Production of indoleacetic acid by strains of the epiphytic bacteria Neptunomonas spp. isolated from the red alga Pyropia yezoensis and the seagrass Zostera marina

Abstract

Neptunomonas sp. BPy-1 is an epiphytic bacterium isolated from in vitro culture of the red alga Pyropia yezoensis. It uses ethanol as a sole carbon source and promotes the growth of host alga. A related bacterium, Neptunomonas sp. BZm-1, was isolated from leaves of Zostera marina found in the Yatsushiro Sea (Japan). BZm-1 showed 99% 16S rRNA sequence identity with Neptunomonas sp. BPy-1. Similar to BPy-1, BZm-1 grew in artificial seawater (ASW) medium containing ethanol or butanol. When thalli were treated with a multi-enzyme cleaner, the growth of treated thalli was retarded, but the addition of BZm-1 to the medium promoted growth. To explore the benefits of epiphytic bacteria, indoleacetic acid (IAA) production by isolated bacteria was examined under conditions of limited nutrients. Salkowski assays and GC-MS analysis revealed that both BZm-1 and BPy-1 excreted IAA during growth in ASW medium containing glucose or ethanol in the presence of tryptophan. In ASW medium containing tryptophan but lacking a carbon source, neither isolate grow, but produced IAA. ASW medium includes nitrate as the sole nitrogen source. In the absence of carbon source, different nitrogen forms in the presence of tryptophan did not affect IAA production by the two isolates. These findings indicate that IAA production by the two isolates is strictly dependent on tryptophan but less affected by carbon and nitrogen sources. Based on the different origins of BPy-1 and BZm-1, this mode of IAA production seems to be conserved among relatives of BPy-1.

Bacillus spp.: potent microfactories of bacterial IAA

“…Auxin is synthesized in aerial parts (shoot apex) and transported to sub-aerial parts of the plants actively by utilizing two common transportational pathways through phloem towards the root via non-directional passive pathway or via cell to by directional active pathway called polar auxin transport (Park et al, 2017). Indole-3-acetic acid (IAA) is a potent signaling molecule essential for plant–microbe interactions and improve plant growth directly (Matsuda et al, 2018). Bacterial auxin changes the auxin pool to either supraoptimal or optimal level and hence improve plant root growth especially the development of secondary roots thereby improving root surface area that promotes plant nutrition and consequently results in better growth and yield of plant.…”

Beneficial bacteria activate nutrients and promote wheat growth under conditions of reduced fertilizer application

“…(3) production of plant growth regulators or phytohormones such as indole-3-acetic acid (IAA), cytokinins, and gibberellins [14,15]; (4) production of siderophores, 1-amino-cyclopropane-1 -carboxylate (ACC) deaminase, and hydrogen cyanate [16,17]; (5) and biological control of phytopathogens and insects by synthesizing antibiotics or fungicidal compounds or competiting with detrimental microorganisms [18,19].…”

Pengaruh Rizobakteri Penghasil Indole-3-Acetic Acid Terhadap Perkecambahan Biji Tanaman Padi (Oryza sativa L.)

“…Rizobakteri tersebut dikenal dengan plant growth-promoting rhizobacteria (PGPR) yang merupakan bakteri yang hidup di area tanah rizosfer dengan peran sebagai pemacu pertumbuhan tanaman serta pelindung dari berbagai cekaman (Timmusk, 2017). PGPR memiliki berbagai mekanisme dalam mendukung pertumbuhan tanaman diantaranya adalah fiksasi nitrogen (Lin et al, 2012), pelarutan fosfat anorganik dan mineralisasi fosfat organic (Zaheer et al, 2019), produksi siderofor, 1-amino-cyclopropane-1 -carboxylate (ACC) deaminase dan hydrogen cyanate (Sulochana et al, 2014), sebagai agen kontrol biologis pathogen tumbuhan dan hama dengan mensintesis antibiotik maupun senyawa fungisida (Sun et al, 2017;Etesami et al, 2017), serta produksi berbagai fitohormon termasuk indole-3-acetic acid (IAA), sitokinin, dan giberelin (Matsuda et al, 2018;Cappellari et al, 2019).…”

“…Indole-3-acetic acid (IAA) merupakan molekul yang berperan penting dalam interaksi antara mikroba dan tanaman serta mampu meningkatkan pertumbuhan tanaman secara langsung (Matsuda et al, 2018). IAA juga berperan dalam tahap awal perkecambahan biji pada banyak spesies tanaman (Pieruzzi et al 2011).…”