Comparative Analysis of Microbial Communities in Fronds and Roots of Three Duckweed Species: <i>Spirodela polyrhiza</i>, <i>Lemna minor</i>, and <i>Lemna aequinoctialis</i>

Abstract

The microbial communities inhabiting the fronds of duckweeds have not been investigated in as much detail as those on the roots. We herein examined the microbial communities in three duckweed species using 16S rRNA amplicon sequencing and compared them to those on the roots. The microbial compositions of the fronds were distinct from those of the roots in the three species. Various types of taxonomic bacteria, including rarely cultivated phyla, Acidobacteria , Armatimonadetes , and Verrucomicrobia , were also isolated from the fronds, but at a slightly lower abundance than those from the roots. These results suggest that duckweed fronds are an alternative source for isolating rare and novel microbes, which may otherwise be recalcitrant to cultivation using conventional strategies.

Synthetic Bacterial Community of Duckweed: A Simple and Stable System to Study Plant-microbe Interactions

“…1) remained unchanged throughout the culture period. These dominant families are consistent with previous findings on the duckweed microbiome (Xie et al, 2015;Acosta et al, 2020;Huang et al, 2020;Ishizawa et al, 2020;Iwano et al, 2020;Iwashita et al, 2020), indicating that duckweed attracts specific bacterial taxa irrespective of the environmental context. On the other hand, the dominant genera or ASVs within each family were repeatedly replaced over 10 days (Fig.…”

Presence of the microbiome decreases fitness and modifies phenotype in the aquatic plant Lemna minor

“…In the wild, the fronds and roots are covered in a species rich assemblage of microbes (Gilbert et al 2018, Acosta et al 2020, which can be removed by sterilisation in the lab when used as an experimental model (Bowker et al 1980). Interest in the L. minor microbiome dates back to the early 20 th C, with the observation of an association with N-fixing bacteria (Bottomley 1920), and has accelerated in recent years (Ishizawa et al 2017a, 2017b, 2019, Gilbert et al 2018, Chen et al 2019, Acosta et al 2020, Iwashita et al 2020, O'Brien et al 2020a, 2020b, Tan et al 2021 with a general consensus that plant-microbe interactions play an important role in mediating plant fitness and function. Although most of this research focuses on identifying specific PGPB strains, recent work has characterised the complete core bacterial assemblage associated with L. minor (Acosta et al 2020), which consists of largely Proteobacteria (Pseudomonas and Actinobacteria) and bears a close resemblance to the leaf microbiome in terrestrial plants like Arabidopsis and rice.…”

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

“…An in-house bacterial library was used to source for strains that could grow rapidly and easily on R2A agar. The library was composed of taxonomically novel bacterial strains obtained from the fronds of the three duckweed species (L. minor, L. aequinoctialis, and S. polyrhiza), including strains that had been isolated in our previous study 18) . Within this library, 25 strains were determined to be suitable for testing in this study (Table 1).…”

“…We have previously reported that the microbial communities in the fronds of three species within the subfamily Lemnoideae (viz., Spirodela polyrhiza, Lemna minor, and Lemna aequinoctialis) were distinct from those growing in the roots 18) , suggesting that the plant part (i.e., fronds or roots) is an important factor to consider when screening for key PGPB that will enhance the functional abilities of duckweed. Moreover, the fronds and roots of duckweed harbor a wide variety of taxonomically novel bacteria (i.e., showing less than 97% of 16S rRNA gene sequence similarity to known type species), including the rarely cultivated phyla Acidobacteria, Armatimonadetes, and Verrucomicrobia 18) . If some of these taxonomically novel and rarely cultivated bacteria are PGPB, they might possess novel plant growth-promoting factors.…”

“…If some of these taxonomically novel and rarely cultivated bacteria are PGPB, they might possess novel plant growth-promoting factors. Therefore, in this study, we aimed to identify novel PGPB using a bacterial library of taxonomically novel strains that we had previously isolated from the fronds of L. minor, L. aequinoctialis, and S. polyrhiza 18) .…”