INTERACTIONS OF MICROBIAL BIOFILMS WITH TOXIC TRACE-METALS .1. OBSERVATION AND MODELING OF CELL-GROWTH, ATTACHMENT, AND PRODUCTION OF EXTRACELLULAR POLYMER

Adsorbent surfaces in natural and engineered systems are frequently mo dified by bacterial attachment, growth of a biofilm, and bacterial pro duction of extracellular polymer. Attached cells or sorbed polymers ma y alter the metal-binding characteristics of the supporting substratum and influence metal partitioning. The interdependent behavior of toxi c trace metal partitioning and biofilm development requires descriptio n of the interaction between cell growth with its accompanying polymer production and metal speciation. in this article, the first of a two part series, a mechanistic model is developed to describe the growth o f a film-forming bacterium which adheres to a substratum through the p roduction of extracellular biopolymers. Each bacterial cell was modele d as a two-component structure consisting of active cell mass and biop olymer. The biopolymer component was further divided into cell-associa ted and dissolved categories to distinguish biopolymer which remained naturally bound to cell surfaces from that which did not. Use of this structured model permitted independent description of the dynamics of cell growth, and polymer production, both of which may influence trace metal behavior. Employing parameters obtained from independent experi ments as well as published values, the model satisfactorily predicts e xperimental observations of bacterial growth, attachment and detachmen t, biopolymer production, and adsorption of polymer onto solid (glass) surfaces. The model simulated transient and steady-state biofilm syst ems equally well. In the second article in this series, we describe ho w this model may be extended and utilized to make predictions of the b ehavior of transient and steady-state biofilm systems in the presence of a toxic transition metal (Pb). (C) 1994 John Wiley & Sons, Inc.