| De Beer, D; Schramm, A: Microenvironments and mass transfer phenomena in biofilms studied with microsensors, Water Science and Technology, 39(7), 173-178 (1999) | |
| Abstract: Direct observations on chemical microenvironment and microbial composition in biofilms are rare. The combination of microsensor- and molecular techniques is highly usefull for studies on the microbial ecology of biofilms. We shortly describe some applications of microsensors to study mass transfer phenomena and microbial processes in biofilms. It has recent been recognized that biofilms are not always flat layers of cells, but can consist of complex structures allowing liquid flow. Thus the classical view, that transport in biofilms is diffusional, is challenged. In laboratory grown biofilms the effect of convection on mass transfer was demonstrated. The microsensor technique has improved, so that direct in situ measurements in living biofilms are possible, also in bioreactors. We show hat also biofilms grown in bioreactors heterogeneity and convectional transport must be taken into account. For the description of the microbial population we use molecular techniques, such as in situ hybridisation with 16S-rRNA probes. In a nitrifying/denitrifying biofilm we found a nitrifying population that was much more complex as normally found with cultivation studies. It has become clear that the main nitrifying species found by cultivation techniques (Nitrosomonas and Nitrobacter) are minor populations in wild-type biofilms, which are dominated by Nitrospira and Nitrosospira strains. |
