Rabab A Metwally, Asmaa S Taha, Asmaa H Mohamed, Shereen A Soliman
Botany and Microbiology Department, Faculty of Science, Zagazig University, Zagazig, 44519, Egypt.
BMC Microbiol. 2025 May 15;25(1):297. doi: 10.1186/s12866-025-04000-9.
Heavy metals (HMs) contamination is a major issue produced by industrial and mining processes, among other human activities. The capacity of fungi to eliminate HMs from the environment has drawn attention. However, the main process by which fungi protect the environment against the damaging effects of these HMs, such as cadmium (Cd), is still unknown. In this study, some fungi were isolated from HMs-polluted soil. The minimum inhibitory concentrations (MICs) and the tolerance indices of the tested isolates against Cd were evaluated. Moreover, molecular identification of the most tolerant fungal isolates (Aspergillus niger and A. terreus) was done and deposited in the GenBank NCBI database. The results showed that the colony diameter of A. niger and A. terreus was decreased gradually by the increase of Cd concentration. Also, all the tested parameters were influenced by Cd concentration. Lipid peroxidation (MDA content) was progressively increased by 12.95-105.95% (A. niger) and 17.27-85.38% (A. terreus), respectively, from 50 to 200 mg/L. PPO, APX, and POD enzymes were elevated in the presence of Cd, thus illustrating the appearance of an oxidative stress action. Compared to the non-stressed A. niger, the POD and PPO activities were enhanced by 92.00 and 104.24% at 200 mg/L Cd. Also, APX activity was increased by 58.12% at 200 mg/L. Removal efficiency and microbial accumulation capacities of A. niger and A. terreus have also been assessed. Production of succinic and malic acids by A. niger and A. terreus was increased in response to 200 mg/L Cd, in contrast to their controls (Cd-free), as revealed by HPLC analysis. These findings helped us to suggest A. niger and A. terreus as the potential mycoremediation microbes that alleviate Cd contamination. We can learn more about these fungal isolates' resistance mechanisms against different HMs through further studies.
重金属（HMs）污染是工业和采矿过程以及其他人类活动产生的一个主要问题。真菌从环境中消除重金属的能力已引起关注。然而，真菌保护环境免受这些重金属（如镉（Cd））破坏作用的主要过程仍然未知。在本研究中，从受重金属污染的土壤中分离出一些真菌。评估了受试分离株对镉的最低抑菌浓度（MICs）和耐受指数。此外，对耐受性最强的真菌分离株（黑曲霉和土曲霉）进行了分子鉴定，并保存在GenBank NCBI数据库中。结果表明，随着镉浓度的增加，黑曲霉和土曲霉的菌落直径逐渐减小。此外，所有测试参数均受镉浓度影响。脂质过氧化（丙二醛含量）分别从50 mg/L增加到200 mg/L时，黑曲霉增加了12.95 - 105.95%，土曲霉增加了17.27 - 85.38%。在镉存在的情况下，多酚氧化酶（PPO）、抗坏血酸过氧化物酶（APX）和过氧化物酶（POD）活性升高，从而表明出现了氧化应激作用。与未受胁迫的黑曲霉相比，在200 mg/L镉浓度下，POD和PPO活性分别提高了92.00%和104.24%。此外，在200 mg/L镉浓度下，APX活性增加了58.12%。还评估了黑曲霉和土曲霉对镉的去除效率和微生物积累能力。高效液相色谱（HPLC）分析显示，与对照（无镉）相比，黑曲霉和土曲霉在200 mg/L镉处理下琥珀酸和苹果酸的产量增加。这些发现有助于我们提出黑曲霉和土曲霉作为缓解镉污染的潜在真菌修复微生物。通过进一步研究，我们可以更多地了解这些真菌分离株对不同重金属的抗性机制。
