Innovative approaches to accurately assess the effectiveness of biocide-based treatments to fight biodeterioration of Cultural Heritage monuments.

The development of diagnostic methods to accurately assess the effects of treatments on lithobiont colonization remains a challenge for the conservation of Cultural Heritage monuments. In this study, we tested the efficacy of biocide-based treatments on microbial colonization of a dolostone quarry, in the short and long-term, using a dual analytical strategy. We applied a metabarcoding approach to characterize fungal and bacterial communities over time, integrated with microscopy techniques to analyze the interactions of microorganisms with the substrate and evaluate the effectiveness.

Dark microbiome and extremely low organics in Atacama fossil delta unveil Mars life detection limits.

Identifying unequivocal signs of life on Mars is one of the most important objectives for sending missions to the red planet. Here we report Red Stone, a 163-100 My alluvial fan-fan delta that formed under arid conditions in the Atacama Desert, rich in hematite and mudstones containing clays such as vermiculite and smectites, and therefore geologically analogous to Mars. We show that Red Stone samples display an important number of microorganisms with an unusual high rate of phylogenetic indeterminacy, what we refer to as "dark microbiome", and a mix of biosignatures from extant and ancient microorganisms that can be barely detected with state-of-the-art laboratory equipment.

Response of Endolithic Strains From the Polyextreme Atacama Desert to Light Radiation.

Cyanobacteria exposed to high solar radiation make use of a series of defense mechanisms, including avoidance, antioxidant systems, and the production of photoprotective compounds such as scytonemin. Two cyanobacterial strains of the genus from the Atacama Desert - which has one of the highest solar radiation levels on Earth- were examined to determine their capacity to protect themselves from direct photosynthetically active (PAR) and ultraviolet radiation (UVR): the UAM813 strain, originally isolated from a cryptoendolithic microhabitat within halite (NaCl), and UAM816 strain originally isolated from a chasmoendolithic microhabitat within calcite (CaCO). The oxidative stress induced by exposure to PAR or UVR + PAR was determined to observe their short-term response, as were the long-term scytonemin production, changes in metabolic activity and ultrastructural damage induced.

Raman imaging of microbial colonization in rock-some analytical aspects.

Raman imaging allows one to obtain spatially resolved chemical information in a nondestructive manner. Herein, we present analytical aspects of effective in situ and in vivo Raman imaging of algae and cyanobacteria from within their native rock habitats. Specifically, gypsum and halite inhabited by endolithic communities from the hyperarid Atacama Desert were analyzed.

sp. Strain SGH1, a Bacterioruberin-Rich, Perchlorate-Tolerant Halophilic Archaeon Isolated From Halite Microbial Communities, Atacama Desert, Chile.

An extreme halophilic archaeon, strain SGH1, is a novel microorganism isolated from endolithic microbial communities colonizing halites at Salar Grande, Atacama Desert, in northern Chile. Our study provides structural, biochemical, genomic, and physiological information on this new isolate living at the edge of the physical and chemical extremes at the Atacama Desert. SGH1 is a Gram-negative, red-pigmented, non-motile unicellular coccoid organism.

Ultrastructural and biochemical analyses reveal cell wall remodelling in lichen-forming microalgae submitted to cyclic desiccation-rehydration.

Background And Aims: One of the most distinctive features of desiccation-tolerant plants is their high cell wall (CW) flexibility. Most lichen microalgae can tolerate drastic dehydration-rehydration (D/R) conditions; however, their mechanisms of D/R tolerance are scarcely understood. We tested the hypothesis that D/R-tolerant microalgae would have flexible CWs due to species-specific CW ultrastructure and biochemical composition, which could be remodelled by exposure to cyclic D/R.

Fundamental drivers for endolithic microbial community assemblies in the hyperarid Atacama Desert.

In hyperarid deserts, endolithic microbial communities colonize the rocks' interior as a survival strategy. Yet, the composition of these communities and the drivers promoting their assembly are still poorly understood. We analysed the diversity and community composition of endoliths from four different lithic substrates - calcite, gypsum, ignimbrite and granite - collected in the hyperarid zone of the Atacama Desert, Chile.

Endolithic microbial habitats as refuges for life in polyextreme environment of the Atacama Desert.

The extremely harsh conditions of hyperarid deserts are a true challenge for microbial life. Microorganisms thriving in such polyextreme environments are fascinating as they can tell us more about life, its strategies and its boundaries than other groups of organisms. The Atacama Desert (North Chile) holds two world records of extreme environmental characteristics: the lowest rainfall and greatest surface ultraviolet radiation and total solar irradiance ever measured on Earth.

Discovery of carotenoid red-shift in endolithic cyanobacteria from the Atacama Desert.

The biochemical responses of rock-inhabiting cyanobacteria towards native environmental stresses were observed in vivo in one of the Earth's most challenging extreme climatic environments. The cryptoendolithic cyanobacterial colonization, dominated by Chroococcidiopsis sp., was studied in an ignimbrite at a high altitude volcanic area in the Atacama Desert, Chile.

Structure and temporal dynamics of the bacterial communities associated to microhabitats of the coral Oculina patagonica.

Corals are known to contain a diverse microbiota that plays a paramount role in the physiology and health of holobiont. However, few studies have addressed the variability of bacterial communities within the coral host. In this study, bacterial community composition from the mucus, tissue and skeleton of the scleractinian coral Oculina patagonica were investigated seasonally at two locations in the Western Mediterranean Sea, to further understand how environmental conditions and the coral microbiome structure are related.

Raman imaging in geomicrobiology: endolithic phototrophic microorganisms in gypsum from the extreme sun irradiation area in the Atacama Desert.

The Raman imaging method was successfully applied for mapping the distribution of biomolecules (e.g., pigments) associated with cryptoendolithic and hypoendolithic microorganisms, as well as the inorganic host mineral matrix that forms the habitat for the biota.

Phylogenetic and Functional Substrate Specificity for Endolithic Microbial Communities in Hyper-Arid Environments.

Under extreme water deficit, endolithic (inside rock) microbial ecosystems are considered environmental refuges for life in cold and hot deserts, yet their diversity and functional adaptations remain vastly unexplored. The metagenomic analyses of the communities from two rock substrates, calcite and ignimbrite, revealed that they were dominated by Cyanobacteria, Actinobacteria, and Chloroflexi. The relative distribution of major phyla was significantly different between the two substrates and biodiversity estimates, from 16S rRNA gene sequences and from the metagenomic data, all pointed to a higher taxonomic diversity in the calcite community.

In situ metabolism in halite endolithic microbial communities of the hyperarid Atacama Desert.

The Atacama Desert of northern Chile is one of the driest regions on Earth, with areas that exclude plants and where soils have extremely low microbial biomass. However, in the driest parts of the desert there are microorganisms that colonize the interior of halite nodules in fossil continental evaporites, where they are sustained by condensation of atmospheric water triggered by the salt substrate. Using a combination of in situ observations of variable chlorophyll fluorescence and controlled laboratory experiments, we show that this endolithic community is capable of carbon fixation both through oxygenic photosynthesis and potentially ammonia oxidation.

Adaptation strategies of endolithic chlorophototrophs to survive the hyperarid and extreme solar radiation environment of the Atacama Desert.

The Atacama Desert, northern Chile, is one of the driest deserts on Earth and, as such, a natural laboratory to explore the limits of life and the strategies evolved by microorganisms to adapt to extreme environments. Here we report the exceptional adaptation strategies of chlorophototrophic and eukaryotic algae, and chlorophototrophic and prokaryotic cyanobacteria to the hyperarid and extremely high solar radiation conditions occurring in this desert. Our approach combined several microscopy techniques, spectroscopic analytical methods, and molecular analyses.

Ignimbrite textural properties as determinants of endolithic colonization patterns from hyper-arid Atacama Desert.

This study explores the photosynthetic microbial colonization of rhyolitic ignimbrites in Lomas de Tilocalar, a hyper-arid region of the Atacama Desert, Chile. Colonization appeared in the form of a green layer a few millimeters beneath the ignimbrite surface. Some ignimbrite rocks revealed two distinct micromorphological areas of identical mineralogical and chemical composition but different textural properties.

Distribution of scytonemin in endolithic microbial communities from halite crusts in the hyperarid zone of the Atacama Desert, Chile.

Scytonemin, a UV-screening molecule produced by certain Cyanobacteria to protect against harmful UV radiation, was studied in endolithic cyanobacterial colonies in the halite crust from one of the driest places on Earth - the hyperarid zone of the Atacama Desert. The distribution of the pigment within the evaporitic crust was studied in detail by various independent analytical methods: Raman spectroscopy (including Raman imaging); advanced microscopic observations (fluorescence microscopy, confocal laser scanning microscopy, low-temperature scanning electron microscopy); and spectrophotometric analyses. The differences in scytonemin biosynthesis were mapped within the colonized interior layers, which can be divided into scytonemin-rich and scytonemin-poor zones.

Eukarya associated with the stony coral Oculina patagonica from the Mediterranean Sea.

Oculina patagonica is a putative alien scleractinian coral from the Southwest Atlantic that inhabits across the Mediterranean Sea. Here, we have addressed the diversity of Eukarya associated with this coral and its changes related to the environmental conditions and coral status. A total of 46 colonies of O.

Microbial diversity and the presence of algae in halite endolithic communities are correlated to atmospheric moisture in the hyper-arid zone of the Atacama Desert.

The Atacama Desert is one of the oldest and driest deserts in the world, and its hyper-arid core is described as 'the most barren region imaginable'. We used a combination of high-throughput sequencing and microscopy methods to characterize the endolithic microbial assemblages of halite pinnacles (salt rocks) collected in several hyper-arid areas of the desert. We found communities dominated by archaea that relied on a single phylotype of Halothece cyanobacteria for primary production.

Salt deliquescence drives photosynthesis in the hyperarid Atacama Desert.

Endolithic cyanobacteria are found in halite nodules in the hyperarid core of the Atacama Desert. Using Pulse Amplitude Modulated Fluorometry, we show here that photosynthetic systems of these cyanobacteria become active when the relative humidity rises above 70% and the salt becomes wet by way of deliquescence. This is the first evidence of active metabolism in the hyperarid core of the Atacama, and supports the view of a microbial community sustained by deliquescence.

Microorganisms in desert rocks: the edge of life on Earth.

This article reviews current knowledge on microbial communities inhabiting endolithic habitats in the arid and hyper-arid regions of our planet. In these extremely dry environments, the most common survival strategy is to colonize the interiors of rocks. This habitat provides thermal buffering, physical stability, and protection against incident UV radiation, excessive photosynthetically active radiation, and freeze-thaw events.

Tannic acid-dependent modulation of selected Lactobacillus plantarum traits linked to gastrointestinal survival.

Background: Owing to its antimicrobial properties dietary tannins may alter the functional efficacy of probiotic lactobacilli in the gastrointestinal (GI)-tract influencing their growth, viability and molecular adaptation to the intestinal environment.

Methods And Findings: The effects of tannic acid on Lactobacillus plantarum WCFS1 were studied by in vitro growth monitoring and visualizing the morphological alteration on the cell wall using transmission electron microscopy. Growth upon tannic acid was characterized by dose-dependent reductions of initial viable counts and extended lag phases.

Early evolution and ecology of camouflage in insects.

Taxa within diverse lineages select and transport exogenous materials for the purposes of camouflage. This adaptive behavior also occurs in insects, most famously in green lacewing larvae who nestle the trash among setigerous cuticular processes, known as trash-carrying, rendering them nearly undetectable to predators and prey, as well as forming a defensive shield. We report an exceptional discovery of a green lacewing larva in Early Cretaceous amber from Spain with specialized cuticular processes forming a dorsal basket that carry a dense trash packet.