Kinetics of malate transport and decomposition in acid soils and isolated bacterial populations: The effect of microorganisms on root exudation of malate under Al stress
Kinetics of malate transport and decomposition in acid soils and isolated bacterial populations: The effect of microorganisms on root exudation of malate under Al stress
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DOI：
10.1007/bf00029055
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发表时间：
1996-05-01
期刊：
影响因子：
4.9
通讯作者：
Kochian, LV
中科院分区：
文献类型：
--
作者：
Jones, DL;Prabowo, AM;Kochian, LV
研究了苹果酸在pH值为4.30 ~ 5.00的4种不同植被类型酸性土壤中的降解动力学和特征。在所有土壤中，苹果酸的分解都很快，半衰期约为1.7小时，Km为1.7 mM，V-max为70 nmol g（-1）土壤h（-1）。苹果酸的分解速率和pH值之间没有关系。与其他C和N底物（葡萄糖，甘氨酸，谷氨酸，柠檬酸盐和琥珀酸盐）的共代谢研究表明，微生物不N限制和竞争性抑制苹果酸分解只观察到琥珀酸盐的存在。与分离的混合细菌培养物的研究表明，细菌的苹果酸摄取介导的能量依赖性，二羧酸转运蛋白，可以抑制琥珀酸，是独立的pH值之间的pH 5.0和7.0。混合细菌培养物的Km和Vmax参数范围为279-955 μ M和0.1-17 μ mol mg（-1）蛋白h（-1），取决于细菌以前的C源。结果表明，在微生物数量较多的酸性表土中，微生物可能为有机酸提供相当大的汇。如果有机酸被释放的根响应于环境胁迫（如铝毒性，磷缺乏），它可以预期，这些根介导的金属抗性机制的效率将显着降低快速微生物降解。
The kinetics and characteristics of malate degradation were studied in four acid soils ranging in both pH (4.30 to 5.00) and vegetation type. The breakdown of malate was rapid in all soils with a half life of approximately 1.7 h, K-m of 1.7 mM and V-max of 70 nmol g(-1) soil h(-1). No relationship was observed between malate decomposition rate and pH. Co-metabolism studies with other C and N substrates (glucose, glycine, glutamate, citrate and succinate) indicated that the microorganisms were not N limited and competitive inhibition of malate breakdown was only observed in the presence of succinate. Studies with isolated mixed bacterial cultures indicated that the bacterial malate uptake was mediated by an energy dependent, dicarboxylate transporter which can be inhibited by succinate and is independent of pH between pH 5.0 and 7.0. The K-m and V-max parameters ranged from 279-955 mu M and 0.1-17 mu mol mg(-1) protein h(-1) for the mixed bacterial cultures depending on the bacteria's previous C source. The results indicate that in acid topsoils where microbial populations are high, the microbes may provide a considerable sink for organic acids. If organic acids are being released by roots in response to an environmental stress (e.g. Al toxicity, P deficiency) it can be expected that the efficiency of these root mediated metal resistance mechanisms will be markedly reduced by rapid microbial degradation.