Microbial communities associated with acetate-rich gas-petroleum reservoir surface facilities.

We evaluated the microbial communities in acetate-rich production waters from separators of a high-temperature gas-petroleum reservoir in Higashi-Niigata, Japan. Bacterial and archaeal 16S rRNA gene libraries constructed from these waters were dominated by Acetobacterium-, Methanofollis-, and Methanosarcina-related sequences. The libraries constructed from enrichment cultures of the production waters were dominated by sequences related to the Acetobacterium- and Methanofollis-related sequences.

Determination of redox potential of sulfidic groundwater in unconsolidated sediments by long-term continuous in situ potentiometric measurements.

This study was undertaken to investigate the redox potential (Eh) of sulfidic groundwater in unconsolidated sediments. The Eh was determined by long-term (several days to several weeks) continuous in situ potentiometric measurements using a platinum (Pt) electrode. The Eh values measured in two monitoring campaigns were -259 and -202 mV, respectively. Chemical analysis of groundwater showed that the redox species in the groundwater were sulfide (S²â») and iron, respectively. The saturation indices calculated from the chemical analysis results indicated that FeS(am) and mainly mackinawite were close to equilibrium in the analyzed waters. Comparison of the measured Eh values with those calculated using different redox couples revealed that the Eh values measured in the first monitoring campaign were nearly equal to those calculated using HS⁻/SO4²â», S²â»/SO4²â», FeS(am)/SO4²â», and mackinawite/SO4²â» redox couples; on the other hand, the Eh values measured in the second monitoring campaign were almost consistent with those measured using the FeS2/SO4²â» redox couple. The good fit between the measured Eh values and the theoretical calculated Eh values suggests that the sulfur system is related to the Eh value of sulfidic groundwater in unconsolidated sediments.

Methanosarcina horonobensis sp. nov., a methanogenic archaeon isolated from a deep subsurface Miocene formation.

A methanogenic organism, designated strain HB-1(T), from the domain Archaea was isolated from groundwater sampled from a subsurface Miocene formation located in Horonobe, Hokkaido, Japan. The strain grew on methanol, dimethylamine, trimethylamine, dimethylsulfide and acetate but not on monomethylamine, H(2)/CO(2), formate, 2-propanol, 2-butanol or cyclopentanol. Cells were Gram-reaction-negative, non-motile, irregular cocci that were 1.4-2.9 µm in diameter and occurred singly or in pairs. The strain grew at 20-42 °C (optimum 37 °C), at pH 6.0-7.75 (optimum pH 7.0-7.25) and in 0-0.35 M NaCl (optimum 0.1 M). The G+C content of the genomic DNA was 41.4 mol%. 16S rRNA gene sequencing revealed that the strain was a member of the genus Methanosarcina but that it clearly differed from all recognized species of this genus (93.1-97.9 % sequence similarity). The phenotypic and phylogenetic features of strain HB-1(T) indicate that it represents a novel species of the genus Methanosarcina, for which the name Methanosarcina horonobensis sp. nov. is proposed. The type strain is HB-1(T) ( = DSM 21571(T)  = JCM 15518(T)  = NBRC 102577(T)).