Zones of Inhibition 2: Roof tops in the Georgian town of New Alresford  showing the Urban Cryptobiotic Crust (please see posts below for a description of the UCC) with obvious  zones of inhibition beneath the windows caused by lead runoff from the flashing beneath them. Lead is inimical to life including microorganisms.  These roof top microbial ecologies are striking in that they are  over 300 years old.