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Articles by Lorraine S. Puckhaber
Total Records ( 2 ) for Lorraine S. Puckhaber
  Michael H. Wheeler , Dariusz Abramczyk , Lorraine S. Puckhaber , Michinori Naruse , Yutaka Ebizuka , Isao Fujii and Paul J. Szaniszlo
  The predominant cell wall melanin of Wangiella dermatitidis, a black fungal pathogen of humans, is synthesized from 1,8-dihydroxynaphthalene (D2HN). An early precursor, 1,3,6,8-tetrahydroxynaphthalene (T4HN), in the pathway leading to D2HN is reportedly produced directly as a pentaketide by an iterative type I polyketide synthase (PKS). In contrast, the bluish-green pigment in Aspergillus fumigatus is produced after the enzyme Ayg1p converts the PKS product, the heptaketide YWA1, to T4HN. Previously, we created a new melanin-deficient mutant of W. dermatitidis, WdBrm1, by random molecular insertion. From this strain, the altered gene WdYG1 was cloned by a marker rescue strategy and found to encode WdYg1p, an ortholog of Ayg1p. In the present study, two gene replacement mutants devoid of the complete WdYG1 gene were derived to eliminate the possibility that the phenotype of WdBrm1 was due to other mutations. Characterization of the new mutants showed that they were phenotypically identical to WdBrm1. Chemical analyses of mutant cultures demonstrated that melanin biosynthesis was blocked, resulting in the accumulation of 2-acetyl-1,3,6,8-tetrahydroxynaphthalene (AT4HN) and its oxidative product 3-acetylflaviolin in the culture media. When given to an albino W. dermatitidis strain with an inactivated WdPKS1 gene, AT4HN was mostly oxidized to 3-acetylflaviolin and deacetylated to flaviolin. Under reduced oxygen conditions, cell-free homogenates of the albino converted AT4HN to D2HN. This is the first report of evidence that the hexaketide AT4HN is a melanin precursor for T4HN in W. dermatitidis.
  Thomas Isakeit , Louis K. Prom , Michael Wheeler , Lorraine S. Puckhaber and Jinggao Liu
  The objective of this study was to determine the mycotoxigenic potential of 12 Fusarium isolates (10 species), including six isolates (4 species) from sorghum. The species were: F. thapsinum, F. semitectum, F. proliferatum and F. chlamydosporum isolated from molded sorghum seed; F. poae, F. graminearum and F. sporotrichioides from barley seed with Fusarium head blight; F. acuminatum from wheat seed; F. verticillioides from infected corn seed; and F. nygamai isolated from soil. Fumonisin and zearalenone concentrations were measured following incubation on autoclaved sorghum seed for 21 days at 25°C, while fusaric acid was measured in mycelia harvested from Czapek Dox broth cultures. F. thapsinum (SC8 and CS121) and F. semitectum (SC7) produced fusaric acid only (4.59-64.13 mg g-1). F. graminearum (KB172) and F. semitectum (CS152) produced zearalenone only (73.4 and 799.3 μg g-1, respectively). F. proliferatum (CS183), F. verticillioides (TX02) and F. nygamai produced both fumonisin (1.92-6.05 μg g-1) and fusaric acid (39.4-234.17 mg g-1). F. poae (KB652), F. acuminatum (Ark), F. chlamydosporum (CS102) and F. sporotrichioides (KB662) did not produce any of these three mycotoxins. Five of the six Fusarium isolates (three species) isolated from sorghum had mycotoxigenic potential. Fusarium spp. naturally occurring on sorghum in the field have the potential to contribute to mycotoxin contamination, either singly or in combination.
 
 
 
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