Ecophysiological responses of desiccation-tolerant cryptobiotic crusts

Abstract

In our present studies, the recovery of photosynthetic activity after rehydration was demonstrated. We measured chlorophyll fluorescence, CO2 gas exchange and the pigment composition in the previously long-term air-dried cryptogamic inselberg crusts collected from two tropical areas. The cryptobiotic crusts were collected from different localities on similar ecological and climatic conditions from extreme habitats of inselbergs (outcrops). These inselbergs are characterized by a dry microclimate and are covered by scarce soil. We found that the ecophysiological responses of both cryptogamic inselberg crusts showed an extremely high degree of desiccation-tolerance due to the fast and full recovery during rehydration. The photosynthetic activity of the cryptobiotic crusts were restored and regained within 15 and 40 min, respectively, after rehydration. Photosynthetic activity of the crusts was retained at all applied light intensities when enough water was available, however the degree of the recovery was different between the crusts. Photosynthetic pigment contents were strongly and positively correlated with water content. Our results indicated that tropical desiccation-tolerant cryptogamic crusts found on inselberg rock surfaces have CO2 fixation ability in the range of cyanobacteria and lichens, suggesting that at a global scale they can assimilate CO2 in a significant amount.

Rapid Reactivation of Cyanobacterial Photosynthesis and Migration upon Rehydration of Desiccated Marine Microbial Mats

“…As Gray et al (2007) note, these ecosystems are comparable despite facing different meteorological conditions because they are both fundamentally reliant on the adaptations of the desiccated cyanobacteria/algae that allow rapid reactivation of photosynthesis during sporadic water availability. We note that photosynthetic production was measured in various desert crusts within 10–15 min of rehydration by Garcia-Pichel and Belnap (1996) , Péli et al (2011) , Abed et al (2014) , and Lan et al (2014) , which is directly comparable to our observations with desiccated marine microbial mats. However, we also note several dissimilarities between the motility adaptations in desert crust studies and our own.…”

“…The rapidity of the reactivation of photosynthesis is remarkable, but remains poorly understood. Several factors have been tested such as temperature during desiccation or water content of the cells ( Péli et al, 2011 ; Lan et al, 2014 ). It is clear that the time required to reactivate photosynthesis (5–15 min) is not enough for de novo synthesis of required proteins or photopigments ( Harel, 2004 ; Abed et al, 2014 ).…”

Response of Biological Soil Crust Diazotrophs to Season, Altered Summer Precipitation, and Year-Round Increased Temperature in an Arid Grassland of the Colorado Plateau, USA

“…Nostoc and Scytonema spp. are well-known inhabitants of biocrusts worldwide and species from both genera are known to survive under extremes of temperature, desiccation, and UV stress, allowing them to colonize some of the harshest terrestrial environments on Earth (Potts, 2000 ; Péli et al, 2011 ). In biocrusts, Nostoc and Scytonema spp.…”

Estimation of growth and exopolysaccharide production by two soil cyanobacteria, Scytonema tolypothrichoides and Tolypothrix bouteillei as determined by cultivation in irradiance and temperature crossed gradients

“…The irradiance requirements indicate an adaptation to relatively low irradiances, which is typical for shaded localities like soil or lower layers of soil crust . Since an irradiance of 50 μmol m −2 s −1 (∼10.9 W m −2 , recalculated according to Ref.…”

“…The data were normalized to minimum and maximum values at a given temperature or irradiance. The letter indicates the homologous groups recognized by the Tukey HSD test at p = 0.05 like soil [40] or lower layers of soil crust [26,41]. Since an irradiance of 50 mol m −2 s −1 (∼10.9 W m −2 , recalculated according to Ref.…”