Impact of nutrient composition on a degradative biofilm community

A microbial community was cultivated in flow cells with 2,4,6-trichlorobenzoic acid (2,4,6-TCB) as sole carbon and energy source and was examined with scanning confocal laser microscopy and fluorescent molecular probes. The biofilm community which developed under these conditions exhibited a characteristic architecture, including a basal cell layer and conspicuous mounds of bacterial cells and polymer (approximately 20 to 30 mu m high and 25 to 40 mu m in diameter) occurring at 20- to 200-mu m intervals. When biofilms grown on 2,4,6-TCB were shifted to a labile, nonchlorinated carbon source (Trypticase soy broth), the biofilms underwent an architectural change which included the loss of mound structures and the formation of a more homogeneous biofilm. Neutrally charged fluorescent dextrans, which upon hydration become cationic, were observed to bind to mounds, as well as to the basal cell layer, in 14-day biofilms. In contrast, polyanionic dextrans bound only to the basal cell layer, indicating that this material incorporated sites with both positive and negative charge. The results from this study indicate that nutrient composition has a significant impact on both the architecture and the physicochemistry of degradative biofilm communities.