CONTROL ANALYSIS OF MICROBIAL INTERACTIONS IN CONTINUOUS-CULTURE - A SIMULATION STUDY

Metabolic Control Analysis (MCA) has been applied to flux of substrate s and products during the growth of a single species and of two intera cting species in a chemostat. Single-species growth was described by c lassical chemostat kinetics and the two-species interaction was commen salism. the first species converting the inflowing limiting substrate to a product which provided the limiting substrate tor the second spec ies. For the single species situation, control of flux to product is s hared by the dilution rate and bacterial specific growth rate, and con trol can be quantified in terms of two flux control coefficients C(D)J and C(mum1)J, representing the fractional changes in flux resulting f rom fractional changes in the dilution rate and maximum specific growt h rate, respectively. At low dilution rates, dilution rate exerts grea ter control, whilst C(mum1)J exceeds C(D)J at high dilution rates. In the two-species commensal interaction, additional control on flux to p roduct is exerted by species 2 and may be quantified in a further flux control coefficient C(mum2)J. Control exerted by a particular species in this interaction increases as factors, e.g. maximum specific growt h rate and saturation constant for growth, change to decrease its spec ific growth rate. Control over flux by a species is also increased by addition of an inhibitor specific to that species and a method is prop osed for determining experimentally the flux control coefficient for a species which can be inhibited in this manner.