The response of carbohydrate metabolism to the fluctuation of relative humidity (RH) in the desert soil cyanobacterium Phormidium tenue

Niche partitioning of bacterial communities in biological crusts and soils under grasses, shrubs and trees in the Kalahari

“…Candidates for a BSC inoculum in the Kalahari rangelands could be identified for testing based upon our data, which is ideal for this purpose because early stage BSCs are likely to still contain in large number the pioneer species which helped them to become established. The Phormidium genus of Cyanobacteria (P. tenue specifically) has been shown by Chen et al (2012) to possess excellent qualities for the stabilisation of sand, and its abundance in our study suggests that deliberate establishment on degraded land in the Kalahari could be feasible. A suitable inoculum to help the establishment of Cyanobacteria in general might include oligotrophic organisms such as Balneomonas species which are able to utilise recalcitrant carbon and quickly stabilise the soil by release of EPS, including beneath the photic zone.…”

“…widespread filamentous Cyanobacteria which are found commonly in hot and cold arid soils but are also found in aquatic habitats including ultra-oligotrophic Antarctic seasonal lakes (Keskitalo et al 2013), demonstrating a great plasticity for the contrasting environmental conditions of relevance to the Kalahari Sand soil surface. Chen et al (2012) found P. tenue to be potentially useful for the stabilisation of sand dunes by inoculation due to the desiccation tolerance afforded by its extracellular polysaccharide (EPS). The EPS of P. tenue has also been shown to promote the germination of seeds and the fitness of seedlings (Xu et al 2013), which may have been related to numerous mechanisms including water retention, provision of nutrients, and protection from oxidative stress.…”

Hydrolase enzyme activities in a successional gradient of biological soil crusts in arid and semi-arid zones

“…The production of invertase implies that the environment surrounding the individuals that form the BSCs contains sucrose, which obviously must have been produced intracellularly by the autotrophic cyanobacteria and excreted to the exterior. The production and excretion of different types of polysaccharides represents, amongst other functions, a protective mechanism for the cyanobacteria against the drying generated by changes in the relative humidity of the air (Mager and Thomas, 2011;Chen et al, 2012), so that the presence of sucrose in these BSCs is perhaps not surprising, although the only sugars identified so far in BSCs dominated by cyanobacteria are monosaccharides such as glucose and galactose (Brüll et al, 2000). However, excretion of sucrose would not make sense as a protective measure against the adverse environmental conditions, as high quantities of the enzyme that hydrolyzes sucrose are being synthesized at the same time.…”

Effect of nitrogen starvation on desiccation tolerance of Arctic Microcoleus strains (cyanobacteria)

“…Numerous studies have uncovered that cyanobacteria cope with desiccation stress through a complex of physiological, biochemical, structural, and morphological adaptations. Mechanisms contributing to this include: modifying the structure and composition of cell envelopes ( Caiola et al, 1996 ), decreased respiration ( Potts, 1994 ), down-regulation of photosynthesis ( Harel et al, 2004 ), producing enzymes eliminating reactive oxygen species ( Chen et al, 2012 ), accumulating sugars which stabilize the lipid membranes ( Hershkovitz et al, 1991 ; Sakamoto et al, 2009 ; Klähn and Hagemann, 2011 ), secreting extracellular polysaccharides that serve as a physical barrier during desiccation that absorb and retain moisture ( Hill et al, 1997 ; Tamaru and Takani, 2005 ), synthesizing UV-absorbing and sun-screening pigments ( Roos and Vincent, 1998 ; Potts, 1999 ; Gao and Ye, 2007 ), and the presence of multiple copies of the genome together with an efficient DNA reparation system ( Ehling-Schulz and Scherer, 1999 ; Potts, 1999 ).…”

“…The closely related genera Phormidium and Microcoleus (Oscillatoriales) are among the most frequently recorded cyanobacterial genera in hot and cold deserts worldwide ( Vincent, 2000 ; Wynn-Williams, 2000 ), and have often been mentioned as desiccation tolerant organisms ( Davey, 1989 ; Hershkovitz et al, 1991 ; Hawes et al, 1992 ; Harel et al, 2004 ; Šabacká and Elster, 2006 ; Chen et al, 2012 ; Olsson-Francis et al, 2013 ). The taxonomy of Oscillatoriales has been recently revised to include some Phormidium species within the Microcoleus genus ( Strunecký et al, 2013 ).…”