ABSTRACT
The method based on characterization of microbial populations in terms of their growth rate in agar plates has been used for testing the prediction of the theory of r- and K-selection in a microbial community from a tropical soil. Conditions which could lead bacterial populations to grow exponentially or to enter into a stationary phase were obtained by growing soil microbial populations in a chemostat and in a chemostat with recycle, respectively. Significant differences in population distribution patterns were observed by comparing results from the two growth systems. When soil community was grown in a chemostat and subjected specifically to well-defined r- and K-conditions, stable associations of organisms with r- and K-type characteristics developed as a consequence of environmental pressure. In contrast, when cultivated in chemostat with recycle under the same r- and K-conditions imposed on chemostat cultures, distribution patterns of r- and K-selected populations appeared very little affected by changes in substrate availability.
