Differential Adhesion, Activity, and Carbohydrate: Protein Ratios of Pseudomonas atlantica Monocultures Attaching to Stainless Steel in a Linear Shear Gradient

Abstract. Biofilm formation on metallic surfaces in marine and freshwater environments often precedes corrosion and other biofouling conditions. Attachment is mediated by such environmental factors as the presence of surface conditioning films, fluid dynamics, bulk-phase nutrient levels, and surface chemistry. In this study, we utihzed a Fowler Cell Adhesion Mea-surement Module to demonstrate hat the changes in cellular concentration and composition of a monoculture of Pseudomonas atlantica biofilms on stainless teel were a function of the applied shear force. At shear forces in the range of 3-10 dynes cm-2 (1.0 liter min-m), attachment as measured by acridine orange direct microscopic ounts was greatest at the higher shear forces. ~4C-Acetate uptake activity on the stainless teel surfaces increased with shear stress. Acetate incorporation ranged from 1 x 10-5 to 19 x 10-3/~mol cm-2 between 0.15 and 30 dynes cm-2 for 30 min uptake periods. On a per cell basis, however, activity decreased with shear, indi-cating a shift in metabolism. Fourier transform infrared spectroscopy re-vealed that protein and carbohydrate concentrations also increased with the applied shear. Increased biofilm C:N ratios and total fatty acids were associated with the higher shear stresses. Neither adius of interaction or biofilm age appeared to significantly influence the relationship between fluid shear and attachment and cellular composition ofP. atlantica biofilms in the range of 1-10 dynes cm-