Diversity, distribution, and bioprospecting potentials of carotenogenic yeast from mangrove ecosystem.

Microbial production of carotenoids has gained significant interest for its cost-effectiveness and sustainable nature. This study focuses on 47 red-pigmented yeasts isolated from sediments and plant parts of 13 species of mangrove trees. The relative abundance and distribution of these yeasts varied with plant species and plant parts. The highest number of red yeasts was associated with the mangrove plant Avicennia officinalis (32%). Notably, the leaves harbored the highest percentage (45%) of carotenogenic yeasts, and definite compartmentalization of these yeast species was noticed in mangrove plant parts. All the isolates were molecularly identified and they belonged to the genera of Rhodotorula, Rhodosporidiobolus, and Cryptococcus. The diversity of the pigmented yeasts isolated from A. officinalis was found to be the greatest. Among these strains, Rhodotorula mucilaginosa PV 8 was identified as the most potent producer of carotenoid pigment. Under optimized conditions of physical parameters - 28 °C, pH 5, and 15% salinity led to biomass production of 9.2 ± 0.12 g/L DCW and a pigment yield of 194.78 µg/g. The pigment produced by PV 8 was identified as ß-carotene by thin layer chromatography (TLC) and Fourier transform infrared spectroscopy (FT-IR). This ß-carotene demonstrated strong antioxidant activity. Moreover, the carotenoid displayed promising antibacterial activity against multidrug-resistant organisms, including Aeromonas sp. and Vibrio sp. In vitro studies revealed the probiotic traits of PV 8. The cytotoxicity of R. mucilaginosa PV 8 was assessed in the invertebrate model Artemia salina and the survival rate showed that it was non-toxic. Furthermore, the ß-carotene from PV 8 demonstrated the ability to transfer its vibrant color to various food products, maintaining color stability even under varied conditions. This research underscores the potential of R. mucilaginosa PV 8, as a versatile and valuable resource for the production of carotenoids.

Formation of Sb2O3 microcrystals by Rhodotorula mucilaginosa.

Antimony (Sb) pollution seriously endangers ecological environment and human health. Microbial induced mineralization can effectively convert metal ions into more stable and less soluble crystalline minerals by extracellular polymeric substance (EPS). In this study, an efficient Sb-resistant Rhodotorula mucilaginosa (R. mucilaginosa) was screened, which can resist 41 mM Sb(III) and directly transform Sb(III) into Sb2O3 microcrystals by EPS. The removal efficiency of R. mucilaginosa for 22 mM Sb(III) reached 70% by converting Sb(III) to Sb2O3. The components of supernatants as well as the effects of supernatants and pH on Sb(III) mineralization verified that inducible and non-inducible extracellular protein/polysaccharide biomacromolecules play important roles in the morphologies and sizes control of Sb2O3 formed by R. mucilaginosa respectively. Sb2O3 microcrystals with different morphologies and sizes can be prepared by the regulation of inducible and non-inducible extracellular biomacromolecules secreted by R. mucilaginosa. This is the first time to identify that R. mucilaginosa can remove Sb(III) by transforming Sb(III) into Sb2O3 microcrystals under the control of EPS. This study contributes to our understanding for Sb(III) biomineralization mechanisms and provides strategies for the remediation of Sb-contaminated environment.

Effect of Rhodotorula mucilaginosa inoculation on the aroma development of a fermented vegetables simulated system.

Fermented vegetables are known for their unique flavors and aromas, which are influenced by the complex microbial processes that occur during fermentation. Rhodotorula mucilaginosa is a red yeast strain that is frequently isolated from fermented vegetables. However, the specific mechanisms underlying their effects on aroma production remain unclear. In this study, a simulated system of vegetables fermented using vegetable juices was used to investigate the effects of R. mucilaginosa inoculation on aroma development. The results demonstrated that this red yeast strain could utilize the nutrients present in the vegetable juices to support its growth and reproduction. Moreover, the inoculation of fermented vegetable juices with this yeast strain led to an increase in the levels of umami amino acids and sweet amino acids. Furthermore, this yeast strain was found able to significantly reduce the content of sulfur-containing compounds, which may decrease the unpleasant odor of fermented vegetables. Additionally, the yeast strain was capable of producing high concentrations of aromatic compounds such as phenylethyl alcohol, methyl 2-methylbutyrate, methyl butyrate, and nonanoic acid in a minimum medium. However, only phenylethyl alcohol has been identified as a core aromatic compound in fermented vegetable juice. The three fermented vegetable juices exhibited significantly different flavor profiles according to comparative analysis. Therefore, the core flavor compounds found in fermented vegetables are primarily derived from the release and modification of endogenous flavors naturally present in the vegetables, facilitated by the yeast during fermentation.

Production optimization of food functional factor ergothioneine in wild-type red yeast Rhodotorula mucilaginosa DL-X01.

BACKGROUND: Ergothioneine (EGT) is a high-value food functional factor that cannot be synthesized by humans and other vertebrates, and the low yield limits its application. RESULTS: In this study, the optimal fermentation temperature, fermentation time, initial pH, inoculum age, and inoculation ratio on EGT biosynthesis of Rhodotorula mucilaginosa DL-X01 were optimized. In addition, the effects of three key precursor substances - histidine, methionine, and cysteine - on fungal EGT synthesis were verified. The optimal conditions were further obtained by response surface optimization. The EGT yield of R. mucilaginosa DL-X01 under optimal fermentation conditions reached 64.48 ± 2.30 mg L-1 at shake flask fermentation level. Finally, the yield was increased to 339.08 ± 3.31 mg L-1 (intracellular) by fed-batch fermentation in a 5 L bioreactor. CONCLUSION: To the best of our knowledge, this is the highest EGT yield ever reported in non-recombinant strains. The fermentation strategy described in this study will promote the efficient biosynthesis of EGT in red yeast and its sustainable production in the food industry. © 2024 Society of Chemical Industry.

Fungal coexistence in the skin mycobiome: a study involving Malassezia, Candida, and Rhodotorula.

Evidence of fungal coexistence in humans points towards fungal adaptation to the host environment, like the skin. The human commensal Malassezia has evolved, especially residing in sebum-rich areas of the mammalian body where it can get the necessary nutrition for its survival. This fungus is primarily responsible for skin diseases like Pityriasis versicolor (PV), characterized by hypo or hyperpigmented skin discoloration and erythematous macules. In this manuscript, we report a 19-year-old healthy female who presented with a one-year history of reddish, hypopigmented, asymptomatic lesions over the chest and a raised erythematous lesion over the face. Upon clinical observation, the patient displayed multiple erythematous macules and erythematous papules over the bilateral malar area of the face, along with multiple hypopigmented scaly macules present on the chest and back. Based on the above clinical findings, a diagnosis of PV and Acne vulgaris (AV) was made. Interestingly, the patient was immunocompetent and didn't have any comorbidities. Upon isolation of skin scrapings and post-culturing, we found the existence of three fungal genera in the same region of the patient's body. We further went on to confirm the identity of the particular species and found it to represent Malassezia, Rhodotorula, and Candida. We report how Malassezia, the predominant microbial resident skin fungus, coexists with other fungal members of the skin mycobiome. This study on an applied aspect of microbiology also shows how important it is to identify the fungal organism associated with skin infections so that appropriate therapeutics can be advised to avoid cases of relapse.

A New Method for Selective Extraction of Torularhodin from Red Yeast Using CO2-SFE Technique.

Torularhodin is a dark pink colored carotenoid belonging to the xanthophylls group that can be biologically synthesized by red yeasts, especially by Rhodotorula and Sporobolomyces genera. The growing interest in this molecule is due to its biological activities such as antioxidant, anticholesterolemic, anti-inflammatory, antimicrobial, and anticancer. To satisfy potential commercial markets, numerous methods have been proposed to develop a cost-effective and environmentally friendly downstream process for the purification of torularhodin. However, obtaining high purity products without resorting to the use of toxic solvents, which can leave residues in the final preparations, remains a major challenge. In this context, the present study aimed to develop a new efficient method for the isolation of torularhodin from the red yeast Rhodotorula strain ELP2022 by applying the extraction technique with supercritical CO2 (CO2-SFE) in two sequential steps. In particular, in the first step, the dried lysed biomass of yeast was subjected to the action of CO2 in supercritical conditions (CO2SC) as sole solvent for extraction of apolar carotenoids. In the second step, the residual biomass was subjected to the action of CO2SC using ethanol as a polar co-solvent for the extraction of torularhodin. Both steps were carried out at different operating parameters of temperature (40 and 60 °C) and pressure (from 300 to 500 bar) with a constant CO2 flow of 6 L min-1. Regardless of the operating conditions used, this method allowed to obtain an orange-colored oily extract and a red-colored extract after the first and second step, respectively. In all trials, torularhodin represented no less than 95.2% ± 0.70 of the total carotenoids in the red extracts obtained from the second step. In particular, the best results were obtained by performing both steps at 40 °C and 300 bar, and the maximum percentage of torularhodin achieved was 97.9% ± 0.88. Since there are no data on the selective recovery of torularhodin from red yeast using the SFE technique, this study may be a good starting point to optimize and support the development of industrial production of torularhodin by microbial synthesis. This new method can significantly reduce the environmental impact of torularhodin recovery and can be considered an innovation for which an Italian patent application has been filed. In a circular bioeconomy approach, this method will be validated up to a pilot scale, culturing the strain Rhodotorula spp. ELP2022 on low-cost media derived from agri-food wastes.

The mitochondrial respiratory chain from Rhodotorula mucilaginosa, an extremophile yeast.

Rhodotorula mucilaginosa survives extreme conditions through several mechanisms, among them its carotenoid production and its branched mitochondrial respiratory chain (RC). Here, the branched RC composition was analyzed by biochemical and complexome profiling approaches. Expression of the different RC components varied depending on the growth phase and the carbon source present in the medium. R. mucilaginosa RC is constituted by all four orthodox respiratory complexes (CI to CIV) plus several alternative oxidoreductases, in particular two type-II NADH dehydrogenases (NDH2) and one alternative oxidase (AOX). Unlike others, in this yeast the activities of the orthodox and alternative respiratory complexes decreased in the stationary phase. We propose that the branched RC adaptability is an important factor for survival in extreme environmental conditions; thus, contributing to the exceptional resilience of R. mucilaginosa.

Detoxification Approaches of Bagasse Pith Hydrolysate Affecting Xylitol Production by Rhodotorula mucilaginosa.

In this study, the potential of bagasse pith (the waste of sugar and paper industry) was investigated for bio-xylitol production for the first time. Xylose-rich hydrolysate was prepared using 8% dilute sulfuric acid, at 120 °C for 90 min. Then, the acid-hydrolyzed solution was detoxified by individual overliming (OL), active carbon (AC), and their combination (OL+AC). The amounts of reducing sugars and inhibitors (furfural and hydroxyl methyl furfural) were measured after acid pre-treatment and detoxification process. Thereafter, xylitol was produced from detoxified hydrolysate by Rhodotorula mucilaginosa yeast. Results showed that after acid hydrolysis, the sugar yield was 20%. Detoxification by overliming and active carbon methods increased the reducing sugar content up to 65% and 36% and decreased the concentration of inhibitors to >90% and 16%, respectively. Also, combined detoxification caused an increase in the reducing sugar content (>73%) and a complete removal of inhibitors. The highest productivity of xylitol (0.366 g/g) by yeast was attained after the addition of 100 g/l non-detoxified xylose-rich hydrolysate into fermentation broth after 96 h, while the xylitol productivity enhanced to 0.496 g/g after adding the similar amount of xylose-rich hydrolysate detoxified by combined method (OL+AC2.5%).

Application of adaptive laboratory evolution to improve the tolerance of Rhodotorula strain to methanol in crude glycerol and development of an effective method for cell lysis.

Rhodotorula toruloides can utilize crude glycerol as the low-cost carbon source for lipid production, but its growth is subjected to inhibition by methanol in crude glycerol. Here, transcriptome profiling demonstrated that 1004 genes were significantly regulated in the strain R. toruloides TO2 under methanol stress. Methanol impaired the function of membrane transport and subsequently weakened the utilization of glycerol, activities of the primary metabolism and functions of nucleus and ribosome. Afterwards the tolerance of TO2 to methanol was improved by using two-round adaptive laboratory evolution (ALE). The final strain M2-ale had tolerance up to 3.5% of methanol. 1 H NMR-based metabolome analysis indicated that ALE not only improved the tolerance of M2-ale to methanol but also tuned the carbon flux towards the biosynthesis of glycerolipid-related metabolites. The biomass and lipid titer of M2-ale reached 14.63 ± 0.45 g L-1 and 7.06 ± 0.44 g L-1 at 96 h in the crude glycerol medium, which increased up to 17.69% and 31.39%, respectively, comparing with TO2. Afterwards, an effective method for cell lysis was developed by combining sonication and enzymatic hydrolysis (So-EnH). The lytic effect of So-EnH was validated by using confocal imaging and flow cytometry. At last, lipid recovery rate reached 95.4 ± 2.7% at the optimized condition.

Cost-effective production of ergothioneine using Rhodotorula mucilaginosa DL-X01 from molasses and fish bone meal enzymatic hydrolysate.

Ergothioneine (EGT) is a high-value natural antioxidant that cannot be synthesized by the human body. This study showed that Rhodotorula mucilaginosa DL-X01 can use untreated molasses and fish bone meal enzymatic hydrolysate as the substrates to synthesize EGT. By optimizing the growth conditions, the EGT yield reached 29.39 mg/L when molasses and fish bone meal (FBM) were added at 60 g/L and 400 g/L respectively. Finally, the EGT yield was increased to 216.25 mg/L by fed-batch fermentation in a 5 L bioreactor. Compared with the fermentation by yeast extract peptone dextrose medium, the feedstock cost of EGT production was reduced by 330.91 % by using molasses and FBM as substrates. These results showed that R. mucilaginosa DL-X01 can produce high-value EGT using two cheap processing by-products, molasses and FBM, which is of great significance for environmental protection and sustainable development.

Agricultural wastes: a new promising source for phenylalanine ammonia-lyase as anticancer agent.

The present study aims to investigate the physicochemical characteristics of phenylalanine ammonia-lyase (PAL) extracted from agricultural waste and its potential use as an anticancer agent in comparison to microbial PAL. We extracted and partially purified PAL from agricultural waste sources. We assessed the temperature and pH range of PAL and determined enzyme kinetics parameters including Michaelis constants (Km), maximum velocity (Vmax), and specificity constant values (Vmax/Km). Additionally, we examined the effects of different storage temperatures on PAL activity. In our analysis, we compared the efficacy of agricultural waste-derived PAL with PAL from Rhodotorula glutinis. The results demonstrated that PAL extracted from agricultural waste exhibited significantly higher specific activity (Vmax/Km) compared to its microbial counterpart. The agricultural waste-derived PAL displayed a stronger affinity for phenylalanine, as indicated by a lower Km value than the microbial PAL did. Furthermore, PAL from agricultural waste maintained activity across a broader temperature and pH range (15-75 °C, pH 5-11), in contrast to microbial PAL (20-60 °C, pH 5.5-10). Importantly, the PAL derived from agricultural waste exhibited superior stability, retaining over 90% of its activity after 6 months of storage at room temperature (25 °C), whereas microbial PAL lost more than 70% of its activity under similar storage conditions. In anticancer experiments against various cancer cell lines, agricultural waste-derived PAL demonstrated greater anticancer activity compared to microbial PAL. These findings suggest that PAL sourced from agricultural waste has the potential to be a safe and effective natural anticancer agent.

Sustainable trehalose lipid production by Rhodotorula sp.: a promising bio-based alternative.

Global environmental concerns drive research toward the development of new eco-friendly compounds to replace pollutant chemicals. This study focuses on optimizing the production of trehalose lipids (TLs), which are glycolipid biosurfactants (BS) with various applications like antimicrobial or surface tension reduction. New microorganism sources, growth conditions, medium composition, purification conditions, and physicochemical properties of TLs are studied. Addressing a microscale approach, TLs production was successfully achieved using Rhodotorula sp. and Rhodococcus erythropolis to compare, with different media compositions including glucose-based and salt media supplemented with glycerol, glucose, n-hexadecane, n-dodecane. Liquid-liquid extraction using ethyl acetate and methanol was employed for compound extraction, followed by characterization using analytical methods such as Thin layer chromatography (TLC), High performance liquid chromatography (HPLC), and UHPLC. The produced TLs exhibited a minimum surface tension of 47 mN/m and a critical micellar concentration of 4.4 mg/mL. This study also identified Rhodotorula sp. as a new sustainable producer of TLs with improved productivity.

Enhancement of novel Endo-polygalacturonase expression in Rhodotorula mucilaginosa PY18: insights from mutagenesis and molecular docking.

Pectinase is a particular type of enzyme that can break down pectin compounds and is extensively utilised in the agricultural field. In this study, twenty yeast isolates were isolated and assayed for pectinase activity. Molecular identification by PCR amplification and sequencing of internal transcribed spacer (ITS) regions of isolate no. 18 had the highest pectinase activity of 46.35 U/mg, was identified as Rhodotorula mucilaginosa PY18, and was submitted under accession no. (OM275426) in NCBI. Rhodotorula mucilaginosa PY18 was further enhanced through sequential mutagenesis, resulting in a mutant designated as Rhodotorula mucilaginosa E54 with a specific activity of 114.2 U/mg. Using Response Surface Methodology (RSM), the best culture conditions for the pectinase-producing yeast mutant Rhodotorula mucilaginosa E54 were pH 5, 72-h incubation, 2.5% xylose, and 2.5% malt extract, with a pectinase-specific activity of 156.55 U/mg. Then, the obtained sequences of the endo-polygalacturonase PGI gene from Rhodotorula mucilaginosa PY18 and mutant Rhodotorula mucilaginosa E54 were isolated for the first time, sequenced, and submitted to NCBI accession numbers OQ283005 and OQ283006, respectively. The modelled 3D structure of the endo-PGI enzyme (485 residues) was validated using Ramachandran's plot, which showed 87.71, 85.56, and 91.57% in the most favourable region for template Rhodotorula mucilaginosa KR, strain Rhodotorula mucilaginosa PY18, and mutant Rhodotorula mucilaginosa E54, respectively. In molecular docking studies, the results of template Rhodotorula mucilaginosa KR endo-PG1 showed an interaction with an affinity score of - 6.0, - 5.9, and - 5.6 kcal/mol for active sites 1, 2, and 3, respectively. Rhodotorula mucilaginosa PY18 endo-PG1 showed an interaction affinity with a score of - 5.8, - 6.0, and - 5.0 kcal/mol for active sites 1, 2, and 3, respectively. Mutant Rhodotorula mucilaginosa E54 endo-PG1 showed an interaction affinity of - 5.6, - 5.5, - 5.5 and - 5.4 kcal/mol for active sites 1, 2, and 3, respectively. The endo-PGI genes of both the yeast strain Rhodotorula mucilaginosa PY18 and mutant Rhodotorula mucilaginosa E54 were successfully cloned and expressed in E. coli DH5α, showing significantly higher endo-PG1 activity, which recorded 94.57 and 153.10 U/mg for recombinant Rhodotorula mucilaginosa pGEM-PGI-PY18 and recombinant mutant Rhotorula pGEM-PGI-E54, respectively.

Raman spectroscopy online monitoring of biomass production, intracellular metabolites and carbon substrates during submerged fermentation of oleaginous and carotenogenic microorganisms.

BACKGROUND: Monitoring and control of both growth media and microbial biomass is extremely important for the development of economical bioprocesses. Unfortunately, process monitoring is still dependent on a limited number of standard parameters (pH, temperature, gasses etc.), while the critical process parameters, such as biomass, product and substrate concentrations, are rarely assessable in-line. Bioprocess optimization and monitoring will greatly benefit from advanced spectroscopy-based sensors that enable real-time monitoring and control. Here, Fourier transform (FT) Raman spectroscopy measurement via flow cell in a recirculatory loop, in combination with predictive data modeling, was assessed as a fast, low-cost, and highly sensitive process analytical technology (PAT) system for online monitoring of critical process parameters. To show the general applicability of the method, submerged fermentation was monitored using two different oleaginous and carotenogenic microorganisms grown on two different carbon substrates: glucose fermentation by yeast Rhodotorula toruloides and glycerol fermentation by marine thraustochytrid Schizochytrium sp. Additionally, the online FT-Raman spectroscopy approach was compared with two at-line spectroscopic methods, namely FT-Raman and FT-infrared spectroscopies in high throughput screening (HTS) setups. RESULTS: The system can provide real-time concentration data on carbon substrate (glucose and glycerol) utilization, and production of biomass, carotenoid pigments, and lipids (triglycerides and free fatty acids). Robust multivariate regression models were developed and showed high level of correlation between the online FT-Raman spectral data and reference measurements, with coefficients of determination (R2) in the 0.94-0.99 and 0.89-0.99 range for all concentration parameters of Rhodotorula and Schizochytrium fermentation, respectively. The online FT-Raman spectroscopy approach was superior to the at-line methods since the obtained information was more comprehensive, timely and provided more precise concentration profiles. CONCLUSIONS: The FT-Raman spectroscopy system with a flow measurement cell in a recirculatory loop, in combination with prediction models, can simultaneously provide real-time concentration data on carbon substrate utilization, and production of biomass, carotenoid pigments, and lipids. This data enables monitoring of dynamic behaviour of oleaginous and carotenogenic microorganisms, and thus can provide critical process parameters for process optimization and control. Overall, this study demonstrated the feasibility of using FT-Raman spectroscopy for online monitoring of fermentation processes.

Fermentative Production of ß-Carotene from Sugarcane Bagasse Hydrolysate by Rhodotorula glutinis CCT-2186.

Β-Carotene is a red-orange pigment that serves as a precursor to important pharmaceutical molecules like vitamin A and retinol, making it highly significant in the industrial sector. Consequently, there is an ongoing quest for more sustainable production methods. In this study, glucose and xylose, two primary sugars derived from sugarcane bagasse (SCB), were utilized as substrates for ß-carotene production by Rhodotorula glutinis CCT-2186. To achieve this, SCB underwent pretreatment using NaOH, involved different concentrations of total solids (TS) (10%, 15%, and 20%) to remove lignin. Each sample was enzymatically hydrolyzed using two substrate loadings (5% and 10%). The pretreated SCB with 10%, 15%, and 20% TS exhibited glucose hydrolysis yields (%wt) of 93.10%, 91.88%, and 90.77%, respectively. The resulting hydrolysate was employed for ß-carotene production under batch fermentation. After 72 h of fermentation, the SCB hydrolysate yielded a ß-carotene concentration of 118.56 ± 3.01 mg/L. These findings showcase the robustness of R. glutinis as a biocatalyst for converting SCB into ß-carotene.

Rhodotorula mucilaginosa ZTHY2 Attenuates Cyclophosphamide-Induced Immunosuppression in Mice.

Rhodotorula mucilaginosa (R. mucilaginosa) can enhance the immune and antioxidant function of the body. However, whether R. mucilaginosa has an immunoregulatory effect on cyclophosphamide (CTX)-induced immunosuppressed animals remains to be clarified. In this study, the R. mucilaginosa ZTHY2 that we isolated from the coastal waters of the South China Sea previously was prepared in order to investigate its immunoprotective effect on CTX-induced immunosuppression in mice, and the effects were compared to those of Lactobacillus acidophilus (LA) (a well-known probiotic). Seventy-two male SPF mice were divided into six groups: The C group (control); IM group (immunosuppressive model group) (+CTX); Rl, Rm, and Rh groups (+CTX+low, medium, and high concentration of R. mucilaginosa, respectively); and PC (positive control) group (+CTX+LA). After a 28-day feeding trial, blood samples were taken for biochemical and serum immunological analysis, and the thymus and spleen were collected to analyze the organ index, lymphocyte proliferation and differentiation, and antioxidant capacity. The findings showed that R. mucilaginosa ZTHY2 improved the spleen and thymus indices, effectively attenuated immune organ atrophy caused by CTX, and enhanced the proliferation of T and B lymphocytes induced by ConA and LPS. R. mucilaginosa ZTHY2 promoted the secretion of cytokines and immunoglobulins and significantly increased the contents of IL-2, IL-4, IL-6, TNF-α, IFN-γ, IgA, IgG, IgM, CD4, CD8, CD19, and CD20 in serum. The proportion of CD4+, CD8+, CD19+, and CD20+ lymphocytes in spleen, thymus, and mesenteric lymph nodes were increased. In addition, R. mucilaginosa ZTHY2 reduced the reactive oxygen species (ROS) and malondialdehyde (MDA) levels and increased glutathione (GSH), total superoxide dismutase (SOD), and catalase (CAT) levels. Our results indicated that R. mucilaginosa ZTHY2 can significantly enhance the immune function of immunosuppressed mice, and improving antioxidant capacity thus attenuates CTX-induced immunosuppression and immune organ atrophy.

Comparative Analysis of Capsular and Secreted Polysaccharides Produced by Rhodotorula mucilaginosa and Cryptococcus neoformans.

Fungal infections are a global public health challenge, especially among immunocompromised patients. Basidiomycetous yeasts, such as Rhodotorula mucilaginosa, have emerged as opportunistic pathogens, but have received less attention than Cryptococcus neoformans. This study aimed to characterize the polysaccharides of R. mucilaginosa and compare them with those of C. neoformans, analyzing their clinical implications. Comprehensive physicochemical, mechanical, and ultrastructural analyses of polysaccharides from both species were performed, revealing correlations with virulence and pathogenicity. R. mucilaginosa cells are surrounded by a capsule smaller than that produced by C. neoformans, but with similar polysaccharides. Those polysaccharides are also secreted by R. mucilaginosa. Cross-reactivity with R. mucilaginosa was observed in a diagnostic C. neoformans antigen test, using both in vitro and in vivo samples, highlighting the need for more reliable tests. Some R. mucilaginosa strains exhibited virulence comparable to that of C. neoformans in an invertebrate experimental model (Tenebrio molitor). This study contributes to a deeper understanding of yeast pathogenicity and virulence, highlighting the need for more accurate diagnostic tests to improve the differential diagnosis of infections caused by basidiomycetous yeasts.

Genomic analysis of the marine yeast Rhodotorula sphaerocarpa ETNP2018 reveals adaptation to the open ocean.

BACKGROUND: Despite a rising interest in the diversity and ecology of fungi in marine environments, there are few published genomes of fungi isolated from the ocean. The basidiomycetous yeast (unicellular fungus) genus Rhodotorula are prevalent and abundant in the open ocean, and they have been isolated from a wide range of other environments. Many of these environments are nutrient poor, such as the Antarctica and the Atacama deserts, raising the question as to how Rhodotorula yeasts may have adapted their metabolic strategies to optimize survival under low nutrient conditions. In order to understand their adaptive strategies in the ocean, the genome of R. sphaerocarpa ETNP2018 was compared to that of fourteen representative Rhodotorula yeasts, isolated from a variety of environments. RESULTS: Rhodotorula sphaerocarpa ETNP2018, a strain isolated from the oligotrophic part of the eastern tropical North Pacific (ETNP) oxygen minimum zone (OMZ), hosts the smallest of the fifteen genomes and yet the number of protein-coding genes it possesses is on par with the other strains. Its genome exhibits a distinct reduction in genes dedicated to Major Facilitator Superfamily transporters as well as biosynthetic enzymes. However, its core metabolic pathways are fully conserved. Our research indicates that the selective pressures of the ETNP OMZ favor a streamlined genome with reduced overall biosynthetic potential balanced by a stable set of core metabolisms and an expansion of mechanisms for nutrient acquisition. CONCLUSIONS: In summary, this study offers insights into the adaptation of fungi to the oligotrophic ocean and provides valuable information for understanding the ecological roles of fungi in the ocean.

Study of Ecological Relationship of Yeast Species with Candida albicans in the Context of Vulvovaginal Infections.

The role of the fungal community, the mycobiota, in the health of the vagina is currently an important area of research. The emergence of new sequencing technologies and advances in bioinformatics made possible the discovery of novel fungi inhabiting this niche. Candida spp. constitutes the most important group of opportunistic pathogenic fungi, being the most prevalent fungal species in vulvovaginal infections. However, fungi such as Rhodotorula spp., Naganishia spp. and Malassezia spp. have emerged as potential pathogens in this niche, and therefore it is clinically relevant to understand their ecological interaction with Candida spp. The main aim of this study was to evaluate the impact of yeasts on Candida albicans' pathogenicity, focusing on in-vitro growth, and biofilm formation at different times of co-culture and germ tube formation. The assays were performed with isolated species or with co-cultures of C. albicans (ATCC10231) with one other yeast species: Rhodotorula mucilaginosa (DSM13621), Malassezia furfur (DSM6170) or Naganishia albida (DSM70215). The results showed that M. furfur creates a symbiotic relationship with C. albicans, enhancing the growth rate of the co-culture (149.69%), and of germ tube formation of C. albicans (119.8%) and inducing a higher amount of biofilm biomass of the co-culture, both when mixed (154.1%) and preformed (166.8%). As for the yeasts R. mucilaginosa and N. albida, the relationship is antagonistic (with a significant decrease in all assays), thus possibly repressing the mixture's pathogenicity. These results shed light on the complex interactions between yeasts in the vaginal mycobiome.