The ecology and biogeography of microorganisms of plant surfaces

The vast surface of the plant axis, stretching from root tips occasionally buried deeply in anoxic sediment, to apical meristems held far aloft, provi des an extraordinarily diverse habitat for microorganisms. Each zone has to a greater or lesser extent its own cohort of microorganisms, in aggregate comprising representatives from all three primary domains of life-Bacteria, Archaea, and Eucarya. While the plant sets the stage for its microbial inh abitants, they, in turn, have established varied relationships with their l arge partner. These associations range from relatively inconsequential (tra nsient epiphytic saprophytes) to substantial (epiphytic commensals, mutuali stic symbionts, endophytes, or pathogens). Through recent technological bre akthroughs, a much better perspective is beginning to emerge on the nature of these relationships, but still relatively little is known about the role of epiphytic microbial associations in the life of the plant.