Necessity of electrically conductive pili for methanogenesis with magnetite stimulation

PeerJ

article

Oumei Wang¹  Shiling Zheng²  Bingchen Wang²  Wenjing Wang²  Fanghua Liu² 

[1] Binzhou Medical University;Key Laboratory of Coastal Biology and Biological Resources Utilization, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences;University of Chinese Academy of Sciences

关键词: Geobacter metallireducens;    Methanosarcina barkeri;    Electrically conductive pili (e-pili);    Direct interspecies electron transfer (DIET);    Magnetite;    Ferrous iron;    Ethanol metabolism;    Stimulation;    Co-cultures;    Methane;   

DOI  :  10.7717/peerj.4541

学科分类：社会科学、人文和艺术（综合）

来源: Inra

【 摘 要 】

BackgroundMagnetite-mediated direct interspecies electron transfer (DIET) between Geobacter and Methanosarcina species is increasingly being invoked to explain magnetite stimulation of methane production in anaerobic soils and sediments. Although magnetite-mediated DIET has been documented in defined co-cultures reducing fumarate or nitrate as the electron acceptor, the effects of magnetite have only been inferred in methanogenic systems.MethodsConcentrations of methane and organic acid were analysed with a gas chromatograph and high-performance liquid chromatography, respectively. The concentration of HCl-extractable Fe(II) was determined by the ferrozine method. The association of the defined co-cultures of G. metallireducens and M. barkeri with magnetite was observed with transmission electron micrographs.ResultsMagnetite stimulated ethanol metabolism and methane production in defined co-cultures of G. metallireducens and M. barkeri; however, magnetite did not promote methane production in co-cultures initiated with a culture of G. metallireducens that could not produce electrically conductive pili (e-pili), unlike the conductive carbon materials that facilitate DIET in the absence of e-pili. Transmission electron microscopy revealed that G. metallireducens and M. barkeri were closely associated when magnetite was present, as previously observed in G. metallireducens/G. sulfurreducens co-cultures. These results show that magnetite can promote DIET between Geobacter and Methanosarcina species, but not as a substitute for e-pili, and probably functions to facilitate electron transfer from the e-pili to Methanosarcina.ConclusionIn summary, the e-pili are necessary for the stimulation of not only G. metallireducens/G. sulfurreducens, but also methanogenic G. metallireducens/M. barkeri co-cultures with magnetite.

【 授权许可】

CC BY