Aquifers- In its simplest hydrogeological sense ground water has been referred to water that is easily extractable from saturated, highly permeable geological strata known as aquifers. In addition to these aquifers, groundwater also includes capillary water and water vapors from the unsaturated zones.
For microorganisms which live within these microhabitats all available forms of water may certainly be important. Moreover, unsaturated zones may be transiently saturated during recharge events and they may influence the microbiology of the saturated zone.
Thus, in a broader sense, groundwater refers to all subsurface water found beneath the soil A and B horizons that is available to sustain and influence microbial life in the terrestrial subsurface (Madsen & Ghiorse, 1993).
