reflection of the many roles of the microbiome, both bacterial and fungal, in the function and dysfunction of the lower urinary tract. As discussed in this issue, the microbiome is ubiquitous, and is found even in the once-considered-sterile urinary system. Moreover, this bacterial and fungal 'occupation' of the urinary tract is multi-faceted, playing protective roles by outcompeting pathogens for necessary nutrients, producing antimicrobial substances, stimulating the immune and neuronal systems, and maintaining homeostasis of the mucosal environment, as well as playing the known deleterious roles associated with pathological infection.
