Antimicrobial drimane sesquiterpenes and their effect on endophyte communities in the medical tree Warburgia ugandensis

Sigrid Drage,Christina Tröls,Franz Hadacek,Alice Muchugi,Angela Sessitsch,Ramni H Jamnadass,Birgit Mitter

doi:10.3389/fmicb.2014.00013

Abstract

Metabolite profiles (GC–−MS), drimane sesquiterpenes, sugars and sugar alcohols, were compared with bacterial and fungal endophyte communities (T-RFLP, DNA clones, qPCR) in leaves and roots of the pepper bark tree, Warburgia ugandensis (Canellaceae). Ten individuals each were assessed from two locations east and west of the Great Rift Valley, Kenya, Africa, which differed in humidity and vegetation, closed forest versus open savannah. Despite organ- and partially site-specific variation of drimane sesquiterpenes, no clear effects on bacterial and fungal endophyte communities could be detected. The former were dominated by gram-negative Gammaproteobacteria, Pseudomonadaceae and Enterobacteriaceae, as well as gram-positive Firmicutes; the fungal endophyte communities were more diverse but no specific groups dominated. Despite initial expectations, the endophyte community of the pepper bark tree did not differ from other trees that much.

Highlights

Warburgia ugandensis Sprague [=W. salutaris (Bertol.f.) Chiov], the pepper bark tree belongs to the Canellaceae, a small family of tropical trees, all of them aromatic and most with medicinal properties
The pepper bark tree represents an interesting model to explore relationships between microbial endophytes and host plant secondary metabolites, in terms of obtaining insights on how those interactions affect biodiversity and community composition, and in terms of how the content of active constituents in plants that are used in traditional medicine—drimane sesquiterpenes from Warburgia are even considered as anti-malaria drugs (Were et al, 2010; Wube et al, 2010)—can be affected by colonization with endophytic microbes
Kitale is located in a moist savannah in western Kenya situated between Mount Elgon and the Cherengani Hills at an elevation of around 2000 m. a. s. l. and has an average annual precipitation of 1269 mm; Rumuruti is located in a savannah with W. ugandensis mostly growing in or close to moist ravines embedded in semi-arid land at an elevation of 1700–2000 m. a. s. l. in the Laikipia district situated northwest of Mount Kenya with 739 mm average annual precipitation (Kindt et al, 2005)

Summary

Introduction

Warburgia ugandensis Sprague [=W. salutaris (Bertol.f.) Chiov], the pepper bark tree belongs to the Canellaceae, a small family of tropical trees, all of them aromatic and most with medicinal properties. W. ugandesis has a restricted distribution in evergreen forests and woodland ravines of northern KwaZuluNatal, Swaziland, Mpumalanga, Uganda, and Kenya. This species is widely used in traditional medicine within local communities in Eastern Africa, known to cure several ailments such as stomach-ache, constipation, toothache, common cold, cough, fever, muscle pains, weak points, measles, and malaria (Beentje and Adamson, 1994; Kokwaro, 2009). The pepper bark tree represents an interesting model to explore relationships between microbial endophytes and host plant secondary metabolites, in terms of obtaining insights on how those interactions affect biodiversity and community composition, and in terms of how the content of active constituents in plants that are used in traditional medicine—drimane sesquiterpenes from Warburgia are even considered as anti-malaria drugs (Were et al, 2010; Wube et al, 2010)—can be affected by colonization with endophytic microbes

Methods

Results

Conclusion