【报告题目】Microbial Resource Management: from high throughput models to pilot reactors
PhD, Professor, Laboratory of Microbial Ecology and Technology, Ghent University, Belgium
Dr. Nico Boon，Professor of Molecular Microbial Ecology, head of Department of Microbial and Biochemical Technology in Ghent University. Dr. Boon obtained his PhD in Applied Biological Sciences, Ghent University, in 2002. Since 1998 the research has focused on the microbial ecology of soil, aquifer, aquaculture systems, drinking water and activated sludge systems. The areas of interests have been the development of molecular methods (Denaturing Gradient Gel Electrophoresis, Fluorescent in situ Hybridisation, Real-Time PCR and Flow Cytometry) for the qualitative and quantitative description of microorganisms and investigations of microbial processes in carbon and nitrogen cycling, novel bioaugmentation strategies for xenobiotics and the bioprecipitation and application of catalytic particles (Pd, Mn, Au and Ag). During the last years, the research interests are focused on the development of new microbial ecological theories to link the microbial community structure to functionality. The central theme of this research is to understand of the composition, functionality and the limits under which a microbial community can (optimally) perform. At present, there is only limited theoretical insight in the ecology of mixed microbial cultures and engineering practices to manage those microbial resources are fragmentary. The final aim is to structure and optimize the performance of the community in respect to a desirable set of outputs. This strategy is called Microbial Resource Management (MRM). The research has resulted in more than 220 accepted/published international publications in journals with peer review (A1 + A2). During the last 3 years, he published in top journals, like Nature, Nature Communications, FEMS Microbiology Reviews, Trends in Biotechnology, PLoS Pathogens, Current Opinion in Biotechnology (2 times), Biotechnology Advances (2 times), Trends in Biotechnology (3 times), …They have been cited 4800 times with a h-index of 36. He has also two patents. More than 30 international conferences have been attended, and the research results have been presented in 50 national and international oral presentations.
Microbial Resource Management: from high throughput models to pilot reactors
The biodiversity-stability relationship between microbial communities and the effect of biodiversity on functioning and invasion have become a major focus in research. While previous studies have mainly focused on how a higher level of species richness can confer a greater stability to specific ecosystem properties, the relationship between functionality, invasion and evenness has not been deeply investigated.
In a first study, the impact of initial community evenness on the functionality of the resident community was assessed by the use of assembled denitrifying bacterial communities; this approach is well suited for validating ecological theories (2). To exclude confounding factors, the tests were conducted with (i) a complex medium to avoid nutrient limitation and (ii) an assembled community composed of bacteria occupying the same functional niche (the capability for nitrite respiration) and isolated from the same sample of homogenised activated sludge. A total of 17 denitrifying strains from 4 phyla were mixed in different proportions to create a few thousand microcosms with different levels of initial evenness but with the same richness. In a first set of experiments, we demonstrated that provided a good level of functional redundancy within microbial populations, the relative degree of evenness plays an important role in conserving a given functionality at short terms under perturbed conditions.
In a follow up study, the degree of invasion of an introduced species (a non-denitrifier) was evaluated and the final effect of this invader on the functionality of the denitrifying community (4). We showed that evenness influences the level of invasion into a community and that the introduced species can promote functionality under specific environmental stressors. The evenness-invasibility relationship was negative in the absence of salinity stress and neutral in the presence of salinity stress. Under such a stress condition, the introduced species is able to maintain the functionality of uneven communities. These results indicate that the invasibility of the ecosystem depends strongly on both the environmental conditions and the evenness of the resident community. Furthermore, an introduced species - generally considered negative - can also be an added value to the community and its functionality.
Besides evenness, richness and the dynamics of change are also postulated to be of importance for functional stability (3). This biodiversity-stability relationship was examined in a granular activated carbon (GAC) filtration (5). GAC filtration is essentially a microbial process that removes all biodegradable organic carbon from the ozonated water and ensures biological stability of the treated water. In this study, the start-up and maturation of an undisturbed pilot-scale GAC filter was monitored at 4 depths (10-45-80-115 cm) over a period of 6 months. New ecological tools, based on DGGE, were linked to filter performance and microbial activity (1) and showed that the stratification in a GAC reactor was of importance. At 10cm, receiving the freshly ozonated water, microbial activity was inhibited by residual ozone. This was reflected in the microbial community where no changes were observed and the richness remained low. However, the GAC samples at 80-115cm showed a 2-3 times higher richness then the 10-45cm samples. The highest biomass densities were observed at 45-80cm, which corresponded with maximum removal of dissolved and assimilable organic carbon. Furthermore, the start-up period was clearly visible from Pareto analysis: after two months, the community shifted to a more even organisation, which was accompanied by an apparent steady state condition. In conclusion, this study clearly shows that microbial community analysis can be linked to a good reactor performance. In the GAC filter sections with high activity, a high richness and evenness is needed for good performance. Moreover, these good performing microbial communities are 4 times more dynamic than the less performing communities.
1. Marzorati, M., L. Wittebolle, N. Boon, D. Daffonchio, and W. Verstraete. 2008. How to get more out of molecular fingerprints: practical tools for microbial ecology. Environmental Microbiology 10:1571-1581.
2. Wittebolle, L., M. Marzorati, A. Balloi, D. Daffonchio, K. Heylen, P. De Vos, W. Verstraete, and N. Boon. 2009. Initial community evenness favors functionality under selective stress. Nature: 458:623-626.
3. Wittebolle, L., H. Vervaeren, W. Verstraete, and N. Boon. 2008. Quantifying community dynamics of nitrifiers in functionally stable reactors. Applied and Environmental Microbiology 74:286-293.
4. De Roy K, Marzorati M, Negroni A., Thas O. Balloi A, Fava F., Verstraete W, Daffonchio D, Boon N. In review. Invasion preserves functionality in uneven stressed communities.
5. Boon, N., B. F. G. Pycke, M. Marzorati, and F. Hammes. 2011. Nutrient gradients in a granular activated carbon biofilter drives bacterial community organization and dynamics. Water Research 45:6355-6361.