Clear differences in metabolic and morphological adaptations of akinetes of two Nostocales living in different habitats

Abstract

2 FIBA-INBIOTEC, Vieytes 3103, Mar del Plata, Buenos Aires, ArgentinaAkinetes are resting spore-like cells formed by some heterocyst-forming filamentous cyanobacteria for surviving long periods of unfavourable conditions. We studied the development of akinetes in two model strains of cyanobacterial cell differentiation, the planktonic freshwater Anabaena variabilis ATCC 29413 and the terrestrial or symbiotic Nostoc punctiforme ATCC 29133, in response to low light and phosphate starvation. The best trigger of akinete differentiation of Anabaena variabilis was low light; that of N. punctiforme was phosphate starvation. Light and electron microscopy revealed that akinetes of both species differed from vegetative cells by their larger size, different cell morphology and large number of intracellular granules. Anabaena variabilis akinetes had a multilayer envelope; those of N. punctiforme had a simpler envelope. During akinete development of Anabaena variabilis, the amount of the storage compounds cyanophycin and glycogen increased transiently, whereas in N. punctiforme, cyanophycin and lipid droplets increased transiently. Photosynthesis and respiration decreased during akinete differentiation in both species, and remained at a low level in mature akinetes. The clear differences in the metabolic and morphological adaptations of akinetes of the two species could be related to their different lifestyles. The results pave the way for genetic and functional studies of akinete differentiation in these species.

Interaction of the Nitrogen Regulatory Protein GlnB (PII) with Biotin Carboxyl Carrier Protein (BCCP) Controls Acetyl-CoA Levels in the Cyanobacterium Synechocystis sp. PCC 6803

“…Even though lipid bodies have been previously described in Synechocystis using electron microscopy, they were suggested to play a role in thylakoid maintenance (van de Meene et al, 2006). Within the last decade lipid droplets have emerged as intracellular inclusions also present in heterotrophic bacteria (Kalscheuer et al, 2001; Yang et al, 2012) or the filamentous cyanobacterium Nostoc punctiforme (Peramuna and Summers, 2014; Perez et al, 2016), where they contain triacylglycerides, α-tocopherol and alkanes (Peramuna and Summers, 2014). Isolated lipids of Synechocystis migrated on TLC similar to sesame oil and a triacylglycerol mixture and GC/MS analysis revealed that they primarily contained C16 and C18 saturated fatty acids with traces of pentadecanoic and heptadecanoic acid as has been observed in exponentially grown N. punctiforme (Peramuna and Summers, 2014).…”

Hopanoids play a role in stress tolerance and nutrient storage in the cyanobacterium Nostoc punctiforme

“…Cyanophycin is a poly amino acid used to store carbon and nitrogen. It occurs in these large refractile granules, in contrast to very small glycogen granules that are below the resolution of light microscopy and only store carbon (Perez et al, 2016). This suggests that hopanoids and 2-methylhopanoids may impact nitrogen storage and thus may facilitate physiological response to environmental nutrient stress.…”

Glycolipid composition of the heterocyst envelope of Anabaena sp. PCC 7120 is crucial for diazotrophic growth and relies on the UDP-galactose 4-epimerase HgdA

“…We analyzed the heterocyst envelope in more detail. We were able to detect both cell layers of the mutant heterocysts with standard labeling methods and light microscopy (41, 42), and the heterocysts appeared normal at this resolution (Fig. 3D).…”

“…Cells were stained with BODIPY (boron dipyrromethene difluoride 493/503, Molecular Probes) following the protocol described by Perez et al (41). Briefly, 1 mL of Anabaena sp.…”