Transformation and tolerance of tellurite by filamentous fungi: accumulation, reduction, and volatilization
Transformation and tolerance of tellurite by filamentous fungi: accumulation, reduction, and volatilization
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DOI：
10.1017/s0953756298007102
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发表时间：
1999-03-01
影响因子：
--
通讯作者：
Gadd, GM
中科院分区：
文献类型：
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作者：
Gharieb, MM;Kierans, M;Gadd, GM
利用固体和液体Czapek Dox培养基研究了一种镰刀菌和桔青霉对亚碲酸盐（TeO ~（32-））的积累和转化。在液体培养基中，亚碲酸盐分配为可溶性和不可溶性物质，在pH 6的含亚碲酸盐（1 mM）液体培养基中，亚碲酸盐分配为可溶性和不可溶性物质。48小时后，60%的添加亚碲酸盐沉淀。实验表明，在含1 mM亚碲酸钠的液体培养基中，镰刀菌对碲的最大积累量约为0.6 μ mol（mg D.W.）(-1)48小时后。桔黄青霉对碲的积累量较低，约为0.07 μ mol（mg D.W.）(-1)降至< 0.02 μ mol（mg D.W.）(-1)48小时后。这两种生物体在培养基的pH变化模式中显示出显著差异，在镰刀菌在1 mM亚碲酸盐中生长期间pH增加，2周后接近pH 6.7。相比之下，pH值下降，在1 mM亚碲酸盐的生长过程中的P. citrinum，2周后的pH值接近2.7的水平。在琼脂培养基上，测试真菌表现出耐受高水平的亚碲酸盐（高达100 mM Na 2 TeO 3），这是与变黑的生长中的菌落以及周围的琼脂。透射电镜显示沉积的大的黑色颗粒，显然是在空泡，这对应于减少碲无定形元素碲。沉淀的无定形碲和周围的生物质也观察到并证实了能量色散X射线微探针分析。除了亚碲酸盐的还原转化外，镰刀菌还表现出亚碲酸盐转化为挥发性形式。由镰刀菌属的挥发性碲的生产。发生在整个生长期，相当于7.8 μ mol Te（类似于0.16%）的平均值从51生长培养基与1 mM Na 2 TeO 3的初始浓度。虽然P. citrinum也将亚碲酸盐转化为元素碲，但没有检测到碲的挥发。它的结论是，不同的机制碲转化是物种依赖性的，可以通过物理化学变化的介质中，例如pH值，这可以影响碲的形态转化为可溶性和不溶性的形式和生物积累的影响。鉴于镰刀菌挥发的Te量极少量，这一过程不能被视为重要的解毒机制。
Accumulation and transformation of tellurite (TeO32-) by a species of Fusarium and Penicillium citrinum was examined using both solid and liquid Czapek Dox medium. In liquid medium, tellurite partitioned into soluble and insoluble species, and in tellurite-containing (1 mM) liquid medium at pH 6, approx. 60% of added tellurite precipitated after 48 h. Experiments showed that in liquid medium containing 1 mM sodium tellurite, the Fusarium sp, accumulated a maximum of similar to 0.6 mu mol Te (mg D.W.)(-1) after 48 h. P. citrinum accumulated a much lower amount of tellurium, similar to 0.07 mu mol (mg D.W.)(-1) falling to < 0.02 mu mol (mg D.W.)(-1) after 48 h. Both organisms showed marked differences in the pattern of pH change of the medium, with the pH increasing during growth of the Fusarium sp. in 1 mM tellurite to similar to pH 6.7 after 2 wk. In contrast the pH decreased during growth of P. citrinum in 1 mM tellurite, to a lever of similar to pH 2.7 after 2 wk. On agar medium, test fungi exhibited tolerance to high levels of tellurite (up to 100 mM Na2TeO3) and this was associated with blackening of the growing colonies as well as the surrounding agar. TEM revealed the deposition of large black granules, apparently in vacuoles, which corresponded with the reduction of tellurite to amorphous elemental tellurium. Precipitation of amorphous tellurium on and around the biomass was also observed and confirmed by energy-dispersive X-ray microprobe analysis. In addition to the reductive transformation of tellurite, Fusarium sp. also displayed transformation of tellurite into a volatile form. The production of volatile tellurium by Fusarium sp. occurred over the whole growth period and amounted to an average value of 7.8 mu mol Te (similar to 0.16%) from 51 growth medium with an initial concentration of 1 mM Na2TeO3. Although P. citrinum also transformed tellurite to elemental tellurium, volatilization of tellurium was not detected. It is concluded that different mechanisms of tellurium transformation are species-dependent and can be influenced by physico-chemical changes in the medium, e.g. pH, which can affect tellurium speciation into soluble and insoluble forms and bioaccumulation. In view of the extremely small amounts of Te volatilized by the Fusarium sp., this process cannot be considered to be an important detoxification mechanism.