ABSTRACT
In situ observations of an ongoing geomicrobial process should include the study of the setting in which it occurs in nature. In a terrestrial environment, the kinds of rocks, soil, or sediment, whichever are involved, and their constituent minerals ought to be characterized, and the prevailing temperature, pH, oxidation-reduction potential (Eh), sunlight intensity, seasonal cycles, and the source and availability of moisture, oxygen or other terminal electron acceptors, and nutrients ought to be identi ed. In an aqueous environment, water depth, availability of oxygen or other terminal electron acceptors, turbidity, light penetration, thermal strati cation, pH, Eh, chemical composition of the solutes in the water, nature of the sediment if part of the habitat, and nutrient sources and availability should be examined.
