During microbial methanogenic hydrocarbon degradation, secondary fermenters that convert the substrates produced by primary fermenters to acetate, carbon dioxide, hydrogen, and formate which could be further transformed into methane by terminal methanogens have received less attention. In this study, we isolated an anaerobic bacterium, designated strain L-13T, from a methanogenic crude oil-degrading enrichment culture. The motile, non-sporulating, tenuous rod cells (0.5–0.8 μm) stained Gram-positive and grew optimally at 37 °C and pH 7.2 with 0.5% NaCl. 16S rRNA gene sequence analysis revealed that strain L-13T was distantly related to members of the genus Aminiphilus (89% similarity) in the family Aminiphilaceae of the phylum Synergistetes, and represented a novel genus-level clade, previously known as EBM-39. Fermentative growth with various amino acids, propionate and some specific sugars was observed, with acetate and hydrogen as the main end products. Syntrophic growth occurred with propionate, butyrate and caprylate in the presence of an H2-utilizing methanogen, and growth on butyrate and caprylate was only observed under syntrophic conditions. Therefore, this strain may play roles as both secondary fermenter and biomass scavenger in the engineered anaerobic bioreactors/digestors and laboratory enrichments, where primary fermentation products and necromass are readily available. Based on chemotaxonomic, phylogenetic and genomic characteristics, strain L-13T (=CGMCC 1.17908) was identified and nominated as Aminirod propionatiphilus gen. nov., sp. nov.
- Methanogenic hydrocarbon degradation
- Secondary fermenter
- Syntrophic metabolism