Surfaces of buildings at the archaeological site of Palenque, Mexico, are colonized by cyanobacteria that form biofilms, which in turn cause aesthetic and structural damage. The structural characterization and species composition of biofilms from the walls of one of these buildings, El Palacio, are reported. The distribution of photosynthetic microorganisms in the biofilms, their relationship with the colonized substratum, and the three-dimensional structure of the biofilms were studied by image analysis. The differences between local seasonal microenvironments at the Palenque site, the bioreceptivity of stone and the relationship between biofilms and their substrata are described. The implications for the development and permanence of species capable of withstanding temporal heterogeneity in and on El Palacio, mainly due to alternating wet and dry seasons, are discussed. Knowledge on how different biofilms contribute to biodegradation or bioprotection of the substratum can be used to develop maintenance and conservation protocols for cultural heritage.

Somatic embryogenesis (SE) is a valuable model for understanding the mechanism of plant embryogenesis and a tool for the mass production of plants. However, establishing SE in avocado has been complicated due to the very low efficiency of embryo induction and plant regeneration. To understand the molecular foundation of the SE induction and development in avocado, we compared embryogenic (EC) and non-embryogenic (NEC) cultures of two avocado varieties using proteomic and metabolomic approaches. Although Criollo and Hass EC exhibited similarities in the proteome and metabolome profile, in general, we observed a more active phenylpropanoid pathway in EC than NEC. This pathway is associated with the tolerance of stress responses, probably through the reinforcement of the cell wall and flavonoid production. We could corroborate that particular polyphenolics compounds, including p-coumaric acid and t-ferulic acid, stimulated the production of somatic embryos in avocado. Exogen phenolic compounds were associated with the modification of the content of endogenous polyphenolic and the induction of the production of the putative auxin-a, adenosine, cellulose and 1,26-hexacosanediol-diferulate. We suggest that in EC of avocado, there is an enhanced phenylpropanoid metabolism for the production of the building blocks of lignin and flavonoid compounds having a role in cell wall reinforcement for tolerating stress response. Data are available at ProteomeXchange with the identifier PXD019705.

An aerophytic Nostoc, from a Mayan monument, has been characterized by phenotypic and molecular approaches, and identified as a morphospecies of Nostoc commune. Phylogenetic analysis indicates that it belongs to a Nostoc sensu stricto clade, w...

This work characterizes a unicellular cyanobacterium with nearly spherical cells and thin-outlined sheaths that divide irregularly, forming small packets immersed in a diffluent mucilaginous layer. It was isolated growing on calcite speleothems and walls in a show cave in Collbató (Barcelona, Spain). Spectral confocal laser and transmission electron microscopy were used to describe the morphology, fine structure and thylakoid arrangement. The pigments identified were phycoerythrin, phycocyanin, allophycocyanin and chlorophyll a. Three-dimensional reconstructions, generated from natural fluorescence z-stacks, revealed a large surface area of nearly flat, arm-like thylakoidal membranes connected to each other and forming a unified structure in a way that, to our knowledge, has never been described before. Phylogenetic analyses using the 16S rRNA gene sequence showed 95 % similarity to strain Chroococcus sp. JJCM (GenBank accession no. AM710384). The diacritical phenotypic features do not correspond to any species currently described, and the genetic traits support the strain being classified as the first member of an independent genus in the order Chroococcales and the family Chroococcaceae. Hence, we propose the name Chalicogloea cavernicola gen. nov., sp. nov. under the provisions of the International Code of Nomenclature for Algae, Fungi and Plants. The type strain of Chalicogloea cavernicola is COLL 3^T ( = CCALA 975^T = CCAP 1424/1^T).