Dávid Rakk

Mr. Dávid Rakk


Research Focus & Metrics

Academic Career Length

9Years (2018-Present)

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

Representative Publications

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7 May 2020 in Microorganisms
Verified
Journal Article
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ATAdiyadolgor Turbat
Adiyadolgor Turbat
DRDávid Rakk
Dávid Rakk
ARAruna Vigneshwari Ramasamy
Aruna Vigneshwari Ramasamy
SKSándor Kocsubé
Sándor Kocsubé
Huynh ThuHuynh Thu
Huynh Thu
Andras SzekeresAndras Szekeres
Andras Szekeres
Endophytic fungi in symbiotic association with their host plant are well known to improve plant growth and reduce the adverse effects of both biotic and abiotic stresses. Therefore, fungal endophytes are beginning to receive increased attention in an effort to find growth-promoting strains that could be applied to enhance crop yield and quality. In our study, the plant growth-promoting activities of endophytic fungi isolated from various parts of Sophora flavescens (a medicinally important plant in Mongolia and China) have been revealed and investigated. Fungal isolates were identified using molecular taxonomical methods, while their plant growth-promoting abilities were evaluated in plate assays. Altogether, 15 strains were isolated, representing the genera Alternaria, Didymella, Fusarium and Xylogone. Five of the isolates possessed phosphate solubilization activities and twelve secreted siderophores, while all of them were able to produce indoleacetic acid (IAA) in the presence or absence of tryptophan. The endogenous and exogenous accumulation of IAA were also monitored in liquid cultures using the HPLC-MS/MS technique to refine the plate assay results. Furthermore, for the highest IAA producer fungi, the effects of their extracts were also examined in plant bioassays. In these tests, the primary root lengths of the model Arabidopsis thaliana were increased in several cases, while the biomasses were significantly lower than the control IAA treatment. Significant alterations have also been detected in the photosynthetic pigment (chlorophyll-a, -b and carotenoids) content due to the fungal extract treatments, but these changes did not show any specific trends.

12 August 2018 in Microorganisms
Verified
Journal Article
Open access
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TMTamás Marik
Tamás Marik
CTChetna Tyagi
Chetna Tyagi
GRGordana Racić
Gordana Racić
DRDávid Rakk
Dávid Rakk
Andras SzekeresAndras Szekeres
Andras Szekeres
LKLaszlo Kredics
Laszlo Kredics
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.

1 January 2021 in Tuberculosis
Verified
Journal Article
Open access
OVOrsolya Anna Váradi
Orsolya Anna Váradi
DRDávid Rakk
Dávid Rakk
OSOlga Spekker
Olga Spekker
TGTerhes Gabriella
Terhes Gabriella
EUEdit Urbán
Edit Urbán
GPGyörgy Pálfi
György Pálfi
Tuberculosis (TB) was a large burden of infections that peaked during the 19th century in Europe. Mummies from the 18th century CE, discovered in the crypt of a church at Vác, Hungary, had high TB prevalence, as revealed by amplification of key fragments of TB DNA and genome-wide TB analysis. Complementary methods are needed to confirm these diagnoses and one approach uses the identification of specific lipid biomarkers, such as TB mycocerosic acids (MCs). Previously, MC derivatives were profiled by specialised gas chromatography-mass spectrometry (GC-MS), so an alternative more direct approach has been developed. Underivatized MCs are extracted and analysed by high-performance liquid chromatography linked to a mass spectrometer, in heated electrospray ionisation mode (HPLC-HESI-MS). The method was validated using representatives of the Mycobacterium tuberculosis complex and other mycobacteria and tested on six Vác mummy cases, previously considered positive for TB infection. Analysing both rib and soft tissue samples, four out of six cases gave profiles of main C32 and major C29 and C39 mycocerosates correlating well with those of M. tuberculosis. Multidisciplinary methods are needed in the diagnosis of ancient tuberculosis; this new protocol accesses important confirmatory evidence, as demonstrated by the confirmation of TB in the Vác mummies.

7 February 2023 in Toxins
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Journal Article
Open access
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DRDávid Rakk
Dávid Rakk
JKJózsef Kukolya
József Kukolya
BSBiljana Skrbic
Biljana Skrbic
CVCsaba Vágvölgyi
Csaba Vágvölgyi
MVMónika Varga
Mónika Varga
Andras SzekeresAndras Szekeres
Andras Szekeres
In routine measurements, the length of the analysis time and nfumber of samples analysed during a time unit are crucial parameters, which are especially important for the food analysis, particularly in the case of mycotoxin determinations. High-resolution equipment, including time-of-flight or Orbitrap analyzators, can provide stable instrumental background for high-throughput analyses. In this report, a short, 1 min MS-based multi-mycotoxin method was developed with the application of a short column as a reduced chromatographic separation, taking advantages of the multiplexing and high-resolution capability of the QExactive Orbitrap MS possessing sub-1 ppm mass accuracy. The performance of the method was evaluated regarding selectivity, LOD, LOQ, linearity, matrix effect, and recovery, and compared to a UHPLC-MS/MS method. The final multiplexing method was able to quantify 11 mycotoxins in defined ranges (aflatoxins (corn, 2.8–600 μg/kg; wheat, 1.5–350 μg/kg), deoxynivalenol (corn, 640–9600 μg/kg; wheat, 128–3500 μg/kg), fumonisins (corn, 20–1500 μg/kg; wheat, 30–3500 μg/kg), HT-2 (corn, 64–5200 μg/kg; wheat, 61–3500 μg/kg), T-2 (corn, 10–800 μg/kg; wheat, 4–250 μg/kg), ochratoxin (corn, 4.7–600 μg/kg; wheat, 1–1000 μg/kg), zearalenone (corn, 64–4800 μg/kg; wheat, 4–500 μg/kg)) within one minute in corn and wheat matrices at the MRL levels stated by the European Union.