INFLUENCE OF CLAY MINERALS ON MICROORGANISMS: I. MONTMORILLONITE AND KAOLINITE ON BACTERIA

Abstract

Respiration of bacteria was stimulated most by montmorillonite, primarily as the result of this clay maintaining the pH at levels adequate for sustained growth; additional mechanisms also appeared to be involved. Kaolinite and montmorillonite served equally as a source of minerals for bacterial nutrition, and the stimulation by montmorillonite above that elicited by kaolinite and attributable to its buffering capacity was, there- fore, not related to its ability to supply inorganic nutrients. Montmorillonite stimulated respiration of a wide spectrum of bacterial species differing in morphology, motility, gram reaction, etc. at all stages of their development, but especially by shortening the lag phase. These results suggest a possible relationship between clay minerals and activity, ecology, and population dynamics of microorganisms in natural habitats.