Special Issue "Antimicrobial Proteins in Filamentous Fungi"

A special issue of Microorganisms (ISSN 2076-2607).

Deadline for manuscript submissions: closed (20 November 2018)

Special Issue Editors

Guest Editor
Dr. Florentine Marx

Division of Molecular Biology, Biocenter, Innsbruck Medical University, Innrain 80-82, 6020 Innsbruck, Austria
Website | E-Mail
Interests: antimicrobial peptide and protein;filamentous fungi
Guest Editor
Dr. László Galgóczy

Institute of Plant Biology, Biological Research Centre, Hungarian Academy of Sciences, Szeged, Hungary H-6726, Szeged, Temesvári krt. 62, Hungary
Website | E-Mail
Interests: https://prateekshettys.wixsite.com/marotilab

Special Issue Information

Dear Colleagues,

One major challenge in this century is to overcome the rapid development of microbial resistance against conventional drugs and to provide a novel, effective arsenal of antimicrobial compounds against emerging pathogens. Filamentous fungi are a rich source of defensin-like proteins and peptides with potent antimicrobial activity. Although showing differences in their primary structure, antimicrobial spectrum and mechanistic function, these bio-molecules exhibit a very similar β-folded structure and high stability against harsh environmental conditions and proteolytic degradation. Therefore, these molecules represent, nowadays, most promising candidates for drug development and may find wide application in medicine, pest control and food preservation.

This Special Issue, "Antimicrobial Proteins in Filamentous Fungi", is designed to highlight the latest research and development on new antimicrobial proteins and peptides of fungal origin with mechanisms of action different from those of licensed drugs.

We kindly invite authors who are experts in this field to submit a review article, an original research article or a short communication to topics related to the identification, isolation, characterization and potential application of antimicrobial proteins from filamentous fungi. In particular, we welcome manuscripts that provide new insights into all aspects of the antimicrobial mode of action, structure and phylogeny from authors who are actively researching these topics.

Dr. Florentine Marx
Dr. László Galgóczy
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Microorganisms is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • filamentous fungi
  • antimicrobial peptide and protein
  • identification
  • isolation
  • mode of action
  • protein structure
  • application

Published Papers (6 papers)

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Editorial

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Open AccessEditorial Do Antimicrobial Proteins Contribute to Overcoming the Hidden Antifungal Crisis at the Dawn of a Post-Antibiotic Era?
Microorganisms 2019, 7(1), 16; https://doi.org/10.3390/microorganisms7010016
Received: 9 January 2019 / Accepted: 10 January 2019 / Published: 11 January 2019
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Abstract
The incidence of fungal infections has been grossly underestimated in the past decades as a consequence of poor identification techniques and a lack of regular epidemiologic surveys in low- and middle-income countries [...] Full article
(This article belongs to the Special Issue Antimicrobial Proteins in Filamentous Fungi)

Research

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Open AccessArticle Rational Design and Biotechnological Production of Novel AfpB-PAF26 Chimeric Antifungal Proteins
Microorganisms 2018, 6(4), 106; https://doi.org/10.3390/microorganisms6040106
Received: 6 September 2018 / Revised: 4 October 2018 / Accepted: 11 October 2018 / Published: 15 October 2018
Cited by 1 | PDF Full-text (3279 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Antimicrobial peptides (AMPs) have been proposed as candidates to develop new antimicrobial compounds for medicine, agriculture, and food preservation. PAF26 is a synthetic antifungal hexapeptide obtained from combinatorial approaches with potent fungicidal activity against filamentous fungi. Other interesting AMPs are the antifungal proteins [...] Read more.
Antimicrobial peptides (AMPs) have been proposed as candidates to develop new antimicrobial compounds for medicine, agriculture, and food preservation. PAF26 is a synthetic antifungal hexapeptide obtained from combinatorial approaches with potent fungicidal activity against filamentous fungi. Other interesting AMPs are the antifungal proteins (AFPs) of fungal origin, which are basic cysteine-rich and small proteins that can be biotechnologically produced in high amounts. A promising AFP is the AfpB identified in the phytopathogen Penicillium digitatum. In this work, we aimed to rationally design, biotechnologically produce and test AfpB::PAF26 chimeric proteins to obtain designed AFPs (dAfpBs) with improved properties. The dAfpB6 and dAfpB9 chimeras could be produced using P. digitatum as biofactory and a previously described Penicillium chrysogenum-based expression cassette, but only dAfpB9 could be purified and characterized. Protein dAfpB9 showed subtle and fungus-dependent differences of fungistatic activity against filamentous fungi compared to native AfpB. Significantly, dAfpB9 lost the fungicidal activity of PAF26 and AfpB, thus disconnecting this activity from the fungistatic activity and mapping fungicidal determinants to the exposed loop L3 of AfpB, wherein modifications are located. This study provides information on the design and development of novel chimeric AFPs. Full article
(This article belongs to the Special Issue Antimicrobial Proteins in Filamentous Fungi)
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Open AccessArticle New 19-Residue Peptaibols from Trichoderma Clade Viride
Microorganisms 2018, 6(3), 85; https://doi.org/10.3390/microorganisms6030085
Received: 2 July 2018 / Revised: 7 August 2018 / Accepted: 10 August 2018 / Published: 12 August 2018
Cited by 1 | PDF Full-text (2240 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Trichoderma koningiopsis and T. gamsii belong to clade Viride of Trichoderma, the largest and most diverse group of this genus. They produce a wide range of bioactive secondary metabolites, including peptaibols with antibacterial, antifungal, and antiviral properties. The unusual amino acid residues [...] Read more.
Trichoderma koningiopsis and T. gamsii belong to clade Viride of Trichoderma, the largest and most diverse group of this genus. They produce a wide range of bioactive secondary metabolites, including peptaibols with antibacterial, antifungal, and antiviral properties. The unusual amino acid residues of peptaibols, i.e., α-aminoisobutyric acid (Aib), isovaline (Iva), and the C-terminal 1,2-amino alcohol make them unique among peptides. In this study, the peptaibiomes of T. koningiopsis and T. gamsii were investigated by HPLC-ESI-MS. The examined strains appeared to produce 19-residue peptaibols, most of which are unknown from literature, but their amino acid sequences are similar to those of trikoningins, tricholongins, trichostrigocins, trichorzianins, and trichorzins. A new group of peptaibols detected in T. koningiopsis are described here under the name “Koningiopsin”. Trikoningin KA V, the closest peptaibol compound to the peptaibols produced by these two strains, was selected for structural investigation by short MD simulation, which revealed that many residues show high preference for left handed helix formation. The bioactivity of the peptaibol mixtures produced by T. koningiopsis and T. gamsii was tested on agar plates against bacteria, yeasts, and filamentous fungi. The results revealed characteristic differences in bioactivities towards the different groups of target microorganisms, which can be explained with the differences in their cell wall structures. Full article
(This article belongs to the Special Issue Antimicrobial Proteins in Filamentous Fungi)
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Open AccessArticle Inhibitory Effect of PgAFP and Protective Cultures on Aspergillus parasiticus Growth and Aflatoxins Production on Dry-Fermented Sausage and Cheese
Microorganisms 2018, 6(3), 69; https://doi.org/10.3390/microorganisms6030069
Received: 31 May 2018 / Revised: 29 June 2018 / Accepted: 11 July 2018 / Published: 13 July 2018
Cited by 2 | PDF Full-text (1417 KB) | HTML Full-text | XML Full-text
Abstract
Aflatoxigenic molds can grow and produce aflatoxins on dry-fermented meat and cheese. The small, basic, cysteine-rich antifungal protein PgAFP displays a time-limited inhibitory ability against unwanted molds by increasing reactive oxygen species (ROS), which can lead to increased aflatoxin production. However, calcium abolishes [...] Read more.
Aflatoxigenic molds can grow and produce aflatoxins on dry-fermented meat and cheese. The small, basic, cysteine-rich antifungal protein PgAFP displays a time-limited inhibitory ability against unwanted molds by increasing reactive oxygen species (ROS), which can lead to increased aflatoxin production. However, calcium abolishes the inhibitory effect of PgAFP on certain Aspergillus spp. To maximize the antifungal effect, this protein may be combined with protective cultures. Yeasts and lactic acid bacteria may counteract the impact of calcium on PgAFP fungal inhibition. The objective of this work was to study the effect of PgAFP and different combined treatments with Debaryomyces hansenii and/or Pediococcus acidilactici against growth of and aflatoxin production by an aflatoxigenic strain of Aspergillus parasiticus in both culture media and dry-fermented foods with low or high calcium levels. Aflatoxins production was increased by PgAFP but dramatically reduced by P. acidilactici in low calcium culture medium, whereas in the Ca-enriched culture medium, all treatments tested led to low aflatoxins levels. To study whether PgAFP and the protective microorganisms interfere with ROS and aflatoxin production, the relative expression of genes foxA, which is involved in peroxisomal β-oxidation, and aflP, which is required for aflatoxin biosynthesis, were evaluated. The aflatoxin overproduction induced by PgAFP seems not to be linked to peroxisomal β-oxidation. The combination of PgAFP and D. hansenii provided a successful inhibitory effect on A. parasiticus growth as well as on aflatoxin production on sliced dry-fermented sausage and cheese ripened up to 15 days, whereas P. acidilactici did not further enhance the protective effect of the two former agents. Therefore, the combined treatment of PgAFP and D. hansenii seems to provide a promising protective mean against aflatoxin-producing A. parasiticus on dry-fermented foods. Full article
(This article belongs to the Special Issue Antimicrobial Proteins in Filamentous Fungi)
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Review

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Open AccessReview Structure and Synthesis of Antifungal Disulfide β-Strand Proteins from Filamentous Fungi
Microorganisms 2019, 7(1), 5; https://doi.org/10.3390/microorganisms7010005
Received: 20 November 2018 / Revised: 24 December 2018 / Accepted: 24 December 2018 / Published: 27 December 2018
Cited by 2 | PDF Full-text (1240 KB) | HTML Full-text | XML Full-text
Abstract
The discovery and understanding of the mode of action of new antimicrobial agents is extremely urgent, since fungal infections cause 1.5 million deaths annually. Antifungal peptides and proteins represent a significant group of compounds that are able to kill pathogenic fungi. Based on [...] Read more.
The discovery and understanding of the mode of action of new antimicrobial agents is extremely urgent, since fungal infections cause 1.5 million deaths annually. Antifungal peptides and proteins represent a significant group of compounds that are able to kill pathogenic fungi. Based on phylogenetic analyses the ascomycetous, cysteine-rich antifungal proteins can be divided into three different groups: Penicillium chrysogenum antifungal protein (PAF), Neosartorya fischeri antifungal protein 2 (NFAP2) and “bubble-proteins” (BP) produced, for example, by P. brevicompactum. They all dominantly have β-strand secondary structures that are stabilized by several disulfide bonds. The PAF group (AFP antifungal protein from Aspergillus giganteus, PAF and PAFB from P. chrysogenum, Neosartorya fischeri antifungal protein (NFAP)) is the best characterized with their common β-barrel tertiary structure. These proteins and variants can efficiently be obtained either from fungi production or by recombinant expression. However, chemical synthesis may be a complementary aid for preparing unusual modifications, e.g., the incorporation of non-coded amino acids, fluorophores, or even unnatural disulfide bonds. Synthetic variants up to ca. 6–7 kDa can also be put to good use for corroborating structure determination. A short overview of the structural peculiarities of antifungal β-strand disulfide bridged proteins will be given. Here, we describe the structural propensities of some known antifungal proteins from filamentous fungi which can also be prepared with modern synthetic chemistry methods. Full article
(This article belongs to the Special Issue Antimicrobial Proteins in Filamentous Fungi)
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Open AccessReview Antifungal Peptides of the AFP Family Revisited: Are These Cannibal Toxins?
Microorganisms 2018, 6(2), 50; https://doi.org/10.3390/microorganisms6020050
Received: 24 April 2018 / Revised: 24 May 2018 / Accepted: 28 May 2018 / Published: 2 June 2018
Cited by 5 | PDF Full-text (1144 KB) | HTML Full-text | XML Full-text
Abstract
The emergence and spread of pathogenic fungi resistant to currently used antifungal drugs represents a serious challenge for medicine and agriculture. The use of smart antimicrobials, so-called “dirty drugs” which affect multiple cellular targets, is one strategy to prevent resistance. Of special interest [...] Read more.
The emergence and spread of pathogenic fungi resistant to currently used antifungal drugs represents a serious challenge for medicine and agriculture. The use of smart antimicrobials, so-called “dirty drugs” which affect multiple cellular targets, is one strategy to prevent resistance. Of special interest is the exploitation of the AFP family of antimicrobial peptides, which include its founding member AFP from Aspergillus giganteus. This latter is a highly potent inhibitor of chitin synthesis and affects plasma membrane integrity in many human and plant pathogenic fungi. A transcriptomic meta-analysis of the afp-encoding genes in A. giganteus and A. niger predicts a role for these proteins during asexual sporulation, autophagy, and nutrient recycling, suggesting that AFPs are molecules important for the survival of A. niger and A. giganteus under nutrient limitation. In this review, we discuss parallels which exist between AFPs and bacterial cannibal toxins and provide arguments that the primary function of AFPs could be to kill genetically identical siblings. We hope that this review inspires computational and experimental biologists studying alternative explanations for the nature and function of antimicrobial peptides beyond the general assumption that they are mere defense molecules to fight competitors. Full article
(This article belongs to the Special Issue Antimicrobial Proteins in Filamentous Fungi)
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