Coexistence of microbial populations and autostabilization of regulating factors in continuous culture: theory and experiments

Abstract

The paper summarizes the author's theoretical and experimental researches aimed at studying the rule of stable coexistence of interacting microbial populations within same trophic level. Populations of yeast and algae interact in open continuous cultures through regulating factors (RFs), which come together by the ability to be released or taken up by a microbial population and affect the growth of this and other population. Theoretical and experimental studies show that in steady state, the number of coexisting species is not greater than the number of RFs. Two-dimensional regions with different resultant species compositions of experimental equilibrium communities are plotted in the coordinates of ''input levels of RFs''. This is perhaps the first study showing that the background steady-state levels of RFs in the system are not related to their input levels. This effect has been termed autostabilization of RFs, and its theoretical basis has been developed. A new criterion of intra-and inter-population microbial interactions has been introduced for RFs-growth acceleration response to a change in population density. Based on the proposed new criterion, experimental and theoretical estimates of the intensity and the sign of interactions between populations are given, allowing the quantification of their complex relationships, which was earlier unattainable. An integrated approach to detection of RFs has been proposed based on this criterion and the autostabilization effect.

Control Factors for the Equilibrium Composition of Microbial Communities in Open Systems: Theory and Experiments

“…It is difficult to present the function g as dependent on R in some general form, although specific cases, e.g., those involving Liebig's law, are known. However, even such a general form shows that in the equilibrium mixture, the number of species is no greater than the total number of RFs (i.e., m ≤ n) [26]. The result of coexistence obtained here is similar to the results obtained by other authors addressing regulation via DDGCFs, but the present rule of coexistence includes not only limitation by substrate, but also a large number of other interspecific relationships.…”

“…ferrugineum (B-21) [39] S1-glucose S2-xylose Х1-Candida mycoderma X2-C. tropicalis [38] S1-glucose S2-galactose X1-Candida mycodermaX2-С. tropicalis[38]…”

The Evolutionary Mechanism of Formation of Biosphere Closure

“…In addition, the well-known competitive exclusion principle (CEP) states that the number of species stably coexisting at the same trophic level cannot exceed the amount of resources available to them [27]. Later, the CEP was expanded, showing that several species can coexist on the same nutrient substrate if their number does not exceed the number of density dependent growth control factors (DDGCFs) in the system [28,29]. DDGCFs also include substances that inhibit or promote growth and predation [30].…”