Long-Term\nFertilization Shapes the Putative Electrotrophic\nMicrobial Community in Paddy Soils Revealed by Microbial Electrosynthesis\nSystems

Abstract

Electrotrophs\nplay\nan important role in biogeochemical cycles, but the effects of long-term\nfertilization on electrotrophic communities in paddy soils remain\nunclear. Here, we explored the responses of electrotrophic communities\nin paddy soil-based microcosms to different long-term fertilization\npractices using microbial electrosynthesis systems (MESs), high-throughput\nquantitative PCR, and 16s rRNA gene-based Illumina sequencing techniques.\nCompared to the case in the unfertilized soil (CK), applications of\nonly manure (M); only chemical nitrogen, phosphorous, and potassium\nfertilizers (NPK); and M plus NPK (MNPK) clearly changed the electrotrophic\nbacterial community structure. The <i>Streptomyces</i> genus\nof the Actinobacteria phylum was the dominant electrotroph in the\nCK, M, and MNPK soils. The latter two soils also favored <i>Truepera</i> of Deinococcus–Thermus or <i>Arenimonas</i> and <i>Thioalkalispira</i> of Proteobacteria. Furthermore, <i>Pseudomonas</i> of Proteobacteria and <i>Bacillus</i> of Firmicutes were major electrotrophs in the NPK soil. These electrotrophs\nconsumed biocathodic currents coupled with nitrate reduction and recovered\n18–38% of electrons via dissimilatory nitrate reduction to\nammonium (DNRA). The increased abundances of the <i>nrfA</i> gene for DNRA induced by electrical potential further supported\nthat the electrotrophs enhanced DNRA for all soils. These expand our\nknowledge about the diversity of electrotrophs and their roles in\nN cycle in paddy soils and highlight the importance of fertilization\nin shaping electrotrophic communities.