一株单环刺螠肠道电活性希瓦氏菌Shewanella marisflavi的生理学特性

Physiological characteristics of an intestinal electroactive strain Shewanella marisflavi UU-3-2 from Urechis unicinctus

摘要:

[目的] 探究以单环刺螠为代表的海洋环节动物肠道中电活性微生物的存在情况，并表征其生理学及电化学特性。[方法] 采用平板划线法、16S rRNA基因测序技术分离纯化菌株并进行菌株鉴定。利用扫描电镜表征菌株形态。高效液相色谱（high performance liquid chromatography，HPLC）检测其无氧呼吸底物氧化及产物生成情况。通过菲啰嗪和甲醛肟显色法检测菌株的异化Fe（Ⅲ）和Mn（Ⅳ）还原能力。借助单室微生物燃料电池（single-chamber microbial fuel cells，SCMFCs）及循环伏安法检测菌株的电化学活性。[结果] 从单环刺螠肠道中成功分离得到了一株兼性厌氧菌，16S rRNA基因序列比对结果显示该菌株与Shewanella marisflavi的相似性达99.93%。扫描电镜结果显示其为杆状，长约2μm，宽度约为0.5μm。HPLC检测结果表明，该菌能以乳酸钠为电子供体，富马酸为电子受体进行无氧呼吸并伴随代谢产物乙酸钠和琥珀酸产生。菲啰嗪和甲醛肟显色法结果证实，该菌具有异化铁、锰还原能力。单室MFCs检测结果发现该菌的最大电流输出密度为146 mA/m²，循环伏安法检测结果显示该菌在0.14 V和-0.51 V位置处分别存在氧化峰和还原峰。[结论] 本研究结果证实以单环刺螠为代表的海洋环节动物肠道中存在以Shewanella marisflavi UU-3-2为代表的电活性微生物。表明电化学活性微生物在海洋环节动物肠道中广泛存在。

Abstract:

[Objective] To explore the electroactive microorganism in the intestinal tract of marine annelids represented by Urechis unicinctus and characterizing its physiological and electrochemical properties.[Methods] The strain was isolated using plate scribing and identified by 16S rRNA gene sequencing. The morphology of the isolate was depicted by scanning electron microscope. High performance liquid chromatography (HPLC) was used to analyze the metabolites. The quantifications of Fe(Ⅱ) and Mn(Ⅱ) reduction were carried out by ferrozine and formaldoxime assays, respectively. Single-chamber microbial fuel cells (SCMFC) were used to test the electrochemical activity by cyclic voltammetry. [Results] A facultative anaerobic bacterium, Shewanella marisflavi UU-3-2 (with the similarity of 99.93%), was successfully isolated which was a rod bacterium with the length about 2 μm and width about 0.5 μm. The metabolic analysis showed that this strain could use sodium lactate as an electron donor, fumarate as an electron acceptor for anaerobic respiration with acetate and succinate production. Ferrozine and formaldoxime assays illustrated that Fe(Ⅲ)/Mn(Ⅳ) in the Fe₂O₃/MnO₂ were reduced. The maximum current density was 146 mA/m², and the results of cyclic voltammetry revealed that the oxidation peak and reduction peak happened at 0.14 V and -0.51 V, respectively. [Conclusion] An electrochemical activity microbe, Shewanella marisflavi UU-3-2, was successfully isolated from marine animals represented by Urechis unicinctus, indicating the widespread existence of electrochemical activity microorganisms in marine annelids' intestine.