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Thermophilic fungi have been seldom studied despite the fact that they can contribute to understanding ecological mechanisms of adaptation in diverse environments and have attractive toolboxes with a wide range of biotechnological applications. This work describes for the first time an endophytic and thermophilic strain of Aspergillus brasiliensis that was isolated in the crater of the active volcano "El Chichonal" in Mexico. This strain was capable of surviving in soil with a temperature of 60 °C and a pH of neutral acidity, which preluded a high thermostability and a potential in industrial application. The complete genome of A. brasiliensis E_15.1 was sequenced and assembled in 37 Mb of genomic DNA. We performed a comprehensive phylogenomic analysis for the precise taxonomic identification of this species as a novel strain of Aspergillus brasiliensis. Likewise, the predicted coding sequences were classified according to various functions including Carbohydrate-Active Enzymes (CAZymes), biosynthetic gene clusters of secondary metabolites (BGCs), and metabolic pathways associated with plant growth promotion. A. brasiliensis E_15.1 was found to degrade chitin, chitooligosaccharides, xylan, and cellulose. The genes to biosynthesize clavaric acid (a triterpene with antitumor activity) were found, thus probably having antitumor activity. In addition to the genomic analysis, a set of enzymatic assays confirmed the thermostability of extracellular xylanases and cellulases of A. brasiliensis E_15.1. The enzymatic repertoire of A. brasiliensis E_15.1 suggests that A. brasiliensis E_15.1 has a high potential for industrial application due to its thermostability and can promote plant growth at high temperatures. Finally, this strain constitutes an interesting source of terpenoids with pharmacological activity.
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Exophiala is a black fungi of the family Herpotrichiellaceae that can be found in a wide range of environments like soil, water and the human body as potential opportunistic pathogen. Some species are known to be extremophiles, thriving in harsh conditions such as deserts, glaciers, and polluted habitats. The identification of novel Exophiala species across diverse environments underlines the remarkable biodiversity within the genus. However, its classification using traditional phenotypic and phylogenetic analyses has posed a challenges. Here we describe a novel taxon, Exophiala chapopotensis sp. nov., strain LBMH1013, isolated from oil-polluted soil in Mexico, delimited according to combined morphological, molecular, evolutionary and statistics criteria. This species possesses the characteristic dark mycelia growing on PDA and tends to be darker in the presence of hydrocarbons. Its growth is dual with both yeast-like and hyphal forms. LBMH1013 differs from closely related species such as E. nidicola due to its larger aseptate conidia and could be distinguished from E. dermatitidis and E. heteromorpha by its inability to thrive above 37°C or 10% of NaCl. A comprehensive genomic analyses using up-to-date overall genome relatedness indices, several multigene phylogenies and molecular evolutionary analyzes using Bayesian speciation models, further validate its species-specific transition from all current Exophiala/Capronia species. Additionally, we applied the phylophenetic conceptual framework to delineate the species-specific hypothesis in order to incorporate this proposal within an integrative taxonomic framework. We believe that this approach to delimit fungal species will also be useful to our peers.
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Ascomicetos , Exophiala , Humanos , Exophiala/genética , Saccharomyces cerevisiae , Filogenia , México , Teorema de BayesRESUMEN
Aspergillus flavus has been found to be an effective entomopathogenic fungus for various arthropods, including ticks. In particular, natural fungal infections in cattle ticks show promise for biocontrol of the Rhipicephalus (Boophilus) microplus tick, which is a major ectoparasite affecting cattle worldwide. Our study aimed to elucidate the specific entomopathogenic virulence factors encoded in the genome of an A. flavus strain isolated from naturally infected cattle ticks. We performed morphological and biochemical phenotyping alongside complete genome sequencing, which revealed that the isolated fungus was A. flavus related to the L morphotype, capable of producing a range of gene-coded entomopathogenic virulence factors, including ribotoxin, aflatoxin, kojic acid, chitinases, killer toxin, and satratoxin. To evaluate the efficacy of this A. flavus strain against ticks, we conducted experimental bioassays using healthy engorged female ticks. A morbidity rate of 90% was observed, starting at a concentration of 105 conidia/mL. At a concentration of 107 conidia/mL, we observed a 50% mortality rate and a 21.5% inhibition of oviposition. The highest levels of hatch inhibition (30.8%) and estimated reproduction inhibition (34.64%) were achieved at a concentration of 108 conidia/mL. Furthermore, the tick larval progeny that hatched from the infected tick egg masses showed evident symptoms of Aspergillus infection after incubation.
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Heavy metal pollution is a worldwide environmental and human health problem. Prosopis laevigata is a hyperaccumulator legume that bioaccumulates Pb, Cu and Zn. With interest in designing phytoremediation strategies for sites contaminated with heavy metals, we isolated and characterized endophytic fungi from the roots of P. laevigata growing on mine tailings located in Morelos, Mexico. Ten endophytic isolates were selected by morphological discrimination and a preliminary minimum inhibitory concentration was determined for zinc, lead and copper. A novel strain of Aspergillus closest to Aspergillus luchuensis was determined to be a metallophile and presented a marked tolerance to high concentrations of Cu, Zn and Pb, so it was further investigated for removal of metals and promotion of plant growth under greenhouse conditions. The control substrate with fungi promoted larger size characters in P. laevigata individuals in comparison with the other treatments, demonstrating that A. luchuensis strain C7 is a growth-promoting agent for P. laevigata individuals. The fungus favors the translocation of metals from roots to leaves in P. laevigata, promoting an increased Cu translocation. This new A. luchuensis strain showed endophytic character and plant growth-promotion activity, high metal tolerance, and an ability to increase copper translocation. We propose it as a novel, effective and sustainable bioremediation strategy for copper-polluted soils.
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The Capsicum genus has significant economic importance since it is cultivated and consumed worldwide for its flavor and pungent properties. In 2021, Mexico produced 3.3 billion tons on 45,000 hectares which yielded USD 2 billion in exports to the USA, Canada, Japan, etc. Soil type has a dramatic effect on phosphorus (P) availability for plantsdue to its ion retention.In a previous study, novel fungal isolates were shown to solubilize and mineralize P in different kinds of soils with different P retention capacities. The aim of this work was to study the effects of the mineralogy of different kinds of "milpa" soils on the germination, biomass production, and P absorption of chili plants (Capsicum annuum). The germination percentage, the germination speed index, and the mean germination time were significantly increased in the plants treated with dual inoculation. Foliar phosphorus, growth variables, and plant biomass of chili plants grown in a greenhouse were enhanced in different soil types and with different inocula. Correlation studies suggested that the most significant performance in the foliar P concentration and in the growth response of plants was achieved in Vertisol with dual inoculation of 7 × 106 mL-1 spores per chili plant, suggesting this would be an appropriate approach to enhance chili cultivation depending on the soil type. This study stresses the importance of careful analysis of the effect of the soil type in the plant-microbe interactions.
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Although various studies have investigated osmoadaptations of halophilic fungi to saline conditions, only few analyzed the fungal mechanisms occurring at saturated NaCl concentrations. Halophilic Aspergillus sydowii is a model organism for the study of molecular adaptations of filamentous fungi to hyperosmolarity. For the first time a multi-omics approach (i.e., transcriptomics and metabolomics) was used to compare A. sydowii at saturated concentration (5.13 M NaCl) to optimal salinity (1 M NaCl). Analysis revealed 1,842 genes differentially expressed of which 704 were overexpressed. Most differentially expressed genes were involved in metabolism and signal transduction. A gene ontology multi-scale network showed that ATP binding constituted the main network node with direct interactions to phosphorelay signal transduction, polysaccharide metabolism, and transferase activity. Free amino acids significantly decreased and amino acid metabolism was reprogrammed at 5.13 M NaCl. mRNA transcriptional analysis revealed upregulation of genes involved in methionine and cysteine biosynthesis at extreme water deprivation by NaCl. No modifications of membrane fatty acid composition occurred. Upregulated genes were involved in high-osmolarity glycerol signal transduction pathways, biosynthesis of ß-1,3-glucans, and cross-membrane ion transporters. Downregulated genes were related to the synthesis of chitin, mannose, cell wall proteins, starvation, pheromone synthesis, and cell cycle. Non-coding RNAs represented the 20% of the total transcripts with 7% classified as long non-coding RNAs (lncRNAs). The 42% and 69% of the total lncRNAs and RNAs encoding transcription factors, respectively, were differentially expressed. A network analysis showed that differentially expressed lncRNAs and RNAs coding transcriptional factors were mainly related to the regulation of metabolic processes, protein phosphorylation, protein kinase activity, and plasma membrane composition. Metabolomic analyses revealed more complex and unknown metabolites at saturated NaCl concentration than at optimal salinity. This study is the first attempt to unravel the molecular ecology of an ascomycetous fungus at extreme water deprivation by NaCl (5.13 M). This work also represents a pioneer study to investigate the importance of lncRNAs and transcriptional factors in the transcriptomic response to high NaCl stress in halophilic fungi.
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Here, we analyzed the effects on Capsicum annuum plants of Trichoderma atroviride P. Karst strains altered in the expression of SWOLLENIN (SWO1), a protein with amorphogenic activity on plant cell wall components. Strains of T. atroviride that overexpressed the Taswo1 gene were constructed as well as deletion mutants. A novel, cheap and accurate method for assessing root colonization was developed. Colonization assays showed that the Taswo1 overexpressing strains invaded the host root better than the WT, resulting in a stronger plant growth-promoting effect. The expression of plant defense marker genes for both the systemic acquired resistance and induced systemic resistance pathways was enhanced in plants inoculated with Taswo1 overexpressing strains, while inoculation with deletion mutant strains resulted in a similar level of expression to that observed upon inoculation with the wild-type strain. Response to pathogen infection was also enhanced in the plants inoculated with the Taswo1 overexpressing strains, and surprisingly, an intermediate level of protection was achieved with the mutant strains. Tolerance to abiotic stresses was also higher in plants inoculated with the Taswo1 overexpressing strains but was similar in plants inoculated with the wild-type or the mutant strains. Compatible osmolyte production in drought conditions was studied. This study may contribute to improving Trichoderma biocontrol and biofertilization abilities.
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Anthracnose caused by the hemibiotroph fungus Colletotrichum gloeosporioides is a devastating plant disease with an extensive impact on plant productivity. The process of colonization and disease progression of C. gloeosporioides has been studied in a number of angiosperm crops. To better understand the evolution of the plant response to pathogens, the study of this complex interaction has been extended to bryophytes. The model moss Physcomitrium patens Hedw. B&S (former Physcomitrella patens) is sensitive to known bacterial and fungal phytopathogens, including C. gloeosporioides, which cause infection and cell death. P. patens responses to these microorganisms resemble that of the angiosperms. However, the molecular events during the interaction of P. patens and C. gloeosporioides have not been explored. In this work, we present a comprehensive approach using microscopy, phenomics and RNA-seq analysis to explore the defense response of P. patens to C. gloeosporioides. Microscopy analysis showed that appressoria are already formed at 24 h after inoculation (hai) and tissue colonization and cell death occur at 24 hai and is massive at 48 hai. Consequently, the phenomics analysis showed progressing browning of moss tissues and impaired photosynthesis from 24 to 48 hai. The transcriptomic analysis revealed that more than 1200 P. patens genes were differentially expressed in response to Colletotrichum infection. The analysis of differentially expressed gene function showed that the C. gloeosporioides infection led to a transcription reprogramming in P. patens that upregulated the genes related to pathogen recognition, secondary metabolism, cell wall reinforcement and regulation of gene expression. In accordance with the observed phenomics results, some photosynthesis and chloroplast-related genes were repressed, indicating that, under attack, P. patens changes its transcription from primary metabolism to defend itself from the pathogen.
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Aspergillus sydowii is a moderate halophile fungus extensively studied for its biotechnological potential and halophile responses, which has also been reported as a coral reef pathogen. In a recent publication, the transcriptomic analysis of this fungus, when growing on wheat straw, showed that genes related to cell wall modification and cation transporters were upregulated under hypersaline conditions but not under 0.5 M NaCl, the optimal salinity for growth in this strain. This led us to study osmolyte accumulation as a mechanism to withstand moderate salinity. In this work, we show that A. sydowii accumulates trehalose, arabitol, mannitol, and glycerol with different temporal dynamics, which depend on whether the fungus is exposed to hypo- or hyperosmotic stress. The transcripts coding for enzymes responsible for polyalcohol synthesis were regulated in a stress-dependent manner. Interestingly, A. sydowii contains three homologs (Hog1, Hog2 and MpkC) of the Hog1 MAPK, the master regulator of hyperosmotic stress response in S. cerevisiae and other fungi. We show a differential regulation of these MAPKs under different salinity conditions, including sustained basal Hog1/Hog2 phosphorylation levels in the absence of NaCl or in the presence of 2.0 M NaCl, in contrast to what is observed in S. cerevisiae. These findings indicate that halophilic fungi such as A. sydowii utilize different osmoadaptation mechanisms to hypersaline conditions.
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White-rot fungi are efficient lignin degraders due to the secretion of lignin peroxidase, manganese peroxidase, laccase, and versatile peroxidase (VP) on decayed wood. The VP is a high-redox-potential enzyme and could be used to detoxify reactive oxygen species (ROS), which accumulate in plants during biotic and abiotic stresses. We cloned the VP gene and expressed it via the Agrobacterium transformation procedure in transgenic tobacco plants to assay their tolerance to different abiotic stress conditions. Thirty independent T2 transgenic VP lines overexpressing the fungal Bjerkandera adustaVP gene were selected on kanamycin. The VP22, VP24, and VP27 lines showed significant manganese peroxidase (MnP) activity. The highest was VP22, which showed 10.87-fold more manganese peroxidase activity than the wild-type plants and led to a 34% increase in plant height and 28% more biomass. The VP22, VP24, and VP27 lines showed enhanced tolerance to drought, 200 mM NaCl, and 400 mM sorbitol. Also, these transgenics displayed significant tolerance to methyl viologen, an active oxygen-generating compound. The present data indicate that overproducing the VP gene in plants increases significantly their biomass and the abiotic stress tolerance. The VP enzyme is an effective biotechnological tool to protect organisms against ROS. In transgenic tobacco plants, it improves drought, salt, and oxidative stress tolerance. Thus, the VP gene represents a great potential for obtaining stress-tolerant crops.
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Polyaromatic phenanthrene (Phe) and benzo[a]pyrene (BaP) are highly toxic, mutagenic, and carcinogenic contaminants widely dispersed in nature, including saline environments. Polyextremotolerant Rhodotorula mucilaginosa EXF-1630, isolated from Arctic sea ice, was grown on a huge concentration range -10 to 500 ppm- of Phe and BaP as sole carbon sources at hypersaline conditions (1 M NaCl). Selected polycyclic aromatic hydrocarbons (PAHs) supported growth as well as glucose, even at high PAH concentrations. Initially, up to 40% of Phe and BaP were adsorbed, followed by biodegradation, resulting in 80% removal in 10 days. While extracellular laccase, peroxidase, and un-specific peroxygenase activities were not detected, NADPH-cytochrome c reductase activity peaked at 4 days. The successful removal of PAHs and the absence of toxic metabolites were confirmed by toxicological tests on moss Physcomitrium patens, bacterium Aliivibrio fischeri, human erythrocytes, and pulmonary epithelial cells (A549). Metabolic profiles were determined at the midpoint of the biodegradation exponential phase, with added Phe and BaP (100 ppm) and 1 M NaCl. Different hydroxylated products were found in the culture medium, while the conjugative metabolite 1-phenanthryl-ß-D-glucopyranose was detected in the medium and in the cells. Transcriptome analysis resulted in 870 upregulated and 2,288 downregulated transcripts on PAHs, in comparison to glucose. Genomic mining of 61 available yeast genomes showed a widespread distribution of 31 xenobiotic degradation pathways in different yeast lineages. Two distributions with similar metabolic capacities included black yeasts and mainly members of the Sporidiobolaceae family (including EXF-1630), respectively. This is the first work describing a metabolic profile and transcriptomic analysis of PAH degradation by yeast.
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Fenantrenos , Hidrocarburos Policíclicos Aromáticos , Benzo(a)pireno/análisis , Benzo(a)pireno/toxicidad , Biodegradación Ambiental , ADN de Hongos , Expresión Génica , Humanos , Metaboloma , RhodotorulaRESUMEN
Polycyclic aromatic hydrocarbons (PAHs) are among the most persistent xenobiotic compounds, with high toxicity effects. Mycoremediation with halophilic Aspergillus sydowii was used for their removal from a hypersaline medium (1 M NaCl). A. sydowii metabolized PAHs as sole carbon sources, resulting in the removal of up to 90% for both PAHs [benzo [a] pyrene (BaP) and phenanthrene (Phe)] after 10 days. Elimination of Phe and BaP was almost exclusively due to biotransformation and not adsorption by dead mycelium and did not correlate with the activity of lignin modifying enzymes (LME). Transcriptomes of A. sydowii grown on PAHs, or on glucose as control, both at hypersaline conditions, revealed 170 upregulated and 76 downregulated genes. Upregulated genes were related to starvation, cell wall remodelling, degradation and metabolism of xenobiotics, DNA/RNA metabolism, energy generation, signalling and general stress responses. Changes of LME expression levels were not detected, while the chloroperoxidase gene, possibly related to detoxification processes in fungi, was strongly upregulated. We propose that two parallel metabolic pathways (mitochondrial and cytosolic) are involved in degradation and detoxification of PAHs in A. sydowii resulting in intracellular oxidation of PAHs. To the best of our knowledge, this is the most comprehensive transcriptomic analysis on fungal degradation of PAHs.
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Hidrocarburos Policíclicos Aromáticos , Transcriptoma , Aspergillus/genética , Biodegradación Ambiental , Perfilación de la Expresión Génica , Transcriptoma/genéticaRESUMEN
Water activity (aw) is critical for microbial growth, as it is severely restricted at aw < 0.90. Saturating NaCl concentrations (~5.0 M) induce extreme water deprivation (aw â 0.75) and cellular stress responses. Halophilic fungi have cellular adaptations that enable osmotic balance and ionic/oxidative stress prevention to grow at high salinity. Here we studied the morphology, osmolyte synthesis, and oxidative stress defenses of the halophile Aspergillus sydowii EXF-12860 at 1.0 M and 5.13 M NaCl. Colony growth, pigmentation, exudate, and spore production were inhibited at NaCl-saturated media. Additionally, hyphae showed unpolarized growth, lower diameter, and increased septation, multicellularity and branching compared to optimal NaCl concentration. Trehalose, mannitol, arabitol, erythritol, and glycerol were produced in the presence of both 1.0 M and 5.13 M NaCl. Exposing A. sydowii cells to 5.13 M NaCl resulted in oxidative stress evidenced by an increase in antioxidant enzymes and lipid peroxidation biomarkers. Also, genes involved in cellular antioxidant defense systems were upregulated. This is the most comprehensive study that investigates the micromorphology and the adaptative cellular response of different non-enzymatic and enzymatic oxidative stress biomarkers in halophilic filamentous fungi.
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Since Aromatic hydrocarbons are recalcitrant and toxic, strategies to remove them are needed. The aim of this work was to isolate fungi capable of using aromatic hydrocarbons as carbon sources. Two isolates from an oil polluted site in Mexico were identified through morphological and molecular markers as a novel Rhodotorula sp. and an Exophiala sp. Both strains were able to grow in a wide range of pH media, from 4 to 12, showing their optimal growth at alkaline pH's and are both halotolerant. The Exophiala strain switched from hyphae to yeast morphotype in high salinity conditions. To the best of our knowledge, this is the first report of salt triggering dimorphism. The Rhodotorula strain, which is likely a new undescribed species, was capable of removing singled ringed aromatic compounds such as benzene, xylene, and toluene, but could not remove benzo[a] pyrene nor phenanthrene. Nevertheless, these hydrocarbons did not impair its growth. The Exophiala strain showed a different removal capacity. It could remove the polyaromatic hydrocarbons but performed poorly at removing toluene and xylene. Nevertheless, it still could grow well in the presence of the aromatic compounds. These strains could have a potential for aromatic compounds removal.
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(1) Background: Mechanisms of cellular and molecular adaptation of fungi to salinity have been commonly drawn from halotolerant strains and few studies in basidiomycete fungi. These studies have been conducted in settings where cells are subjected to stress, either hypo- or hyperosmotic, which can be a confounding factor in describing physiological mechanisms related to salinity. (2) Methods: We have studied transcriptomic changes in Aspergillussydowii, a halophilic species, when growing in three different salinity conditions (No NaCl, 0.5 M, and 2.0 M NaCl). (3) Results: In this fungus, major physiological modifications occur under high salinity (2.0 M NaCl) and not when cultured under optimal conditions (0.5 M NaCl), suggesting that most of the mechanisms described for halophilic growth are a consequence of saline stress response and not an adaptation to saline conditions. Cell wall modifications occur exclusively at extreme salinity, with an increase in cell wall thickness and lamellar structure, which seem to involve a decrease in chitin content and an augmented content of alfa and beta-glucans. Additionally, three hydrophobin genes were differentially expressed under hypo- or hyperosmotic stress but not when the fungus grows optimally. Regarding compatible solutes, glycerol is the main compound accumulated in salt stress conditions, whereas trehalose is accumulated in the absence of salt. (4) Conclusions: Physiological responses to salinity vary greatly between optimal and high salt concentrations and are not a simple graded effect as the salt concentration increases. Our results highlight the influence of stress in reshaping the response of extremophiles to environmental challenges.
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Hongos/química , Estrés Fisiológico/fisiología , Hongos/citología , Humanos , SalinidadRESUMEN
Heavy metal pollution has become an environmental and health problem worldwide. With the aim of finding novel strategies for metal bioremediation, endophytic fungi from the heavy metal hyperaccumulator plant Vachellia farnesiana were isolated and characterized. The plants were growing in mine tailings, rich in Zn, Pb, and Cu. Morphological and phylogenetic analyses indicated that the fungal strains belonged to Neocosmospora and Aspergillus genera. The Neocosmospora isolate belongs to the Fusarium solani species complex (FSSC) that groups phytopathogen species. However, in this case the plants from which it was isolated did not show any signs of disease. Both fungal strains were able to remove significant amounts of heavy metals from liquid cultures, either in a mixture of the three metals or each metal in a single culture. In response to lead exposure, the Neocosmospora sp. strain secreted specific novel phenolic compounds other than anthraquinones or naphtoquinones, which have been described in similar situations. The Aspergillus sp. dropped the pH in the medium. High-performance liquid chromatography determinations indicated that this strain secreted mainly glutamic acid in response to lead, a novel mechanism, which has not been reported elsewhere. Malic and succinic acids were also produced in response to lead exposure. Possibly, glutamic and succinic acids (synthesized in the Krebs cycle) can be used to cope with metal toxicity due to the plant providing photosynthates to the fungus. These fungi showed the potential to be used for bioremediation or restoration of metal-polluted environments.
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Extreme ecosystems are a possible source of new interesting microorganisms, in this study the isolation of psychrophilic and psychrotolerant plant growth promoting microorganisms was pursued in a cold habitat, with the aim of finding novel microbes that can protect crops from cold. Eight yeast and four bacterial strains were isolated from rhizospheric soil collected from the Xinantécatl volcano in Mexico, and characterized for plant growth promoting properties. Most of the yeasts produced indole acetic acid and hydrolytic enzymes (cellulases, xilanases and chitinases), but none of them produced siderophores, in contrast to their bacterial counterparts. Inorganic phosphate solubilization was detected for all the bacterial strains and for two yeast strains. Yeast and bacterial strains may inhibit growth of various pathogenic fungi, propounding a role in biological control. Microorganisms were identified up to genera level, by applying ribotyping techniques and phylogenetic analysis. Bacterial strains belonged to the genus Pseudomonas, whereas yeast strains consisted of Rhodotorula sp. (4), Mrakia sp. (3) and Naganishia sp. (1). New species belonging to the aforementioned genera seem to have been isolated from both bacteria and yeasts. Germination promoting activity on Solanum lycopersicum seeds was detected for all strains compared to a control, whereas tomato plantlets, grown at 15 °C in the presence of some of the strains, performed better than the non-inoculated plantlets. This study offers the possibility of using these strains as an additive to improve culture conditions of S. lycopersicum in a more environmentally compatible way. This is the first study to propose psychrophilic/psychrotolerant yeasts, as plant growth promoting microbes.
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Bacterias/clasificación , Bacterias/aislamiento & purificación , Fenómenos Fisiológicos Bacterianos , Filogenia , Desarrollo de la Planta , Levaduras/clasificación , Levaduras/aislamiento & purificación , Altitud , Frío , ADN/aislamiento & purificación , Ecosistema , Hongos/patogenicidad , Germinación , Ácidos Indolacéticos/metabolismo , Solanum lycopersicum/crecimiento & desarrollo , México , Enfermedades de las Plantas , Rizosfera , Semillas/crecimiento & desarrollo , Sideróforos/metabolismo , Microbiología del Suelo , Estrés Fisiológico , Erupciones Volcánicas , Levaduras/fisiologíaRESUMEN
The nixtamalized maize pericarp (NMP) is a plentiful by-product of the tortilla industry and an important source of fermentable sugars. The aim of this study was to describe the degradation profile of NMP by the action of a consortium (PM-06) obtained from the native microbial community of this residue. The degradation was analyzed in terms of the changes in the community dynamics, production of enzymes (endo-xylanase and endo-cellulase), physicochemical parameters, and substrate chemical and microstructural characteristics, to understand the mechanisms behind the process. The consortium PM-06 degraded 86.8 ± 3.3% of NMP after 192 h of growth. Scanning electron microscopy images, and the composition and weight of the residual solids, showed that degradation was sequential starting with the consumption of hemicellulose. Xylanase was the highest enzyme activity produced, with a maximum value of 12.45 ± 0.03 U mL-1. There were fluctuations in the pH during the NMP degradation, starting with the acidification of the culture media and finishing with a pH close to 8.5. The most abundant species in the consortium, at the moment of maximum degradation activity, were Aneurinibacillus migulanus, Paenibacillus macerans, Bacillus coagulans, Microbacterium sp. LCT-H2, and Bacillus thuringiensis. The diversity of PM-06 provided metabolic abilities that in combination helped to produce an efficient process. The consortium PM-06 generated a set of different tools that worked coordinated to increase the substrate availability through the solubilization of components and elimination of structural diffusion barriers. This is the first report about the degradation of NMP using a microbial consortium.
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Polycyclic aromatic hydrocarbons (PAH) and pharmaceutical compounds (PhC) are xenobiotics present in many saline wastewaters. Although fungi are known for their ability to remove xenobiotics, the potential of halophilic fungi to degrade highly persistent pollutants was not yet investigated. The use of two halophilic fungi, Aspergillus sydowii and Aspergillus destruens, for the elimination of PAH and PhC at saline conditions was studied. In saline synthetic medium both fungi used benzo-α-pyrene and phenanthrene as sole carbon source and removed over 90% of both PAH, A. sydowii due to biodegradation and A. destruens to bioadsorption. They removed 100% of a mixture of fifteen PAH in saline biorefinery wastewater. Test using Cucumis sativus demonstrated that wastewater treated with the two fungi lowered considerably the phytotoxicity. This study is the first demonstration that ascomycetous halophilic fungi, in contrast to other fungi (and in particular basidiomycetes) can be used for mycotreatments under salinity conditions.
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Aspergillus/metabolismo , Xenobióticos/metabolismo , Fenantrenos/metabolismo , Hidrocarburos Policíclicos Aromáticos/metabolismo , SalinidadRESUMEN
Legumes establish symbiotic relationships with different microorganisms, which could function as plant growth promotion microorganisms (PGPM). The finding of new PGPM strains is important to increase plant production avoiding or diminishing the use of industrial fertilizers. Thus, in this work we evaluated the plant growth promotion traits of ten strains isolated from Mimosa pudica root nodules. According to the 16S rDNA sequence, the microorganisms were identified as Enterobacter sp. and Serratia sp. To the best of our knowledge this is the first report describing and endophytic interaction between Mimosa pudica and Enterobacter sp. These strains have some plant growth promoting traits such as phosphate solubilization, auxin production and cellulase and chitinase activity. Strains identified as Serratia sp. inhibited the growth of the phytopathogenic fungi Fusarium sp., and Alternaria solani and the oomycete Phytophthora capsici. According to their biochemical characteristics, three strains were selected to test their plant growth promoting activity in a medium with an insoluble phosphate source. These bacteria show low specificity for their hosts as endophytes, since they were able to colonize two very different legumes: Phaseolus vulgaris and M. pudica. Seedlings of P. vulgaris were inoculated and grown for fifteen days. Enterobacter sp. NOD1 and NOD10, promoted growth as reflected by an increase in shoot height as well as an increase in the size and emergence of the first two trifolia. We could localize NOD5 as an endophyte in roots in P. vulgaris by transforming the strain with a Green Fluorescent Protein carrying plasmid. Experiments of co-inoculation with different Rhizobium etli strains allowed us to discard that NOD5 can fix nitrogen in the nodules formed by a R. etli Fix- strain. The isolates described in this work show biotechnological potential for plant growth promoting activity and production of indoleacetic acid and siderophores.