Isolation and characterization of new plant growth-promoting bacterial endophytes

Those bacterial endophytes that also provide some benefit to plants may be considered to be plant growth-promoting bacteria (PGPB) and can facilitate plant growth by a number of different mechanisms. In the work that is reported here, soil samples from several locales around the world were used as a starting point for the isolation of new endophytes. Subsequently, those newly isolated endophytes that were able to utilize the plant compound 1-aminocyclopropane-1-carboxylate (ACC) as a sole source of nitrogen, as a consequence of possessing the enzyme ACC deaminase, were selected for additional characterization. More specifically, ACC deaminase-expressing strains were tested for IAA synthesis, siderophore production, phosphate solubilization activity, optimal growth temperature, salt tolerance, and antibiotic sensitivity. In addition, the partial DNA sequences of the 16S rRNA genes of the characterized strains were determined so that the taxonomic identity of each strain could be assessed, and the ability of some of these strains to facilitate the growth of canola plant roots under controlled gnotobiotic conditions was measured. (c) 2011 Elsevier B.V. All rights reserved.