A comparative study between Fusarium solani and Neocosmospora vasinfecta revealed differential profile of fructooligosaccharide production

Fructooligosaccharides (FOS) are fructose-based oligosaccharides employed as additives to improve the food's nutritional and technological properties. The rhizosphere of plants that accumulate fructopolysaccharides as inulin has been revealed as a source of filamentous fungi. These fungi can produce FOS either by inulin hydrolysis or by biosynthesis from sucrose, including unusual FOS with enhanced prebiotic properties. Here, we investigated the ability of Fusarium solani and Neocosmospora vasinfecta to produce FOS from different carbon sources. Fusarium solani and N. vasinfecta grew preferentially in inulin instead of sucrose, resulting in the FOS production as the result of endo-inulinase activities. N. vasinfecta was also able to produce the FOS 1-kestose and 6-kestose from sucrose, indicating transfructosylating activity, absent in F. solani. Moreover, the results showed how these carbon sources affected fungal cell wall composition and the expression of genes encoding for β-1,3-glucan synthase and chitin synthase. Inulin and fructose promoted changes in fungal macroscopic characteristics partially explained by alterations in cell wall composition. However, these alterations were not directly correlated with the expression of genes related to cell wall synthesis. Altogether, the results pointed to the potential of both F. solani and N. vasinfecta to produce FOS at specific profiles.

Disentangling the role of extracellular polysaccharides in desiccation tolerance in lichen-forming microalgae. First evidence of sulfated polysaccharides and ancient sulfotransferase genes

Trebouxia sp. TR9 and Coccomyxa simplex are desiccation-tolerant microalgae with flexible cell walls, which undergo species-specific remodelling during dehydration-rehydration (D/R) due to their distinct ultrastructure and biochemical composition. Here, we tested the hypothesis that extracellular polysaccharides excreted by each microalga could be quantitatively and/or qualitatively modified by D/R. Extracellular polysaccharides were analysed by size exclusion and anion exchange chromatography, specific stains after gel electrophoresis and gas chromatography/mass spectrometry of trimethylsilyl derivatives (to determine their monosaccharide composition). The structure of a TR9-sulfated polymer was deduced from nuclear magnetic resonance (NMR) analyses. In addition, sugar-sulfotransferase encoding genes were identified in both microalgae, and their expression was measured by RT-qPCR. D/R did not alter the polydispersed profile of extracellular polysaccharides in either microalga but did induce quantitative changes in several peaks. Furthermore, medium-low-sized uronic acid-containing polysaccharides were almost completely substituted by higher molecular mass carbohydrates after D/R. Sulfated polysaccharide(s) were detected, for the first time, in the extracellular polymeric substances of both microalgae, but only increased significantly in TR9 after cyclic D/R, which induced a sugar-sulfotransferase gene and accumulated sulfated ß-D-galactofuranan(s). Biochemical remodelling of extracellular polysaccharides in aeroterrestrial desiccation-tolerant microalgae is species-specific and seems to play a role in the response to changes in environmental water availability.

Ultrastructural and biochemical analyses reveal cell wall remodelling in lichen-forming microalgae submitted to cyclic desiccation-rehydration

BACKGROUND AND AIMS

One of the most distinctive features of desiccation-tolerant plants is their high cell wall (CW) flexibility. Most lichen microalgae can tolerate drastic dehydration-rehydration (D/R) conditions; however, their mechanisms of D/R tolerance are scarcely understood. We tested the hypothesis that D/R-tolerant microalgae would have flexible CWs due to species-specific CW ultrastructure and biochemical composition, which could be remodelled by exposure to cyclic D/R.

METHODS

Two lichen microalgae, Trebouxia sp. TR9 (TR9, adapted to rapid D/R cycles) and Coccomyxa simplex (Csol, adapted to seasonal dry periods) were exposed to no or four cycles of desiccation [25-30 % RH (TR9) or 55-60 % RH (Csol)] and 16 h of rehydration (100 % RH). Low-temperature SEM, environmental SEM and freeze-substitution TEM were employed to visualize structural alterations induced by D/R. In addition, CWs were extracted and sequentially fractionated with hot water and KOH, and the gel permeation profile of polysaccharides was analysed in each fraction. The glycosyl composition and linkage of the main polysaccharides of each CW fraction were analysed by GC-MS.

KEY RESULTS

All ultrastructural analyses consistently showed that desiccation caused progressive cell shrinkage and deformation in both microalgae, which could be rapidly reversed when water availability increased. Notably, the plasma membrane of TR9 and Csol remained in close contact with the deformed CW. Exposure to D/R strongly altered the size distribution of TR9 hot-water-soluble polysaccharides, composed mainly of a β-3-linked rhamnogalactofuranan and Csol KOH-soluble β-glucans.

CONCLUSIONS

Cyclic D/R induces biochemical remodelling of the CW that could increase CW flexibility, allowing regulated shrinkage and expansion of D/R-tolerant microalgae.

Metabolic Changes on the Acquisition of Desiccation Tolerance in Seeds of the Brazilian Native Tree Erythrina speciosa

Erythrina speciosa Andrews (Fabaceae) is a native tree of Atlantic forest from Southern and Southeastern Brazil. Although this species is found in flooded areas, it produces highly desiccation tolerant seeds. Here, we investigated the physiological and metabolic events occurring during seed maturation of E. speciosa aiming to better understand of its desiccation tolerance acquisition. Seeds were separated into six stages of maturation by the pigmentation of the seed coat. Water potential (WP) and water content (WC) decreased gradually from the first stage to the last stage of maturation (VI), in which seeds reached the highest accumulation of dry mass and seed coat acquired water impermeability. At stage III (71% WC), although seeds were intolerant to desiccation, they were able to germinate (about 15%). Desiccation tolerance was first observed at stage IV (67% WC), in which 40% of seeds were tolerant. At stage V (24% WC), all seeds were tolerant to desiccation and at stage VI all seeds germinated. Increased deposition of the arabinose-containing polysaccharides, which are known as cell wall plasticizers polymers, was observed up to stage IV of seed maturation. Raffinose and stachyose gradually increased in axes and cotyledons with greater increment in the fourth stage. Metabolic profile analysis showed that levels of sugars, organic, and amino acids decrease drastically in embryonic axes, in agreement with lower respiratory rates during maturation. Moreover, a non-aqueous fractionation revealed a change on the proportions of sugar accumulation among cytosol, plastid, and vacuoles between the active metabolism (stage I) and the dormant seeds (stage VI). The results indicate that the physiological maturity of the seeds of E. speciosa is reached at stage V and that the accumulation of raffinose can be a result of the change in the use of carbon, reducing metabolic activity during maturation. This work confirms that raffinose is involved in desiccation tolerance in seeds of E. speciosa, especially considering the different subcellular compartments and suggests even that the acquisition of desiccation tolerance in this species occurs in stages prior to the major changes in WC.

Suppression of a single BAHD gene in Setaria viridis causes large, stable decreases in cell wall feruloylation and increases biomass digestibility

Feruloylation of arabinoxylan (AX) in grass cell walls is a key determinant of recalcitrance to enzyme attack, making it a target for improvement of grass crops, and of interest in grass evolution. Definitive evidence on the genes responsible is lacking so we studied a candidate gene that we identified within the BAHD acyl-CoA transferase family. We used RNA interference (RNAi) silencing of orthologs in the model grasses Setaria viridis (SvBAHD01) and Brachypodium distachyon (BdBAHD01) and determined effects on AX feruloylation. Silencing of SvBAHD01 in Setaria resulted in a c. 60% decrease in AX feruloylation in stems consistently across four generations. Silencing of BdBAHD01 in Brachypodium stems decreased feruloylation much less, possibly due to higher expression of functionally redundant genes. Setaria SvBAHD01 RNAi plants showed: no decrease in total lignin, approximately doubled arabinose acylated by p-coumarate, changes in two-dimensional NMR spectra of unfractionated cell walls consistent with biochemical estimates, no effect on total biomass production and an increase in biomass saccharification efficiency of 40-60%. We provide the first strong evidence for a key role of the BAHD01 gene in AX feruloylation and demonstrate that it is a promising target for improvement of grass crops for biofuel, biorefining and animal nutrition applications.

Contrasting strategies used by lichen microalgae to cope with desiccation-rehydration stress revealed by metabolite profiling and cell wall analysis

Most lichens in general, and their phycobionts in particular, are desiccation tolerant, but their mechanisms of desiccation tolerance (DT) remain obscure. The physiological responses and cell wall features of two putatively contrasting lichen-forming microalgae, Trebouxia sp. TR9 (TR9), isolated from Ramalina farinacea (adapted to frequent desiccation-rehydration cycles), and Coccomyxa solorina-saccatae (Csol), obtained from Solorina saccata (growing in usually humid limestone crevices, subjected to seasonal dry periods) was characterized. Microalgal cultures were desiccated under 25%-30% RH and then rehydrated. Under these conditions, RWC and ψw decreased faster and simultaneously during dehydration in Csol, whereas TR9 maintained its ψw until 70% RWC. The metabolic profile indicated that polyols played a key role in DT of both microalgae. However, TR9 constitutively accumulated higher amounts of polyols, whereas Csol induced the polyol synthesis under desiccation-rehydration. Csol also accumulated ascorbic acid, while TR9 synthesized protective raffinose-family oligosaccharides (RFOs) and increased its content of phenolics. Additionally, TR9 exhibited thicker and qualitatively different cell wall and extracellular polymeric layer compared with Csol, indicating higher water retention capability. The findings were consistent with the notion that lichen microalgae would have evolved distinct strategies to cope with desiccation-rehydration stress in correspondence with the water regime of their respective habitats.

Ecotoxicological effect of zinc pyrithione in the freshwater fish Gambusia holbrooki

Currently diverse biocidal agents can be used for distinct applications, such as personal hygiene, disinfection, antiparasitic activity, and antifouling effects. Zinc pyrithione is an organometallic biocide, with bactericidal, algicidal and fungicidal activities. It has been recently incorporated in antifouling formulas, such as paints, which prevent the establishment of a biofilm on surfaces exposed to the aquatic environment. It has also been used in cosmetics, such as anti-dandruff shampoos and soaps. Previously reported data has shown the presence of this substance in the aquatic compartment, a factor contributing to the potential exertion of toxic effects, and there is also evidence that photodegradation products of zinc pyrithione were involved in neurotoxic effects, namely by inhibiting cholinesterases in fish species. Additional evidence points to the involvement of zinc pyrithione in alterations of metal homeostasis and oxidative stress, in both aquatic organisms and human cell models. The present work assesses the potential ecotoxicity elicited by zinc pyrithione in the freshwater fish Gambusia holbrooki after an acute (96 h) exposure. The oxidative stress was assessed by the quantification of the activities of specific enzymes from the antioxidant defense system, such as catalase, and glutathione-S-transferases; and the extent of peroxidative damage was quantified by measuring the thiobarbituric acid reactive substances levels. Neurotoxicity was assessed through measurement of acetylcholinesterase activity; and a standardized method for the description and assessment of histological changes in liver and gills of was also used. Zinc pyrithione caused non-specific and reversible tissue alterations, both in liver and gills of exposed organisms. However, histopathological indices were not significantly different from the control group. In terms of oxidative stress biomarkers, none of the tested biomarkers indicated the occurrence of pro-oxidative effects, suggesting that the oxidative pathway is not the major toxicological outcome of exposure to zinc pyrithione.

Differences in the cell walls and extracellular polymers of the two Trebouxia microalgae coexisting in the lichen Ramalina farinacea are consistent with their distinct capacity to immobilize extracellular Pb

Trebouxia TR1 and T. TR9 are the two microalgae that coexist within Ramalina farinacea thalli. In the presence of Pb, TR9 formed extracellular aggregates, while TR1 showed a lower wall lead retention capability. Herein, we studied the cell walls and extracellular polymers (EPS) of TR1 and TR9, and their possible implication in the different Pb retention capacity of these microalgae. The proportion of cell walls on the overall cell biomass was 2.6 times higher in TR9 than in TR1. Glycosyl linkage analysis indicated the presence of hot-water soluble β-galactofuranan(s) in both cell walls, distinct from that previously described in Asterochloris, with increased rhamnose content in TR9 and a higher substitution by side chains in TR1. In the EPS of both microalgae, monosaccharide composition resembled their cell walls; however, TR9 produced two times more EPS than TR1. EPS also contained proteins, displaying distinct polypeptide patterns, modulated by Pb in TR9. Uronic acid content in EPS was higher in TR9, and increased in this phycobiont after the addition of Pb. Our findings suggest that the differential extracellular Pb retention capabilities of TR1 and TR9 microalgae can be related to differences in the main features of their cell walls and EPS.

Acute effects of tetracycline exposure in the freshwater fish Gambusia holbrooki: antioxidant effects, neurotoxicity and histological alterations

A large body of evidence was compiled in the recent decades showing a noteworthy increase in the detection of pharmaceutical drugs in aquatic ecosystems. Due to its ubiquitous presence, chemical nature, and practical purpose, this type of contaminant can exert toxic effects in nontarget organisms. Exposure to pharmaceutical drugs can result in adaptive alterations, such as changes in tissues, or in key homeostatic mechanisms, such as antioxidant mechanisms, biochemical/physiological pathways, and cellular damage. These alterations can be monitored to determine the impact of these compounds on exposed aquatic organisms. Among pharmaceutical drugs in the environment, antibiotics are particularly important because they include a variety of substances widely used in medical and veterinary practice, livestock production, and aquaculture. This wide use constitutes a decisive factor contributing for their frequent detection in the aquatic environment. Tetracyclines are the individual antibiotic subclass with the second highest frequency of detection in environmental matrices. The characterization of the potential ecotoxicological effects of tetracycline is a much-required task; to attain this objective, the present study assessed the acute toxic effects of tetracycline in the freshwater fish species Gambusia holbrooki by the determination of histological changes in the gills and liver, changes in antioxidant defense [glutathione S-transferase (GST), catalase (CAT), and lipoperoxidative damage] as well as potential neurotoxicity (acetylcholinesterase activity). The obtained results suggest the existence of a cause-and-effect relationship between the exposure to tetracycline and histological alterations (more specifically in gills) and enzymatic activity (particularly the enzyme CAT in liver and GST in gills) indicating that this compound can exert a pro-oxidative activity.

Ecotoxicological effects of salicylic acid in the freshwater fish Salmo trutta fario: antioxidant mechanisms and histological alterations

The presence of pharmaceutical drugs in aquatic ecosystems has been widely reported during the past years. Salicylic acid (SA) is mainly used in human medicine as an analgesic and antipyretic drug, being also active in preventing platelet aggregation. To study the ecotoxicological effects potentially elicited by SA in freshwater fish, brown trout individuals (Salmo trutta fario) were chronically exposed (28 days) to this drug, in order to evaluate the enzymatic and histological effects, in both gills and liver. A qualitative and semi-qualitative evaluation of the gills and liver was performed, and also a quantitative evaluation of various lamellar structures. Oxidative stress was quantified trough the determination of glutathione S-transferases (GSTs), glutathione reductase (GRed), total and selenium-dependent glutathione peroxidase (GPx) and Catalase (Cat) activities. Lipid peroxidative damage was also assessed by the quantification of thiobarbituric acid reactive substances (TBARS) in the liver. The here-obtained data showed the occurrence of oxidative stress, reflected by an increased activity of GPx and GRed in the liver; additionally, it was possible to observe non-specific histological changes in gills. The global significance of the entire set of results is discussed, giving emphasis to the ecological relevance of the responses.

Leaf metabolite profile of the Brazilian resurrection plant Barbacenia purpurea Hook. (Velloziaceae) shows two time-dependent responses during desiccation and recovering

Barbacenia purpurea is a resurrection species endemic to rock outcrops, in Rio de Janeiro, Brazil. It tolerates great temperature variations, which are associated to periods of up to 30 days without precipitation. Using a metabolomic approach, we analyzed, under winter and summer conditions, changes in the leaf metabolite profile (MP) of potted plants of B. purpurea submitted to daily watered and water deficit for at least 20 days and subsequent slow rehydration for 5 days. Leaves were collected at different time points and had their MP analyzed by GC/MS, HPAEC, and UHPLC techniques, allowing the identification of more than 60 different compounds, including organic and amino acids, sugars, and polyols, among others. In the winter experiment, results suggest the presence of two time-dependent responses in B. purpurea under water stress. The first one starts with the increase in the content of caffeoyl-quinic acids, substances with strong antioxidant activity, until the 16th day of water suppression. When RWC reached less than 80 and 70%, in winter and summer respectively, it was observed an increase in polyols and monosaccharides, followed by an increment in the content of RFO, suggesting osmotic adjustment. Amino acids, such as GABA and asparagine, also increased due to 16 days of water suppression. During rehydration, the levels of the mentioned compounds became similar to those found at the beginning of the experiment and when compared to daily watered plants. We conclude that the tolerance of B. purpurea to dehydration involves the perception of water deficit intensity, which seems to result in different strategies to overcome the gradient of water availability imposed along a certain period of stress mainly during winter. Data from summer experiment indicate that the metabolism of B. pupurea was already primed for drought stress. The accumulation of phenolics in summer seemed to be more temperature and irradiance-dependent than on the RWC.

Characterization of an extracellular endopolygalacturonase from the saprobe Mucor ramosissimus Samutsevitsch and its action as trigger of defensive response in tropical plants

In recent years, interest in the ability of non-pathogenic microorganisms to induce resistance in plants has grown, particularly with respect to their use as environmentally safe controllers of plant disease. In this study, we investigated the capacity of Mucor ramosissimus Samutsevitsch to release pectinases able to degrade cell walls of Palicourea marcgravii St. Hil., a tropical forest native Rubiaceae on which the spores of this saprobic fungus have been found. The fungus was grown in liquid culture medium containing pectin as the sole carbon source and filtrates were analyzed for pectinase activity. An endopolygalacturonase was partially purified by ion exchange chromatography, gel filtration, and preparative isoelectrofocusing, and characterized. This enzyme was more active upon pectic substrates with a low degree of methyl esterification. The products of hydrolysis of different pectic substrates (including pectin from P. marcgravii) by the action of this endopolygalacturonase elicited to different extents the phytoalexin production in soybean cotyledons. Also, the enzyme itself and the products of its action on the pectic fraction of P. marcgravii elicited the production of defensive compounds in the leaves of the plant. These results suggest that, besides the role in recycling organic matter, saprobes may also play an important role in the induction of defensive mechanisms in wild plants by enhancing their non-specific resistance against pathogens. Furthermore, they set the stage for future studies on the role of saprobic fungi in inducing resistance of host plants to pathogens.

Cell-wall structure and composition of Penicillium janczewskii as affected by inulin

Penicillium janczewskii, a filamentous fungus isolated from the rhizosphere of Vernonia herbacea (Asteraceae), grows rapidly on media containing either sucrose or inulin as carbon sources. Maintenance of P. janczewskii on inulin medium induces secretion of proteins with high inulinase activity but results in a mycelium that easily collapses and breaks. We evaluated the influence of inulin on fungal growth and colony morphology and on cell-wall structure and composition in comparison with growth and wall characteristics on sucrose-containing medium. P. janczewskii grown on Czapek medium with agar containing 1% (w/v) sucrose or inulin showed differences in the color and morphology of the colonies, although growth rates were similar on both carbon sources. Scanning-electron microscopy revealed that the hyphae from fungus grown on inulin-containing medium are much thinner than those from fungus cultivated on sucrose. Ultrastructural analysis of 5 d old cultures using transmission-electron microscopy indicated significant differences in the cell-wall thickness between hyphae grown on inulin or sucrose media. No differences were detected in the overall carbohydrate and protein contents of cell walls isolated from cultures grown on the two carbon sources. Glycosyl composition analyses showed glucose and galactose as the predominant neutral monosaccharides in the walls but showed no differences attributable to the carbon source. Glycosyl linkage composition analyses indicated a predominance of 3-linked glucopyranosyl in the hyphal walls when P. janczewskii was grown on inulin-containing medium. Our results suggest that growth on inulin as the sole carbon source results in structural changes in the mycelia of P. janczewskii that lead to mycelial walls with altered physical and biological properties.

Extracellular inulinases from Penicillium janczewskii, a fungus isolated from the rhizosphere of Vernonia herbacea (Asteraceae)

Extracellular inulinases from Penicillium janczewskii were obtained from the filtrate of 12 day-old cultures supplemented with inulin from Vernonia herbacea. Crude filtrates and partially-purified enzyme preparations (peaks I and II) were active on inulin, sucrose and raffinose. The apparent M(r) of the enzymes from peaks I and II were 48 and 66 kDa, respectively. The apparent K(m) (mmol l-1) values of peak I were 0.43 for inulin and 18.7 for sucrose; for peak II they were 0.87 and 18.5 for inulin and sucrose, respectively. Their temperature and pH optima were 55 degrees C and 5.0, respectively. Both peaks catalysed the hydrolysis of beta-(2,1) fructans more rapidly than beta-(2,6) fructans. Free fructose was the predominant product released from inulin, indicating that these enzymes display exo-inulinase activity. In view of these characteristics, the yield and the high specific activity towards beta-(2,1) fructans, inulinases from P. janczewskii can be utilized for the preparation of fructose syrup from inulin.

[Oral communication with hematologic patients: facilitating and blocking behaviors]

In this descriptive study we adopted the model of FORREST (1983) for the categorization of oral utterances by the members of the nursing team when caring for hematological patients with oncological alterations. In order to identify the frequency of facilitating(F) and blocking(B) categories of communication and of their subcategories, we videotaped and observed the interactions between 8 patients and 14 members of the Nursing team in a Teaching Hospital in the city of Ribeirão Preto-SP. We recorded 8822 categories, 56.9% of which were facilitating. The most frequent of these were: providing information (50.3%), clarifying (28.0%) and recognizing the presence (11.2%). The most frequent blocking categories were: closed questions (64.6%), giving advice (13.9%) and approving or agreeing (10%). The remaining F and B subcategories were observed at frequencies of less than 4.5%. We suggest the more frequent use of other facilitating categories and the use of closed questions in special situations. We believe that, for a more profound relationship between nursing team and patients, it is of fundamental importance to reduce the "giving advice" and "approval" categories as they are being used now.

[Blastomycotic granuloma of the cervical spine. Report of a case]

A case of blastomycotic granuloma of the spinal cord is reported. The patient had a Brown-Séquard syndrome. He was submitted to myelography and he was underwent a cervical laminectomy. The mass was removed being lately confirmed by histology as a blastomycotic granuloma. Despite the medical treatment with Amphotericin B and physical therapy there was no improvement of the condition.