Abstract

Actinomycetes populations in rhizosphere soils of mangrove forests in Cox’s Bazar and medicinal plant in Dhaka, Bangladesh were examined by simple dilution and an agar plate method. Actinomycetes populations (colony forming units/g, soil samples) ranged from 1x10³ to 157x10³ among 20 mangrove rhizosphere soil samples and 22x10³ to 168x10³in 12 medicinal plant rhizosphere soil samples of Bangladesh. Total population and distribution of rare genera of actinomycetes were varied with the different rhizosphere samples and populations in mangrove rhizosphere soil were lower compared to medicinal plant rhizosphere soil. Strains under the genus Micromonospora were observed as major isolates in both mangrove and rhizosphere soil samples. About 17 genera of rare actinomycetes were observed in mangrove rhizosphere soil and 11 genera in medicinal plant rhizosphere soil with 20 or 40% unknown isolates. The further chemotaxonomic data of 19 unidentified randomly selected actinomycetes from mangrove rhizosphere soil indicated that the isolates belonged to the rare genera Micromonospora, Catellatospora,Nonomuraea, Actinomadura, Microbispora and 4 other unknown genera in the familyMicromonosporaceae, Streptosporangiaceae and Thermomonosporaceae. This is the first intensive study and we confirmed that the mangrove and medicinal plant rhizosphere areas of Bangladesh are good sources for the isolation of diverse rare actinomycetes.

Key words: Isolation, diversity, chemotaxonomy, scanning electron microscopy, rare actinomycetes, mangrove rhizosphere soil.