Monike Oggerin

Specific jarosite biomineralization by Purpureocillium lilacinum, an acidophilic fungi isolated from Río Tinto

Río Tinto (Huelva, southwestern Spain) is an extreme environment with a remarkably constant acidic pH and a high concentration of heavy metals, conditions generated by the metabolic activity of chemolithotrophic microorganisms thriving in the rich complex sulfides of the Iberian Pyrite Belt (IPB). Fungal strains isolated from the Tinto basin were characterized morphologically and phylogenetically. The strain identified as Purpureocillium lilacinum specifically induced the formation of a yellow-ocher precipitate, identified as hydronium-jarosite, an iron sulfate mineral which appears in abundance on the banks of Río Tinto. The biomineral was characterized by X-ray diffraction (XRD) and its formation was observed with high-resolution transmission electron microscopy (TEM) and scanning electron microscopy (SEM) coupled to energy-dispersive X-ray spectroscopy (EDX) microanalysis. Jarosite began to nucleate on the fungal cell wall, associated to the EPS, due to a local increase in the Fe(3+) /Fe(2+) ratio which generated supersaturation. Its formation has been also observed in non-viable cells, although with much less efficiency. The occurrence of P. lilacinum in an ecosystem with high concentrations of ferric iron and sulfates such as Río Tinto suggests that it could participate in the process of jarosite precipitation, helping to shape and control the geochemical properties of this environment.

A micromorphological and phylogenetic study of Sarcocornia (Chenopodiaceae) of the Iberian Peninsula

This study presents a comprehensive revision of the genus Sarcocornia (Chenopodiaceae) on the Iberian Peninsula based on macromorphological, micromorphological and phylogenetic data, and considering caryological, ecological and biogeographical information. Three species of Sarcocornia have been identified on the Iberian Peninsula: Sarcocornia perennis (Miller) A.J. Scott, Sarcocornia fruticosa (L.) A.J. Scott and Sarcocornia alpini (Lag.) Rivas-Martínez. Several authors have proposed that S. alpini is a specific and subspecific rank of S. perennis. Fuente, Rufo and Sánchez-Mata have recently described a new species, Sarcocornia hispanica. The micromorphological and molecular studies (sequence of the internal transcribed spacer region) indicate that there is a broad diversity within Sarcocornia in the Western Mediterranean. This article proposes a new species (Sarcocornia pruinosa) and subspecies (S. alpini subsp. carinata) in view of the new data.

Identification of Beijerinckia fluminensis strains CIP 106281T and UQM 1685T as Rhizobium radiobacter strains, and proposal of Beijerinckia doebereinerae sp. nov. to accommodate Beijerinckia fluminensis LMG 2819

During the course of a research project with free-living, nitrogen-fixing bacteria, we determined the 16S rRNA gene sequence of Beijerinckia fluminensis strains UQM 1685T and CIP 106281T and discovered that they were only 90.6-91.2% similar to the sequences of strains of other Beijerinckia species and subspecies. Moreover, the highest similarity to these sequences (99.7%) corresponded to strains of Rhizobium radiobacter (including Agrobacterium tumefaciens). Other diagnostic features confirmed that the two strains have the same origin but do not descend from the nomenclatural type. At the same time, B. fluminensis LMG 2819 was characterized and it was found that its properties also do not agree with the original description of the species, although it can be considered a member of the genus. Further characterization, including chemotaxonomic and other phenotypic traits, allows us to propose (i) the identification of B. fluminensis strains CIP 106281T and UQM 1685T as strains of Rhizobium radiobacter and (ii) the designation of strain LMG 2819T (=CECT 7311T) as the type strain of a novel species, Beijerinckia doebereinerae sp. nov.

Active microbial biofilms in deep poor porous continental subsurface rocks

Deep continental subsurface is defined as oligotrophic environments where microorganisms present a very low metabolic rate. To date, due to the energetic cost of production and maintenance of biofilms, their existence has not been considered in poor porous subsurface rocks. We applied fluorescence in situ hybridization techniques and confocal laser scanning microscopy in samples from a continental deep drilling project to analyze the prokaryotic diversity and distribution and the possible existence of biofilms. Our results show the existence of natural microbial biofilms at all checked depths of the Iberian Pyrite Belt (IPB) subsurface and the co-occurrence of bacteria and archaea in this environment. This observation suggests that multi-species biofilms may be a common and widespread lifestyle in subsurface environments.

Viable cyanobacteria in the deep continental subsurface

Significance Cyanobacteria were responsible for the origin of oxygenic photosynthesis, and have since come to colonize almost every environment on Earth. Here we show that their ecological range is not limited by the presence of sunlight, but also extends down to the deep terrestrial biosphere. We report the presence of microbial communities dominated by cyanobacteria in the continental subsurface using microscopy, metagenomics, and antibody microarrays. These cyanobacteria were related to surface rock-dwelling lineages known for their high tolerance to environmental and nutritional stress. We discuss how these adaptations allow cyanobacteria to thrive in the dark underground, a lifestyle that might trace back to their nonphotosynthetic ancestors. Cyanobacteria are ecologically versatile microorganisms inhabiting most environments, ranging from marine systems to arid deserts. Although they possess several pathways for light-independent energy generation, until now their ecological range appeared to be restricted to environments with at least occasional exposure to sunlight. Here we present molecular, microscopic, and metagenomic evidence that cyanobacteria predominate in deep subsurface rock samples from the Iberian Pyrite Belt Mars analog (southwestern Spain). Metagenomics showed the potential for a hydrogen-based lithoautotrophic cyanobacterial metabolism. Collectively, our results suggest that they may play an important role as primary producers within the deep-Earth biosphere. Our description of this previously unknown ecological niche for cyanobacteria paves the way for models on their origin and evolution, as well as on their potential presence in current or primitive biospheres in other planetary bodies, and on the extant, primitive, and putative extraterrestrial biospheres.

Fungal Mineralization Processes in Rio Tinto

Eukaryotic diversity in Río Tinto turns out to be unexpectedly high when compared to the prokaryotic one. Unlike the prokaryotic community, little is known about the role of the most abundant eukaryotes, mainly algae and fungi, in this ecosystem. Previous studies using acidophilic fungi isolated from the Tinto basin have shown their ability to specifically sequester toxic metals. We have also been able to demonstrate their direct implication in the geochemical cycles through biomineralization processes. Although the role that fungi may play in the Tinto basin is still poorly understood, is becoming clear that they participate very actively in the geological conformation of the environment, generating minerals of possible economical interest.