Publications by authors named "Corrado Nai"

9 Publications

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Construction of an improved Aspergillus niger platform for enhanced glucoamylase secretion.

Microb Cell Fact 2018 Jun 16;17(1):95. Epub 2018 Jun 16.

Department Applied and Molecular Microbiology, Institute of Biotechnology, Technische Universität Berlin, Gustav-Meyer-Allee 25, 13355, Berlin, Germany.

Background: The lifestyle of filamentous fungi depends on the secretion of hydrolytic enzymes into the surrounding medium, which degrade polymeric substances into monomers that are then taken up to sustain metabolism. This feature has been exploited in biotechnology to establish platform strains with high secretory capacity including Aspergillus niger. The accepted paradigm is that proteins become mainly secreted at the tips of fungal hyphae. However, it is still a matter of debate if the amount of growing hyphal tips in filamentous fungi correlates with an increase in secretion, with previous studies showing either a positive or no correlation.

Results: Here, we followed a systematic approach to study protein secretion in A. niger. First, we put the glaA gene encoding for glucoamylase (GlaA), the most abundant secreted protein of A. niger, under control of the tunable Tet-on system. Regulation of glaA gene expression by omitting or adding the inducer doxycycline to cultivation media allowed us to study the effect of glaA under- or overexpression in the same isolate. By inducing glaA expression in a fluorescently tagged v-SNARE reporter strain expressing GFP-SncA, we could demonstrate that the amount of post-Golgi carriers indeed depends on and correlates with glaA gene expression. By deleting the racA gene, encoding the Rho-GTPase RacA in this isolate, we generated a strain which is identical to the parental strain with respect to biomass formation but produces about 20% more hyphal tips. This hyperbranching phenotype caused a more compact macromorphology in shake flask cultivations. When ensuring continuous high-level expression of glaA by repeated addition of doxycycline, this hyperbranching strain secreted up to four times more GlaA into the culture medium compared to its parental strain.

Conclusion: The data obtained in this study strongly indicate that A. niger responds to forced transcription of secretory enzymes with increased formation of post-Golgi carriers to efficiently accommodate the incoming cargo load. This physiological adaptation can be rationally exploited to generate hypersecretion platforms based on a hyperbranching phenotype. We propose that a racA deletion background serves as an excellent chassis for such hypersecretion strains.
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http://dx.doi.org/10.1186/s12934-018-0941-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6004097PMC
June 2018

How a fungus shapes biotechnology: 100 years of research.

Fungal Biol Biotechnol 2018 24;5:13. Epub 2018 May 24.

Department of Applied and Molecular Microbiology, Institute of Biotechnology, Technische Universität Berlin, Gustav-Meyer-Allee 25, 13355 Berlin, Germany.

In 1917, a food chemist named James Currie made a promising discovery: any strain of the filamentous mould would produce high concentrations of citric acid when grown in sugar medium. This tricarboxylic acid, which we now know is an intermediate of the Krebs cycle, had previously been extracted from citrus fruits for applications in food and beverage production. Two years after Currie's discovery, industrial-level production using began, the biochemical fermentation industry started to flourish, and industrial biotechnology was born. A century later, citric acid production using this mould is a multi-billion dollar industry, with additionally producing a diverse range of proteins, enzymes and secondary metabolites. In this review, we assess main developments in the field of biology over the last 100 years and highlight scientific breakthroughs and discoveries which were influential for both basic and applied fungal research in and outside the community. We give special focus to two developments of the last decade: systems biology and genome editing. We also summarize the current international research community, and end by speculating on the future of fundamental research on this fascinating fungus and its exploitation in industrial biotechnology.
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http://dx.doi.org/10.1186/s40694-018-0054-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5966904PMC
May 2018

From Axenic to Mixed Cultures: Technological Advances Accelerating a Paradigm Shift in Microbiology.

Trends Microbiol 2018 06 27;26(6):538-554. Epub 2017 Nov 27.

Department of Applied and Molecular Microbiology, Institute of Biotechnology, Technische Universität Berlin, Gustav-Meyer-Allee 25, 13355 Berlin, Germany. Electronic address:

Since the onset of microbiology in the late 19th century, scientists have been growing microorganisms almost exclusively as pure cultures, resulting in a limited and biased view of the microbial world. Only a paradigm shift in cultivation techniques - from axenic to mixed cultures - can allow a full comprehension of the (chemical) communication of microorganisms, with profound consequences for natural product discovery, microbial ecology, symbiosis, and pathogenesis, to name a few areas. Three main technical advances during the last decade are fueling the realization of this revolution in microbiology: microfluidics, next-generation 3D-bioprinting, and single-cell metabolomics. These technological advances can be implemented for large-scale, systematic cocultivation studies involving three or more microorganisms. In this review, we present recent trends in microbiology tools and discuss how these can be employed to decode the chemical language that microorganisms use to communicate.
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http://dx.doi.org/10.1016/j.tim.2017.11.004DOI Listing
June 2018

Openness and visibility of fungal bio(techno)logy.

Fungal Biol Biotechnol 2017 23;4. Epub 2017 Oct 23.

School of BioSciences, The University of Melbourne, Building 122, Parkville, VIC 3010 Australia.

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http://dx.doi.org/10.1186/s40694-017-0038-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5651607PMC
October 2017

The beauty and the morbid: fungi as source of inspiration in contemporary art.

Fungal Biol Biotechnol 2016 29;3:10. Epub 2016 Nov 29.

Department Applied and Molecular Microbiology, Institute of Biotechnology, Berlin University of Technology, Gustav-Meyer-Allee 25, 13355 Berlin, Germany.

The arts have the power to irritate, to provoke and to let us think and dream about the impossible. The relationship of the arts and fungi is not immediate; however, fungi are ideal subjects for artists. They are both visible and invisible. They irritate. They evoke within each of us different feelings and inner pictures. Some are perceived as disgusting or dangerous because associated with dirt or death. Others are appreciated for their unique and delicious taste in our eating culture. Microbiologists further consider them as useful for industrial exploitation or per se as interesting because they are gratifying objects to study basic phenomena of life. To stimulate a fertile and interdisciplinary dialogue between artists and fungal scientists, we here present some examples of the inspirational powers of fungi and fungal science for contemporary art. Astonishing, poetic and perplexing artistic works could release scientific creativity and overcome the boundaries between art and science.
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http://dx.doi.org/10.1186/s40694-016-0028-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5611638PMC
November 2016

Southern promises: a snapshot of the microbiology research landscape in South America based on bibliometric data.

Authors:
Corrado Nai

FEMS Microbiol Lett 2017 Sep;364(16)

Department of Applied and Molecular Microbiology, Institute of Biotechnology, Technische Universität Berlin, Gustav-Meyer-Allee 25, Berlin 13355, Germany.

Scientists have a single currency for productivity and impact: published articles. In an effort to map the global research landscape in microbiology, and to obviate the current lack of bibliometric analysis in the field, FEMS-the Federation of European Microbiological Societies-generated a dataset encompassing an exhaustive, worldwide list of microbiology studies for 2013-14, which further includes information as author affiliation, funding agency and number of citations. The manually curated database is useful in assessing the impact and regional productivity of microbiology research at different levels. Here, the data for microbiology research in South America are presented and discussed in detail. Based on the analysis, it emerged that despite great degrees of variation between number of published articles among the countries, a more levelled research productivity was observed when considering further dimensions like population size or number of research institutes. Normalised productivity and impact increase in countries with a 'central research hub', i.e. an institute or university producing a substantial portion of the national output (15% or more). From these observations, a possible strategy to increase impact and productivity in (microbiology) research for emerging countries is outlined.
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http://dx.doi.org/10.1093/femsle/fnx162DOI Listing
September 2017

Let microorganisms do the talking, let us talk more about microorganisms.

Fungal Biol Biotechnol 2016 21;3. Epub 2016 Jul 21.

Hamburg, Germany.

Microorganisms are of uttermost importance, yet in the eyes of the general public they are often associated with dirt and diseases. At the same time, microbiologists have access to and comprehensive knowledge of just a tiny minority of the microbial diversity existing in nature. In this commentary, we present these issues of public misconception and scientific limitations and their possible consequences, and propose ways to overcome them. A particular interest is directed toward the secondary metabolism of filamentous fungi as well as novel outreach activities, including so-called "science slams" and interactions between the arts and the sciences, to raise awareness about the relevance of microorganisms.
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http://dx.doi.org/10.1186/s40694-016-0023-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5611652PMC
July 2016

Nutritional physiology of a rock-inhabiting, model microcolonial fungus from an ancestral lineage of the Chaetothyriales (Ascomycetes).

Fungal Genet Biol 2013 Jul 12;56:54-66. Epub 2013 Apr 12.

Federal Institute for Materials Research and Testing, Bundesanstalt für Materialforschung und - prüfung BAM, Department 4 Materials & Environment, Unter den Eichen 87, 12205 Berlin, Germany.

Rock-inhabiting black fungi [also microcolonial or meristematic fungi (MCF)] are a phylogenetically diverse group of melanised ascomycetes with distinctive morphological features that confer extensive stress tolerance and permit survival in hostile environments. The MCF strain A95 Knufia petricola (syn. Sarcinomyces petricola) belongs to an ancestral lineage of the order Chaetothyriales (class Eurotiomycetes). K. petricola strain A95 is a rock-inhabiting MCF and its growth requirements were studied using the 96-well plate-based Biolog System under ∼1070 different conditions (osmotic stress, pH growth optima, growth factor requirements and nutrient catabolism). A95 is an osmotolerant, oligotrophic MCF that grows best around pH 5. Remarkably, A95 shows metabolic activity in the absence of added nitrogen, phosphorus or sulphur. Correlations could be drawn between the known nutrient requirements of A95 and what probably is available in sub-aerial systems (rock and other material surfaces). Detailed knowledge of A95's metabolic requirements allowed formulation of a synthetic medium that supports strong fungal growth.
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http://dx.doi.org/10.1016/j.fgb.2013.04.001DOI Listing
July 2013

Identification of apolipoprotein N-acyltransferase (Lnt) in mycobacteria.

J Biol Chem 2009 Oct 6;284(40):27146-56. Epub 2009 Aug 6.

Institut für Medizinische Mikrobiologie, Universität Zürich, Gloriastrasse 30/32, CH-8006 Zurich, Switzerland.

Lipoproteins of Gram-negative and Gram-positive bacteria carry a thioether-bound diacylglycerol but differ by a fatty acid amide bound to the alpha-amino group of the universally conserved cysteine. In Escherichia coli the N-terminal acylation is catalyzed by the N-acyltransferase Lnt. Using E. coli Lnt as a query in a BLASTp search, we identified putative lnt genes also in Gram-positive mycobacteria. The Mycobacterium tuberculosis lipoprotein LppX, heterologously expressed in Mycobacterium smegmatis, was N-acylated at the N-terminal cysteine, whereas LppX expressed in a M. smegmatis lnt::aph knock-out mutant was accessible for N-terminal sequencing. Western blot analyses of a truncated and tagged form of LppX indicated a smaller size of about 0.3 kDa in the lnt::aph mutant compared with the parental strain. Matrix-assisted laser desorption ionization time-of-flight/time-of-flight analyses of a trypsin digest of LppX proved the presence of the diacylglycerol modification in both strains, the parental strain and lnt::aph mutant. N-Acylation was found exclusively in the M. smegmatis parental strain. Complementation of the lnt::aph mutant with M. tuberculosis ppm1 restored N-acylation. The substrate for N-acylation is a C16 fatty acid, whereas the two fatty acids of the diacylglycerol residue were identified as C16 and C19:0 fatty acid, the latter most likely tuberculostearic acid. We demonstrate that mycobacterial lipoproteins are triacylated. For the first time to our knowledge, we identify Lnt activity in Gram-positive bacteria and assigned the responsible genes. In M. smegmatis and M. tuberculosis the open reading frames are annotated as MSMEG_3860 and M. tuberculosis ppm1, respectively.
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http://dx.doi.org/10.1074/jbc.M109.022715DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2785642PMC
October 2009