Assimilation Of Carbon Sources Research Articles

Succinate-mediated symbiosis between Dialister hominis and an uncharacterized Segatella-like pectinophile

Syntrophy has been documented between pectinophiles and methanol-utilizing bacteria, along with instances of cross-feeding between pectinophiles and methanogens. However, studies on the ecology of pectinophiles in anaerobic digestion (AD) are lacking. Therefore, in this study, we aimed to elucidate the ecology of pectinophiles by isolating novel pectinophile forms and conducting a comprehensive analysis of their physiology and ecology. Complex microbial communities from AD systems were enriched in a pectin-containing medium; subsequently, specific strains were isolated using a pectinophile isolation method. The carbon source assimilation and growth ability of the isolates, along with their symbiotic relationships, were evaluated using batch tests. Strain LPYR103-Pre exhibited 16S rRNA gene sequence similarity and average nucleotide identity values of 94.3% and 77.9%, respectively, compared to its closest related species, Segatella cerevisiae. Strain LPYR103-Pre demonstrated attenuated growth in the presence of eight common sugars but exhibited remarkably high growth in the presence of pectin, D-galacturonate, and D-glucuronate, with succinate being identified as a primary metabolite. Accumulation of succinate inhibited the growth of strain LPYR103-Pre. However, this growth impediment was alleviated by Dialister hominis LPYG114-Dih, whose growth required succinate. Our results elucidate the specific carbon source requirements of the Segatella-like strain LPYR103-Pre and succinate-mediated symbiosis involving D. hominis. These findings provide new insights into the degradation of pectin and its degradation products during AD, contributing to the identification of unknown pectinophiles.

Efficient production 2,3-butanediol from biomass-derived sugars by Raoultella ornithinolytica TH-21, a newly isolated lignocellulose-degrading bacterium

Efficient bioconversion of lignocellulose to valuable products can be performed by bacteria that are both capable of degrading biomass and producing platform chemicals. This study reported a newly isolated lignocellulolytic strain, Raoultella ornithinolytica TH-21 showing great potential as an ideal biocatalyst for producing 2,3-butanediol (2,3-BDO). Strain TH-21 exhibited the capability of assimilation of multiple carbon sources for 2,3-BDO production. It could directly convert 50 g/L of xylose, mannitol, cellobiose and xylan into 2,3-BDO with the maximum production of 20.04 g/L, 16.56 g/L, 20.06 g/L and 11.25 g/L, respectively. In addition, the lignin, cellulose, and hemicellulose present in sugarcane bagasse were degraded by strain TH-21 with a rate of 26.96%, 24.6%, and 33% after 7 days of treatment, respectively. Furthermore, FTIR, XRD and SEM analysis revealed that strain TH-21 can effectively depolymerize the lignin and holocellulose in sugarcane bagasse through its efficient secretion of lignocellulolytic enzymes. Thus, these findings indicated that strain TH-21 might be a promising biocatalyst for the effective bioconversion of lignocellulose to high-value chemicals.

Curtobacterium salicis sp. nov., isolated from willow tree stems in Washington state.

Curtobacterium sp. strain WW7 is a Gram-positive, non-motile, orange rod-shaped bacterium isolated from branches of wild willow (Salix sitchensis) trees. The WW7T strain has optimum growth in the temperature range between 25 and 30°C, a pH range of 6-7.7, and tolerates up to 5.5% (w/v) of NaCl. The genome sequencing of strain WW7T revealed a genome size of approximately 3.8 Mbp and a G + C content of 71.3mol%. The phylogenomic analyses support the WW7T affiliation to a novel Curtobacterium lineage, with Curtobacterium herbarum being the closest type-strain. Chemotaxonomic analysis indicates that the carbon sources assimilation profile of strain WW7T was similar to the type strains, i.e. Curtobacterium luteum, Curtobacterium albidum, and Curtobacterium flaccumfaciens, while no assimilation of the organic acids succinate, alpha-ketobutyrate, mono methyl-succinate, and lactate was observed. Finally, fatty acid methyl ester analysis identifies anteiso-C15:0 and anteiso-C17:0 as major cellular fatty acids which is a common feature for members of the Curtobacterium genus. Based on the results of phylogenomic and chemotaxonomic analyses, strain WW7T represents a novel Curtobacterium lineage, for which the name Curtobacterium salicis sp. nov. is proposed. The type strain is WW7T (DSM 34805T-NRRL B-68078T).

Evaluation of Cellular Responses of Heterotrophic Escherichia coli Cultured with Autotrophic Chlamydomonas reinhardtii as a Nutrient Source by Analyses Based on Microbiology and Transcriptome.

Heterotrophic microorganism Escherichia coli LS5218 was cultured with flesh green alga Chlamydomonas reinhardtii C-9: NIES-2235 as a nutrient supplier. In order to evaluate the cell response of Escherichia coli with Chlamydomonas reinhardtii, Escherichia coli was evaluated with microbial methods and comprehensive gene transcriptional analyses. Escherichia coli with Chlamydomonas reinhardtii showed a specific growth rate (µmax) of 1.04 ± 0.27, which was similar to that for cells growing in Luria-Bertani medium (µmax = 1.20 ± 0.40 h-1). Furthermore, comparing the cellular responses of Escherichia coli in a green-algae-containing medium with those in the Luria-Bertani medium, transcriptomic analysis showed that Escherichia coli upregulated gene transcription levels related to glycolysis, 5-phospho-d-ribosyl-1-diphosphate, and lipid synthesis; on the other hand, it decreased the levels related to lipid degradation. In particular, the transcription levels were increased by 103.7 times on pgm (p * < 0.05 (p = 0.015)) in glycolysis, and decreased by 0.247 times on fadE (p * < 0.05 (p = 0.041)) in lipolysis. These genes are unique and could regulate the direction of metabolism; these responses possibly indicate carbon source assimilation as a cellular response in Escherichia coli. This paper is the first report to clarify that Escherichia coli, a substance-producing strain, directly uses Chlamydomonas reinhardtii as a nutrient supplier by evaluation of the cellular responses analyzed with microbial methods and transcriptome analysis.

Syncephalastrum massiliense sp. nov. and Syncephalastrum timoneanum sp. nov. Isolated from Clinical Samples.

Mucormycosis is known to be a rare opportunistic infection caused by fungal organisms belonging to the Mucorales order, which includes the Syncephalastrum species. These moulds are rarely involved in clinical diseases and are generally seen as contaminants in clinical laboratories. However, in recent years, case reports of human infections due to Syncephalastrum have increased, especially in immunocompromised hosts. In this study, we described two new Syncephalastrum species, which were isolated from human nails and sputum samples from two different patients. We used several methods for genomic and phenotypic characterisation. The phenotypic analysis relied on the morphological features, analysed both by optical and scanning electron microscopy. We used matrix-assisted laser desorption-ionization time-of-flight mass spectrometry, energy-dispersive X-ray spectroscopy, and BiologTM technology to characterise the proteomic, chemical mapping, and carbon source assimilation profiles, respectively. The genomic analysis relied on a multilocus DNA sequence analysis of the rRNA internal transcribed spacers and D1/D2 large subunit domains, fragments of the translation elongation factor-1 alpha, and the β-tubulin genes. The two novel species in the genus Syncephalastrum, namely S. massiliense PMMF0073 and S. timoneanum PMMF0107, presented a similar morphology: irregular branched and aseptate hyphae with ribbon-like aspects and terminal vesicles at the apices all surrounded by cylindrical merosporangia. However, each species displayed distinct phenotypic and genotypic features. For example, S. timoneanum PMMF0107 was able to assimilate more carbon sources than S. massiliense PMMF0073, such as adonitol, α-methyl-D-glucoside, trehalose, turanose, succinic acid mono-methyl ester, and alaninamide. The polyphasic approach, combining the results of complementary phenotypic and genomic assays, was instrumental for describing and characterising these two new Syncephalastrum species.

Neodothiora pruni sp. nov., a Biosurfactant-Producing Ascomycetous Yeast Species Isolated from Flower of Prunus mume

A yeast strain, designated as JAF-11T, was isolated from flower of Prunus mume Sieb. et Zucc. in Gwangyang, Republic of Korea. Phylogenetic analysis showed that strain JAF-11T was closely related to Neodothiora populina CPC 39399T with 2.07 % sequence divergence (12 nucleotide substitutions and three gaps in 581 nucleotides) in the D1/D2 domain of the large subunit (LSU) rRNA gene, and Rhizosphaera macrospora CBS 208.79T with 4.66 % sequence divergence (25 nucleotide substitutions and five gaps in 535 nucleotides) in the internal transcribed spacer (ITS) region. Further analysis based on the concatenated sequences of the D1/D2 domain of the LSU rRNA gene and the ITS region confirmed that strain JAF-11T was well-separated from Neodothiora populina CPC 39399T. In addition to the phylogenetic differences, strain JAF-11T was distinguished from its closest species, Neodothiora populina CPC 39399T and Rhizosphaera macrospora CBS 208.79T belonging to the family Dothioraceae by its phenotypic characteristics, such as assimilation of carbon sources. Hence, the name Neodothiora pruni sp. nov. is proposed with type strain JAF-11T (KACC 48808T; MB 850034).

Simultaneous carbon catabolite repression governs sugar and aromatic co-utilization in Pseudomonas putida M2.

Pseudomonas putida have emerged as promising biocatalysts for the conversion of sugars and aromatic compounds obtained from lignocellulosic biomass. Understanding the role of carbon catabolite repression (CCR) in these strains is critical to optimize biomass conversion to fuels and chemicals. The CCR functioning in P. putida M2, a strain capable of consuming both hexose and pentose sugars as well as aromatic compounds, was investigated by cultivation experiments, proteomics, and CRISPRi-based gene repression. Strain M2 co-utilized sugars and aromatic compounds simultaneously; however, during cultivation with glucose and aromatic compounds (p-coumarate and ferulate) mixture, intermediates (4-hydroxybenzoate and vanillate) accumulated, and substrate consumption was incomplete. In contrast, xylose-aromatic consumption resulted in transient intermediate accumulation and complete aromatic consumption, while xylose was incompletely consumed. Proteomics analysis revealed that glucose exerted stronger repression than xylose on the aromatic catabolic proteins. Key glucose (Eda) and xylose (XylX) catabolic proteins were also identified at lower abundance during cultivation with aromatic compounds implying simultaneous catabolite repression by sugars and aromatic compounds. Reduction of crc expression via CRISPRi led to faster growth and glucose and p-coumarate uptake in the CRISPRi strains compared to the control, while no difference was observed on xylose+p-coumarate. The increased abundances of Eda and amino acid biosynthesis proteins in the CRISPRi strain further supported these observations. Lastly, small RNAs (sRNAs) sequencing results showed that CrcY and CrcZ homologues levels in M2, previously identified in P. putida strains, were lower under strong CCR (glucose+p-coumarate) condition compared to when repression was absent (p-coumarate or glucose only). IMPORTANCE A newly isolated Pseudomonas putida strain, P. putida M2, can utilize both hexose and pentose sugars as well as aromatic compounds making it a promising host for the valorization of lignocellulosic biomass. Pseudomonads have developed a regulatory strategy, carbon catabolite repression, to control the assimilation of carbon sources in the environment. Carbon catabolite repression may impede the simultaneous and complete metabolism of sugars and aromatic compounds present in lignocellulosic biomass and hinder the development of an efficient industrial biocatalyst. This study provides insight into the cellular physiology and proteome during mixed-substrate utilization in P. putida M2. The phenotypic and proteomics results demonstrated simultaneous catabolite repression in the sugar-aromatic mixtures, while the CRISPRi and sRNA sequencing demonstrated the potential role of the crc gene and small RNAs in carbon catabolite repression.

Environmentally Friendly Strategies for Controlling the European Grapevine Moth, Lobesia botrana (Lepidoptera: Tortricidae)

Terlemezyan, H., M. Sargsyan, H. Harutyunyan, S. Sargsyan and N. Zarikian. 2023. Environmentally Friendly Strategies for Controlling the European Grapevine Moth, Lobesia botrana (Lepidoptera: Tortricidae). Arab Journal of Plant Protection, 41(3): 272-277. https://doi.org/10.22268/AJPP-041.3.272277 The European grapevine moth, Lobesia botrana (Denis &amp; Schiffermüller, 1775) (Lepidoptera: Tortricidae), a palearctic pest, has been the target of an international control campaign. Agricultural production areas in Armenia were identified as lacking effective control in 2019- 2020. The results of using a mixture of bacterial and chemical insecticides (BTTER-55 + Coragen, BTTER-94 + Coragen) were effective in controlling this pest. Coragen combined with sublethal concentration of bacterial insecticides (BTTER-55 + Coragen, BTTER-94 + Coragen) showed high biological efficiency against young larvae of grapevine moth under vineyard conditions. It has been proven also that, Coragen together with the applied insecticides that fell on the soil after spraying were less dangerous ecologically since they reduced the number of soil-living ammonifiers for only a short period (1-2 months). In addition, results obtained confirmed that the bacterial insecticides BTTER-55 and BTTER-94 differed in morphological and physiological features, particularly in the size of vegetative cells and spores formed by them, as well as in the size of insecticidal crystalline bodies, colonies shape and assimilation of carbon and nitrogen sources. Keywords: Armenia, European grapevine moth, insecticide, Invasive pests, Plant protection.

The genome-scale metabolic model for the purple non-sulfur bacterium Rhodopseudomonas palustris Bis A53 accurately predicts phenotypes under chemoheterotrophic, chemoautotrophic, photoheterotrophic, and photoautotrophic growth conditions.

The purple non-sulfur bacterium Rhodopseudomonas palustris is recognized as a critical microorganism in the nitrogen and carbon cycle and one of the most common members in wastewater treatment communities. This bacterium is metabolically extremely versatile. It is capable of heterotrophic growth under aerobic and anaerobic conditions, but also able to grow photoautotrophically as well as mixotrophically. Therefore R. palustris can adapt to multiple environments and establish commensal relationships with other organisms, expressing various enzymes supporting degradation of amino acids, carbohydrates, nucleotides, and complex polymers. Moreover, R. palustris can degrade a wide range of pollutants under anaerobic conditions, e.g., aromatic compounds such as benzoate and caffeate, enabling it to thrive in chemically contaminated environments. However, many metabolic mechanisms employed by R. palustris to breakdown and assimilate different carbon and nitrogen sources under chemoheterotrophic or photoheterotrophic conditions remain unknown. Systems biology approaches, such as metabolic modeling, have been employed extensively to unravel complex mechanisms of metabolism. Previously, metabolic models have been reconstructed to study selected capabilities of R. palustris under limited experimental conditions. Here, we developed a comprehensive metabolic model (M-model) for R. palustris Bis A53 (iDT1294) consisting of 2,721 reactions, 2,123 metabolites, and comprising 1,294 genes. We validated the model using high-throughput phenotypic, physiological, and kinetic data, testing over 350 growth conditions. iDT1294 achieved a prediction accuracy of 90% for growth with various carbon and nitrogen sources and close to 80% for assimilation of aromatic compounds. Moreover, the M-model accurately predicts dynamic changes of growth and substrate consumption rates over time under nine chemoheterotrophic conditions and demonstrated high precision in predicting metabolic changes between photoheterotrophic and photoautotrophic conditions. This comprehensive M-model will help to elucidate metabolic processes associated with the assimilation of multiple carbon and nitrogen sources, anoxygenic photosynthesis, aromatic compound degradation, as well as production of molecular hydrogen and polyhydroxybutyrate.

Adaptation of yeast Saccharomyces cerevisiae to grape-skin environment

Saccharomyces cerevisiae, an essential player in alcoholic fermentation during winemaking, is rarely found in intact grapes. Although grape-skin environment is unsuitable for S. cerevisiae’s stable residence, Saccharomycetaceae-family fermentative yeasts can increase population on grape berries after colonization during raisin production. Here, we addressed adaptation of S. cerevisiae to grape-skin ecosystem. The yeast-like fungus Aureobasidium pullulans, a major grape-skin resident, exhibited broad spectrum assimilation of plant-derived carbon sources, including ω-hydroxy fatty acid, arising from degradation of plant cuticles. In fact, A. pullulans encoded and secreted possible cutinase-like esterase for cuticle degradation. When intact grape berries were used as a sole carbon source, such grape-skin associated fungi increased the accessibility to fermentable sugars by degrading and assimilating the plant cell wall and cuticle compounds. Their ability seems also helpful for S. cerevisiae to obtain energy through alcoholic fermentation. Thus, degradation and utilization of grape-skin materials by resident microbiota may account for their residence on grape-skin and S. cerevisiae’s possible commensal behaviors. Conclusively, this study focused on the symbiosis between grape-skin microbiota and S. cerevisiae from the perspective of winemaking origin. Such plant–microbe symbiotic interaction may be a prerequisite for triggering spontaneous food fermentation.

Enhanced acetate utilization for value-added chemicals production in Yarrowia lipolytica by integration of metabolic engineering and microbial electrosynthesis.

The limited supply of reducing power restricts the efficient utilization of acetate in Yarrowia lipolytica. Here, microbial electrosynthesis (MES) system, enabling direct conversion of inward electrons to NAD(P)H, was used to improve the production of fatty alcohols from acetate based on pathway engineering. First, the conversion efficiency of acetate to acetyl-CoA was reinforced by heterogenous expression of ackA-pta genes. Second, a small amount of glucose was used as cosubstrate to activate the pentose phosphate pathway and promote intracellular reducing cofactors synthesis. Third, through the employment of MES system, the final fatty alcohols production of the engineered strain YLFL-11 reached 83.8 mg/g dry cell weight (DCW), which was 6.17-fold higher than the initial production of YLFL-2 in shake flask. Furthermore, these strategies were also applied for the elevation of lupeol and betulinic acid synthesis from acetate in Y. lipolytica, demonstrating that our work provides a practical solution for cofactor supply and the assimilation of inferior carbon sources.

Metabolic phenotype analysis of Trichophyton rubrum after laser irradiation

BackgroundBiological phenotypes are important characteristics of microorganisms, and often reflect their genotype and genotype changes. Traditionally, Trichophyton rubrum (T. rubrum) phenotypes were detected using carbon source assimilation tests, during which the types of tested substances are limited. In addition, the operation is complicated, and only one substance can be tested at once. To observe the changes of the metabolic phenotype of T. rubrum after laser irradiation, a high-throughput phenotype microarray system was used to analyze the metabolism of different carbon, nitrogen, phosphorus and sulfur source substrates in a Biolog metabolic phenotyping system.ResultsThe strain of T. rubrum used in this study can effectively utilize 33 carbon, 20 nitrogen, 16 phosphorus, and 13 sulfur source substrates prior to laser irradiation. After laser irradiation, the strain was able to utilize 10 carbon, 12 nitrogen, 12 phosphorus, and 8 sulfur source substrates. The degree of utilization was significantly decreased compared with the control. Both groups efficiently utilized saccharides and organic acids as carbon sources as well as some amino acids as nitrogen sources for growth. The number of substrates utilized by T. rubrum after laser irradiation were significantly reduced, especially carbon substrates. Some substrates utilization degree in the laser treated group was higher than control, such as D-glucosamine, L-glutamine, D-2-Phospho-Glyceric Acid, D-glucosamine-6-phosphate, and D-methionine.ConclusionLaser irradiation of T. rubrum may lead to changes in the metabolic substrate and metabolic pathway, thus weakening the activity of the strain.

MCT1 plays crucial roles in conidiation, lactate metabolism and pathogenicity in Colletotrichum gloeosporioides

Monocarboxylate transporters (MCTs) play vital roles in carbon source assimilation, drug resistance, and virulence. However, the underlying function of MCTs in fungal pathogenesis and development has not been investigated in detail. In this study, we identified and characterized the monocarboxylate transporter gene MCT1 of Colletotrichum gloeosporioides, which is the causal agent of Glomerella leaf spot of apple. Mct1 is localized to the mitochondria and may mediate the uptake of lactate to the cell. However, MCT1 was constitutively expressed but showed an enhanced expression level in response to the presence of the extracellular lactate. Our results indicate that Mct1 plays a role in the metabolism of lactate. More importantly, the Δmct1 mutant showed significantly poor conidiation and a defect in host infection. Taken together, our studies provide evidence for Mct1 as a mitochondrial transmembrane protein mediating conidiation, the metabolism of lactate, and the pathogenicity of C. gloeosporioides.

Insight rifampicin-resistant (rpoB) mutation in Pseudomonas stutzeri leads to enhance the biosynthesis of secondary metabolites to survive against harsh environments.

In this study, a wild-type and five distinct rifampicin-resistant (Rifr) rpoB mutants of Pseudomonas stutzeri (i.e., Q518R, D521Y, D521V, H531R and I614T) ability were investigated against harsh environments (particularly nutritional complexity). Among these, the robust Rifr phenotype of P. Stutzeri was associated only with base replacements of the amino deposits. The use of carboxylic and amino acids significantly increased in various Rifr mutants than that of wild type of P. stutzeri. The assimilation of carbon and nitrogen (N) sources of Rifr mutants' confirmed that the organism maintains the adaptation in nutritionally complex environments. Acetylene reduction assay at different times also found the variability for N-fixation in all strains. Among them, the highest nitrogenase activity was determined in mutant 'D521V'. The assimilation of carbon and nitrogen sources of P. stutzeri and its Rifr mutants ensures that the organism maintains the adaptability in nutritionally complex environments through fixing more nitrogen.

Analysis of the fermentative profile of yeasts isolated from natural sources

The natural environment aggregates an immense amount of microorganisms, some unknown and others still unexplored and that may have the potential for the production of compounds. Thus, this study aims to evaluate the fermentative profile of isolates from natural sources under different growing conditions. For this purpose, the plating performing on a 2% YPD solid medium incubating in an oven at 30 °C. The isolated colonies use for the carbon source assimilation test, which carried out through cell growth. Carrying out in test tubes containing the YP fermentative added with carbon sources (glucose, lactose, sucrose, fructose, mannose, maltose, starch) with a concentration of 17 ºBrix, at pH 4 and 6, incubated at 28 and 35 ºC and at different times of cultivation, aliquots removed for analysis. For the control, the yeast Catanduva-1 was used. The isolates grew in the range of pH 4 and pH 6 at 28 ºC and isolate A4 showed greater growth at a temperature of 35 °C. Isolates A4, A5, and A6 used most sugars except for lactose. Isolate A2 assimilated glucose and fructose and A6 showed a fermentation profile similar to standard yeast.

Significance of the presence of antibiotics on the microbial consortium in wastewater – The case of nitrofurantoin and furazolidone

Antibiotics in wastewater leads to migration of pollutants and disrupts natural processes of mineralization of organic matter. In order to understand the mechanism of this, research was undertaken on the influence of nitrofurantoin (NFT) and furazolidone (FZD), on the behaviour of a consortium of microorganisms present in a model wastewater in a bioreactor. Our study confirmed biodegradation of the antibiotics by the microbial consortium, with the degradation efficiency within 10 days of 65% for FZD, but only 20% for NFT. The kinetic study proved that the presence of analysed antibiotics had no adverse effect on the microbes, but the consortium behaviour differ significantly with the NFT reducing the consumption of organic carbon in wastewater and increasing the production of extracellular biopolymeric and volatile organic compounds, and the FZD reducing assimilation of other carbon sources to a less extent, at the expense of cellular focus on biodegradation of this antibiotic.

Supplementation of critical amino acids improves glycerol and lactose uptake and enhances recombinant protein production in Escherichia coli.

Lactose-based induction strategy in E. coli cultivation has several advantages over IPTG as it is cheap, does not impart metabolic stress to cells, and is non-toxic to cells. However, complexity of lactose as an inducer limits its application in fed-batch cultivation. A mixed glycerol-lactose based induction strategy is generally opted during fed-batch cultivation of E. coli. However, slow growth of E. coli in glycerol and lactose results in slower induction of heterologous protein. In this study, initially we have demonstrated supplementation of critical amino acids (AAs) improves uptake rate of glycerol and lactose in wildtype E. coli BL21(DE3) in defined medium. A feeding strategy of mixed glycerol-lactose feed along with supplement of critical AAs enhances recombinant production of pramlintide multimer (rPramlintide). High cell density cultivation of E. coli using mixed glycerol-lactose feed and critical AAs supplement resulted in final cell density of 52.2±0.90g L-1 andrPramlintidetiter of 7.8g L-1 . RT-qPCR analysis of genes involved in glycerol and lactose metabolism of recombinant culture showed upregulation with AAs supplementation. We hypothesize that supplementation of critical AAs serves dual purpose: (i) faster assimilation of carbon sources, and (ii) combating metabolic stress arises due to AAs starvation. The substrate uptake and gene expression profiles demonstrate that AAs addition enhances glycerol and lactose assimilation due to overall improvement in their metabolism governed by global regulators of carbon metabolism.

Delineation of a novel environmental phylogroup of the genus Acinetobacter encompassing Acinetobacter terrae sp. nov., Acinetobacter terrestris sp. nov. and three other tentative species

This study aimed to define the taxonomic position and structure of a novel, taxonomically unique group of 26 Acinetobacter strains, provisionally designated Taxon 24 (T24). The strains were recovered from soil and freshwater ecosystems (n = 21) or animals (n = 5) in Czechia, Scotland, Germany, the Netherlands and Turkey between 1993 and 2015. They were non-glucose-acidifying, nonhemolytic, nonproteolytic, growing at 32 °C and on acetate and ethanol as single carbon sources, but not on 4-hydroxybenzoate and mostly not at 37 °C. Their whole-genome sequences were 3.0–3.7 Mb in size, with GC contents of 39.8–41.3%. Based on core genome phylogenetic analysis, the 26 strains formed a distinct clade within the genus Acinetobacter, with strongly supported subclades termed T24A (n = 11), T24B (n = 8), T24C (n = 2), T24D (n = 3) and T24E (n = 2). The internal genomic ANIb values for these subclades were >94.8%, while the ANIb values between them were <92.5%. The results of MALDI-TOF MS-based analyses agreed with this classification. The five subclades differed from each other in the results of one to six carbon source assimilation tests. Given the genomic and phenotypic distinctness, internal coherence, numbers of available strains and geographically diverse origin of T24A and T24B, we propose the names Acinetobacter terrae sp. nov. and Acinetobacter terrestris sp. nov. for these two taxa, respectively. The type strains are ANC 4282v (= CCM 8986T = CCUG 73811T = CNCTC 8082T) and ANC 4471T (= CCM 8985T = CCUG 73812T = CNCTC 8093T), respectively. We conclude that these two species together with the other T24 strains represent a widely dispersed Acinetobacter clade primarily associated with terrestrial ecosystems.

Candida albicans Hexokinase 2 Challenges the Saccharomyces cerevisiae Moonlight Protein Model.

Survival of the pathogenic yeast Candida albicans depends upon assimilation of fermentable and non-fermentable carbon sources detected in host microenvironments. Among the various carbon sources encountered in a human body, glucose is the primary source of energy. Its effective detection, metabolism and prioritization via glucose repression are primordial for the metabolic adaptation of the pathogen. In C. albicans, glucose phosphorylation is mainly performed by the hexokinase 2 (CaHxk2). In addition, in the presence of glucose, CaHxK2 migrates in the nucleus and contributes to the glucose repression signaling pathway. Based on the known dual function of the Saccharomyces cerevisiae hexokinase 2 (ScHxk2), we intended to explore the impact of both enzymatic and regulatory functions of CaHxk2 on virulence, using a site-directed mutagenesis approach. We show that the conserved aspartate residue at position 210, implicated in the interaction with glucose, is essential for enzymatic and glucose repression functions but also for filamentation and virulence in macrophages. Point mutations and deletion into the N-terminal region known to specifically affect glucose repression in ScHxk2 proved to be ineffective in CaHxk2. These results clearly show that enzymatic and regulatory functions of the hexokinase 2 cannot be unlinked in C. albicans.

Genetic Interactions Between Aspergillus fumigatus Basic Leucine Zipper (bZIP) Transcription Factors AtfA, AtfB, AtfC, and AtfD.

Aspergillus fumigatus is an opportunistic fungus, capable of causing Invasive Aspergillosis in immunocompromised patients, recently transplanted or undergoing chemotherapy. In the present work, we continued the investigation on A. fumigatus AtfA-D transcription factors (TFs) characterizing possible genetic and physical interactions between them after normal growth and stressing conditions. We constructed double null mutants for all the possible combinations of ΔatfA-, -B, -C, and -D, and look into their susceptibility to different stressing conditions. Our results indicate complex genetic interactions among these TFs that could impact the response to different kinds of stressful conditions. AtfA-D interactions also affect the A. fumigatus virulence in Galleria mellonella. AtfA:GFP is ~97% located in the nucleus while about 20-30% of AtfB, -C, and -D:GFP locate into the nucleus in the absence of any stress. Under stressing conditions, AtfB, -C, and -D:GFP translocate to the nucleus about 60-80% upon the addition of sorbitol or H2O2. These four TFs are also interacting physically forming all the possible combinations of heterodimers. We also identified that AtfA-D physically interact with the MAPK SakA in the absence of any stress and upon osmotic and cell wall stresses. They are involved in the accumulation of trehalose, glycogen and metabolic assimilation of different carbon sources.