Background

Synthetic algal–fungal and algal–bacterial cultures have been investigated as a means to enhance the technological applications of the algae. This inclusion of other microbes has enhanced growth and improved stress tolerance of the algal culture. The goal of the current study was to investigate natural microbial consortia to gain an understanding of the occurrence and benefits of these associations in nature. The photosynthetic protist Euglena mutabilis is often found in association with other microbes in acidic environments with high heavy metal (HM) concentrations. This may suggest that microbial interactions are essential for the protist’s ability to tolerate these extreme environments. Our study assessed the Cd tolerance of a natural fungal–algal–bacterial (FAB) association whereby the algae is E. mutabilis.

Results

This study provides the first assessment of antibiotic and antimycotic agents on an E. mutabilis culture. The results indicate that antibiotic and antimycotic applications significantly decreased the viability of E. mutabilis cells when they were also exposed to Cd. Similar antibiotic treatments of E. gracilis cultures had variable or non-significant impacts on Cd tolerance. E. gracilis also recovered better after pre-treatment with antibiotics and Cd than did E. mutabilis. The recoveries were assessed by heterotrophic growth without antibiotics or Cd. In contrast, both Euglena species displayed increased chlorophyll production upon Cd exposure. PacBio full-length amplicon sequencing and targeted Sanger sequencing identified the microbial species present in the E. mutabilis culture to be the fungus Talaromyces sp. and the bacterium Acidiphilium acidophilum.

Conclusion

This study uncovers a possible fungal, algal, and bacterial relationship, what we refer to as a FAB consortium. The members of this consortium interact to enhance the response to Cd exposure. This results in a E. mutabilis culture that has a higher tolerance to Cd than the axenic E. gracilis. The description of this interaction provides a basis for explore the benefits of natural interactions. This will provide knowledge and direction for use when creating or maintaining FAB interactions for biotechnological purposes, including bioremediation.

中文翻译：

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Euglena mutabilis 与增强镉耐受性的微生物存在于 FAB 联盟中

背景

合成藻类-真菌和藻类-细菌培养物已被研究作为增强藻类技术应用的一种手段。其他微生物的加入促进了藻类培养物的生长并提高了其抗逆性。当前研究的目标是调查天然微生物群落，以了解这些群落在自然界中的发生和益处。在重金属 (HM) 浓度较高的酸性环境中，经常发现光合原生生物眼虫与其他微生物共生。这可能表明微生物相互作用对于原生生物耐受这些极端环境的能力至关重要。我们的研究评估了天然真菌-藻类-细菌 (FAB) 组合的镉耐受性，其中藻类是E. mutabilis。

结果

这项研究首次对E. mutabilis培养物中的抗生素和抗真菌药物进行了评估。结果表明，当E. mutabilis细胞也暴露于镉时，抗生素和抗真菌药物的应用显着降低了它们的活力。对细小桉培养物进行类似的抗生素处理对镉耐受性有不同或不显着的影响。在用抗生素和镉预处理后，E. gracilis也比E. mutabilis恢复得更好。通过不使用抗生素或镉的异养生长来评估回收率。相比之下，两种眼虫物种在接触镉后都表现出叶绿素产量增加。PacBio 全长扩增子测序和靶向桑格测序鉴定出E. mutabilis培养物中存在的微生物物种是真菌Talaromyces sp。和细菌嗜酸菌。

结论

这项研究揭示了真菌、藻类和细菌之间可能存在的关系，我们称之为 FAB 联合体。该联盟的成员进行互动，以增强对镉暴露的响应。这导致E. mutabilis培养物比无菌E. gracilis具有更高的 Cd 耐受性。这种交互的描述为探索自然交互的好处提供了基础。这将为生物技术目的（包括生物修复）创建或维护 FAB 相互作用提供知识和指导。