Photoecology of the Antarctic cyanobacterium Leptolyngbya sp. BC1307 brought to light through community analysis, comparative genomics and in vitro photophysiology.

Nathan A M Chrismas,Patricia Sánchez‐Baracaldo,Marian L Yallop,Alexandre M Anesio,Christopher J Williamson

doi:10.1111/mec.14953

Nathan A M Chrismas, Patricia Sánchez‐Baracaldo + Show 3 more

Open Access

https://doi.org/10.1111/mec.14953

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Abstract

Cyanobacteria are important photoautotrophs in extreme environments such as the McMurdo Dry Valleys, Antarctica. Terrestrial Antarctic cyanobacteria experience constant darkness during the winter and constant light during the summer which influences the ability of these organisms to fix carbon over the course of an annual cycle. Here, we present a unique approach combining community structure, genomic and photophysiological analyses to understand adaptation to Antarctic light regimes in the cyanobacterium Leptolyngbya sp. BC1307. We show that Leptolyngbya sp. BC1307 belongs to a clade of cyanobacteria that inhabits near-surface environments in the McMurdo Dry Valleys. Genomic analyses reveal that, unlike close relatives, Leptolyngbya sp. BC1307 lacks the genes necessary for production of the pigment phycoerythrin and is incapable of complimentary chromatic acclimation, while containing several genes responsible for known photoprotective pigments. Photophysiology experiments confirmed Leptolyngbya sp. BC1307 to be tolerant of short-term exposure to high levels of photosynthetically active radiation, while sustained exposure reduced its capacity for photoprotection. As such, Leptolyngbya sp. BC1307 likely exploits low-light microenvironments within cyanobacterial mats in the McMurdo Dry Valleys.

Highlights

Inland polar regions are harsh environments, providing a challenge to even the most resilient microorganisms
BC1307 genome (Table 1), we further identified the activation of a photoprotective mechanism additional to state transitions at photosynthetically active radiation (PAR)>Ek (Figure 4b), demonstrating the capacity for orange carotenoid protein (OCP)‐driven Nonphotochemical quenching (NPQ) in Leptolyngbya sp
We show that genomic information from an organism can be used to infer their information about their ecological niche; by linking comparative genomics, photophysiology and microbial community analysis, ecological insights can be obtained

Summary

| INTRODUCTION

Inland polar regions are harsh environments, providing a challenge to even the most resilient microorganisms. Many prokaryotic and eukary‐ otic microorganisms thrive in the McMurdo Dry Valleys Amongst these are the cyanobacteria, which represent an important compo‐ nent of Antarctic photoautotrophic assemblages. Cyanobacteria are common in many habitats of the McMurdo Dry Valleys, including cryoconite sediment (Porazinska et al, 2004), rocks (Pointing et al, 2009) and deep lakes that remain permanently wet throughout the annual cycle (Laybourn‐Parry & Wadham, 2014; Zhang et al, 2015). The lakes of the McMurdo Dry Valleys are a collection of stratified, perennially ice‐covered closed basin lakes that have long been stud‐ ied in terms of their biological, chemical and physical properties (Laybourn‐Parry & Wadham, 2014) They range from freshwater to saline (Green & Lyons, 2009) and exhibit a variety of geochemical properties. Findings provide first insight into the photoecology of this Antarctic photoautotroph

| MATERIALS AND METHODS

Findings

| DISCUSSION

| CONCLUSION