Altomare C, Norvell WA, Bjorkman T, Harman GE
Istituto Tossine e Micotossine da Parassiti Vegetali, C.N.R., Bari 70125, Italy.
Appl Environ Microbiol. 1999 Jul;65(7):2926-33. doi: 10.1128/AEM.65.7.2926-2933.1999.
We investigated the capability of the plant-growth-promoting and biocontrol fungus Trichoderma harzianum Rifai 1295-22 (T-22) to solubilize in vitro some insoluble or sparingly soluble minerals via three possible mechanisms: acidification of the medium, production of chelating metabolites, and redox activity. T-22 was able to solubilize MnO2, metallic zinc, and rock phosphate (mostly calcium phosphate) in a liquid sucrose-yeast extract medium, as determined by inductively coupled plasma emission spectroscopy. Acidification was not the major mechanism of solubilization since the pH of cultures never fell below 5.0 and in cultures containing MnO2 the pH rose from 6.8 to 7.4. Organic acids were not detected by high-performance thin-layer chromatography in the culture filtrates. Fe2O3, MnO2, Zn, and rock phosphate were also solubilized by cell-free culture filtrates. The chelating activity of T-22 culture filtrates was determined by a method based on measurement of the equilibrium concentration of the chrome azurol S complex in the presence of other chelating substances. A size exclusion chromatographic separation of the components of the culture filtrates indicated the presence of a complexed form of Fe but no chelation of Mn. In liquid culture, T. harzianum T-22 also produced diffusible metabolites capable of reducing Fe(III) and Cu(II), as determined by the formation of Fe(II)-Na2-bathophenanthrolinedisulfonic acid and Cu(I)-Na2-2, 9-dimethyl-4,7-diphenyl-1,10-phenanthrolinedisulfonic acid complexes. This is the first report of the ability of a Trichoderma strain to solubilize insoluble or sparingly soluble minerals. This activity may explain, at least partially, the ability of T-22 to increase plant growth. Solubilization of metal oxides by Trichoderma involves both chelation and reduction. Both of these mechanisms also play a role in biocontrol of plant pathogens, and they may be part of a multiple-component action exerted by T-22 to achieve effective biocontrol under a variety of environmental conditions.
我们研究了具有促进植物生长和生物防治功能的哈茨木霉里氏木霉1295-22（T-22）通过三种可能机制在体外溶解一些不溶性或微溶性矿物质的能力：培养基酸化、螯合代谢产物的产生以及氧化还原活性。通过电感耦合等离子体发射光谱法测定，T-22能够在液体蔗糖 - 酵母提取物培养基中溶解二氧化锰、金属锌和磷矿粉（主要是磷酸钙）。酸化不是主要的溶解机制，因为培养物的pH值从未降至5.0以下，并且在含有二氧化锰的培养物中，pH值从6.8升至7.4。通过高效薄层色谱法未在培养滤液中检测到有机酸。Fe2O3、MnO2、Zn和磷矿粉也能被无细胞培养滤液溶解。T-22培养滤液的螯合活性通过一种基于在其他螯合物质存在下测量铬天青S络合物平衡浓度的方法来测定。对培养滤液成分进行的尺寸排阻色谱分离表明存在铁的络合形式，但不存在锰的螯合。在液体培养中，通过形成Fe(II)-Na2-邻二氮菲二磺酸和Cu(I)-Na2-2,9-二甲基-4,7-二苯基-1,10-菲二磺酸络合物测定，哈茨木霉T-22还产生了能够还原Fe(III)和Cu(II)的可扩散代谢产物。这是关于木霉菌株溶解不溶性或微溶性矿物质能力的首次报道。这种活性至少可以部分解释T-22促进植物生长的能力。木霉菌对金属氧化物的溶解涉及螯合和还原。这两种机制在植物病原体的生物防治中也起作用，并且它们可能是T-22在各种环境条件下实现有效生物防治所发挥的多组分作用的一部分。
