Bart Kraak

Mr. Bart Kraak

orcid

Research Focus & Metrics

Academic Career Length

7Years (2020-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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10 May 2024 in Environmental Microbiology
Verified
Journal Article
Open access
VAVioleta Angulo
Violeta Angulo
RBRobert-Jan Bleichrodt
Robert-Jan Bleichrodt
JDJan Dijksterhuis
Jan Dijksterhuis
AEAmandine Erktan
Amandine Erktan
MHMariet M. Hefting
Mariet M. Hefting
GKGeorge A. Kowalchuk
George A. Kowalchuk
Soil structure and aggregation are crucial for soil functionality, particularly under drought conditions. Saprobic soil fungi, known for their resilience in low moisture conditions, are recognized for their influence on soil aggregate dynamics. In this study, we explored the potential of fungal amendments to enhance soil aggregation and hydrological properties across different moisture regimes. We used a selection of 29 fungal isolates, recovered from soils treated under drought conditions and varying in colony density and growth rate, for single‐strain inoculation into sterilized soil microcosms under either low or high moisture (≤−0.96 and –0.03 MPa, respectively). After 8 weeks, we assessed soil aggregate formation and stability, along with soil properties such as soil water content, water hydrophobicity, sorptivity, total fungal biomass and water potential. Our findings indicate that fungal inoculation altered soil hydrological properties and improved soil aggregation, with effects varying based on the fungal strains and soil moisture levels. We found a positive correlation between fungal biomass and enhanced soil aggregate formation and stabilization, achieved by connecting soil particles via hyphae and modifying soil aggregate sorptivity. The improvement in soil water potential was observed only when the initial moisture level was not critical for fungal activity. Overall, our results highlight the potential of using fungal inoculation to improve the structure of agricultural soil under drought conditions, thereby introducing new possibilities for soil management in the context of climate change.

11 June 2020 in Microorganisms
Verified
Journal Article
Open access
PDF file
SPSimone Di Piazza
Simone Di Piazza
JHJos Houbraken
Jos Houbraken
MMMartin Meijer
Martin Meijer
GCGrazia Cecchi
Grazia Cecchi
BKBart Kraak
Bart Kraak
ZMZotti Mirca
Zotti Mirca
Composting is a complex process in which various micro-organisms, mainly fungi and bacteria, are involved. The process depends on a large number of factors (biological, chemical, and physical) among which microbial populations play a fundamental role. The high temperatures that occur during the composting process indicate the presence of thermotolerant and thermophilic micro-organisms that are key for the optimization of the process. However, the same micro-organisms can be harmful (allergenic, pathogenic) for workers that handle large quantities of material in the plant, and for end users, for example, in the indoor environment (e.g., pots in houses and offices). Accurate knowledge of thermotolerant and thermophilic organisms present during the composting stages is required to find key organisms to improve the process and estimate potential health risks. The objective of the present work was to study thermotolerant and thermophilic mycobiota at different time points of compost maturation. Fungi were isolated at four temperatures (25, 37, 45, and 50 °C) from compost samples collected at five different steps during a 21-day compost-maturation period in an active composting plant in Liguria (northwestern Italy). The samples were subsequently plated on three different media. Our results showed a high presence of fungi with an order of magnitude ranging from 1 × 104 to 3 × 105 colony-forming units (CFU) g−1. The isolated strains, identified by means of specific molecular tools (ITS, beta-tubulin, calmodulin, elongation factor 1-alpha, and LSU sequencing), belonged to 45 different species. Several thermophilic species belonging to genera Thermoascus and Thermomyces were detected, which could be key during composting. Moreover, the presence of several potentially harmful fungal species, such as Aspergillus fumigatus, A. terreus, and Scedosporium apiospermum, were found during the whole process, including the final product. Results highlighted the importance of surveying the mycobiota involved in the composting process in order to: (i) find solutions to improve efficiency and (ii) reduce health risks.

4 August 2021 in Journal of Fungi
Verified
Journal Article
Open access
PDF file
DEDaniella Ekpakpale
Daniella Ekpakpale
BKBart Kraak
Bart Kraak
MMMartin Meijer
Martin Meijer
KAKola Ayeni
Kola Ayeni
JHJos Houbraken
Jos Houbraken
CEChibundu N. Ezekiel
Chibundu N. Ezekiel
Grains and cassava-based foods serve as major dietary sources for many households in Nigeria. However, these foods are highly prone to contamination by moulds and aflatoxins owing to poor storage and vending practices. Therefore, we studied the fungal diversity in maize, cassava-based flour (pupuru), and rice vended in markets from Ondo state, Nigeria, and assessed their aflatoxin levels using an enzyme-linked immunosorbent assay. Molecular analysis of 65 representative fungal isolates recovered from the ground grains and pupuru samples revealed 26 species belonging to five genera: Aspergillus (80.9%), Penicillium (15.4%), and Talaromyces (1.9%) in the Ascomycota; Syncephalastrum (1.2%) and Lichtheimia (0.6%) in Mucoromycota. Aspergillus flavus was the predominant species in the ground grains and pupuru samples. Aflatoxins were found in 73.8% of the 42 representative food samples and 41.9% exceeded the 10 μg/kg threshold adopted in Nigeria for total aflatoxins.

5 March 2021 in Microorganisms
Verified
Journal Article
Open access
PDF file
ADAnna-Maria Dietl
Anna-Maria Dietl
Roya Vahedi ShahandashtiRoya Vahedi Shahandashti
Roya Vahedi Shahandashti
CKCarmen Kandelbauer
Carmen Kandelbauer
BKBart Kraak
Bart Kraak
Michaela LacknerMichaela Lackner
Michaela Lackner
CLCornelia Lass-Flörl
Cornelia Lass-Flörl
Fungal infections due to Aspergillus species have become a major cause of morbidity and mortality among immunocompromised patients. At the Medical University of Innsbruck, A. terreus and related species are the second most common causative agents of aspergillosis. In this one-year study we collected environmental samples to investigate (i) the environmental distribution, (ii) the ecological niche of A. terreus in Tyrol, (iii) the genetic relatedness of environmental and clinical isolates and the correlation between those two groups of isolates, and (iv) the antifungal susceptibility patterns. A. terreus was present in 5.4% of 3845 environmental samples, with a significantly higher frequency during winter (6.8%) than summer (3.9%). An increased A. terreus abundance in Tyrol’s Eastern part was detected which is in agreement with the proof of clinical cases. In total, 92% of environmental and 98% of clinical A. terreus isolates were amphotericin B resistant; 22.6% and 9.8% were resistant against posaconazole. Overall, 3.9% of clinical isolates were resistant against voriconazole. Short tandem repeat analysis identified three major genotypes persisting in Tyrol. Soil from agricultural cornfields seems to be an important source; the environmental frequency of A. terreus correlates with the high incidence of A. terreus infections in certain geographical areas.

22 September 2023 in International Journal of Food Microbiology
Verified
Journal Article
Closed access
Manuela ZadravecManuela Zadravec
Manuela Zadravec
TLTina Lešić
Tina Lešić
Dragan BrnićDragan Brnić
Dragan Brnić
Jelka PleadinJelka Pleadin
Jelka Pleadin
BKBart Kraak
Bart Kraak
JHJos Houbraken
Jos Houbraken

13 January 2024 in Antonie van Leeuwenhoek
Verified
Journal Article
Closed access
PDF file
CVCobus M. Visagie
Cobus M. Visagie
MMMartin Meijer
Martin Meijer
BKBart Kraak
Bart Kraak
MGMarizeth Groenewald
Marizeth Groenewald
JHJos Houbraken
Jos Houbraken
TBTeunis Boekhout
Teunis Boekhout