Substrate Interaction During Shock
Loadings to Biological Treatment
Processes
K. K0M0LR1T, Research Assistant
A. F. GAUDY, JR., Professor
Bio-Engineering Laboratories
School of Civil Engineering
Oklahoma State University
Stillwater, Oklahoma
INTRODUCTION
A considerable research effort concerning substrate interactions during waste
water purification is currently under way in our laboratory. This line of investigation stems from the discovery of the occurrence of sequential substrate removal
in heterogeneous populations (1). The finding of such an effect with heterogeneous
populations is somewhat surprising and in many respects is in opposition to current
concepts in the pollution control field, where it is usually considered that the
many compounds in a waste are attacked concurrently by the many different
species present in the waste. While this expectation does not appear unreasonable,
we have amassed sufficient data to be able to state conclusively that sequential
substrate removal in heterogeneous populations can occur (1,2, 3,4,5). Of greater
significance to the pollution control field is the finding that a heterogeneous
population which is already acclimated to a specific compound can be prevented
from removing this compound by the action of a second substrate. This inhibition
prevails until the second compound has been metabolized; thereafter the original
compound is removed (2,3,4,5). It has been shown that the occurrence of this
phenomenon is not restricted to growth systems, since we have found it to occur
in large populations of pre-acclimated cells, which already possess a sufficient
complement of the required enzyme(s) (2). We have also observed the phenomenon in nonproliferating systems (3).
These findings have led us to the conclusion that there exists during cata-
bolism a previously unstudied metabolic control mechanism, which acts to prevent the functioning of existing inducible enzyme(s), in addition to the well-
known repression of the synthesis of inducible enzyme systems (3). Very recent
investigations in the basic fields have shown that several mechanisms of metabolic control may be operative in bacteria. It would be beyond the scope of this
report to discuss these in detail. However, since the various metabolic control
mechanisms have serious ramifications to shock loading considerations and bear
comparison with the new mechanism uncovered by our recent research, it is appropriate to review briefly the current state of knowledge in this area.
In biosynthetic (anabolic) pathways two types of controls have been shown to
prevent unnecessary expenditures of the energy and building blocks available to
the cell (6, 7). The first of these, repression, operates to prevent the synthesis of
enzymes involved in a biosynthetic pathway when the final product of those enzymes is supplied exogenously to the cell. This repression takes place at the level
of gene function; that is, the copying of the  structural  information  for  enzyme
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