Occurrence and potential activity of denitrifiers and methanogens in groundwater at 140 m depth in Pliocene diatomaceous mudstone of northern Japan.

Anaerobic microbial activity has a major influence on the subsurface environment. We investigated the denitrification and methanogenesis in anoxic groundwater at a depth of 140 m in two boreholes drilled in a sedimentary geological setting, where the redox potential fluctuated. The average maximum potential denitrification rates, measured under anaerobic conditions in the two boreholes using an (15) N tracer, were 0.

Population dynamics of Crenarchaeota and Euryarchaeota in the mixing front of river and marine waters.

A transect from the Tomoe River Mouth through Shimizu Port to Suruga Bay, Japan, was examined between 2005 and 2009 to reveal the population dynamics of Crenarchaeota and Euryarchaeota in an estuary environment. Crenarchaeota tended to increase in abundance in waters deeper than 100 m compared with Euryarchaeota, and comprised 11% of total direct counts. Archaeal abundance was highest in the Tomoe River Mouth, with a strong negative correlation between surface euryarchaeal abundance and salinity (P<0.

Unique distribution of deep groundwater bacteria constrained by geological setting.

We collected groundwater samples at depths of up to 482 m from three boreholes drilled into sedimentary rock within two formations in Hokkaido, Japan. The prokaryotic community in each subsurface groundwater sample was analysed by microscopic counts and cloning-sequencing the 16S rRNA genes. On total direct counts, there were between 4.

Denitrification activity and relevant bacteria revealed by nitrite reductase gene fragments in soil of temperate mixed forest.

Denitrification activity and bacterial community constituents were investigated in both well-drained and poorly drained soils of a temperate forest in central Japan by (15)N tracer experiments and a cloning-sequencing approach. Denitrification activity was much higher in wet soil than in dry soil, based on (15)N(15)N ((30)N(2)) and (15)N(15)NO ((46)N(2)O) production. Labeled nitrate ((15)NO(3)(-)) was immediately reduced to (30)N(2) in wet soil, whereas it was only reduced to (46)N(2)O in dry soil.