Ecotoxicological assessment of cyclic peptides produced by a Planktothrix rubescens bloom: Impact on aquatic model organisms.

Cyanobacterial blooms, a natural phenomenon in freshwater ecosystems, have increased in frequency and severity due to climate change and eutrophication. Some cyanobacteria are able to produce harmful substances called cyanotoxins. These metabolites possess different chemical structures and action mechanisms representing a serious concern for human health and the environment. The most studied cyanotoxins belong to the group of microcystins which are potent hepatotoxins. Anabaenopeptins are another class of cyclic peptides produced by certain species of cyanobacteria, including Planktothrix spp. Despite limited knowledge regarding individual effects of anabaenopeptins on freshwater organisms, reports have identified in vivo toxicity in representatives of freshwater zooplankton by cyanobacterial extracts or mixtures containing anabaenopeptins. This study focused on the isolation and toxicity evaluation of the cyanotoxins produced in the 2022 Planktothrix rubescens bloom in Averno lake, Italy. The three main cyclic peptides have been isolated and identified by nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry (MS) and optical analyses as anabaenopeptins A and B, and oscillamide Y. Ecotoxicological tests on the aquatic model organisms Daphnia magna (crustacean), Raphidocelis subcapitata (algae), and Aliivibrio fischeri (bacterium) revealed that anabaenopeptins A and B do not generate significant toxicity at environmentally relevant concentrations, being also found a stimulatory effect on R. subcapitata in the case of anabaenopeptin A. By contrast, oscillamide Y displayed toxicity. Ecological implications based on ECOSAR predictions align with experimental data. Moreover, long-term exposure bioassays on different green unicellular algae species showed that R. subcapitata was not significantly affected, while Scenedesmus obliquus and Chlorella vulgaris exhibited altered growth patterns. These results, together with the already-known background in literature, highlight the complexity of interactions between organisms and the tested compounds, which may be influenced by species-specific sensitivities, physiological differences, and modes of action, possibly affected by parameters like lipophilicity.

Health-Promoting Properties of Natural Flavonol Glycosides Isolated from Staphylea pinnata L.

Staphylea, also called bladdernuts, is a genus of plants belonging to the family Staphyleaceae, widespread in tropical or temperate climates of America, Europe, and the Far East. Staphylea spp. produce bioactive metabolites with antioxidant properties, including polyphenols which have not been completely investigated for their phytotherapeutic potential, even though they have a long history of use for food. Here, we report the isolation of six flavonol glycosides from the hydroalcoholic extract of aerial parts of Staphylea pinnata L., collected in Italy, using a solid-phase extraction technique. They were identified using spectroscopic, spectrometric, and optical methods as three quercetin and three isorhamnetin glycosides. Among the flavonol glycosides isolated, isoquercetin and quercetin malonyl glucoside showed powerful antioxidant, antimicrobial, and wound healing promoting activity and thus are valuable as antiaging ingredients for cosmeceutical applications and for therapeutic applications in skin wound repair.

Ecotoxicity and Mutagenicity Assessment of Novel Antifungal Agents VT-1161 and T-2307.

Antifungal substances are essential for managing fungal infections in humans, animals, and plants, and their usage has significantly increased due to the global rise in fungal infections. However, the extensive application of antifungal agents in pharmaceuticals, personal care products, and agriculture has led to their widespread environmental dissemination through various pathways, such as excretion, improper disposal, and agricultural runoff. Despite advances in wastewater treatment, many antifungal compounds persist in the environment, affecting non-target organisms and contributing to resistance development. This study investigates the environmental impact of two novel antifungal agents, VT-1161 and T-2307, recently introduced as alternatives for treating resistant Candida spp. We assessed their ecotoxicity and mutagenicity using multiple bioassays: immobilization of Daphnia magna, growth inhibition of Raphidocelis subcapitata, luminescence inhibition of Aliivibrio fischeri, and mutagenicity on Salmonella typhimurium strain TA100. Results indicate that both VT-1161 and T-2307 exhibit lower toxicity compared to existing antifungal compounds, with effective concentrations (EC50) causing 50% response ranging from 14.34 to 27.92 mg L-1. Furthermore, both agents were classified as less hazardous based on the Globally Harmonized System of Classification and Labeling of Chemicals. Despite these favorable results, further research is needed to understand their environmental behavior, interactions, and potential resistance development among non-target species. Our findings highlight the importance of comprehensive environmental risk assessments to ensure the sustainable use of new antifungal agents.

A Re-Purposing Strategy: Sub-Lethal Concentrations of an Eicosanoid Derived from the Omega-3-Polyunsaturated Fatty Acid Resolvin D1 Affect Dual Species Biofilms.

The fungal species Candida parapsilosis and the bacterial species Staphylococcus aureus may be responsible for hospital-acquired infections in patients undergoing invasive medical interventions or surgical procedures and often coinfect critically ill patients in complicating polymicrobial biofilms. The efficacy of the re-purposing therapy has recently been reported as an alternative to be used. PUFAs (polyunsaturated fatty acids) may be used alone or in combination with currently available traditional antimicrobials to prevent and manage various infections overcoming antimicrobial resistance. The objectives of the study were to evaluate the effects of Resolvin D1 (RvD1) as an antimicrobial on S. aureus and C. parapsilosis, as well as the activity against the mixed biofilm of the same two species. Microdilution assays and time-kill growth curves revealed bacterial and fungal inhibition at minimum concentration values between 5 and 10 µg mL-1. In single-species structures, an inhibition of 55% and 42% was reported for S. aureus and C. parapsilosis, respectively. Moreover, RvD1 demonstrated an eradication capacity of 60% and 80% for single- and mixed-species biofilms, respectively. In association with the inhibition activity, a downregulation of genes involved in biofilm formation as well as ROS accumulation was observed. Eradication capability was confirmed also on mature mixed biofilm grown on silicone platelets as shown by scanning electron microscopy (SEM). In conclusion, RvD1 was efficient against mono and polymicrobial biofilms in vitro, being a promising alternative for the treatment of mixed bacterial/fungal infections.

Possible Molecular Mechanisms Underlying the Decrease in the Antibacterial Activity of Protamine-like Proteins after Exposure of Mytilus galloprovincialis to Chromium and Mercury.

Natural bioactive compounds represent a new frontier of antimicrobial molecules, and the marine ecosystem represents a new challenge in this regard. In the present work, we evaluated the possibility of changes in the antibacterial activity of protamine-like (PL) proteins, the major nuclear basic protein components of Mytilus galloprovincialis sperm chromatin, after the exposure of mussels to subtoxic doses of chromium (VI) (1, 10, and 100 nM) and mercury (1, 10, and 100 pM) HgCl2, since these metals affect some properties of PL. After exposure, we analyzed the electrophoretic pattern of PLs by both acetic acid-urea polyacrylamide gel electrophoresis (AU-PAGE) and SDS-PAGE and determined the MIC and MBC of these proteins on different gram+ and gram- bacteria. PLs, particularly after mussels were exposed to the highest doses of chromium and mercury, showed significantly reduced antibacterial activity. Just at the highest doses of exposure to the two metals, changes were found in the electrophoretic pattern of PLs, suggesting that there were conformational changes in these proteins, which were confirmed by the fluorescence measurements of PLs. These results provide the first evidence of a reduction in the antibacterial activity of these proteins following the exposure of mussels to these metals. Based on the results, hypothetical molecular mechanisms that could explain the decrease in the antibacterial activity of PLs are discussed.

Polystyrene Microplastics Exacerbate Candida albicans Infection Ability In Vitro and In Vivo.

Plastic pollution is an important environmental problem, and microplastics have been shown to have harmful effects on human and animal health, affecting immune and metabolic physiological functions. Further, microplastics can interfere with commensal microorganisms and exert deleterious effects on exposure to pathogens. Here, we compared the effects of 1 µm diameter polystyrene microplastic (PSMPs) on Candida albicans infection in both in vitro and in vivo models by using HT29 cells and Galleria mellonella larvae, respectively. The results demonstrated that PSMPs could promote Candida infection in HT29 cells and larvae of G. mellonella, which show immune responses similar to vertebrates. In this study, we provide new experimental evidence for the risk to human health posed by PSMPs in conjunction with Candida infections.

Catalytic Activity of Rare Earth Elements (REEs) in Advanced Oxidation Processes of Wastewater Pollutants: A Review.

In recent years, sewage treatment plants did not effectively remove emerging water pollutants, leaving potential threats to human health and the environment. Advanced oxidation processes (AOPs) have emerged as a promising technology for the treatment of contaminated wastewater, and the addition of catalysts such as heavy metals has been shown to enhance their effectiveness. This review focuses on the use of rare earth elements (REEs) as catalysts in the AOP process for the degradation of organic pollutants. Cerium and La are the most studied REEs, and their mechanism of action is based on the oxygen vacancies and REE ion concentration in the catalysts. Metal oxide surfaces improve the decomposition of hydrogen peroxide to form hydroxide species, which degrade the organics. The review discusses the targets of AOPs, including pharmaceuticals, dyes, and other molecules such as alkaloids, herbicides, and phenols. The current state-of-the-art advances of REEs-based AOPs, including Fenton-like oxidation and photocatalytic oxidation, are also discussed, with an emphasis on their catalytic performance and mechanism. Additionally, factors affecting water chemistry, such as pH, temperature, dissolved oxygen, inorganic species, and natural organic matter, are analyzed. REEs have great potential for enhancing the removal of dangerous organics from aqueous solutions, and further research is needed to explore the photoFenton-like activity of REEs and their ideal implementation for wastewater treatment.

Hormetic Effects of Cerium, Lanthanum and Their Combination at Sub-micromolar Concentrations in Sea Urchin Sperm.

Rare earth elements (REEs) cerium (Ce) and lanthanum (La) and their combination were tested across a concentration range, from toxic (10-4 to 10-5 M) to lower concentrations (10-6 to 10-8 M) for their effects on sea urchin (Sphaerechinus granularis) sperm. A significantly decreased fertilization rate (FR) was found for sperm exposed to 10-5 M Ce, La and their combination, opposed to a significant increase of FR following 10-7 and 10-8 M REE sperm exposure. The offspring of REE-exposed sperm showed significantly increased developmental defects following sperm exposure to 10-5 M REEs vs. untreated controls, while exposure to 10-7 and 10-8 M REEs resulted in significantly decreased rates of developmental defects. Both of observed effects-on sperm fertilization success and on offspring quality-were closely exerted by Ce or La or their combination.

Hygienic assessment of digestate from a high solids anaerobic co-digestion of sewage sludge with biowaste by testing Salmonella Typhimurium, Escherichia coli and SARS-CoV-2.

Anaerobic digestion is a consolidated technology to convert sewage sludge and other organic wastes into biogas and a nutrient-rich fertilizer (i.e. digestate). The origin of sewage sludge does not exclude the potential presence of pathogens (e.g. Salmonella spp. and SARS-CoV-2) in mature digestate that hence could represent a source of sanitary concerns when it is spread on soil for agriculture purpose. Therefore, an experimental study aimed at proving the sanitizing effect of a full scale thermophilic high solids anaerobic digestion process was conducted by monitoring the hygienic characteristics of mature digestate. Although Salmonella spp. was detected in the sewage sludge fed to the full scale plant, the anaerobic digestion treatment demonstrated sanitization capacity since the monitored pathogens were never found in the mature digestate over the entire duration of the monitoring survey. Furthermore, tests on the regrowth of Salmonella Typhimurium and Escherichia coli, artificially inoculated on mature digestate, were also conducted under both anaerobic and aerobic conditions with the aim to assess the effectiveness of mature digestate as microbial growth medium. Concentrations of Salmonella Typhimurium and Escherichia coli were drastically reduced after a short time of incubation under anaerobic process and the two microorganisms already resulted undetectable after 24-48 h, whereas, under aerobic conditions, two microorganisms' concentrations were stably high for longer than 10 days. The combination of no free oxygen, high temperature, anaerobic metabolites (e.g. total ammonium nitrogen, and volatile fatty acids) production, bacteria competition and lack of nutritional elements in mature digestate considerably reduced in 24-48 h the sanitary risks associated to accidently contaminated digestate. Furthermore, a SARS-CoV-2 monitoring survey on mature digestate during 13 months, resulted in the absence of the virus RNA in the analyzed digestate.

The Arylamidine T-2307 as a Novel Treatment for the Prevention and Eradication of Candida tropicalis Biofilms.

Candida tropicalis is an emerging pathogen with a high mortality rate due to its virulence factors, including biofilm formation, that has important repercussions on the public health system. The ability of C. tropicalis to form biofilms, which are potentially more resistant to antifungal drugs and the consequent increasing antimicrobial resistance, highlights an urgent need for the development of novel antifungal. The present study analyzed the antibiofilm capacity of the arylamidine T-2307 on two strains of Candida tropicalis. Antimicrobial activity and time-killing assays were performed to evaluate the anticandidal effects of T-2307, the antibiofilm ability on biomass inhibition and eradication was evaluated by the crystal violet (CV) method. Furthermore, in Galleria mellonella infected larvae an increased survival after pre-and post- treatment with T-2307 was observed. The MTT test was used to determine the viability of immortalized human prostate epithelial cells (PNT1A) after exposure to different concentrations of T-2307. Levels of interleukin IL-4, IL-8, IL-10 were quantified after Candida infection of PNT1A cells and treatment. Active doses of T-2307 did not affect the viability of PNT1A cells, and drug concentrations of 0.005 or 0.01 µg mL-1 inhibited the secretion of inflammatory cytokines. Taken together, these results provide new information on T-2307, indicating this drug as a new and promising alternative therapeutic option for the treatment of Candida infections.

WMR Peptide as Antifungal and Antibiofilm against Albicans and Non-Albicans Candida Species: Shreds of Evidence on the Mechanism of Action.

Candida species are the most common fungal pathogens infecting humans and can cause severe illnesses in immunocompromised individuals. The increased resistance of Candida to traditional antifungal drugs represents a great challenge in clinical settings. Therefore, novel approaches to overcome antifungal resistance are desired. Here, we investigated the use of an antimicrobial peptide WMR against Candida albicans and non-albicans Candida species in vitro and in vivo. Results showed a WMR antifungal activity on all Candida planktonic cells at concentrations between 25 µM to >50 µM and exhibited activity at sub-MIC concentrations to inhibit biofilm formation and eradicate mature biofilm. Furthermore, in vitro antifungal effects of WMR were confirmed in vivo as demonstrated by a prolonged survival rate of larvae infected by Candida species when the peptide was administered before or after infection. Additional experiments to unravel the antifungal mechanism were performed on C. albicans and C. parapsilosis. The time-killing curves showed their antifungal activity, which was further confirmed by the induced intracellular and mitochondrial reactive oxygen species accumulation; WMR significantly suppressed drug efflux, down-regulating the drug transporter encoding genes CDR1. Moreover, the ability of WMR to penetrate within the cells was demonstrated by confocal laser scanning microscopy. These findings provide novel insights for the antifungal mechanism of WMR against Candida albicans and non-albicans, providing fascinating scenarios for the identification of new potential antifungal targets.

Octocrylene: From Sunscreens to the Degradation Pathway during Chlorination Processes: Formation of Byproducts and Their Ecotoxicity Assessment.

Octocrylene is an organic sunscreen whose main action is to absorb UVB radiation and short UVA wavelengths; it is used in various cosmetic products in order to provide an adequate sun-protection factor or to protect the cosmetic formulations themselves from UV radiation. This filter is believed to be a possible endocrine disruptor and is also questioned due to its allergic and/or photoallergic potential. However, it continues to be widely used, and it has been found in various environments, not least those of swimming pools, where it is evidently released by consumers, to the point that it is now considered an emerging micropollutant. The present investigation presents the possible chemical fate of octocrylene in the typical chlorination conditions of wastewater or swimming pools. A total of 11 disinfection byproducts were identified, and 6 were identified for the first time, and separated by HPLC. These products were identified through careful mass spectrometry studies and 1D and 2D NMR experiments. A formation mechanism has been proposed that justifies the chemical structures of all of the compounds identified. The ecotoxicological assessment of octocrylene and their products was carried out by employing Phaeodactylum tricornutum, Brachionus plicatilis and Aliivibrio fischeri as bioindicators. The ecotoxicity results reveal that toxic byproducts might be generated during the oxidation process, increasing the potential risk to the marine environment.

Interaction of the Fungal Metabolite Harzianic Acid with Rare-Earth Cations (Pr3+, Eu3+, Ho3+, Tm3+).

Rare-earth elements (REEs) are in all respect a class of new contaminants that may have toxic effects on organisms and microorganisms and information on their interactions with natural ligands should be of value to predict and control their diffusion in natural environments. In the current study, we investigate interactions of tripositive cations of praseodymium, europium, holmium, and thulium with harzianic acid (H2L), a secondary metabolite produced by selected strains of fungi belonging to the Trichoderma genus. We applied the same techniques and workflow previously employed in an analogous study concerning lanthanum, neodymium, samarium, and gadolinium tripositive cations. Therefore, in the current study, HPLC-ESI-HRMS experiments, circular dichroism (CD), and UV-Vis spectrophotometric absorption data, as well as accurate pH measurements, were applied to characterize bonding interactions between harzianic acid and Pr3+, Eu3+, Ho3+, and Tm3+ cations. Problems connected to the low solubility of harzianic acid in water were overcome by employing a 0.1 M NaClO4/(CH3OH + H2O 50/50 w/w) mixed solvent. For Pr3+, Ho3+, and Tm3+, only the mono complexes PrL+, HoL+, and TmL+ were detected and their formation constant determined. Eu3+ forms almost exclusively the bis complex EuL2- for which the corresponding formation constant is reported; under our experimental conditions, the mono complex EuL+ is irrelevant. Combining the results of the present and previous studies, a picture of interactions of harzianic acid with rare-earth cations extending over 8 of the 17 REEs can be composed. In order to complement chemical information with toxicological information, a battery of bioassays was applied to evaluate the effects of praseodymium, europium, holmium, and thulium tripositive cations on a suite of bioindicators including Aliivibrio fischeri (Gram-negative bacterium), Raphidocelis subcapitata (green alga), and Daphnia magna (microcrustacean), and median effective concentration (EC50) values of Pr3+, Eu3+, Ho3+, and Tm3+ for the tested species were assessed.

Interaction of the Fungal Metabolite Harzianic Acid with Rare-Earth Cations (La3+, Nd3+, Sm3+, Gd3+).

Rare-earth elements are emerging contaminants of soil and water bodies which destiny in the environment and effects on organisms is modulated by their interactions with natural ligands produced by bacteria, fungi and plants. Within this framework, coordination by harzianic acid (H2L), a Trichoderma secondary metabolite, of a selection of tripositive rare-earth cations Ln3+ (Ln3+ = La3+, Nd3+, Sm3+, and Gd3+) was investigated at 25 °C, and in a CH3OH/0.1 M NaClO4 (50/50 w/w) solvent, using mass spectrometry, circular dichroism, UV-Vis spectrophotometry, and pH measurements. Experimental data can be satisfactorily explained by assuming, for all investigated cations, the formation of a mono-complex (LnL+) and a bis-complex (LnL2-). Differences were found between the formation constants of complexes of different Ln3+ cations, which can be correlated with ionic radius. Since gadolinium is the element that raises the most concern among lanthanide elements, its effects on organisms at different levels of biological organization were explored, in the presence and absence of harzianic acid. Results of ecotoxicological tests suggest that harzianic acid can decrease gadolinium biotoxicity, presumably because of complex formation with Gd3+.

Hydrochemical, isotopic and microbiota characterization of telese mineral waters (Southern Italy).

The study deals with the analyses of springs and wells at the base of Montepugliano Hill that represents the SE edge of the wide carbonate Matese massif (Campania, southern Italy). At the base of the hill, from west to east and for almost one kilometre, cold springs HCO3-Ca type (Grassano springs, ~ 4.5 m3/s; TDS: about 0.45 g/L) pass to hypothermal, HCO3-Ca type, sulphurous and CO2-rich springs (~ 1 m3/s with TDS > 1 g/L). Some of the latter are widely used in Telese Spa and Centro Relax Spa. Chemical and isotopic analyses carried out for this study support the hypothesis that all these waters (mineral and non-mineral) have the same catchment area, which is located in the Matese massif. As regards the sulphurous springs, they receive both meteoric waters infiltration and uprising of deeper waters rich in endogenous CO2 and H2S gases through important faults systems. Far from these faults, the chemistry of groundwater is scarcely (or not at all) affected by these deep fluid enrichment processes. This scheme is very significant; in fact, when very important groundwater resources are present, it is possible to use both mineral waters in Spa and, in areas far from the faults, those not yet mineralized. Finally, at Montepugliano Hill, in the final stage of the flow path, groundwater is also affected by change in the microbiome: this could provide a basis for comparison between various mineral waters.

Ecotoxicity and photodegradation of Montelukast (a drug to treat asthma) in water.

The present work focuses on the ecotoxicological effects of montelukast sodium (MTL) and its photoproducts, obtained under environmentally-like conditions. Despite of the potential presence in surface waters and the common use of MTL as asthma drug, limited data has been published for its photodegradation, while no information is available for its ecotoxicity. Light-induced degradation is an effective way for drugs to degrade in aquatic environments, and MTL is highly photosensitive, even by exposure to sunlight. In this study, solar-simulated irradiation of the drug in water was investigated. The drug was quickly converted into a series of photoproducts that were spectroscopically characterized. The possible photoreaction pathways were proposed. Ecotoxicity tests were performed on parent compound and mixture of photoproducts towards two bioindicators (Raphidocelis subcapitata and Daphnia magna). Results evidenced that effects of MTL on D. magna (EC50 = 16.4 mg/L) were greater than effects on R. subcapitata (EC50 = 195.7 mg/L). Microscopy observations revealed that MTL had mainly accumulated in the gut of daphnia. Toxicity data on photolysed solutions highlighted the presence of residual toxicity in all samples, evidencing that no complete mineralization occurred. Future research should focus on monitoring of MTL concentrations in the environment and study its effects in bioaccumulation tests.

Sub-Chronic Effects of Slight PAH- and PCB-Contaminated Mesocosms in Paracentrotus lividus Lmk: A Multi-Endpoint Approach and De Novo Transcriptomic.

Sediment pollution is a major issue in coastal areas, potentially endangering human health and the marine environments. We investigated the short-term sublethal effects of sediments contaminated with polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) on the sea urchin Paracentrotus lividus for two months. Spiking occurred at concentrations below threshold limit values permitted by the law (TLVPAHs = 900 µg/L, TLVPCBs = 8 µg/L, Legislative Italian Decree 173/2016). A multi-endpoint approach was adopted, considering both adults (mortality, bioaccumulation and gonadal index) and embryos (embryotoxicity, genotoxicity and de novo transcriptome assembly). The slight concentrations of PAHs and PCBs added to the mesocosms were observed to readily compartmentalize in adults, resulting below the detection limits just one week after their addition. Reconstructed sediment and seawater, as negative controls, did not affect sea urchins. PAH- and PCB-spiked mesocosms were observed to impair P. lividus at various endpoints, including bioaccumulation and embryo development (mainly PAHs) and genotoxicity (PAHs and PCBs). In particular, genotoxicity tests revealed that PAHs and PCBs affected the development of P. lividus embryos deriving from exposed adults. Negative effects were also detected by generating a de novo transcriptome assembly and its annotation, as well as by real-time qPCR performed to identify genes differentially expressed in adults exposed to the two contaminants. The effects on sea urchins (both adults and embryos) at background concentrations of PAHs and PCBs below TLV suggest a need for further investigations on the impact of slight concentrations of such contaminants on marine biota.

PAHs and PCBs Affect Functionally Intercorrelated Genes in the Sea Urchin Paracentrotus lividus Embryos.

Polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) represent the most common pollutants in the marine sediments. Previous investigations demonstrated short-term sublethal effects of sediments polluted with both contaminants on the sea urchin Paracentrotus lividus after 2 months of exposure in mesocosms. In particular, morphological malformations observed in P. lividus embryos deriving from adults exposed to PAHs and PCBs were explained at molecular levels by de novo transcriptome assembly and real-time qPCR, leading to the identification of several differentially expressed genes involved in key physiological processes. Here, we extensively explored the genes involved in the response of the sea urchin P. lividus to PAHs and PCBs. Firstly, 25 new genes were identified and interactomic analysis revealed that they were functionally connected among them and to several genes previously defined as molecular targets of response to the two pollutants under analysis. The expression levels of these 25 genes were followed by Real Time qPCR, showing that almost all genes analyzed were affected by PAHs and PCBs. These findings represent an important further step in defining the impacts of slight concentrations of such contaminants on sea urchins and, more in general, on marine biota, increasing our knowledge of molecular targets involved in responses to environmental stressors.

GC-MS-Based Metabolomics Study of Single- and Dual-Species Biofilms of Candida albicans and Klebsiella pneumoniae.

Candida albicans and Klebsiella pneumoniae frequently co-exist within the human host as a complex biofilm community. These pathogens are of interest because their association is also related to significantly increased morbidity and mortality in hospitalized patients. With the aim of highlighting metabolic shifts occurring in the dual-species biofilm, an untargeted GC-MS-based metabolomics approach was applied to single and mixed biofilms of C. albicans and K. pneumoniae. Metabolomic results showed that among the extracellular metabolites identified, approximately 40 compounds had significantly changed relative abundance, mainly involving central carbon, amino acid, vitamin, and secondary metabolisms, such as serine, leucine, arabitol, phosphate, vitamin B6, cyclo-(Phe-Pro), trehalose, and nicotinic acid. The results were related to the strict interactions between the two species and the different microbial composition in the early and mature biofilms.

An Integrated Analysis of Intracellular Metabolites and Virulence Gene Expression during Biofilm Development of a Clinical Isolate of Candida tropicalis on Distinct Surfaces.

Emergence of Candida tropicalis, which causes potential life-threatening invasive candidiasis, is often associated with colonization of medical devices as biofilm. Biofilm plays an important role in the virulence of the pathogen because of its complex structure, which provides resistance to conventional antimicrobials. In this study, the metabolic response of a clinical strain of C. tropicalis colonizing three distinct surfaces (polytetrafluoroethylene (PTFE), polystyrene, and polycarbonate) as well as the expression of virulence and stress related genes (ALS3, Hsp21, SAP1, SAP2, SAP3, and CYR1), were explored. Our results showed that lesser biofilm was developed on PTFE compared to polystyrene and polycarbonate. GS-MS metabolic analysis identified a total of 36 metabolites in the intracellular extract of cells grown on polystyrene, polycarbonate, and PTFE, essentially belonging to central carbon metabolism, amino acids, and lipids metabolism. The metabolic analysis showed that saturated and unsaturated fatty acids are preferentially produced during biofilm development on polycarbonate, whereas trehalose and vitamin B6, known as cellular protectors against a variety of stressors, were characteristic of biofilm on PTFE. The results of the transcriptomic analysis consider the different degrees of colonization of the three substrates, being CYR1, which encodes the component of signaling pathway of hyphal formation-cAMP-PKA, downregulated in PTFE biofilm compared to polycarbonate or polystyrene biofilms, while Hsp21 was upregulated in concomitance with the potential unfavorable conditions for biofilm formation on PTFE. Overall, this work provides new insights into the knowledge of C. tropicalis biofilm development on surfaces of medical relevance in the perspective of improving the management of Candida infections.