Strain diversity within a microbial collection.

Random subsets of a modest-sized microbial collection have been examined for culture redundancy, initially by morphology, both to the naked eye and microscopically, of cultures grown on a variety of agar-based solid media. Subsequent analysis, by simple TLC, of the extractable metabolites produced by morphologically similar cultures grown in submerged shaken fermentation was carried out. Apparent duplicate cultures were further examined on Biolog SF-P MicroPlates for differentiation. The results were subjected to a statistical analysis and the contribution of each stage in the process to resolving culture uniqueness was noted. A statistical extrapolation of the results, from the subsets of each culture type, to the total for that type within the entire collection, with 95% confidence limits, is presented. Morphological comparison, on four different agar media, gives a significant underestimation of the metabolic diversity of the collection. The weighted mean from the three types of cultures indicate that the expected content of the collection is approximately 93% unique strains.