异化铁还原细菌Clostridium sp.LQ25分离及其产氢与铁还原特性

背景] 一些异化铁还原细菌兼具铁还原和发酵产氢能力，可作为发酵型异化铁还原细菌还原机制研究的对象。目的] 筛选出一株发酵型异化铁还原细菌。在异化铁还原细菌培养体系中，设置不同电子供体并分析电子供体。方法] 通过三层平板法从海洋沉积物中筛选纯菌株，基于16S rRNA基因序列进行菌株鉴定。通过测定细菌培养液Fe （II）浓度及发酵产氢量分析菌株异化铁还原和产氢性质。结果] 菌株LQ25与Clostridium butyricum的16S rRNA基因序列相似性达到100%，结合电镜形态观察，菌株命名为Clostridium sp.LQ25。在氢氧化铁为电子受体培养条件下，菌株生长较对照组（未添加氢氧化铁）显著提高。菌株LQ25能够利用丙酮酸钠、葡萄糖和乳酸钠进行生长。丙酮酸钠为电子供体时，菌株LQ25细胞生长和异化铁还原效率最高，菌体蛋白质含量是（78.88±3.40） mg/L，累积产生Fe （II）浓度为（8.27±0.23） mg/L。以葡萄糖为电子供体时，菌株LQ25发酵产氢量最高，达（475.2±14.4） mL/L，相比对照组（未添加氢氧化铁）产氢量提高87.7%。结论] 筛选到一株具有异化铁还原和发酵产氢能力的菌株Clostridium sp.LQ25，为探究发酵型异化铁还原细菌胞外电子传递机制提供了新的实验材料。

Isolation of Fe(III)-reducing bacterium Clostridium sp. LQ25 and characteristics of Fe(III) reduction and hydrogen production

Background] Some dissimilatory Fe(III)-reducing bacteria have the ability of dissimilatory iron reduction and fermentative hydrogen production, which can provide an important way to study the mechanism of fermentative Fe(III)-reducing bacteria. Objective] This study aimed to screen a fermentative Fe(III)-reducing bacterium with the characteristics of microbial Fe(III) reduction and hydrogen production. Methods] The strain was screened by three-layer plate method and identified by sequencing the 16S rRNA gene. Fe(II) concentration and hydrogen production were investigated to analyze the characteristics of microbial Fe(III)-reducing and hydrogen-producing by this strain. Results] Compared to Clostridium butyricum, the similarity was 100% by strain LQ25 based on 16S rRNA gene sequence. The results show that cell growth by strain LQ25 under Fe(III)-reducing conditions using Fe(OH)₃ as electron acceptor were significantly enhanced compared with the control (no adding Fe(III)). Strain LQ25 was able to grow, reduce Fe(III) and produce hydrogen when using pyruvate, glucose and lactate as electron donor respectively. The highest Fe(II) concentration and cell growth by strain LQ25 was achieved when pyruvate was used as electron donor, with protein content (78.88±3.40) mg/L and Fe(II) concentration (8.27±0.23) mg/L. When glucose was used as electron donor, hydrogen production was (475.2±14.4) mL/L under Fe(III)-reducing conditions with the adding Fe(III), which was 87.7% higher compared to the control (no adding Fe(III)). Conclusion] A fermentative Fe(III)-reducing bacterium Clostridium sp. LQ25 which is capable of microbial Fe(III) reduction and hydrogen production was successfully screened in this study. The result will provide new experimental evidence for the mechanism of extracellular electron transfer by fermentative Fe(III)-reducing bacteria.