ABSTRACT
Fungal primary pathogenicity on vertebrates is here described as a deliberate strategy where the host plays a role in increasing the species fitness. Opportunism is defined as coincidental survival of an individual strain in host tissue using properties that are designed for life in an entirely different habitat. In that case the host's infection control is largely based on innate immunity, and the etiologic agent is not transmitted after infection, and thus fungal evolution is not possible. Primary pathogens encompass two types, depending on their mode of transmission. Environmental pathogens have a double life cycle, and tend to become enzootic, adapted to a preferred host in a particular habitat. In contrast, pathogens that have a host-to-host transmission pattern are prone to shift to a neighboring, immunologically naive host, potentially leading to epidemics. Beyond these prototypical life cycles, some environmental fungi are able to make large leaps between dissimilar hosts/habitats, probably due to similarity of key factors enabling survival in an entirely different niche, and thus allowing a change from opportunistic to primary pathogenicity. Mostly, such factors seem to be associated with extremotolerance.
ABSTRACT
Dimorphism is known among the etiologic agents of endemic mycoses as well as in filamentous Mucorales. Under appropriate thermal conditions, mononuclear yeast forms alternate with multi-nucleate hyphae. Here, we describe a dimorphic mucoralean fungus obtained from the sputum of a patient with Burkitt lymphoma and ongoing graft-versus-host reactions. The fungus is described as Mucor germinans sp. nov. Laboratory studies were performed to simulate temperature-dependent dimorphism, with two environmental strains Mucor circinelloides and Mucor kunryangriensis as controls. Both strains could be induced to form multinucleate arthrospores and subsequent yeast-like cells in vitro. Multilateral yeast cells emerge in all three Mucor species at elevated temperatures. This morphological transformation appears to occur at body temperature since the yeast-like cells were observed in the lungs of our immunocompromised patient. The microscopic appearance of the yeast-like cells in the clinical samples is easily confused with that of Paracoccidioides. The ecological role of yeast forms in Mucorales is discussed.IMPORTANCEMucormycosis is a devastating disease with high morbidity and mortality in susceptible patients. Accurate diagnosis is required for timely clinical management since antifungal susceptibility differs between species. Irregular hyphal elements are usually taken as the hallmark of mucormycosis, but here, we show that some species may also produce yeast-like cells, potentially being mistaken for Candida or Paracoccidioides. We demonstrate that the dimorphic transition is common in Mucor species and can be driven by many factors. The multi-nucleate yeast-like cells provide an effective parameter to distinguish mucoralean infections from similar yeast-like species in clinical samples.
Subject(s)
Mucor , Mucormycosis , Humans , Mucormycosis/microbiology , Mucormycosis/diagnosis , Mucor/isolation & purification , Mucor/genetics , Mucor/classification , Paracoccidioides/isolation & purification , Paracoccidioides/genetics , Sputum/microbiology , Phylogeny , DNA, Fungal/genetics , DNA, Fungal/chemistry , Immunocompromised Host , Male , Sequence Analysis, DNA , TemperatureABSTRACT
Aspergillus flavus is a commonly encountered pathogen responsible for fungal rhinosinusitis (FRS) in arid regions. The species is known to produce aflatoxins, posing a significant risk to human health. This study aimed to investigate the aflatoxin profiles of A. flavus isolates causing FRS in Sudan. A total of 93 clinical and 34 environmental A. flavus isolates were studied. Aflatoxin profiles were evaluated by phenotypic (thin-layer and high-performance chromatography) and genotypic methods at various temperatures and substrates. Gene expression of aflD and aflR was also analyzed. A total of 42/93 (45%) isolates were positive for aflatoxin B1 and AFB2 by HPLC. When the incubation temperature changed from 28°C to 36°C, the number of positive isolates decreased to 41% (38/93). Genetic analysis revealed that 85% (79/93) of clinical isolates possessed all seven aflatoxin biosynthesis-associated genes, while 27% (14/51) of non-producing isolates lacked specific genes (aflD/aflR/aflS). Mutations were observed in aflS and aflR genes across both aflatoxin-producers and non-producers. Gene expression of aflD and aflR showed the highest expression between the 4th and 6th days of incubation on the Sabouraud medium and on the 9th day of incubation on the RPMI (Roswell Park Memorial Institute) medium. Aspergillus flavus clinical isolates demonstrated aflatoxigenic capabilities, influenced by incubation temperature and substrate. Dynamic aflD and aflR gene expression patterns over time enriched our understanding of aflatoxin production regulation. The overall findings underscored the health risks of Sudanese patients infected by this species, emphasizing the importance of monitoring aflatoxin exposure.
Aspergillus flavus, mainly causing fungal rhinosinusitis in Sudan, poses health risks due to aflatoxin production. This study revealed diverse levels of aflatoxin and gene expression of clinical isolates by pheno- and genotypic methods, emphasizing the need for vigilant monitoring in the region.
Subject(s)
Aflatoxins , Aspergillus flavus , Rhinosinusitis , Humans , Aspergillosis/microbiology , Aspergillus flavus/genetics , Aspergillus flavus/isolation & purification , Aspergillus flavus/classification , Fungal Proteins/genetics , Genotype , Rhinosinusitis/microbiology , Sudan , TemperatureABSTRACT
The present paper includes a meta-analysis of literature data on 318 species of fungi belonging to 34 orders in their response to 8 antifungal agents (amphotericin B, caspofungin, fluconazole, itraconazole, ketoconazole, posaconazole, terbinafine, and voriconazole). Main trends of MIC results at the ordinal level were visualized. European Committee on Antimicrobial Susceptibility Testing and Clinical & Laboratory Standards Institute (CLSI) clinical breakpoints were used as the staff gauge to evaluate MIC values ranging from resistance to susceptibility, which were subsequently compared with a phylogenetic tree of the fungal kingdom. Several orders (Hypocreales, Microascales, and Mucorales) invariably showed resistance. Also the basidiomycetous orders Agaricales, Polyporales, Sporidiales, Tremellales, and Trichosporonales showed relatively high degrees of azole multi-resistance, while elsewhere in the fungal kingdom, including orders with numerous pathogenic and opportunistic species, that is, Onygenales, Chaetothyiales, Sordariales, and Malasseziales, in general were susceptible to azoles. In most cases, resistance vs susceptibility was consistently associated with phylogenetic distance, members of the same order showing similar behavior. IMPORTANCE: A kingdom-wide the largest set of published wild-type antifungal data comparison were analyzed. Trends in resistance in taxonomic groups (monophyletic clades) can be compared with the phylogeny of the fungal kingdom, eventual relationships between fungus-drug interaction and evolution can be described.
Subject(s)
Antifungal Agents , Fluconazole , Humans , Antifungal Agents/pharmacology , Phylogeny , Microbial Sensitivity Tests , Voriconazole , Azoles/pharmacology , Drug Resistance, FungalABSTRACT
Since Carl Woese's discovery of archaea as a third domain of life, numerous archaeal species have been discovered, yet archaeal diversity is poorly characterized. Culturing archaea is complicated, but several queries about archaeal cell biology, evolution, physiology, and diversity need to be solved by culturing and culture-dependent techniques. Increasing interest in demand for innovative culturing methods has led to various technological and methodological advances. The current review explains frequent hurdles hindering uncultured archaea isolation and discusses features for more archaeal cultivation. This review also discusses successful strategies and available media for archaeal culturing, which might be helpful for future culturing practices.
ABSTRACT
Bacterial biofilms are formed by communities, which are encased in a matrix of extracellular polymeric substances (EPS). Notably, bacteria in biofilms display a set of 'emergent properties' that vary considerably from free-living bacterial cells. Biofilms help bacteria to survive under multiple stressful conditions such as providing immunity against antibiotics. Apart from the provision of multi-layered defense for enabling poor antibiotic absorption and adaptive persistor cells, biofilms utilize their extracellular components, e.g., extracellular DNA (eDNA), chemical-like catalase, various genes and their regulators to combat antibiotics. The response of biofilms depends on the type of antibiotic that comes into contact with biofilms. For example, excessive production of eDNA exerts resistance against cell wall and DNA targeting antibiotics and the release of antagonist chemicals neutralizes cell membrane inhibitors, whereas the induction of protein and folic acid antibiotics inside cells is lowered by mutating genes and their regulators. Here, we review the current state of knowledge of biofilm-based resistance to various antibiotic classes in bacteria and genes responsible for biofilm development, and the key role of quorum sensing in developing biofilms and antibiotic resistance is also discussed. In this review, we also highlight new and modified techniques such as CRISPR/Cas, nanotechnology and bacteriophage therapy. These technologies might be useful to eliminate pathogens residing in biofilms by combating biofilm-induced antibiotic resistance and making this world free of antibiotic resistance.
ABSTRACT
The present study was carried out to clarify the taxonomic position of Bacillus massiliigorillae and Bacillus sinesaloumensis. The 16S rRNA gene sequences extracted from the Bacillus sinesaloumensis Marseille-P3516T (FTOX00000000) and Bacillus massiliigorillae G2T (CAVL000000000) genomes showed 98.5 and 99.1% similarity with the type strains of Ferdinandcohnia humi and Peribacillus endoradicis, respectively. The amino acid identity (AAI) values of Bacillus sinesaloumensis Marseille-P3516T were higher with Ferdinandcohnia members, while Bacillus massiliigorillae G2T with Peribacillus members. In phylogenomic and phylogenetic trees, Bacillus sinesaloumensis Marseille-P3516T and Bacillus massiliigorillae G2T clade with members of the genera Ferdinandcohnia and Peribacillus, respectively. Based on the above results, we propose to transfer Bacillus massiliigorillae to the genus Peribacillus as Peribacillus massiliigorillae comb. nov., and Bacillus sinesaloumensis to the genus Ferdinandcohnia as Ferdinandcohnia sinesaloumensis comb. nov.
ABSTRACT
Fungal rhinosinusitis (FRS) is a common problem worldwide, with an increasing burden in arid climate regions. Aspergillus species are the most common causative agents involved. In the present study, we investigated the prevalence, molecular characterization, and antifungal susceptibility of opportunists causing FRS in Sudan on the basis of strains collected over a period of 5 years. ß-Tubulin and calmodulin sequencing were used for species identification, and antifungal susceptibility profiles were evaluated by the protocol of the European Committee on Antimicrobial Susceptibility Testing (EUCAST). Predominant species belonged to the Aspergillus flavus complex (n = 244), A. terreus complex (n = 16), A. fumigatus complex (n = 7), and other fungi (n = 17). Molecular identification of 94 strains of Aspergillus revealed the following species: A. flavus (n = 88), A. terreus (n = 1), A. citrinoterreus (n = 2), A. fumigatus (n = 1), A. caespitosus (n = 1), and A. sydowii (n = 1). Several A. flavus and an A. fumigatus isolates showed reduced susceptibility to azoles (minimum inhibitory concentrations above the clinical breakpoints or epidemiological cutoff values). Despite several mutations revealed in cyp51A of these isolates, none could be directly linked to azole resistance. Molecular identification of fungi causing FRS is useful to identify cryptic species and for epidemiologic studies. IMPORTANCE Fungal rhinosinusitis (FRS) is a significant clinical problem in arid regions. This study provides new insights into the prevalence, etiology, and antifungal susceptibility of FRS pathogens in Sudan, where the disease burden is high. Aspergillus species, particularly the A. flavus complex, were identified as the primary FRS pathogens in the region, with some evidence of antifungal resistance. The molecular identification of fungal species causing FRS is useful for detecting antifungal resistance, identifying cryptic species, and characterizing the epidemiology of the disease. The emergence of Azole resistance Aspergilli in Sudan highlights the need for continued surveillance and appropriate use of antifungal agents. These findings have important implications for clinical management, public health policy, and future research on FRS. Publishing this study in Microbiology Spectrum would enable other researchers and clinicians to build on these findings, ultimately improving the diagnosis, treatment, and prevention of FRS.
ABSTRACT
The Microsporum canis complex consists of one zoophilic species, M. canis, and two anthropophilic species, M. audouinii and M. ferrugineum. These species are the most widespread zoonotic pathogens causing dermatophytosis in cats and humans worldwide. To clarify the evolutionary relationship between the three species and explore the potential host shift process, this study used phylogenetic analysis, population structure analysis, multispecies coalescent analyses, determination of MAT idiomorph distribution, sexual crosses, and macromorphology and physicochemical features to address the above questions. The complex of Microsporum canis, M. audouinii and M. ferrugineum comprises 12 genotypes. MAT1-1 was present only in M. canis, while the anthropophilic entities contained MAT1-2. The pseudocleistothecia were yielded by the mating behaviour of M. canis and M. audouinii. Growth rates and lipase, keratinolysis and urea hydrolytic capacities of zoophilic M. canis isolates were all higher than those of anthropophilic strains; DNase activity of M. ferrugineum exceeded that of M. canis. The optimum growth temperature was 28 °C, but 22 °C favoured the development of macroconidia. Molecular data, physicochemical properties and phenotypes suggest the adaptation of zoophilic M. canis to anthropophilic M. ferrugineum, with M. audouinii in an intermediate position.
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Antioxidant activity and volatiles of kiwifruit wine with different flesh colors were investigated in this study. Green (Guichang and Xuxiang), red (Donghong and Hongyang), and yellow (Jinyan) kiwifruits were analyzed to determine their alcohol content, phenolic profiles, antioxidant activity, and aroma composition. The results showed that Hongyang and Donghong wines had higher antioxidant activity and content of antioxidant substances. Hongyang wine possessed the most abundance of polyphenolic compounds, chlorogenic acid and catechins were the main polyphenols of kiwi wines. The 101 aromatic components were detected, Xuxiang wine possessed 64 aromatic compounds, Donghong and Hongyang wines had the higher esters compositions, 79.87%, and 78.0% respectively. From PCA (Principal Component Analysis), the volatile substances of kiwi wine with the same flesh color were similar. Five kinds of kiwi wines shared 32 kinds of volatile compounds, these compounds may be the core volatiles in kiwi wine. Therefore, the color of kiwi flesh can impact wine flavor, with Hongyang and Donghong kiwis owning red flesh being the most suitable for producing kiwi wine which would be a new milestone to the wine manufactures.
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During an investigation of Diatrypaceae from southern China, 10 xylariales-like taxa have been collected. Morphological and multi-gene analyses confirmed that these taxa reside in Diatrypaceae and represent eight novel taxa and two new records belonging to six genera (viz., Allocryptovalsa, Diatrype, Diatrypella, Paraeutypella, Peroneutypa, and Vasilyeva gen. nov.). Vasilyeva gen. nov. was proposed to accommodate Vasilyeva cinnamomi sp. nov. Among the other collections, seven new species were introduced (viz., Diatrype camelliae-japonicae sp. nov., Diatrype rubi sp. nov., Diatrypella guiyangensis sp. nov., Diatrypella fatsiae-japonicae sp. nov., Paraeutypella subguizhouensis sp. nov., Peroneutypa hainanensis sp. nov., and Peroneutypa qianensis sp. nov.), while two were reported as new records from China (Allocryptovalsa rabenhorstii and Diatrype enteroxantha). For Diatrypaceae, the traditional taxonomic approach based on morphology may not be applicable.
ABSTRACT
Chinese baijiu, an ancient fermented alcoholic beverage, contains ethanol and a variety of compounds. One of the most popular types of Chinese baijiu is Jiang-flavor baijiu. To investigate the effects of Jiang-flavor baijiu on organ function and gut microbiota, we developed a moderate drinking mouse model and studied its effects on the liver, kidney biomarkers, memory function, and gut microbiota. The results showed that ethanol caused more hepatic steatosis, liver and kidney damage, and memory impairment than Jiang-flavour baijiu consumption. Furthermore, Jiang-flavor baijiu altered the gut microbiota by increasing the abundance of beneficial taxa such as Lactobacillus and Akkermansia, whereas ethanol increased the abundance of harmful bacteria such as Prevotella and Mucispirillum. Our findings provide preliminary evidence that moderate dose Jiang-flavor baijiu regulates gut microbiota and organ function and provide a theoretical foundation for future research on the positive health effects of particular varieties of Chinese baijiu.
Subject(s)
Gastrointestinal Microbiome , Animals , Mice , Fermentation , Alcoholic Beverages/analysis , Ethanol , BacteriaABSTRACT
Nocardia farcinica is an opportunistic pathogen that causes nocardiosis primarily in patients with compromised immune systems. In this study, we used the genetically tractable organism Caenorhabditis elegans as a model to study the innate immune responses to N. farcinica infection. We found that unlike other pathogenic bacteria such as Pseudomonas aeruginosa and Staphylococcus aureus, N. farcinica failed to kill adult worms. In another words, adult worms exposed to N. farcinica exhibited a normal lifespan, compared with those fed the standard laboratory food bacterium Escherichia coli OP50. Interestingly, deletion of three core genes (pmk-1, nsy-1 and sek-1) in the p38 MAPK/PMK-1 pathway reduced the survival of worm exposure to N. farcinica, highlighting a crucial role of this pathway for C. elegans in resistance to N. farcinica. Furthermore, our results revealed that N. farcinica exposure up-regulated the level of PMK-1 phosphorylation. The activation of PMK-1 promoted nuclear translocation of a transcription factor SKN-1/Nrf2, which in turn mediated N. farcinica infection resistance in C. elegans. Our results provide an excellent example that the integrity of immune system is key aspect for counteract with pathogenesis of N. farcinica.
ABSTRACT
A resistant and hypervirulent dermatophyte from India has been described as a taxonomic novelty, Trichophyton indotineae, a species of the Trichophyton mentagrophytes complex. Rapid detection and correct identification of closely similar dermatophytes with different predilections are essential for efficient clinical management. We evaluated the efficacy of rapid diagnostic methods clinical and environmental strains in the T. mentagrophytes complex. The methods included Real-time-PCR, DermaGenius, LAMP, and MALDI-ToF MS, using rDNA ITS sequences as taxonomic standard. The results show that only MALDI-ToF MS can distinguish 96.97% T. indotineae from other closely related species. The complex comprises numerous clones which may differ in anonymous markers but with similar evolutionary behavior. Therefore, we recommend to distinguish species only when they show an appreciable degree of adaptation and thus are clinically significant. The distinction of remaining clonal diversity is an epidemiological query and can be solved by haplotype numbering.
ABSTRACT
In the present study, the taxonomic position of Bacillus lacisalsi YSP-3T was evaluated using phylogenetic and genome-based comparison. B. lacisalsi YSP-3T showed the highest 16S rRNA gene sequence similarity to Alteribacter natronophilus M30T (98.4â%), followed by Alteribacter aurantiacus K1-5T (97.5â%) and Alteribacter populi FJAT-45347T (97.2â%). In phylogenetic (based on 16S rRNA gene sequences) and phylogenomic (based on 71 bacterial single-copy genes) trees, B. lacisalsi YSP-3T clustered with the members of the genus Alteribacter. The amino acid identity (AAI) values between B. lacisalsi YSP-3T and the members of the genus Alteribacter were >65â%, which is above the cut-off level (65-95â%) for genus delineation. The average nucleotide identity (ANI) values between B. lacisalsi YSP-3T and the members of the genus Alteribacter were <95â%, which is lower than the threshold value (95-96â%) for bacterial species delineation. The AAI value suggested that B. lacisalsi YSP-3T was a member of the genus Alteribacter while the ANIb value suggested it as a novel species of the genus Alteribacter. Based on the results, we propose to transfer Bacillus lacisalsi to the genus Alteribacter as Alteribacter lacisalsi comb. nov.
Subject(s)
Bacillaceae , Bacillus , Amino Acids , Bacillus/genetics , Bacterial Typing Techniques , Base Composition , DNA, Bacterial/genetics , Fatty Acids/chemistry , Nucleotides , Phylogeny , RNA, Ribosomal, 16S/genetics , Sequence Analysis, DNAABSTRACT
The involvement of the MET5 gene in virulence of Cryptococcus neoformans was examined using the silkworm Bombyx mori infection model. In the virulence assay, the met5Δ mutant showed virulence not significantly different from the wild-type strain, suggesting that the MET5 gene is not essential for full virulence of C. neoformans. The effect of silkworm hemolymph on the survival of the met5Δ mutant was also tested. The C. neoformans met5Δ strain incubated in the silkworm hemolymph for five days remained viable, suggesting that silkworm hemolymph supports survival of the met5Δ strain.
Subject(s)
Bombyx , Cryptococcosis , Cryptococcus neoformans , Animals , Hemolymph , Virulence/geneticsABSTRACT
Background: The extensive deployment of molecular genotyping methods is the top reliable keyword to characterize the population genetic structure of C. neoformans in the past decade. However, studies involving genotypic analysis of C. neoformans var. grubii from China and Japan are limited. Objectives: We address this challenge to determine the genotype distribution of C. neoformans var. grubii strains from China and Japan. Methods: Genotypic analysis of 52 C. neoformans var. grubii isolates was performed using multilocus microsatellite typing (MLMT) based on the sequence analysis of 3 functional genes. In order to place the herein-studied strains into the global picture, 22 strains randomly selected from the 52 strains studied by MLMT were also analyzed by restriction fragment length polymorphism analysis of the orotidine monophosphate pyrophosphorylase gene (URA5-RFLP), M13 PCR-fingerprinting, and multilocus sequence typing (MLST). Results: MLMT classified 46 (88.5%) of the 52 strains as genotype MLMT-17. The high prevalence of the MLMT-17 type was observed for environmental and clinical isolates from China and Japan. URA5-RFLP analysis, M13 PCR-fingerprinting, and MLST showed that most of these belong to the VNI/ST5 (M5) genotype. Conclusions: Our study suggests the predominance of a specific genotype of C. neoformans var. grubii in China and Japan.
Subject(s)
Cryptococcosis , Cryptococcus neoformans , Genotype , Humans , Japan , Multilocus Sequence Typing , Mycological Typing TechniquesABSTRACT
BACKGROUND: Riboflavin is a precursor of FMN and FAD which act as coenzymes of numerous enzymes. Riboflavin is an important biotechnological commodity with annual market sales exceeding nine billion US dollars. It is used primarily as a component of feed premixes, a food colorant, a component of multivitamin mixtures and medicines. Currently, industrial riboflavin production uses the bacterium, Bacillus subtilis, and the filamentous fungus, Ashbya gossypii, and utilizes glucose and/or oils as carbon substrates. RESULTS: We studied riboflavin biosynthesis in the flavinogenic yeast Candida famata that is a genetically stable riboflavin overproducer. Here it was found that the wild type C. famata is characterized by robust growth on lactose and cheese whey and the engineered strains also overproduce riboflavin on whey. The riboflavin synthesis on whey was close to that obtained on glucose. To further enhance riboflavin production on whey, the gene of the transcription activator SEF1 was expressed under control of the lactose-induced promoter of the native ß-galactosidase gene LAC4. These transformants produced elevated amounts of riboflavin on lactose and especially on whey. The strain with additional overexpression of gene RIB6 involved in conversion of ribulose-5-phosphate to riboflavin precursor had the highest titer of accumulated riboflavin in flasks during cultivation on whey. Activation of riboflavin synthesis was also obtained after overexpression of the GND1 gene that is involved in the synthesis of the riboflavin precursor ribulose-5-phosphate. The best engineered strains accumulated 2.5 g of riboflavin/L on whey supplemented only with (NH4)2SO4 during batch cultivation in bioreactor with high yield (more than 300 mg/g dry cell weight). The use of concentrated whey inhibited growth of wild-type and engineered strains of C. famata, so the mutants tolerant to concentrated whey were isolated. CONCLUSIONS: Our data show that the waste of dairy industry is a promising substrate for riboflavin production by C. famata. Possibilities for using the engineered strains of C. famata to produce high-value commodity (riboflavin) from whey are discussed.
Subject(s)
Cheese , Candida/genetics , Flavin Mononucleotide , Glucose , Lactose , Phosphates , Riboflavin , WheyABSTRACT
BACKGROUND: Fuel ethanol from lignocellulose could be important source of renewable energy. However, to make the process feasible, more efficient microbial fermentation of pentose sugars, mainly xylose, should be achieved. The native xylose-fermenting thermotolerant yeast Ogataea polymorpha is a promising organism for further development. Efficacy of xylose alcoholic fermentation by O. polymorpha was significantly improved by metabolic engineering. Still, genes involved in regulation of xylose fermentation are insufficiently studied. RESULTS: We isolated an insertional mutant of O. polymorpha with impaired ethanol production from xylose. The insertion occurred in the gene HXS1 that encodes hexose transporter-like sensor, a close homolog of Saccharomyces cerevisiae sensors Snf3 and Rgt2. The role of this gene in xylose utilization and fermentation was not previously elucidated. We additionally analyzed O. polymorpha strains with the deletion and overexpression of the corresponding gene. Strains with deletion of the HXS1 gene had slower rate of glucose and xylose consumption and produced 4 times less ethanol than the wild-type strain, whereas overexpression of HXS1 led to 10% increase of ethanol production from glucose and more than 2 times increase of ethanol production from xylose. We also constructed strains of O. polymorpha with overexpression of the gene AZF1 homologous to S. cerevisiae AZF1 gene which encodes transcription activator involved in carbohydrate sensing. Such transformants produced 10% more ethanol in glucose medium and 2.4 times more ethanol in xylose medium. Besides, we deleted the AZF1 gene in O. polymorpha. Ethanol accumulation in xylose and glucose media in such deletion strains dropped 1.5 and 1.8 times respectively. Overexpression of the HXS1 and AZF1 genes was also obtained in the advanced ethanol producer from xylose. The corresponding strains were characterized by 20-40% elevated ethanol accumulation in xylose medium. To understand underlying mechanisms of the observed phenotypes, specific enzymatic activities were evaluated in the isolated recombinant strains. CONCLUSIONS: This paper shows the important role of hexose sensor Hxs1 and transcription factor Azf1 in xylose and glucose alcoholic fermentation in the native xylose-fermenting yeast O. polymorpha and suggests potential importance of the corresponding genes for construction of the advanced ethanol producers from the major sugars of lignocellulose.
Subject(s)
Fungal Proteins/metabolism , Xylose , Ethanol/metabolism , Glucose/metabolism , Monosaccharide Transport Proteins/genetics , Monosaccharide Transport Proteins/metabolism , Pichia/metabolism , Transcription Factors/genetics , Transcription Factors/metabolism , Xylose/metabolismABSTRACT
The taxonomic position of Bacillus alkalicola was evaluated using phylogenetic and genome-based comparisons. In phylogenetic (based on 16S rRNA gene sequence) and phylogenomic (based on concatenation of protein-marker genes) trees, Bacillus alkalicola clade with the members of the genus Evansella. The amino acid identity (AAI) values suggested to reclassify Bacillus alkalicola as a member of the genus Evansella. The average nucleotide identity (ANI) value between Bacillus alkalicola and the members of the genus Evansella was lower than the threshold values for bacterial species delineation. Based on the results, we propose to transfer Bacillus alkalicola to the genus Evansella as Evansella alkalicola comb. nov. The type strain is Zby6T (=CGMCC 1.10368T=JCM 17098T=NBRC 107743T).