Biofilm dynamics studied with microsensors and molecular techniques

Here we present preliminary data on the development of a biofilm from a wastewater treatment plant studied with microsensors and molecular techniques. The development during biofilm growth of oxygen, sulfide and pH profiles was measured with microsensors. Anoxic zones developed within one week and further increased during the following weeks. However, sulfide production was delayed and was first detected in a six-week-old biofilm. With denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S rRNA gene fragments the sequence of the bacterial community was followed showing an increasing complexity of the biofilm community during development. In a mature biofilm the influence of nitrate on sulfide production was studied by measuring oxygen, sulfide, pH, nitrite and nitrate profiles with microsensors. Sulfide production was detected deeper in the biofilm and in lower concentrations, when nitrate was added to the medium. The DGGE pattern of the mature biofilm showed both differences and similarities with the DGGE pattern of the 12-week-old biofilm. In particular the RNA pattern changed when nitrate was added to the medium, indicating a change in activity of certain strains.