This publication brings together the background paper and summary report from a moderated e-mail conference that was organised by FAO as one of its initiatives to mark World Water Day 2007, whose theme was "Coping with water scarcity". The conference's main focus was on the use of biotechnologies to increase the efficiency of water use in agriculture, while a secondary focus was on two specific water-related applications of micro-organisms, in wastewater treatment and in inoculation of crops and forest trees with mycorrhizal fungi.