Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, China.
ISME J. 2018 Sep;12(9):2142-2151. doi: 10.1038/s41396-018-0193-y. Epub 2018 Jun 6.
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.
直接种间电子转移 (DIET) 可能在表现出产甲烷作用和厌氧甲烷氧化作用的微生物群落中占主导地位，并且可以作为支持厌氧光合作用的电子源。先前对定义明确的 Geobacter 物种共培养物的诱变研究表明，导电菌毛和细胞外细胞色素都是 DIET 的必需条件。然而，菌毛在 DIET 中的实际功能作用尚不确定，因为这些研究中使用的菌毛突变策略会影响细胞外细胞色素的图谱。在这里，我们通过在两种 Geobacter 物种中删除菌毛聚合马达 PilB 来抑制菌毛的功能。PilB 突变抑制了菌毛的组装，但没有改变细胞外细胞色素的模式。我们报告说，两种无菌毛的 Geobacter 物种可以形成聚集体并与 DIET 共生生长。结果表明，Geobacter metallireducens 的 Gmet_2896 细胞色素在 DIET 中起着关键作用，并且导电菌毛对于 Geobacter 物种共培养物中促进 DIET 并非必需，这表明细胞色素本身可以介导 DIET，加深了对 DIET 的理解。
