Cyanobacteria biomasses are sources of secondary metabolites and nutritious ingredients such as vitamins, essential amino acids, and unsaturated fatty acids. Biochemical composition, presence of cyanotoxins and contaminants are major concerns to be addressed on such edible biomasses. Macrocolonies of a filamentous diazotrophic Nostoc species known as Llayta are found at Andean wetlands and consumed since pre-Columbian times in South America. Its biochemical composition has been previously conducted to assess their nutritious quality and cyanotoxicity. Macrocolonies of filamentous cyanobacteria are niches for colonization by diverse microorganisms; however, the Llayta microcolonies cyanosphere is unknown. Based on a culture-independent approach, we report the identification of members of the resilient microflora associated with Llayta trichomes after Gentamicin treatments. We have also reconstructed the genomes of the Llayta macrocolony-forming Nostoc sp. cyanobacterium (6,781,030 bp; GC content of 41.2%) and the genomes of five dominant bacteria genera (Mesorhizobium, Microvirga, Paracoccus, Aquimonas, and Blastomonas). The detection of genes and genes clusters involved in primary and secondary metabolism is described. Our results provide new insights on the metabolic capabilities and biotechnological potential of the Andean Nostoc cyanobacterium, and the ecological role and adaptive strategies of microorganisms living under extreme environmental conditions at the Andean wetlands.

Llayta is a dietary supplement used by rural communities in Perú and northern Chile since pre-Columbian days. Llayta is the biomass of colonies of a Nostoc cyanobacterium grown in wetlands of the Andean highlands, harvested, sun-dried and sold as an ingredient for human consumption. The biomass has a substantial content of essential amino acids (58% of total amino acids) and polyunsaturated fatty acids (33% total fatty acids). This ancestral practice is being loss and the causes were investigated by an ethnographic approach to register the social representations of Llayta, to document how this Andean feeding practice is perceived and how much the community knows about Llayta. Only 37% of the participants (mostly adults) have had a direct experience with Llayta; other participants (mostly children) did not have any knowledge about it. These social responses reflect anthropological and cultural tensions associated to lack of knowledge on Andean algae, sites where to find Llayta, where it is commercialized, how it is cooked and on its nutritional benefits. The loss of this ancestral feeding practice, mostly on northern Chile, is probably associated to cultural changes, migration of the rural communities, and a very limited access to the available information. We propose that Llayta consumption can be revitalized by developing appropriate educational strategies and investigating potential new food derivatives based on the biomass from the isolated Llayta cyanobacterium.

Azolla is the only plant with a co-evolving nitrogen-fixing (diazotrophic) cyanobacterial symbiont (cyanobiont), Nostoc azollae, resulting from Whole Genome Duplication (WGD) 80 million years ago in Azolla’s ancestor. Additional genes from the WGD resulted in genetic, biochemical and morphological changes in the plant that enabled transmission of the cyanobiont to successive generations via its megaspores. The resulting permanent symbiosis and co-evolution led to loss, downregulation or conversion of non-essential genes to pseudogenes in the cyanobiont, changing it from a free-living organism to an obligate symbiont. Upregulation of other genes in the cyanobiont increased its atmospheric dinitrogen fixation and provision of nitrogen-based products to the plant. As a result, Azolla can double its biomass in less than two days free-floating on fresh water and sequester large amounts of atmospheric CO2, giving it the potential to mitigate anthropogenic climate change through Carbon Capture and Storage. Azolla’s biomass can also provide local, low-cost food, biofertiliser, feed and biofuel that are urgently needed as our population increases by a billion every twelve years. This paper integrates data from biology, genetics, geology and paleontology to identify the location, timing and mechanism for the acquisition of a co-evolving diazotrophic cyanobiont by Azolla’s ancestor in the Late Cretaceous (Campanian) of North America.