Information on functional diversity (metabolic potential) is essential for understanding the role of microbial communities in different environments. Variations of the commercially available BIOLOG bacterial identification system plates are now widely used to assess functional diversity of microorganisms from environmental samples, based on utilisation patterns of a wide range (up to 95) of single carbon sources. There are many problems as well as benefits of using the approach, but the former are often disregarded. Here the basis of the approach is summarised, including type of plate to use, treatment of samples, replication, incubation conditions, monitoring of plates, and statistical analysis. The pros and cons of its use are critically assessed, inherent biases and limitations are pointed out and methodological difficulties are considered. Possible ways of overcoming some of the difficulties are suggested.

Ecdysteroid, Ponasterone A, 20-Hhydroxyecdysone Phytoecdysteroid (PE) production and accumulation in Limnanthes alba Hartw. ex Benth. is associated with flowering. PE content per plant remains fairly constant during the primary growth phase of the plant and only begins to increase significantly above amounts found in the seed once the development of the flower stalk has begun. Both content and concentration increase concomitantly from this point. Distributions in individual plants also associated the highest levels of PE accumulation with the reproductive tissues. This substantiates the association of PE with tissues of greatest fitness value and therefore the hypothesis that they contribute to defence. Analysis of extracts of L. alba tissues by reversed-phase HPLC coupled with ecdysteroid-specific RIA was used to monitor ecdysteroid profiles. RIA-positive peaks co-chromatographing with 20-hydroxyecdysone, ecdysone and ponasterone A were detected and several tissues also contain PE conjugates. Seedmeal of L. alba appears to be a convenient and promising source for the commercial isolation of the potent PE ponasterone A.