Ultrastructure and development of “coccoid cells” ofNostoc commune (Cyanophyta)

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

“…Changes in in morphology, cell structure (Roldán et al 2006), and external sheaths or deposits are coupled to physiological changes. Mass formation of akinetes and subsequent hormogonia development, observed in the cultured sample, occur very rarely in the field, as reported for N. commune (geitleR 1932;Kantz & Bold 1969;aBdelaHad & BazzicHelli 1989). Formation of akinetes is not the only mechanism to ensure persistence of cyanobacterial populations.…”

“…Although Sites I and II are very close (less than 50 m apart), the biofilms at Site I (for example, those with Trentepohlia aurea) are subject to less extreme conditions. Striking changes in the fluorescence properties-and therefore, presumably in the synthesis of PE by vegetative cells, in lightexposed habitats during the dry season -could be an adaptation to high irradiation energies and protection from photodamage of PSII, given that much of the energy absorbed by PE is lost as fluorescence (aRáoz & HädeR 1999;FuKuda et al 2008). Factors that may affect PE production, such as developmental stage-specific changes in pigment composition (millie et al 2002;WolF & scHüssleR 2005), were ruled out upon comparison of vegetative cells and akinetes.…”

“…Adaptation to drying and subsequent recovery of physiological capacities and active growth upon rehydration require protection of cell components and repair processes. Responses to drying and rewetting include: changes in the glycan layer, which protects and provides a repository for water (Hill et al 1997;Potts 2000;tamaRu et al 2005); induction of photoprotective pigments, carotenoids and external ultraviolet light (UV) (gaRcia-PicHel & castenHolz 1991;eHlingscHulz et al 1997); accumulation of non-reducing dissacharides, such as trehalosa, to stabilize drying cells (Billi & Potts 2002;saKamoto et al 2009); preservation of cell fine structure and cellular integrity during desiccation and upon rehydration (Peat & Potts 1987); and deactivation of PSII with diminution of photosynthesis and loss of PSI activity and dissipation of light energy absorbed by pigment-protein complexes (aRáoz & HädeR 1999;satoH et al 2002;HiRai et al 2004;FuKuda et al 2008). As light-harvesting pigments, cyanobacteria contain chlorophyll a, carotenoids and phycobiliproteins: phycoerythrin (PE, λ em ~ 575 nm), phycocyanin (PC, λ em ~ 645 nm) and allophycocyanin (APC, λ em ~ 658 nm) (KeRänen et al 1999, WolF & scHüssleR, 2005.…”

STUDIES ON POLYSACCHARIDES FROM THREE EDIBLE SPECIES OF NOSTOC (CYANOBACTERIA) WITH DIFFERENT COLONY MORPHOLOGIES: COMPARISON OF MONOSACCHARIDE COMPOSITIONS AND VISCOSITIES OF POLYSACCHARIDES FROM FIELD COLONIES AND SUSPENSION CULTURES

“…Some special characteristics in the colony formation and life cycle of Nostoc are well known and are quite different from those of the other cyanobacteria. The morphological aspects concerning the polymorphic life cycle and colony development of Nostoc are well documented (Lazaroff 1973, Abdelahad andBazzichelli 1989), and metabolic differences in strains and life cycle stages leading to different shapes of colonies have been reported (Dodds 1989, Bilger et al 1994. However, there has not been a systematic investigation of the biochemistry of the colony-supporting matrix, i.e.…”