# Abundance and Diversity of Aerobic Anoxygenic Phototrophic Bacteria in Polar Plant Microbiomes

## TL;DR

This study explores the presence and diversity of light-harvesting bacteria in plants from polar regions, revealing their widespread occurrence and potential ecological roles.

## Contribution

The study provides the first comprehensive analysis of aerobic anoxygenic phototrophic bacteria in polar plant microbiomes across both hemispheres.

## Key findings

- AAPBs were commonly found in plant tissues across polar regions in both hemispheres.
- Sphingomonas was the most abundant taxon, while Methylobacteria were less prevalent in high-latitude sites.
- A diversity of Alphaproteobacteria with AAP capabilities was identified in polar plant microbiomes.

## Abstract

Here, we examined the occurrence of plant‐associated aerobic anoxygenic phototrophic bacteria (AAPB) across polar regions. Recently found in polar soils and cold‐climate plants, AAPBs are photoheterotrophs that rely on environmental organic carbon but capture solar energy via anoxygenic photosynthesis. We revealed the abundance of AAPBs by extracting bacteria from plant tissues and imaging the colonies with bacteriochlorophyll‐based near‐infrared fluorescence. The taxonomic distribution of AAPBs was determined via 16S rRNA gene analysis. From the northern hemisphere, we describe AAPBs from the leaf endo‐ and phyllospheres of numerous sub‐ and Arctic plant species in Northern Finland, Svalbard, and Greenland. In the southern hemisphere, we focused on AAPBs in the root and leaf endospheres and the phyllospheres of
Deschampsia antarctica
in Chilean Patagonia and maritime Antarctica. Additionally, we describe AAPB from the tissues of several other plant species in Patagonia. We found AAPBs commonly associated with the sampled plant species across both hemispheres. A diversity of Alphaproteobacteria was found to contain the AAP capability: at all sampling sites, Sphingomonas was the most abundant taxon (up to 60%), while Methylobacteria made up a notable proportion of sub‐Arctic and sub‐Antarctic AAPB samples (up to 32%). In contrast to previous studies describing Methylobacteria frequently in various plant communities, AAP‐containing Methylobacteria were virtually absent from our high‐latitude sites. With diverse AAPB taxa found ubiquitously across polar regions and plant tissues, our results call attention to the potential ecological interaction between AAPBs and their plant hosts.