Effects of co-inoculation of two different plant growth-promoting bacteria on duckweed

Abstract

Aseptic Lemna minor was soaked for 4 h in pond water where wild L. minor was naturally flourishing. Seven of the eight surface-colonizing bacterial strains were found capable of promoting the growth of L. minor. This high appearance of plant growth-promoting bacteria (PGPB) suggests that association of environmental bacteria is generally beneficial rather than harmful for host plants. One of the PGPB, Pseudomonas sp. Ps6, enhanced the growth of L. minor by 2-2.5-fold in 10 days. This activity was higher than that previously reported for Acinetobacter calcoaceticus P23, which enhanced growth of L. minor by 1.5-2-fold. Ps6 mostly adhered to and colonized the root rather than the frond, a leaf-like structure of duckweed where P23 preferentially adheres. It was expected that these two strains can share niches, coexist, and enhance the growth of duckweed additively upon co-inoculation. However, contrary to expectation, the growth of L. minor was enhanced by only 2.3-fold by co-inoculation of these two bacteria. P23 lowered the initial adhesion of Ps6 cells by 98.2% on the fronds and by 79.5% on the roots. However, initial adhesion of P23 cells to the roots increased dramatically, by 47.2-fold, following co-inoculation with Ps6. However, the number of P23 cells decreased dramatically to 0.7% on the root and to 3.6% on the frond after 10 days, whereas Ps6 cells increased by 12.5-fold on the frond and kept 69% on the root, thereby eventually restoring the population on the plant surfaces. Because duckweed is the fastest growing vascular plant and it is easy to grow an aseptic and axenic plant, the duckweed/bacteria co-culture system will be a model platform for studying multiple interactions among host plants and the associated bacteria.

The extracellular matrix protects Bacillus subtilis colonies from Pseudomonas invasion and modulates plant co-colonization

“…In summary, our work increases our understanding of the mechanics of complex and multifactorial bacterial social interactions, demonstrating that the strategies adopted by two bacterial species may co-exist and lead to the formation of stable bacterial communities in plants, either mixed or as physically separated sub-domains. The findings obtained could be potentially relevant for agricultural purposes as shown by other studies 65,66 where the application of bacterial consortia has demonstrated promising effects in plant growth and biocontrol.…”

“…Raw reads were quality-trimmed with cutadapt. Then, trimmed reads were mapped against P. chlororaphis PCL1606, B. subtilis 3610 reference genomes using EDGE-pro 65 software, which is specially designed to process prokaryotic RNA-Seq data. Quantification was also performed with EDGE-pro.…”

Multifaceted roles of duckweed in aquatic phytoremediation and bioproducts synthesis

“…Ps6, another PGPB strain, frequently adheres to and colonizes on the root of duckweed ( L. minor ). It enhances the growth of L. minor by 2‐ to 2.5‐fold in 10 days, displaying a much higher activity than that of A. calcoaceticus P23 (Yamakawa, Jog, & Morikawa, 2018). The growth of duckweed rhizosphere‐associated bacteria is dependent on the quality of water.…”

Isolation and Characterization of Novel Plant Growth-Promoting Bacteria from the Fronds of Duckweed

“…Acinetobacter calcoaceticus strain P23, which was the first plant growth-promoting bacterial strain isolated from the whole body of Lemna aoukikusa, almost doubled the biomass productivity of this duckweed species 14), 16) . To date, over 15 strains of PGPB belonging to the genera, such as Pseudomonas, Acinetobacter, Sphingomonas, Azospirillum, and Aeromonas have been isolated from duckweed roots or whole plant bodies 14), 15), 17) . However, to the best of our knowledge, PGPB have never been isolated from the fronds of duckweeds.…”