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Cueva del Viento, located in the Canary Islands, Spain, is the Earth's sixth-longest lava tube, spanning 18,500 m, and was formed approximately 27,000 years ago. This complex volcanic cave system is characterized by a unique geomorphology, featuring an intricate network of galleries. Despite its geological significance, the geomicrobiology of Cueva del Viento remains largely unexplored. This study employed a combination of culture-dependent techniques and metabarcoding data analysis to gain a comprehensive understanding of the cave's microbial diversity. The 16S rRNA gene metabarcoding approach revealed that the coloured microbial mats (yellow, red and white) coating the cave walls are dominated by the phyla Actinomycetota, Pseudomonadota and Acidobacteriota. Of particular interest is the high relative abundance of the genus Crossiella, which is involved in urease-mediated biomineralization processes, along with the presence of genera associated with nitrogen cycling, such as Nitrospira. Culture-dependent techniques provided insights into the morphological characteristics of the isolated species and their potential metabolic activities, particularly for the strains Streptomyces spp., Paenarthrobacter sp. and Pseudomonas spp. Our findings underscore the potential of Cueva del Viento as an ideal environment for studying microbial diversity and for the isolation and characterization of novel bacterial species of biotechnological interest.

Olive cultivation is a crucial driver of the economy in the European Mediterranean basin, particularly in Spain, where it occupies about 2.75 million ha [1]. In recent years, there has been an expansion of super-intensive olive farming, which ensures high productivity but requires irrigation and is expected to increase organic waste generation and water demand. Consequently, it is imperative to adopt more sustainable approaches to manage the agricultural waste generated during olive harvesting and agro-industrial processing. To tackle that challenge, there is a renewed emphasis on utilizing organic amendments derived from agricultural residues. Biochar (B), a highly aromatic carbon obtained through biomass pyrolysis, has the potential to sequester carbon in the soil for extended periods and its unique physical properties increase soil porosity [2]. Nevertheless, B effects on SOM composition and functionality in the medium and long term are largely unknown. Additionally, green compost (Cp) is rich in nutrients and labile organic carbon, making it a valuable soil amendment for improving soil fertility, structure, and moisture retention. The two main goals of this study are: i) To discern the effects of transforming traditional olive orchards into bushrow olive cultivation on soil organic matter (SOM) composition, which plays an essential role in the carbon cycle and on soil quality, and ii) To assess the effects of of B and Cp on SOM composition two years after application. With such purposes, soil samples were taken from super-intensive olive orchards (1650 trees/ha; irrigated 30% water needs) amended with (B), green compost (Cp), a combination of B+Cp, as well as control plots [3]. Soil samples were also collected from traditional olive orchards in the same farm (La Hampa, Coria del Río) for comparative purposes. The free lipid fraction and volatile SOM were studied by using GC/MS and analytical pyrolysis (Py-GC/MS) respectively. Control soils, particularly those fr

Life in arid regions and, in particular, hot deserts is often limited due to their harsh environmental conditions, such as large temperature fluctuations and low amounts of water. These extreme environments can influence the microbial community present on the surface sands and any rhizosphere members surrounding desert plant roots. The Jizan desert area, located in Saudi Arabia, supports particular vegetation that grows in the large sandy flat terrain. We examined five different samples, four from the rhizosphere of pioneer plants plus a surface sand sample, and used pyrosequencing of PCR-amplified V1-V3 regions of 16S rDNA genes from total extracted DNA to reveal and compare the bacterial population diversity of the samples. The results showed a total of 3,530 OTUs in the five samples, calculated using ≥ 97% sequence similarity levels. The Chao1 estimation of the bacterial diversity fluctuated from 637 to 2,026 OTUs for a given sample. The most abundant members found in the samples belong to the Bacteroidetes, Firmicutes and Proteobacteria phyla. This work shows that the Jizan desert area of Saudi Arabia can contain a diverse bacterial community on the sand and surrounding the roots of pioneer desert plants. It also shows that desert sand microbiomes can vary depending on conditions, with broad implications for sandstone monument bacterial communities