Microbial communities and their interactions in biofilm systems: an overview

• Published in: Water science and technology 2004-01, Vol.49 (11-12), p.327-336
• Main Authors: Wuertz, S, Okabe, S, Hausner, M
• Format: Article
• Language: English
• Subjects: Abundance; Architecture; Bacteria; Bacteria - growth & development; Biofilms; Bioreactors; Carbon sources; Cloning; Community structure; Conjugation; Deoxyribonucleic acid; DNA; DNA, Bacterial - analysis; Environmental conditions; Fingerprinting; Fluorescence; Function analysis; Gene sequencing; Gene transfer; Genetics, Population; Image analysis; In Situ Hybridization, Fluorescence; Introduced species; Microbial activity; Microorganisms; Nitrogen dioxide; Nucleic acids; Nutrients; Oligonucleotide Array Sequence Analysis; Open channels; Physicochemical properties; Population Dynamics; Populations; Ribonucleic acid; RNA; Rotating disks; Scanning microscopy; Spatial analysis; Substrates; Waste Disposal, Fluid - methods; Water Movements
• ISSN: 0273-1223; 1996-9732
• DOI: 10.2166/wst.2004.0873

Several important advances have been made in the study of biofilm microbial populations relating to their spatial structure (or architecture), their community structure, and their dependence on physicochemical parameters. With the knowledge that hydrodynamic forces influence biofilm architecture came the realization that metabolic processes may be enhanced if certain spatial structures can be forced. An example is the extent of plasmid-mediated horizontal gene transfer in biofilms. Recent in situ work in defined model systems has shown that the biofilm architecture plays a role for genetic transfer by bacterial conjugation in determining how far the donor cells can penetrate the biofilm. Open channels and pores allow for more efficient donor transport and hence more frequent cell collisions leading to rapid spread of the genes by horizontal gene transfer. Such insight into the physical environment of biofilms can be utilized for bioenhancement of catabolic processes by introduction of mobile genetic elements into an existing microbial community. If the donor organisms themselves persist, bioaugmentation can lead to successful establishment of newly introduced species and may be a more successful strategy than biostimulation (the addition of nutrients or specific carbon sources to stimulate the authochthonous population) as shown for an enrichment culture of nitrifying bacteria added to rotating disk biofilm reactors using fluorescent in situ hybridization (FISH) and microelectrode measurements of NH4+, NO2-, NO3-, and O2. However, few studies have been carried out on full-scale systems. Bioaugmentation and bioenhancement are most successful if a constant selective pressure can be maintained favoring the promulgation of the added enrichment culture. Overall, knowledge gain about microbial community interactions in biofilms continues to be driven by the availability of methods for the rapid analysis of microbial communities and their activities. Molecular tools can be grouped into those suitable for ex situ and in situ community analysis. Non-spatial community analysis, in the sense of assessing changes in microbial populations as a function of time or environmental conditions, relies on general fingerprinting methods, like DGGE and T-RFLP, performed on nucleic acids extracted from biofilm. These approaches have been most useful when combined with gene amplification, cloning and sequencing to assemble a phylogenetic inventory of microbial species. It is expe