How bladder cells kick out unwelcome intruders

Abstract

Microbiology The bladder epithelium acts as the front line of the urinary defense system against microbial infection. Miao et al. examined urine samples from humans and mice and the extracellular medium of cultured bladder epithelial cells after infection by uropathogenic Escherichia coli . Remarkably, they found numerous viable bacteria encased in host-derived membrane-bound vesicles. Intracellular bacteria were initially taken up by autophagosomes and targeted to lysosomes. The bacteria raised the normally low lysosomal pH, which might be expected to protect them from lysosomal degradation. However, the bladder cells sensed the neutralized lysosomes and exocytosed them, expelling the membrane-encased bacteria. The bacteria were thus incapable of reinfection, and the bladder cells defended against their unwelcome visitors. Cell 161 , 1306 (2015).