Preface Substrate utilization tests in microbial ecology

Carbon source utilization tests based on the reducdefining a coloration threshold for positive controls tion of a tetrazolium dye were developed for the or a certain average absorption value improves identification of bacteria [1]. Since Garland and reproducibility, but which threshold gives the best Mills [2] first used such Biolog (Hayward, Ca., resolution? It was also proposed to determine the USA) substrate utilisation tests to characterize microkinetics of well coloration rather than single point bial communities of terrestrial and aquatic ecoreadings, but it is difficult to find simple parameters systems, this approach has repeatedly been applied in adequately describing the kinetics. Further, a multiMicrobial Ecology. It has successfully been used for tude of statistical approaches have been applied for ecological and applied studies in terrestrial and data evaluation, like principal component analysis, aquatic ecosystems. New approaches and applicadiscriminant analysis and detrended correspondence tions were presented at a meeting in Innsbruck, analysis, each with its own strengths and weaknesAustria. ses. Despite several promising results for different In the light of all these questions, we announced a applications in our research and in other laboratories, workshop involving researchers using Biolog for we increasingly became aware of problems conmicrobial community studies. The response was cerning the assay and interpretation of carbon utilizaextraordinary, and instead of a small workshop it tion tests. As has been found by Haack et al. [3], the became an international meeting with almost 150 oxidation of substrates on the Biolog plates by participants. The meeting was named ‘Substrate use microbial communities is not simply the sum of the for characterization of microbial communities in activity of individual members. A prerequisite for terrestrial ecosystems’(SUBMECO) and was held in obtaining reproducible data from communities is a Innsbruck, Austria, from Oct. 16–18, 1996. similar inoculation density. It is disputed if this can Some of the topics concerned improvements of be obtained through prior determination of colony current inoculation and incubation techniques, rangforming units or total counts of bacteria, followed by ing from sample pre-treatment, inoculum density and dilution of the samples. Other questions relate to the incubation temperature to statistical data handling, incubation time: selecting the time of reading by including several methods of multivariate statistics. New methods for calculating microbial diversity were proposed, as well as bootstrap methods that