Identification of an Indole-3-Acetic Acid-Producing Plant Growth-Promoting Bacterium (PGPB) Isolated from the Roots of Centrosema pubescens Benth

摘要

Isolate TCeRe 37w obtained from the root extract of butterfly-pea (Centrosema pubescens Benth.) was found previously to produce indole-3-acetic acid (IAA) and promote the growth of plants. Colorimetric (Salkowski) assay exhibited a production of 291 and 736 mu g IAA equivalent mL~(-1) of minimal salts medium supplemented with 1000 ppm tryptophan after 24 and 48 h of incubation, respectively. HPLC analysis confirmed the production of 116/sg IAA mL~(-1) of culture after 48 h. Biochemical characterization using API 20E indicated that TCeRe 37w belongs to the genus Klebsiella. The major fatty acids of TCeRe 37w include C16:0, C18:1w7c and C17:0 CYCLO. In addition, straight chain, unsaturated, cyclopropane and hydroxy fatty acids make up 39.75%, 24.57%,14.48% and 0.65%, respectively, of its total cellular fatty acid. This fatty acid profile is most similar to that of Klebsiella pneumoniae-pneumoniae-GC subgroup B with a similarity index of 0.848. Alignment of the partial 16S rDNA sequence of TCeRe 37wshowed closest relation with the 16S rDNA of Klebsiella pneumonias. BLAST analysis further supports that the isolate is K. pneumoniae exhibiting 521 similar nucleotides out of 526 total nucleotides aligned (99% identity).