Ferric tron reduction by Cryptococcus neoformans

被引:96
作者
Nyhus, KJ
Wilborn, AT
Jacobson, ES
机构
[1] MCGUIRE DEPT VET AFFAIRS MED CTR,RES SERV,RICHMOND,VA 23249
[2] VIRGINIA COMMONWEALTH UNIV,DEPT INTERNAL MED,RICHMOND,VA 23298
关键词
D O I
10.1128/IAI.65.2.434-438.1997
中图分类号
R392 [医学免疫学]; Q939.91 [免疫学];
学科分类号
100102 ;
摘要
The pathogenic yeast Cryptococcus neoformans must reduce Fe(III) to Fe(II) prior to uptake. We investigated mechanisms of reduction using the chromogenic ferrous chelator bathophenanthroline disulfonate, Iron-depleted cells reduced 57 nmol of Fe(III) per 10(6) cells per h, while iron-replete cells reduced only 8 nmol of Fe(III). Exponential-phase cells reduced the most and stationary-phase cells reduced the least Fe(III), independent of iron status. Supernatants from iron-depleted cells reduced up to 2 nmol of Fe(III) per 10(6) cells per h, while supernatants from iron-replete cells reduced 0.5 nmol of Fe(III), implying regulation of the secreted reductant(s). One such reductant is 3-hydroxyanthranilic acid (3HAA), which was found at concentrations up to 29 mu M in iron-depleted cultures but <2 mu M in cultures supplemented with iron, Moreover, when washed and resuspended in low iron medium, iron-depleted cells secreted 20.4 mu M 3HAA, while iron-replete cells secreted only 4.5 mu M 3HAA. Each mole of 3HAA reduced 3 mol of Fe(III), and increasing 3HAA concentrations correlated with increasing reducing activity of supernatants; however, 3HAA. accounted for only half of the supernatant's reducing activity, indicating the presence of additional reductants. Finally, we found that melanized stationary-phase cells reduced 2 nmol of Fe(III) per 10(6) cells per h-16 times the rate of nonmelanized cells-suggesting that this redox polymer participates in reduction of Fe(III).
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页码:434 / 438
页数:5
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