Isolation and characterization of culturable seed-associated bacterial endophytes from gnotobiotically grown Marama bean seedlings.
Marama bean (Tylosema esculentum) is an indigenous non-nodulating legume to the arid agro-ecological parts of Southern Africa. It is a staple food for the Khoisan and Bantu people from these areas. It is intriguing how it is able to synthesize the high-protein content in the seeds since its natural habitat is nitrogen deficient. The aim of the study was to determine the presence of seed transmittable bacterial endophytes that may have growth promoting effects, which may be particularly important for the harsh conditions. Marama bean seeds were surface sterilized and gnotobiotically grown to 2 weeks old seedlings. From surface-sterilized shoots and roots, 123 distinct bacterial isolates were cultured using three media, and identified by BOX-PCR fingerprinting and sequence analyses of the 16S rRNA and nifH genes. Phylogenetic analyses of 73 putative endophytes assigned them to bacterial species from 14 genera including Proteobacteria (Rhizobium, Massilia, Kosakonia, Pseudorhodoferax, Caulobacter, Pantoea, Sphingomonas, Burkholderia, Methylobacterium), Firmicutes (Bacillus), Actinobacteria (Curtobacterium, Microbacterium) and Bacteroidetes (Mucilaginibacter, Chitinophaga). Screening for plant growth-promoting activities revealed that the isolates showed production of IAA, ACC deaminase, siderophores, endoglucanase, protease, AHLs and capacities to solubilize phosphate and fix nitrogen. This is the first report that marama bean seeds may harbor endophytes that can be cultivated from seedlings; in this community of bacteria, physiological characteristics that are potentially plant growth promoting are widespread.
Department of Biological Sciences, University of Namibia, Private Bag 13301, Windhoek, Namibia Department of Microbe-Plant Interactions, University of Bremen, PO Box 330440, D-28334 Bremen, Germany.
Percy Maruwa
PM
Chimwamurombe
Department of Microbe-Plant Interactions, University of Bremen, PO Box 330440, D-28334 Bremen, Germany.
Jann Lasse
JL
Grönemeyer
Department of Microbe-Plant Interactions, University of Bremen, PO Box 330440, D-28334 Bremen, Germany breinhold@uni-bremen.de.
Barbara
B
Reinhold-Hurek
D000353:Africa, Southern; D001419:Bacteria / Q000235:genetics / Q000378:metabolism*; D019755:Carbon-Carbon Lyases / Q000378:metabolism; D004463:Ecology; D017753:Ecosystem; D060026:Endophytes / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification; D007887:Fabaceae / Q000254:growth & development / Q000382:microbiology*; D004693:Glucan Endo-1,3-beta-D-Glucosidase / Q000378:metabolism; D010088:Oxidoreductases / Q000235:genetics; D010802:Phylogeny; D018517:Plant Roots / Q000382:microbiology*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D036226:Seedlings / Q000382:microbiology*; D012639:Seeds / Q000382:microbiology
D012336:RNA, Ribosomal, 16S; D010088:Oxidoreductases; C029130:nitrogenase reductase; D004693:Glucan Endo-1,3-beta-D-Glucosidase; C033634:1-aminocyclopropane-1-carboxylate deaminase; D019755:Carbon-Carbon Lyases
Namibia; non-nodulation; phylogenetic analysis; plant growth promoting bacteria