The 11th Nitrogen Cycle Meeting 2005 169 Approaches to assess the biodiversity of bacteria in natural habitats

Any attempt to characterize a bacterial community and their functional genes coding for enzymes of the nitrogen cycle is faced with its extreme biodiversity. Novel techniques, based on PCR amplification of target genes in DNA from environmental samples, have been developed for characterizing both cultured and as yet uncultured bacteria in the last few years. Computer-based assignment tools have now been developed utilizing terminal restriction fragments obtained from digestions with multiple restriction enzymes. Such programs allow the gross characterization of bacterial life in any complex bacterial community with confidence. The complexity of bacterial communities The species richness and complexity in environmental sam-ples is enormous. A soil, for example, harbours approx. 104 ribotypes (∼different bacteria) per g of sample [1,2]. Early attempts (e.g. by us [3]) were restricted to the characterization of bacteria which could be isolated from plates after growth on conventional media. Southern hybridizations using DN