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Summary: Under methanogenic conditions, short‐chain fatty acids are common byproducts from degradation of organic compounds and conversion of these acids is an important component of the global carbon cycle. Due to the thermodynamic difficulty of propionate degradation, this process requires syntrophic interaction between a bacterium and partner methanogen; however, the metabolic strategies and behaviour involved are not fully understood. In this study, the first genome analysis of obligately syntrophic propionate degraders (Pelotomaculum schinkii HH and P. propionicicum MGP) and comparison with other syntrophic propionate degrader genomes elucidated novel components of energy metabolism behind Pelotomaculum propionate oxidation. Combined with transcriptomic examination of P. schinkii behaviour in co‐culture with Methanospirillum hungatei, we found that formate may be the preferred electron carrier for P. schinkii syntrophy. Propionate‐derived menaquinol may be primarily re‐oxidized to formate, and energy was conserved during formate generation through newly proposed proton‐pumping formate extrusion. P. schinkii did not overexpress conventional energy metabolism associated with a model syntrophic propionate degrader Syntrophobacter fumaroxidans MPOB (i.e., CoA transferase, Fix and Rnf). We also found that P. schinkii and the partner methanogen may also interact through flagellar contact and amino acid and fructose exchange. These findings provide new understanding of syntrophic energy acquisition and interactions. [ABSTRACT FROM AUTHOR]

In an acetate-fed anaerobic-aerobic membrane bioreactor with deteriorated enhanced biological phosphorus removal ( EBPR), D efluviicoccus-related tetrad-forming organisms ( DTFO) were observed to predominate in the microbial community. Using metagenomics, a partial genome of the predominant DTFO, ' C andidatus Defluviicoccus tetraformis strain TFO71', was successfully constructed and characterized. Examining the genome confirmed the presence of genes related to the synthesis and degradation of glycogen and polyhydroxyalkanoate ( PHA), which function as energy and carbon storage compounds. TFO71 and ' C andidatus Accumulibacter phosphatis' ( CAP) UW-1 and CAP UW-2, representative polyphosphate-accumulating organisms ( PAO), have PHA metabolism-related genes with high homology, but TFO71 has unique genes for PHA synthesis, gene regulation and granule management. We further discovered genes encoding DTFO polyphosphate ( polyP) synthesis, suggesting that TFO71 may synthesize polyP under untested conditions. However, TFO71 may not activate these genes under EBPR conditions because the retrieved genome does not contain all inorganic phosphate transporters that are characteristic of PAOs ( CAP UW-1, CAP UW-2, M icrolunatus phosphovorus NM-1 and T etrasphaera species). As a first step in characterizing EBPR-associated DTFO metabolism, this study identifies important differences between DTFO and PAO that may contribute to EBPR community competition and deterioration. [ABSTRACT FROM AUTHOR]

A low-diversity microbial community, dominated by the γ-proteobacterium H alomonas sulfidaeris, was detected in samples of warm saline formation porewater collected from the Cambrian Mt. Simon Sandstone in the Illinois Basin of the North American Midcontinent (1.8 km/5872 ft burial depth, 50° C, pH 8, 181 bars pressure). These highly porous and permeable quartz arenite sandstones are directly analogous to reservoirs around the world targeted for large-scale hydrocarbon extraction, as well as subsurface gas and carbon storage. A new downhole low-contamination subsurface sampling probe was used to collect in situ formation water samples for microbial environmental metagenomic analyses. Multiple lines of evidence suggest that this H. sulfidaeris-dominated subsurface microbial community is indigenous and not derived from drilling mud microbial contamination. Data to support this includes V1- V3 pyrosequencing of formation water and drilling mud, as well as comparison with previously published microbial analyses of drilling muds in other sites. Metabolic pathway reconstruction, constrained by the geology, geochemistry and present-day environmental conditions of the Mt. Simon Sandstone, implies that H. sulfidaeris-dominated subsurface microbial community may utilize iron and nitrogen metabolisms and extensively recycle indigenous nutrients and substrates. The presence of aromatic compound metabolic pathways suggests this microbial community can readily adapt to and survive subsurface hydrocarbon migration. [ABSTRACT FROM AUTHOR]