Polyphasic approach and adaptative strategies of Nostoc cf. commune (Nostocales, Nostocaceae) growing on Mayan monuments.

Abstract

An aerophytic Nostoc, from a Mayan monument, has been characterized by phenotypic and molecular approaches, and identified as a morphospecies of Nostoc commune. Phylogenetic analysis indicates that it belongs to a Nostoc sensu stricto clade, which contains strains identified as N. commune. Nostoc cf. commune is found in two close areas: Site I (protected from direct sunlight by a wall), where it forms biofilms on mortar with Trentepohlia aurea; and Site II, where it grows on exposed stucco with the accompanying organism Scytonema guyanense. Over the year, in a habitat dictated by alternating wet and dry seasons, the organisms vary in appearance. Its life cycle comprises two seasonally-determined developmental stages (growth during the wet season and dormancy during the dry season) and two transitional stages (preparation for the dry season, and rehydration and recovery). At the beginning of the wet season the resistant stages from the previous dry season are rehydrated and form propagula, that adopt a colonial shape surrounded by a gelatinous sheath. As conditions become drier, clearly more in Site II, N. cf. commune employs adaptative strategies agains the drought, such as reducing the number of cells inside thick ensheathed colonies. Akinetes were observed, although only in Site II and in cultures of an isolated strain. Their fine structure shows parallel arrays of whorled thylakoids and septal intercellular connections. Spectral confocal laser scanning microscopy was used to analyze the fluorescence spectra of the photosynthetic pigments. N. cf. commune shows phycocyanin, allophycocyanin and chlorophyll a in both sites. Moreover, spectra of vegetative ensheathed cells, collected at Site II at the dry season, differed in their fluorescence spectrum: they feature a peak at 564 nm, attributed to phycoerythrin, which increases cell tolerance against the detrimental effects of strong light. These findings indicate that both the distribution and persistence of N. cf. commune might stem from cumulative adaptative strategies that increase its resistance to extreme desiccation.

Fluorescent Fingerprints of Endolithic Phototrophic Cyanobacteria Living within Halite Rocks in the Atacama Desert

“…The bandwidth of these emissions was wider in the green than in the red range. This is because red fluorescence is produced by photosynthetic pigments (mostly Chl a and phycobiliproteins) with defined emission peaks (11,15,17,20). In contrast, GAF may be attributable to fluorescence emitted by different molecules with different widely overlapping emission spectra.…”

“…Besides desiccation, microbial communities inside halite crusts have to deal with conditions of extreme salinity (5,6) and excess light, which have a direct effect on their physiology. In response to varying light conditions, photosynthetic microorganisms undergo structural, behavioral, physiological, and chemical modifications (12,13), such as changing the quality and concentration of their light-harvesting pigments (12,14,15) and pigment degradation (11,16,17). This suggests that the state of photosynthetic pigments can be an indicator of cell viability.…”

The lampenflora in show caves and its treatment: an emerging ecological problem

“…and Nostoc sp. may become desiccated without dying (Alpert, 2006) moisture and surviving in the most extreme habitats for long periods of time (Potts, 2001;Wierzchos et al, 2006;Ramírez et al, 2011).…”

Tolerance of the widespread cyanobacterium Nostoc commune to extreme temperature variations (−269 to 105°C), pH and salt stress

“…Its geographical distribution ranges from polar to tropical regions, and the biomes includes deserts, semi-deserts, dry grasslands and rock surfaces (Marsh et al 2006;Novis et al 2007;Holst et al 2009;Aboal et al 2010;Ramirez et al 2011). N. commune survives extended periods of frost and drought as inactive crusts, but the gelatinous colony rapidly swells and reactivates ion exchange, respiration and photosynthesis when water becomes available (Scherer et al 1984;Satoh et al 2002).…”