17 research outputs found
Expanding the Paradigms of Plant Pathogen Life History and Evolution of Parasitic Fitness beyond Agricultural Boundaries
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Ferric reductase, superoxide dismutase and alkaline phosphatase activities in siderophore producing fungi
217-219Enzymes associated with release of iron from
internalized ferrated siderophore (ferrisiderophore reductase), with damage to the
cell at high iron concentration (superoxide dismutase) and siderophore synthesis
(alkaline phosphatase), were examined in 3 test fungi viz., Aspergillus sp.
ABp4, Aureobasidium pullulans and Rhizopus sp. Extracellular
ferrisiderophore reductase activity was present in all the three fungi, but Aureobasidium
pullulans, that showed the highest activity (84.3 μM min-1)
, was the only one to produce intra-cellular ferric reductase (147.9μM min-1)
. Superoxide dismutase was produced by Aureobasidium pullulans and Rhizopus
sp., but not by Aspergillus sp. ABp4, that showed
intra-cellular enzyme activity in case of
ferric reductase and alkaline phosphatase. Maximum SOD activity was seen in Aureobasidium
pullulans both extra-cellularly (93.83 ng ml-1) and
intra-cellularly (57.14 ng ml-1)
. All the test fungi examined, produced intra-cellular alkaline phosphatase. There
was no extracellular alkaline phosphatase. Among the three fungi,
Aureobasidium pullulans showed highest alkaline phosphatise
activity (129.9 μM min-1) and Aspergillus sp. ABp4 the
least (76.4 μM min-1)
Chemical nature, ligand denticity and quantification of fungal siderophores
96-105Thirtyfive siderophore producing fungi
were categorized for their hydroxamate, catecholate or carboxylate nature by chemical
and bioassays. Out of 35 fungi, 30 were hydroxamates and 5 showed carboxylate nature.
However, none of the fungi produced catecholate type of siderophores. Eighteen out
of 29 fungi were trihydroxamate and the rest 11 fungi were
dihydroxamates. Twenty three fungi were hexadentate
and 6 were tetradentate in nature. Quantification of siderophores using standard
compounds deferrioxamine mesylate and rhizoferrin revealed that Phanerochaete
chrysosporium produced maximum among the hydroxamate producing fungi and Mycotypha
africana resulted maximum among the carboxylate producing fungi
Chemical properties and NMR spectroscopic identification of certain fungal siderophores
880-886Siderophores of six fungi viz. Aspergillus
sp. ABp4, Aureobacidium pullulans, Penicillium oxalicum, P. chrysosporium,
Mycotypha africana and Syncephalastrum racemosum were examined for
their (1) electrophoretic mobilities to determine the acidic, basic or
neutral charge; (2) Fe (III) binding nature viz., mono-, di-, or
trihydroxamate; (3) amino acid composition; and (4) NMR (nuclear magnetic
resonance) spectroscopy to determine their structure. Electrophoretic mobilities
of siderophores of 3 fungi (P. oxalicum, P. chrysosporium, and M. africana)
exhibited net basic charge, siderophores of 2 fungi (Aspergillus sp.
ABp4 and S. racemosum) were acidic and 1 fungus (A. pullulans)
was
neutral. Electrophoresis of ferrated siderophore
at pH 2 and colour of the spots indicated that siderophores of Aspergillus
sp. ABp4 and P. oxalicum and A. pullulans were trihydroxamates,
whereas siderophore of P. chrysosporium was dihydroxamate. Amino acid composition
of siderophores purified by XAD-2 column chromatography, revealed the presence of
asparagine, histidine, and proline in Aspergillus sp. ABp4, serine and
alanine in P. chrysosporium, and valine in M. africana. The structure
of purified siderophores as revealed by NMR spectroscopy identified siderophore
of AB – 2670 (A. pullulans) as asperchrome F1, and AB-513 (M. africana)
as rhizoferrin. The peak obtained for siderophore AB-5 (Aspergillus sp.
ABp4) did not show resemblance to any known siderophore, therefore may be an exception
A comparative study of siderophore production by fungi from marine and terrestrial habitats
Siderophore producing potential of 20 fungal isolates (same 10 species from each marine and
terrestrial habitat) were examined and compared. Except marine Aspergillus flavus, all isolates
produced siderophores as evidenced by positive reaction in FeCl3 test, CAS assay and CAS agar plate
test. The results indicated widespread occurrence of siderophores in both the habitats. Examination of
the chemical nature of siderophores revealed that mucoraceous fungi produced carboxylate, while
others produced hydroxamate siderophores. Thus, the nature of siderophore was found to be
independent of habitat. Among all the isolates, Cunninghamella elegans (marine form) was maximum
siderophore producer (1987.5 Ag/ml) followed by terrestrial form of C. elegans (1248.75 Ag/ml).
There was no marked variation in siderophore concentration of Penicillium funiculosum strains.
Comparison of quantification of siderophore production between marine and terrestrial revealed that
four terrestrial isolates (Aspergillus niger, Aspergillus ochraceous, Penicillium chrysogenum,
Penicillium citrinum) were ahead in siderophore production, while, the other four marine isolates
(Aspergillus versicolor, C. elegans, Rhizopus sp., Syncephalastrum racemosum) were found to be
more potent siderophore producers, indicating that they were equally competent