https://hdl.handle.net/10481/23714 2026-04-13T20:53:21Z 2026-04-13T20:53:21Z Pérez Mendoza, Daniel Schmid, Jochen Döring, Manuel Rühmann, Broder Rodríguez Carvajal, Miguel Ángel Bermudo Molina, Manuel Sieber, Volker Sanjuan, Juan https://hdl.handle.net/10481/112273 2026-03-19T08:51:30Z

Bioprospecting c-di-GMP-activated exopolysaccharides in bacteria: isolation of a novel atypical sphingan Pérez Mendoza, Daniel; Schmid, Jochen; Döring, Manuel; Rühmann, Broder; Rodríguez Carvajal, Miguel Ángel; Bermudo Molina, Manuel; Sieber, Volker; Sanjuan, Juan The genetic and physiological diversity of bacteria are critical resources for discovering new exopolysaccharides (EPS) as raw materials with biotechnological applications. However, uncovering new EPS is limited by their lack of production in laboratory cultures, as EPS are often cryptic, and their biosynthesis only proceeds upon unknown environmental cues. The dinucleotide cyclic diguanosine monophosphate (c-di-GMP) has emerged as a universal second messenger in bacteria and a common activator of many EPS. Here, a pleD* transformation to elevate intracellular c-di-GMP levels and a carbohydrate fingerprinting analysis were combined for high-throughput screening of 330 bacterial strains (~70% exhibiting robust growth under the conditions tested) in search of c-di-GMP-activated EPS. Nearly 10% of strains were revealed as promising candidates to overproduce novel EPS composites in a c-di-GMP-dependent manner. Under these conditions, Sphingomonas sp. SphC10 massively produced an EPS with an unusual monosaccharide composition compared with known biotechnologically relevant sphingans.

Castellano-Sánchez, Leticia Rosales-Castillo, Antonio Olvera-Porcel, María del Carmen Gutiérrez Fernández, José https://hdl.handle.net/10481/111807 2026-03-02T12:38:54Z

Characteristics and Clinical Relevance of Candiduria in Hospitalized Patients Castellano-Sánchez, Leticia; Rosales-Castillo, Antonio; Olvera-Porcel, María del Carmen; Gutiérrez Fernández, José Background: Candiduria is a common finding in hospitalized patients, particularly in intensive care units (ICUs) and in those with indwelling urinary catheters. Additionally, Candida spp. is among the most frequent causes of healthcare-associated urinary tract infections and can lead to severe clinical manifestations in specific scenarios involving risk factors. Objective: The objective of this study is to describe and analyze the epidemiological features, clinical risk factors, therapeutic approaches, and clinical outcomes in a cohort of hospitalized patients with candiduria at a regional hospital. Methods: This was a retrospective, descriptive, cross-sectional study based on the selection of 207 urine cultures positive for Candida spp. between 1 February 2024, and 31 August 2024, at the Microbiology Laboratory of the Virgen de las Nieves University Hospital in Granada, Spain. Results: The most frequently isolated species was Nakaseomyces glabratus (42.03%), with no sex differences and a predominant occurrence in ICU patients (36.71%). Most patients had comorbidities (86.47%), urinary catheters (72.46%), and prior antibiotic use (75.85%). Less than half of the cases presented clinical symptoms (41.55%). Antifungal therapy was administered in 38.65% of cases, predominantly fluconazole (61/207; 29.47%), followed by echinocandins (12/207; 5.8%). Use of sodium-glucose co-transporter-2 inhibitors (SGLT2i) was documented in 36.71% of patients. Conclusions: Candiduria is more frequently observed in elderly patients with multiple comorbidities, ICU admission, indwelling urinary catheters, prior antibiotic therapy, and SGLT2i use. Fewer than half of the episodes are symptomatic. Non-albicans yeast species, which often display distinct resistance patterns, are increasingly prevalent, with N. glabratus being the most frequently isolated.

López Fernández, Margarita Fernández-Sanfrancisco, Omar Moreno-García, Alberto Martín Sánchez, Inés Sánchez-Castro, Iván Merroun, Mohamed Larbi https://hdl.handle.net/10481/111650 2026-02-27T08:38:26Z

Microbial communities in bentonite formations and their interactions with uranium López Fernández, Margarita; Fernández-Sanfrancisco, Omar; Moreno-García, Alberto; Martín Sánchez, Inés; Sánchez-Castro, Iván; Merroun, Mohamed Larbi A reliable performance assessment of deep geological disposal of nuclear waste depends on better knowledge of radionuclide interactions with natural microbes of geological formations (granitic rock, clay, salts) used to host these disposal systems. In Spain, clay deposits from Cabo de Gata region, Almeria, are investigated for this purpose. The present work characterizes the culture-dependent microbial diversity of two bentonite samples (BI and BII) recovered from Spanish clay deposits. The evaluation of aerobe and facultative anaerobe microbial populations shows the presence of a high number of cultivable bacteria (e.g. Stenotrophomonas, Micrococcus, Arthrobacter, Kocuria, Sphingomonas, Bacillus, Pseudomonas, etc.) affiliated to three phyla Proteobacteria, Actinobacteria, and Firmicutes. In addition, a pigmented yeast strain BII-R8 related to Rhodotorula mucilaginosa was also recovered from these formations. The minimal inhibitory concentrations of uranium for the growth of these natural isolates were found to range from 4 to 10.0 mM. For instance, strain R. mucilaginosa BII-R8 was shown to tolerate up to 8 mM of U. Flow cytometry studies indicated that the high U tolerance of this yeast isolate is a biologically mediated process. Microscopically dense intracellular and cell wall-bound precipitates were observed by Scanning Transmission Electron Microscopy-High-Angle Annular Dark-Field (STEM-HAADF). Energy Dispersive X-ray (EDX) element-distribution maps showed the presence of U and P within these accumulates, indicating the ability of cells to precipitate U as U(VI) phosphate minerals. Fundamental understanding of the microbial diversity of clays and microbial interaction with radionuclides will be useful in predicting the microbial impacts on the performance of the waste repositories, as well as in the development of bioremediation strategies for U contaminated sites. No es open access, pero tenemos permiso para su deposito

Bachran, Madlen Kluge, S Lopez-Fernandez, Margarita Cherkouk, Andrea https://hdl.handle.net/10481/111647 2026-02-27T08:20:03Z

Microbial Diversity in an Arid, Naturally Saline Environment Bachran, Madlen; Kluge, S; Lopez-Fernandez, Margarita; Cherkouk, Andrea The Arava Valley in is a rock desert within the Great African Rift valley. Soil from this area is covered with a salt crust. Here, we report microbial diversity from arid, naturally saline samples collected near Ein Yahav from the Arava Valley by cultureindependent as well as culture-dependent analysis. High-throughput sequencing of the hypervariable region V4 of the 16S rRNA gene revealed that the microbial community consists of halophiles from the domain Bacteria as well as Archaea. Bacterial diversity was mainly represented by the genus Salinimicrobium of the order Flavobacteriales within the phylum Bacteroidetes, from the gammaproteobacterial orders Alteromonadales and Oceanospirillales as well as representatives from the order Bacillales of the phylum Firmicutes. Archaeal diversity was dominated by euryarchaeal Halobacteria from the orders Halobacteriales, Haloferacales, and Natrialbales. But more than 40% of the sequences affiliated with Archaea were assigned to unknown or unclassified archaea. Even if taxonomic resolution of the 16S rRNAgeneV4 region for Archaea is limited, this study indicates the need of further and more detailed studies of Archaea. By using culture-dependent analysis, bacteria of the order Bacillales as well as archaea from all three halobacterial orders Halobacteriales, Haloferacales, and Natrialbales including potentially novel species from the genera Halorubrum and Haloparvum were isolated.

Merroun, Mohamed Larbi Nedelkova, Marta Ojeda, Jesús J. Reitz, Thomas López Fernández, Margarita Arias, José M. Romero-González, María Selenska-Pobell, Sonja https://hdl.handle.net/10481/111640 2026-02-27T08:00:53Z

Bio-precipitation of uranium by two bacterial isolates recovered from extreme environments as estimated by potentiometric titration, TEM and X-ray absorption spectroscopic analyses Merroun, Mohamed Larbi; Nedelkova, Marta; Ojeda, Jesús J.; Reitz, Thomas; López Fernández, Margarita; Arias, José M.; Romero-González, María; Selenska-Pobell, Sonja This work describes the mechanisms of uranium biomineralization at acidic conditions by Bacillus sphaericus JG-7B and Sphingomonas sp. S15-S1 both recovered from extreme environments. The U–bacterial interaction experiments were performed at low pH values (2.0–4.5) where the uranium aqueous speciation is dominated by highly mobile uranyl ions. X-ray absorption spectroscopy (XAS) showed that the cells of the studied strains precipitated uranium at pH 3.0 and 4.5 as a uranium phosphate mineral phase belonging to the meta-autunite group. Transmission electron microscopic (TEM) analyses showed strain-specific localization of the uranium precipitates. In the case of B. sphaericus JG-7B, the U(VI) precipitate was bound to the cell wall. Whereas for Sphingomonas sp. S15-S1, the U(VI) precipitates were observed both on the cell surface and intracellularly. The observed U(VI) biomineralization was associated with the activity of indigenous acid phosphatase detected at these pH values in the absence of an organic phosphate substrate. The biomineralization of uranium was not observed at pH 2.0, and U(VI) formed complexes with organophosphate ligands from the cells. This study increases the number of bacterial strains that have been demonstrated to precipitate uranium phosphates at acidic conditions via the activity of acid phosphatase. This work was supported partly by grant FIKW-CT-2000-00105 (BORIS) from the European Community and also from the Grant No. CGL2009-09760 and CGL2007-61489 from the Ministerio de Ciencia e Innovación, and Ministerio de Educación y Ciencia, respectively, Spain. Merroun, M.L. is a “Ramón y Cajal Fellow” of the University of Granada. We thank A. Scheinost and H. Funke from ROBL, ESRF, Grenoble for their help in the EXAFS measurements. J. J. Ojeda acknowledges funding from the UK Engineering and Physical Sciences Research Council (EPSRC), as part of the DIAMOND Consortium: Decommissioning, Immobilisation and Management of Nuclear wastes for Disposal (EP/F055412/1).; No es open access, pero tenemos permiso para su deposito.