https://hdl.handle.net/10481/23713 Fri, 17 Apr 2026 19:23:09 GMT 2026-04-17T19:23:09Z https://hdl.handle.net/10481/112846 Pseudomonas halotolerans sp. nov., a halotolerant biocontrol agent with plant-growth properties Sánchez Aranda, Patricia; Castillo, Inés; Martínez-Checa Barrero, Fernando José; Sampedro Quesada, María Inmaculada; Llamas Company, Inmaculada A polyphasic taxonomic approach was conducted to characterize the bacterial strain B22T isolated from the rhizospheric soil of the halophyte Salicornia hispanica. This strain is aerobic, Gram-negative, rod-shaped, catalase and oxidase positive, motile, reduces nitrates and chemoheterotrophic. It is halotolerant, exhibiting optimal growth at 28°C and pH 7.0 in the presence of 0.5-2.5% (w/v) of NaCl. The B22T genome size is 5.7 Mbp, with a G+C content of 60.5 mol%. This strain has the capacity to promote tomato growth by producing siderophores, indole-3-acetic acid and enzymes such as phytase and acid phosphatase. Additionally, strain B22T produces a quorum quenching (QQ) enzyme capable of degrading synthetic N-acylhomoserine lactones (AHLs) as well as those produced by phytopathogens. The interference of plant pathogen communication reduced virulence in tomato fruits and plants. Phylogenetic analysis revealed that the closest relatives of strain B22T was Pseudomonas tehranensis SWRI 196T. The average nucleotide identity values between strain B22T and P. tehranensis SWRI 196T was 95.1% while digital DNA-DNA hybridization values was 64.5% The main cellular fatty acids of strain B22T were C16:0, summed feature 3 (C16:1 w7c/C16:1 w6c) and summed feature 8 (C18:1 w7c/ C18:1 w6c). The major polar lipids identified were diphosphatidylglycerol and phosphatidylethanolamine, while the predominant respiratory quinone was ubiquinone (Q-9). Based on genomic, phylogenetic and chemotaxonomic data, strain B22T (=CECT 31209; =LMG33902) represents a novel species within the genus Pseudomonas. The name Pseudomonas halotolerans sp. nov. is proposed. Additionally, this study highlights the potential of P. halotolerans as a sustainable biocontrol agent due to its plant growth-promoting activity in tomato plants and its ability to reduce phytopathogen virulence factors, mitigating damage to fruits and plants. The author(s) declare that financial support was received for the research and/or publication of this article. This research was supported by the following grants: PDI2023-1501540B-I00 funded by MICIU/AEI/10.13039/501100011033 and by ERDF/EU; PID2019-106704RB-I00 funded by MCIN/AEI/10.13039/ 501100011033 and B-AGR-222-UGR20 funded by Consejerıa de ́ Universidad, Investigación e Innovación de la Junta de Andalucıá and ERDF A way of making Europe. Patricia Sánchez is supported by the grant B-AGR-222-UGR20 funded by Consejerı́ a de Universidad, Investigación e Innovación de la Junta de Andalucıá and ERDF A way of making Europe. https://hdl.handle.net/10481/112846 https://hdl.handle.net/10481/112844 Quorum-quenching halotolerant bacteria as biocontrol agents against potato phytopathogens Sánchez Aranda, Patricia; Monzón-Ramos, Ana; Sampedro Quesada, María Inmaculada; Llamas Company, Inmaculada; Palma Martín, Francisco José Potato is highly susceptible to phytopathogens such as Dickeya solani, Pectobacterium atrosepticum and P. carotovorum, which cause an oxidative stress in the vegetal tissues, promote necrosis, and ultimately compromise postharvest quality. In many Gram-negative bacteria, virulence is regulated by quorum sensing (QS) via N-acyl homoserine lactones (AHLs). Quorum quenching (QQ), the enzymatic degradation of AHLs, has emerged as a promising biocontrol strategy. This study evaluated the biocontrol potential of two halotolerant bacterial strains, Pseudomonas kilonensis B34 and Psychrobacter sp. B38, capable of partially degraded AHLs produced by these phytopathogens. Co-cultures of these QQ strains with the mentioned pathogens significantly reduced tissue maceration in potato tubers, with strongest protective effect observed against D. solani. Under this biotic stress, both strains enhanced antioxidant defense responses in potato tissues, with strain B38 demonstrating the highest effectiveness. This protection was related with higher levels of phenolic compounds, which supported the antioxidant machinery and preserved tissue integrity. Overall, these results highlight the potential of halotolerant QQ bacteria as efficient biocontrol agents and sustainable alternatives to chemical treatments in potato disease management. This research was funded by PID2023-150154OB-I00 funded by MICIU/AEI /10.13039/501100011033 and by ERDF/EU, PID2019-106704RB-100 funded by MICIU/AEI /10.13039/501100011033/ AEI/10.13039/501100011033 and B-AGR-222-UGR20 funded by Consejería de Universidad, Investigación e Innovación de la Junta de Andalucía and, ERDF A way of making Europe. https://hdl.handle.net/10481/112844 https://hdl.handle.net/10481/112273 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. https://hdl.handle.net/10481/112273 https://hdl.handle.net/10481/111807 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. https://hdl.handle.net/10481/111807 https://hdl.handle.net/10481/111650 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 https://hdl.handle.net/10481/111650