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Syntrophic growth with direct interspecies electron transfer between pili-free Geobacter species

The ISME Journal (2018) | Download Citation


Direct interspecies electron transfer (DIET) may prevail in microbial communities that show methanogenesis and anaerobic methane oxidation and can be an electron source to support anaerobic photosynthesis. Previous mutagenic studies on cocultures of defined Geobacter species indicate that both conductive pili and extracellular cytochromes are essential for DIET. However, the actual functional role of the pili in DIET is uncertain, as the pilus mutation strategy used in these studies affected the extracellular cytochrome profile. Here we repressed the function of pili by deleting the pilus polymerization motor PilB in both Geobacter species. The PilB mutation inhibited the pilus assembly but did not alter the pattern of extracellular cytochromes. We report that the two pilus-free Geobacter species can form aggregates and grow syntrophically with DIET. The results demonstrate that the Gmet_2896 cytochrome of Geobacter metallireducens plays a key role in DIET and that conductive pili are not necessary to facilitate DIET in cocultures of Geobacter species, and they suggest cytochromes by themselves can meditate DIET, deepening the understanding of DIET.

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We sincerely thank Prof. Shiming Wang of Nanjing University of Science and Technology for kindly providing plasmid pCM158, and we thank Prof. Derek Lovley of University of Massachusetts, Amherst for providing the OmcS mutant of G. sulfurreduces. We thank Prof. Xiangzhen Li for constructive criticism of the manuscript. We also thank Dr. Qianzhuo Mao and the Center for Molecular Cell and Systems Biology of Fujian Agriculture and Forestry University, respectively, for electron microscopy and laser scanning confocal microscopy. This research was supported by the National Natural Science Foundation of China, grants no. 31600089, no. 41671264 and no. 91751109.

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  1. Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, China

    • Xing Liu
    • , Shiyan Zhuo
    • , Christopher Rensing
    •  & Shungui Zhou


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Correspondence to Shungui Zhou.

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