Establishment and Use of Gellan Gum Media for Selective Isolation and Distribution Survey of Specific Rare Actinomycetes.

Abstract

Streptomyces strains produce wide varieties of bioactive compounds. However, the discovery rate of new antibi- otics from ubiquitous strains has been declining. In order to discover new bioactive compounds, one should screen varieties of genera as wide as possible, especially those rarely isolated. It is therefore necessary to improve or establish isolation methods of specific rare actino- mycete genera such as Actinobispora1–2), Sporichthya3), Planobispora4), Planomonospora5) and Actinomadura rugatobispora6). For this purpose, the author attempted to use gellan gum as the medium-solidifying agent instead of agar. Gellan gum is a polysaccharide produced by “Pseudomonas elodea” and is used for plant tissue culture as a solidify- ing agent with growth stimulatory effect. First, the author examined the effect of a variety of solidifying agents in- cluding conventional agar on the growth of Actinobispora yunnanensis IFO 15681T, and found that gellan gum best stimulated the formation of aerial mycelium as well as aer- ial spore. The same effect of gellan gum was also exhibited in other actinomycete genera so that identifi- cation of Sporichthya, Planobispora, Planomonospora, and A. rugatobispora was facilitated. Consequently, the isolate profile on the newly established media allowed the author to survey and discuss ecological aspects of these genera. 2.