Early growth of the filamentous actinomycete Srreptomyces coelicolor A3(2) on solid medium was investigated. Growth kinetics were similar to those of filamentous fungi in that total mycelial length and the number of branches increased exponentially at the same specific rate, with attainment of a constant hyphal growth unit. However, both germ tube and branch hyphae showed initial linear, rather than exponential extension. Logarithmic relationships were found between branch order and both branch length and branch number, although the constancy of these relationships varied during growth. Length ratio, obtained from branch pattern analysis, reached a constant value as did the hyphal growth unit, but branch ratio did not become constant during the period of study. There was some evidence of mycelial development analogous to that found in filamentous fungi.
A. melegueta, Z. officinale and P. guineense have the potential for use in the protection of stored grains by resource-poor farmers with local access to these plants.
Aims: To develop an ELISA for the detection of antigens derived from stable Bacillus subtilis L-form bacteria and to detect these in plants injected with L-form bacteria. Methods and Results: A sandwich ELISA was developed and its speci®city was investigated using L-forms and cell-walled forms of B. subtilis, different Bacillus species and a range of bacteria isolated from glasshouse-grown strawberry plants. The detection limits of the ELISA were approximately 10 3 viable cells ml À1 for L-forms compared with 10 7 viable cells ml À1 for cell-walled forms. Results showed that L-forms survived and moved within strawberry tissues injected with L-form bacteria. Conclusion: An ELISA that selectively detects B. subtilis L-form bacteria was developed and shown to con®rm the presence of L-forms in plants. Signi®cance and Impact of the Study: This will be a valuable rapid method to further studies on L-form plant interactions.
Callus produced from leaves of a Ghanaian strain of the neem tree, Azadirachta indica A. Juss has been shown to produce the natural insecticide azadirachtin when grown in a defined medium. The azadirachtin was isolated by standard procedures of solvent partition and column chromatography monitored by supercritical fluid chromatography. Biological activity was monitored with antifeedant tests using the desert locust (Schistocerca gregaria Forsk.). The azadirachtin was identified by chromatography on three independent chromatographic systems (SFC, HPLC & TLC) and two thin-layer colour tests. It has 100% antifeedant activity at <0.04 mg litre-'. The yield of azadirachtin was 0.0007% based on dry weight of callus.
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