• Energy Research

Biogenic manganese oxide (BioMnOx) can efficiently adsorb various minor metals. The production of BioMnOx in reactors to remove metals during wastewater treatment processes is a promising biotechnological method. However, it is difficult to preferentially enrich manganese-oxidizing bacteria (MnOB) to produce BioMnOx during wastewater treatment processes. A unique method of cultivating MnOB using methane-oxidizing bacteria (MOB) to produce soluble microbial products is proposed here. MnOB were successfully enriched in a methane-fed reactor containing MOB. BioMnOx production during the wastewater treatment process was confirmed. Long-term continual operation of the reactor allowed simultaneous removal of Mn(II), Co(II), and Ni(II). The Co(II)/Mn(II) and Ni(II)/Mn(II) removal ratios were 53% and 19%, respectively. The degree to which Mn(II) was removed indicated that the enriched MnOB used utilization-associated products and/or biomass-associated products. Microbial community analysis revealed that methanol-oxidizing bacteria belonging to the Hyphomicrobiaceae family played important roles in the oxidation of Mn(II) by using utilization-associated products. Methane-oxidizing bacteria were found to be inhibited by MnO2, but the maximum Mn(II) removal rate was 0.49 kg m-3 d-1.

A novel methane-producing archaeon, designated strain HASU(T), was isolated from a lotus field. Cells were Gram-negative, non-motile, irregular cocci, 2-3 mum in diameter, and occurred singly. Growth was observed at 15-40 degrees C (optimum, 37 degrees C) and pH 6.5-7.5 (optimum, pH 7.0). The G+C content of the genomic DNA was 60.9 mol%. Strain HASU(T) utilized ethanol, 1-propanol, 1-butanol, hydrogen and formate for growth and methane production. It converted ethanol to methane and acetate. Based on comparative 16S rRNA gene sequence analysis, strain HASU(T) was shown to be affiliated with the genus Methanofollis. It was related most closely to the type strain of Methanofollis liminatans (96.1 % 16S rRNA gene sequence similarity). Based on phylogenetic analysis and phenotypic characteristics, strain HASU(T) is considered to represent a novel species of the genus Methanofollis, for which the name Methanofollis ethanolicus sp. nov. is proposed. The type strain is HASU(T) (=NBRC 104120(T)=JCM 15103(T)=DSM 21041(T)).

Biogenic manganese oxides (bio-MnO₂) have been shown to absorb minor metals. Bioreactor cultivation of heterotrophic manganese oxidizing bacteria (MnOB), which produce bio-MnO₂ via oxidation of Mn (II), can be expected to be involved in a promising system for removal and recovery of minor metals from wastewater. However, MnOB enrichment in wastewater treatment is difficult. This study investigated whether MnOB can be cultivated when coupled with nitrification in a system in which soluble microbial products (SMP) from nitrifiers are provided to MnOB as a substrate. A downflow hanging sponge (DHS) reactor was applied for MnOB cultivation with ammonium (NH₄⁺) and Mn (II) continuously supplied. During long-term operation, Mn (II) oxidation was successfully established at a rate of 48 g Mn m⁻³ d⁻¹ and bio-MnO₂ that formed on the sponges were recovered from the bottom of the reactor. The results also revealed that Ni and Co added to the influent were simultaneously removed. Microbial 16S rRNA gene clone analysis identified nitrifiers supporting MnOB growth and showed that only one clone of Bacillus subtilis, which was affiliated with a known MnOB cluster, was present, suggesting the existence of other novel bacteria with the ability to oxidize Mn (II).

m CSF = depth of Core below Sea Floor in meters / m CSF-A: Distance from sea floor to sample within recovered core. This scale allows overlap at core and section boundaries. /m CSF-B: Distance from sea floor to sample within recovered core is compressed, if core recovery > 100%.

AbstractOceanic methane from global deep-sea sediment is largely consumed through microbially mediated sulfate-coupled oxidation, resulting in 13C-depleted cell biomass of anaerobic methanotrophic archaea (ANME). The general ecological importance of subseafloor ANME has been well recognized in the last two decades. However, the crucial biochemical pathways for the overall anaerobic oxidation of methane (AOM) still remain enigmatic. Here, methanotrophic pathways were analyzed to trace 13C-depleted amino acid biosynthesis in two clades of ANME (ANME-1 and ANME-2) from the Black Sea. Compound-specific analysis of ANME-dominated microbial mats showed a significant 13C-depletion trend in association with increasing carbon numbers in protein-derived amino acid families (e.g., the pyruvate family in the order of alanine, valine, isoleucine and leucine was down to −114‰). This result indicates a stepwise elongation of 13C-depleted carbon during amino acid biosynthesis. The overall results suggest that intracellular protein amino acids and the most 13C-depleted signature of leucine, which has a specific branched-chain structure, are potentially propagated as isoprenoid precursor molecules into archaeal biosynthesis, resulting in the extremely 13C- and 14C-depleted nature of ANME cells in the deep microbial oasis.