ON PHYSIOLOGICAL MULTIPLICITY AND POPULATION HETEROGENEITY OF BIOLOGICAL-SYSTEMS

The theory of steady-state multiplicity has been used to analyze the a daptive behavior associated with two experimentally well characterized biological systems; the bacteriophage I,and the Escherichia coli lact ose operon. The ability to observe such systems in distinct physiologi cal forms within a unique environment was found to be consistent with the existence of multiple stable solutions of the representative balan ce equations. Additionally, transitions between physiological states w ere found to be controlled by threshold mechanisms that altered the st eady-state solution structure in a manner analogous to the ignition-ex tinction behavior exhibited by non-isothermal chemical reactors. These findings indicate that the population heterogeneity observed in these systems can be explained on the basis of steady-state multiplicity wh ereby a nonuniform population response acts to generate a culture comp rised of physiologically distinct forms. Since multiple solutions of t he conservation equations were found to originate from interactions be tween conserved nonlinear kinetic and feedback mechanisms, these resul ts appear general and the conclusions derived should be applicable to other less characterized biological systems. These findings also sugge st that the physiological homogeneity assumption routinely employed in theoretical and experimental analysis of cellular behavior may lack t heoretical justification.