Assay Methods for Detection and Quantification of Antimicrobial Metabolites Produced by Streptomyces clavuligerus

Streptomyces clavuligerus is used as model to illustrate the determination and quantification of antimicrobial metabolites with different biological activities produced by cultures of this strain. S. clavuligerus produces an array of compounds with different structures. It produces cephamycin C, a β-lactam antibiotic acting on cell wall biosynthesis, the β-lactamase inhibitor clavulanic acid, which contains a clavam nucleus, as well as other clavams structures with antibacterial or antifungal activities. Also, S. clavuligerus has been described as a producer of the compounds with pyrrothin structure holomycin and holothin, which might act as antitumor agents. The production of each of these compounds depends on the culture medium and the culture conditions used and, occasionally, is related to specific strains or mutants of S. clavuligerus. Although a final characterization of the different compounds depends on fine chemical analytical methods, the detection and quantification of these compounds by high-performance liquid chromatography or by microbiological assays based in their different properties is possible. In this chapter, we provide some of the protocols routinely used for this purpose.