Niche Differentiation in the Composition, Predicted Function, and Co-occurrence Networks in Bacterial Communities Associated With Antarctic Vascular Plants.

Qian Zhang,Jacquelinne J Acuña,Paola Duran,Milko A Jorquera,María L Mora,Nitza G Inostroza,Michael J Sadowsky

doi:10.3389/fmicb.2020.01036

Qian Zhang, Jacquelinne J Acuña + Show 5 more

Open Access

https://doi.org/10.3389/fmicb.2020.01036

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Abstract

Climate change directly affecting the Antarctic Peninsula has been reported to induce the successful colonization of ice-free lands by two Antarctic vascular plants (Deschampsia antarctica and Colobanthus quitensis). While studies have revealed the importance of microbiota for plant growth and stress tolerance in temperate climates, the role that plant-associated microbes play in the colonization of ice-free lands remains unknown. Consequently, we used high-throughput DNA sequence analyses to explore the composition, predicted functions, and interactive networks of plant-associated microbial communities among the rhizosphere, endosphere, and phyllosphere niches of D. antarctica and C. quitensis. Here we report a greater number of operational taxonomic units (OTUs), diversity, and richness in the microbial communities from the rhizosphere, relative to endosphere and phyllosphere. While taxonomic assignments showed greater relative abundances of Proteobacteria, Bacteroidetes, and Actinobacteria in plant niches, principal coordinate analysis revealed differences among the bacterial communities from the other compartments examined. More importantly, however, our results showed that most of OTUs were exclusively found in each plant niche. Major predicted functional groups of these microbiota were attributed to heterotrophy, aerobic heterotrophy, fermentation, and nitrate reduction, independent of plant niches or plant species. Co-occurrences network analyses identified 5 (e.g., Microbacteriaceae, Pseudomonaceae, Lactobacillaceae, and Corynebacteriaceae), 23 (e.g., Chitinophagaceae and Sphingomonadaceae) and 7 (e.g., Rhodospirillaceae) putative keystone taxa present in endosphere, phyllosphere, and rhizosphere, respectively. Our results revealed niche differentiation in Antarctic vascular plants, highlighting some putative microbial indicators and keystone taxa in each niche. However, more studies are required to determine the pivotal role that these microbes play in the successful colonization of ice-free lands by Antarctic plants.

Highlights

Climate change has become of global concern over the last several decades
Rhizosphere soils from D. antarctica showed higher contents of available P, K, and organic matter compared with that from C. quitensis
Our analysis revealed that 24.2% (1,109 of 4,587) and 16.2% (678 of 4,181) of operational taxonomic units (OTUs) were shared between the three plant niches of D. antarctica and C. quitensis, respectively (Figure 4)

Summary

Introduction

Climate change has become of global concern over the last several decades. This is of particular importance to the polar regions of the world, such as the Antarctic Peninsula. Studies have reported that the Antarctic Peninsula has been subjected to recent warming and cooling events, suggesting the uncovering of new ice-free lands (Lee et al, 2017). Recent Antarctic cooling events have resulted in deleterious effect on lichens, which are a dominant vegetation type in the Antarctic peninsula, creating new opportunities for expansion by other vegetation species (Sancho et al, 2017). In this context, the expansion of Antarctic vascular plants has been attributed to their efficient nitrogen acquisition capacity, competing with both soil microorganisms and lichens (Hill et al, 2011). Studies have shown that warming due to global climate events have significantly influenced the abundance, composition, and activity of soil microorganisms from Antarctic environments (Yergeau et al, 2012)

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