Internal structure and photosynthetic performance of Nostoc sp. colonies in the high Arctic

Jana Kvíderová

doi:10.5586/asbp.3602

Abstract

The physiological performance of <em>Nostoc</em> sp. colonies in the high Arctic was investigated based on their structure and function. To investigate the internal colony structure, a method based on vertical stacking of individual light microscopy images was tested under the conditions at a polar field station. The physiological state of sun-exposed and shaded surfaces of the colonies was assessed using variable chlorophyll fluorescence imaging under two distinct low- and high-light conditions. The 3D image of the internal structure of the colonies revealed a high number of cells in the central part of the colony. Two peaks of maximum cell density were observed, probably caused by two overlapping colony lobes or subcolonies. Light was the driving factor of photosynthetic activity, and the colony structure played a role in the rate of response to incoming light. Fluorescence imaging revealed heterogeneity of the photosynthetic activity in the colonies, with the maximum photosynthetic activity at the colony edge due to better access to nutrients. The differences between exposed and shaded surfaces were not as pronounced as was expected, either due to good photoacclimation to a broad range of light conditions, light distribution through translucent extracellular matrixes, or integration of fluorescence signals throughout the colonies. The slightly better photosynthetic performance under high light conditions may indicate photoacclimation of <em>Nostoc</em> sp. to a broad range of light conditions encountered in the field.

Highlights

In the Polar regions, algae and cyanobacteria are important, if not the only, primary producers in hydro-terrestrial and terrestrial ecosystems [1,2,3,4,5]
The consortia may be formed by one species, by several species or, in the most extreme cases, by strictly symbiotic microorganisms [14,15]
One sequence of 69 microphotographs was found to be sufficient to create a 3D image of the Nostoc sp. colony

Summary

Introduction

In the Polar regions, algae and cyanobacteria are important, if not the only (in cases of specific and very extreme environments), primary producers in hydro-terrestrial and terrestrial ecosystems [1,2,3,4,5]. To survive in harsh polar environments, algae and cyanobacteria developed various mechanisms of adaptation/acclimation [5,6,7]. The consortia may be formed by one species (i.e., colonies, which are sometimes even macroscopic [9,10]), by several species (for example microbial mats [11] or soil crusts [12,13]) or, in the most extreme cases, by strictly symbiotic microorganisms (lichens) [14,15]. The ratio of the consortium components may reflect the species-specific internal structure, e.g., in lichens, or may be influenced by the environment, e.g., the Published by Polish Botanical Society

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Conclusion