CHAPTER 1 - Aerobic Actinomycetes: A Continuing Source of Novel Natural Products

Abstract

This chapter describes the importance of aerobic actinomycetes as a continuing source of novel natural products. The micromonosporae have been crucial to the success of the Natural Products Program at Schering-Plough. The exploitation of these bacteria proved that nonstreptomycetes were valuable sources of novel natural products. Micromonosporae are the second largest group of actinomycetes in soil, surpassed only by the streptomycetes. They have been isolated from a variety of habitats. Jensen isolated micromonosporae from dry, neutral, and alkaline soils. They are found to be widely distributed, occurring preferentially in moist Russian soils. Shearer reported that two or three micromonosporae can be isolated from most soil types. Cross places the number at 10 × 106 cfu per gram of soil. Micromonosporae have been isolated from freshwater lakes and lake mud, where they are the most frequently isolated mesophilic actinomycetes. The surface of lake mud was reported to contain 2.4 × 106 micromonosporae cfu per gram, which represented 50% of the total population and deep mud contained 4 × 105 cfu per gram, and in which the micromonosporae predominated. Micromonosporae have also been isolated from the marine environment, from a salt marsh, from sea water and sand, and antibiotic producers have been isolated from marine sediments.