REGULAR ARTICLE Isolation and characterization of root-associated bacteria from agricultural crops in the Kavango region of Namibia Jann Lasse Grönemeyer & Claudia Sofía Burbano & Thomas Hurek & Barbara Reinhold-Hurek Received: 8 February 2011 /Accepted: 15 April 2011 /Published online: 13 May 2011 # Springer Science+Business Media B.V. 2011 Abstract Root-associated bacteria can have beneficial effects on their host plants. Microbial products can promote and stimulate plant growth or lead to biopro- tection against pathogens. This study aimed to isolate putatively beneficial bacteria from traditional cereals grown by subsistence farmers in the Kavango of Namibia. Bacteria were isolated from surface-sterilized roots of Pennisetum glaucum, Sorghum bicolor , and Zea mays, and subjected to phenotypic and phyloge- netic analyses. A total of 44 root-associated bacterial strains were isolated. From 33 distinct isolates, 22 belonged to Firmicutes and Actinobacteria, while 11 were Proteobacteria. Eleven novel phylotypes were among the isolates. Features known to contribute to plant growth-promotion and biocontrol were tested in vitro and revealed promising candidates with multiple beneficial characteristics. This is the first report on the characterization of native isolates associated with important agriculture crops in the Kavango region of Namibia. Such isolates have the potential for applica- tion as inoculants adapted to poor soils and local crops. Desiccation-tolerant or sporulating Gram-positive bacteria are of particular interest for this region, which is characterized by a long dry season. Keywords Root-associated bacteria . Sorghum . Pennisetum . Maize . Plant growth-promotion Introduction Microorganisms in the rhizosphere of plants are important players in the terrestrial ecosystem. They are involved in the cycling of nutrients, the decomposition and mineralization of organic matter, and are essential for long-term soil sustainability (Germida et al. 1998). More specifically, plant-bacteria associations can help plants to establish in degraded landscapes, protect plants against diseases or even promote plant growth (Glick 1995). Exploring the diversity of plant–bacteria associations is indispensable if these associations are to be used further to increase crop production, conserve biodiversity and sustain agro-ecosystems (Germida et al. 1998). Plant growth-promoting rhizobacteria (PGPR) are a group of microorganisms able to colonize the rhizosphere or roots of many plant species, conferring beneficial effects on their host (Kloepper et al. 1980). Plant Soil (2012) 356:67–82 DOI 10.1007/s11104-011-0798-7 Responsible Editor: Euan K. James. Jann Lasse Grönemeyer and Claudia Sofía Burbano contributed equally to this study. Electronic supplementary material The online version of this article (doi:10.1007/s11104-011-0798-7) contains supplementary material, which is available to authorized users. J. L. Grönemeyer : C. S. Burbano : T. Hurek : B. Reinhold-Hurek (*) Department of Microbe-Plant Interactions, Center for Biomolecular Interactions Bremen, University of Bremen, Postfach 33 04 40, 28334 Bremen, Germany e-mail: breinhold@uni-bremen.de