Pantoea ananatis, a plant growth stimulating bacterium, and its metabolites isolated from Hydrocotyle umbellata (dollarweed)

Authors: Meepagala, Kumudini; Anderson, Caleb; TECHEN, NATASHA - University Of Mississippi; Duke, Stephen

Submitted to: Plant Signaling and Behavior
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/22/2024
Publication Date: 3/22/2024
Citation: Meepagala, K.M., Anderson, C.M., Techen, N., Duke, S.O. 2024. Pantoea ananatis, a plant growth stimulating bacterium, and its metabolites isolated from Hydrocotyle umbellata (dollarweed). Plant Signaling and Behavior. 19:1. https://doi.org/10.1080/15592324.2024.2331894.
DOI: https://doi.org/10.1080/15592324.2024.2331894

Interpretive Summary: Utilization of plant growth promoting bacteria (PGPB) and nitrogen fixing microorganisms are useful and economical alternatives to synthetic chemical fertilizers in crop production and for enhancing crop yields. In this paper we describe isolation and identification of a plant growth promoting bacterium from an infected dollarweed plant. This bacterium has shown high growth promotion activity on duckweed plants, cucumber plants and sorghum plants. Thus, there is a potential for use of this bacterium as a soil treatment in agriculture and as a supplement or as an alternative to synthetic fertilizers.

Technical Abstract: A bacterium growing on infected leaves of Hydrocotyle umbellata, commonly known as dollarweed, was isolated and identified as Pantoea ananatis. An ethyl acetate extract of tryptic soy broth (TSB) liquid culture filtrate of the bacterium was subjected to silica gel chromatography to isolate bioactive molecules. Indole was isolated as the major compound that gave a distinct, foul odor to the extract, together with phenethyl alcohol, phenol, tryptophol, N-acyl-homoserine lactone, 3-(methylthio)-1-propanol, cyclo (L-pro-L-tyr), and cyclo(dehydroAla-L-Leu). This is the first report of the isolation of cyclo(dehydroAla- L-Leu) from a Pantoea species. Even though tryptophol is an intermediate in the indoleacetic acid (IAA) pathway, we were unable to detect or isolate IAA. We investigated the effect of P. ananatis inoculum on the growth of plants. Treatment of Lemna paucicostata Hegelm plants with 4 × 109 colony forming units of P. ananatis stimulated their growth by ca. five-fold after 13 days. After 13 days of treatment, some control plants were browning, but treated plants were greener and no plants were browning. The growth of both Cucumis sativus (cucumber) and Sorghum bicolor (sorghum) plants was increased by ca. 20 to 40%, depending on the growth parameter and species, when the rhizosphere was treated with the bacterium after germination at the same concentration. Plant growth promotion by Pantoea ananatis could be due to the provision of the IAA precursor indole.