Biology subjects

Jimenez, I. A.

Publications and source records attributed to Jimenez, I. A..

4 recordsLinked to original sources

bioRxiv2026

Strain-specific thermotolerance, UV-C tolerance, and biofilm formation on clinically relevant plastic substrates in the emerging opportunistic pathogen Rhodotorula mucilaginosa

Rhodotorula mucilaginosa is an emerging opportunistic fungal pathogen increasingly associated with catheter-related bloodstream infections. Although biofilm formation is considered a major virulence trait for R. mucilaginosa, factors contributing to biofilm persistence on medical devices remain poorly understood. Here, we characterized the thermotolerance, biofilm formation, UV resistance, and cell surface hydrophobicity profiles of eight R. mucilaginosa strains representing clinical and non-clinical (laboratory, environmental, and marine mammal) isolates. All strains grew optimally at 30C and exhibited restricted growth at 35C and 37C, although one environmental isolate maintained robust growth at 37C. All strains exhibited moderate to high cell surface hydrophobicity. We then assessed biofilm formation for each strain, including adherence to two different plastic substrates, development of biofilm biomass, comparison of biofilm metabolic activity, and the effects of temperature on biofilm formation. Under static conditions, biofilm biomass of most isolates on 96-well polystyrene plates was greatest at 24C. Clinical isolates generally maintained higher biofilm metabolic activity at 37C than nonclinical isolates, while at lower temperatures, clinical and non-clinical isolates did not differ significantly in metabolic activity. All strains readily formed biofilms on polyurethane intravenous catheters under dynamic conditions, as confirmed by scanning electron microscopy and metabolic activity. While planktonic cells already displayed substantial UV-C tolerance, biofilm-associated cells remained viable following exposure to UV-C doses up to eightfold higher than those that impaired planktonic growth. These findings document differences in thermotolerance and biofilm formation by isolate origin and identify biofilm formation as a major factor promoting persistence of R. mucilaginosa on clinically relevant materials and reduced susceptibility to UV-C sterilization.

microbiology↗

bioRxiv2026

Reverse gingival venipuncture: a refined technique for serial blood collection in small rodents

ObjectiveTo assess the safety, efficacy, and repeatability of a novel blood collection technique, percutaneous reverse gingival venipuncture (RGV), across multiple rodent species, and to characterize the associated anatomy through dissection and histopathology. MethodsSuccess rate and complications of RGV were evaluated at a private practice between December 2024 and September 2025 in client-owned chinchillas (Chinchilla lanigera) (n=102), guinea pigs (Cavia porcellus) (n=78), Syrian hamsters (Mesocricetus auratus) (n=32), dwarf hamsters (Phodopus campbelli and P. sungorus) (n=4), squirrels (Callosciurus erythraeus, C. finlaysonii) (n=7), prairie dogs (Cynomys ludovicianus) (n=2), a capybara (Hydrochoerus hydrochaeris) (n=1) and a Patagonian mara (Dolichotis patagonum) (n=1). An experimental study was conducted in laboratory rats (Rattus norvegicus) (n=5), Chinese hamsters (Cricetulus griseus) (n=12), and chinchillas (n=11) from February 2026 to March 2026 to evaluate RGV success rate, serial hematology, and histopathology. ResultsThe success rate of RGV was 100% in most rodent species, but was lower in guinea pigs (44.87%, n=78) and chinchillas (64.60%, n=113). No animals experienced clinical complications. No significant changes in serial hematology were appreciated in Chinese hamsters (n=6) on days 0, 7, and 14. Histopathology did not reveal any complications. ConclusionsRGV in anesthetized rodents is safe, effective, minimally invasive, and repeatable, yielding clinically relevant blood volumes with precise control and minimal risks. Clinical RelevanceRGV may facilitate more routine hematology and chemistry analysis in rodents by veterinary practitioners, with few risks and complications. In research settings, RGV may improve animal welfare and contribute to refinement and reduction.

zoology↗

bioRxiv2026

A role for aquaporin (Aqp1) in the control of Cryptococcus neoformans cell morphology

Aquaporins are small, integral membrane channels that facilitate the transport of water across cellular membranes and, in the case of aquaglyceroporins, can also conduct specific neutral solutes, such as glycerol. These proteins are conserved across biological kingdoms, yet their roles in fungal virulence remain relatively understudied. In Cryptococcus neoformans, an opportunistic fungal pathogen, we examined the organisms single aquaporin, Aqp1, and uncovered unanticipated influences on cellular morphology. Loss of Aqp1 resulted in smaller cells, whereas its presence promoted the formation of enlarged titan-like cells. This shift in size was closely linked to intracellular redox physiology. Consequently, the overexpression of the cryptococcal aquaporin increased sensitivity to oxidative stress and led to the largest titan-like cells; antioxidant supplementation suppressed this enlargement, consistent with a ROS-dependent regulatory mechanism. Additionally, Aqp1 overexpression produced vacuolar abnormalities in titan-like cells, suggesting that excessive water influx strained intracellular organization during rapid cell expansion. These findings position Aqp1 at a functional crossroads connecting membrane transport, oxidative balance, and size control, and they support a model in which an aquaporin contributes to the morphological plasticity that allows C. neoformans to adapt to environmental pressures.

microbiology↗

bioRxiv2024

The buoyancy of cryptococcal cells and its implications for transport and persistence of Cryptococcus in aqueous environments

Cryptococcus is a genus of saprophytic fungi with global distribution. Two species complexes, C. neoformans and C. gattii, pose health risks to humans and animals. Cryptococcal infections result from inhalation of aerosolized spores and/or desiccated yeasts from terrestrial reservoirs such as soil, trees, and avian guano. More recently, C. gattii has been implicated in infections in marine mammals, suggesting that inhalation of liquid droplets or aerosols from the air-water interface is also an important, yet understudied, mode of respiratory exposure. Water transport has also been suggested to play a role in the spread of C. gattii from tropical to temperate environments. However, the dynamics of fungal survival, persistence, and transport via water have not been fully studied. The size of the cryptococcal capsule was previously shown to reduce cell density and increase buoyancy. Here, we demonstrate that cell buoyancy is also impacted by the salinity of the media in which cells are suspended, with formation of a halocline interface significantly slowing the rate of settling of cryptococcal cells through water, resulting in persistence of C. neoformans within 1 cm of the air-water interface for over 60 min and C. gattii for 4-6 h. Our data also showed that during culture in yeast peptone dextrose media (YPD), polysaccharide accumulating in the supernatant formed a raft that augmented buoyancy and further slowed settling of cryptococcal cells. These findings illustrate new mechanisms by which cryptococcal cells may persist in aquatic environments, with important implications for aqueous transport and pathogen exposure. ImportanceCryptococcosis is a major fungal disease leading to morbidity and mortality worldwide. C. neoformans is a major fungal species of public health concern, causing opportunistic systemic infections in immunocompromised patients. C. gattii was traditionally a tropical pathogen, but in the 1990s emerged in the temperate climates of British Columbia and the Pacific Northwest United States. Outbreaks in these areas also led to the first host record of cryptococcosis in free-ranging cetaceans. C. gattii is particularly concerning as an emerging fungal pathogen due to its capacity to cause clinical disease in immunocompetent patients, its recent spread to a new ecological niche, and its higher resistance to antifungal therapies. Our research defines characteristics that influence transport of cryptococci through water and its persistence at the air-water interface, which improve our understanding of mechanisms for cryptococcal aqueous transport and persistence.

microbiology↗