Maturation of conidia on conidiophores of Aspergillus niger

Teertstra, Wieke R.; Tegelaar, Martin; Dijksterhuis, Jan; Golovina, Elena A.; Ohm, Robin A.; Wösten, Han A. B.

doi:10.1016/j.fgb.2016.12.005

Cited by 54 publications

(57 citation statements)

References 52 publications

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“…The sequences were then aligned to the A. niger ATCC 1015 genome assembly (version Aspni7) (42) obtained from MycoCosm (43) using HISAT2 version 2.0.5 (44). Functional annotation of the predicted genes was obtained from MycoCosm as described previously (5), which, in the case of the differentially expressed genes, was manually approved by examining the GO and KEGG terms and by blastp search. However, ribosomal subunits were named by homology with S. cerevisiae, as proposed by Nakamura et al (45).…”

Section: Methodsmentioning

confidence: 99%

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FlbA-Regulated Gene rpnR Is Involved in Stress Resistance and Impacts Protein Secretion when Aspergillus niger Is Grown on Xylose

Aerts

Bergh

Post

et al. 2019

Appl Environ Microbiol

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Proteins are secreted throughout the mycelium of Aspergillus niger except for the sporulating zone. A link between sporulation and repression of protein secretion was underlined by the finding that inactivation of the sporulation gene flbA results in mycelial colonies that secrete proteins throughout the colony. However, ΔflbA strain hyphae also lyse and have thinner cell walls. This pleiotropic phenotype is associated with differential expression of 36 predicted transcription factor genes, one of which, rpnR, was inactivated in this study. Sporulation, biomass, and secretome complexity were not affected in the ΔrpnR deletion strain of the fungus. In contrast, ribosomal subunit expression and protein secretion into the medium were reduced when A. niger was grown on xylose. Moreover, the ΔrpnR strain showed decreased resistance to H 2 O 2 and the proteotoxic stress-inducing agent dithiothreitol. Taking the data together, RpnR is involved in proteotoxic stress resistance and impacts protein secretion when A. niger is grown on xylose. IMPORTANCE Aspergillus niger secretes a large amount and diversity of industrially relevant enzymes into the culture medium. This makes the fungus a widely used industrial cell factory. For instance, carbohydrate-active enzymes of A. niger are used in biofuel production from lignocellulosic feedstock. These enzymes represent a major cost factor in this process. Higher production yields could substantially reduce these costs and therefore contribute to a more sustainable economy and less dependence on fossil fuels. Enzyme secretion is inhibited in A. niger by asexual reproduction. The sporulation protein FlbA is involved in this process by impacting the expression of 36 predicted transcription factor genes. Here, we show that one of these predicted transcriptional regulators, RpnR, regulates protein secretion and proteotoxic stress resistance. The gene is thus an interesting target to improve enzyme production in A. niger.

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Section: Methodsmentioning

confidence: 99%

“…It results in conidiophores that form conidia. These spores are heterogeneous in cellular composition and germination rate (5); are dispersed by wind, water, and insects; and give rise to new mycelia. The mycelia, also known as colonies, consist of zones that show heterogeneity in function and composition (3).…”

mentioning

confidence: 99%

FlbA-Regulated Gene rpnR Is Involved in Stress Resistance and Impacts Protein Secretion when Aspergillus niger Is Grown on Xylose

Aerts

Bergh

Post

et al. 2019

Appl Environ Microbiol

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“…The genus Aspergillus is a filamentous ascomycete fungus and is among the most abundant on Earth, due to their tolerance towards a range of environments e.g. low humidities and a wide range of temperatures (6-55 °C) [18]. The utilisation of a wide range of organic conditioning films as nutrient sources, coupled with the vast number of conidia released by Aspergillus colonies has contributed to the success of this genus [18].…”

Section: Introductionmentioning

confidence: 99%

The Effect of Surface Hydrophobicity on the Attachment of Fungal Conidia to Substrates of Polyvinyl Acetate and Polyvinyl Alcohol

et al. 2020

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Biofouling of PVAc and PVOH surfaces by fungal conidia can result in surface discolouration and subsequent biodeterioration. In order to understand the interactions of fungal conidia on polymer surfaces, the surface properties of PVAc and PVOH and the hydrophobicity, size and shape of three type of fungal conidia was determined (Aspergillus niger 1957, Aspergillus niger 1988 and Aureobasidium pullulans). Fungal conidia were used in a range of binding assays (attachment, adhesion and retention). The PVAc and PVOH demonstrated different surface topographies and the PVAc demonstrated a higher maximum height (300.6 nm) when compared to the PVOH (434.2 nm). The PVAc surfaces was less wettable (75°) than the PVOH surface (62°). The FTIR demonstrated differences in the chemistries of the two surfaces, whereby the PVOH confirmed the presence of polar moieties. Hydrophobicity assays demonstrated that both A. niger species' were more non-wettable than the A. pullulans. Following the attachment assays, the more hydrophobic Aspergillus spp. conidia attached in greater numbers to the more wettable surface and the A. pullulans was retained in greater numbers to the less wettable PVAc surface. The adhesion and retention assays demonstrated that the more polar surface retained all the types of conidia, regardless of their surface hydrophobicities. This study demonstrated that conidial binding to the surfaces were influenced by the chemistry and physicochemistry of the surfaces and spores. However, the inclusion of a washing stage influenced the adhesion of conidia to surfaces. In environments that were indicative of a attachment or retention assay a PVAc surface would reduce the number of A. niger spp. spores whilst a PVOH surface would reduce the number of A. pullulans spores. However, in an environment similar to a adhesion assay, a PVAc surface would be most beneficial to reduce spore retention. Thus, the use of the correct methodology that reflects the environment in which the surface is to be used is important in order to accurately inform hygienic surface development.

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“…As reviewed recently, conidia vary in several parameters (Dijksterhuis, ). For instance, Aspergillus niger conidia of 5 days old showed higher trehalose content compared with spores of younger age (Teertstra et al ., ). Conidia of Aspergillus fumigatus showed differences in pigmentation, compatible solute content and oxidative‐ and heat‐resistance, dependent on the growth temperature of the conidia‐forming colony (Hagiwara et al ., ).…”

Section: Introductionmentioning

confidence: 97%

The most heat‐resistant conidia observed to date are formed by distinct strains of Paecilomyces variotii

Brule

Punt

Teertstra

et al. 2019

Environmental Microbiology

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Summary Fungi colonize habitats by means of spores. These cells are stress‐resistant compared with growing fungal cells. Fungal conidia, asexual spores, formed by cosmopolitan fungal genera like Penicillium, Aspergillus and Peacilomyces are dispersed by air. They are present in places where food products are stored and as a result, they cause food spoilage. Here, we determined the heterogeneity of heat resistance of conidia between and within strains of Paecilomyces variotii, a spoiler of foods such as margarine, fruit juices, canned fruits and non‐carbonized sodas. Out of 108 strains, 31 isolates showed a conidial survival >10% after a 10‐min‐heat treatment at 59°C. Three strains with different conidial heat resistance were selected for further phenotyping. Conidia of DTO 212‐C5 and DTO 032‐I3 showed 0.3% and 2.6% survival in the screening respectively, while survival of DTO 217‐A2 conidia was >10%. The decimal reduction times of these strains at 60°C (D60 value) were 3.7 ± 0.08, 5.5 ± 0.35 and 22.9 ± 2.00 min respectively. Further in‐depth analysis revealed that the three strains showed differences in morphology, spore size distributions, compatible solute compositions and growth under salt stress. Conidia of DTO 217‐A2 are the most heat‐resistant reported so far. The ecological consequences of this heterogeneity of resistance, including food spoilage, are discussed.

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Maturation of conidia on conidiophores of Aspergillus niger

Cited by 54 publications

References 52 publications

FlbA-Regulated Gene rpnR Is Involved in Stress Resistance and Impacts Protein Secretion when Aspergillus niger Is Grown on Xylose

FlbA-Regulated Gene rpnR Is Involved in Stress Resistance and Impacts Protein Secretion when Aspergillus niger Is Grown on Xylose

The Effect of Surface Hydrophobicity on the Attachment of Fungal Conidia to Substrates of Polyvinyl Acetate and Polyvinyl Alcohol

The most heat‐resistant conidia observed to date are formed by distinct strains of Paecilomyces variotii

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