Microbial biomass and activity in subsurface sediments from Vejen, Denmark

Abstract

Subsurface sediment samples were collected from 4 to 31 m below landsurface in glacio-fluvial sediments from the Quaternary period. The samples were described in terms of pH, electrical conductivity, chloride concentration, organic matter content, and grain size distribution. Viable counts of bacteria varied from 0.5 to 1,203 x 103 colony forming units/g dry weight (gdw); total numbers of bacteria acridine orange direct counts (AODC) varied from 1.7 to 147 × 10(7) cells/gdw; growth rates (incorporation of [(3)H]-thymidine) varied from 1.4 to 60.7 × 10(4) cells/(gdw · day); and rate constants for mineralization of (14)C-labelled compounds varied from 0.2 to 2.3 × 10(-3) ml/(dpm · day) for acetate, and from 0 to 2.0 × 10(-3) ml/(dpm · day) for phenol. Sediment texture influenced the total number of bacteria and potential for mineralization; with increasing content of clay and silt and decreasing content of sand, AODC increased and the mineralization rate declined. Intrinsic permeability calculated from grain size correlated positively with mineralization rate for acetate. Statistical correlation analysis showed high correlations between some of the abiotic parameters, but it was not possible to point out a single abiotic parameter that could explain the variation of size and activity of the microbial population. The microbial data obtained in these geologically young sediments were compared to literature data from older sediments, and this comparison showed that age and type of geological formation might be important for the size and activity of the microbial populations.

Relationships between Microbial Community Structure and Hydrochemistry in a Landfill Leachate-Polluted Aquifer

“…In contrast to the groundwater results, no relationship to pollution was apparent from the analysis of the microbial community structure of sediment. The number of particle-bound microorganisms per gram of sediment is usually 1 order of magnitude higher than the number of free-living microorganisms per milliliter in landfill leachatepolluted aquifers (4,22). Since 1 cm 3 of sediment weights 2.65 g and contains about 30% water, the number of sedimentassociated microorganisms is about 2 orders of magnitude higher than the number present in water.…”

“…Oxygen content, pH, and electrical conductivity were measured in the field with electrodes placed in flow cells. Hydrochemical parameters (alkalinity; benzene, toluene, ethylbenzene, xylene, naphthalene, Mn, Fe, Si, Al, Mg, NH 4 , Ca, K, Na, Cl, SO 4 , H 2 S, NO 2 , NO 3 , CH 4 , and dissolved organic carbon contents) and sedimentological parameters (lime, humus, sand, clay, silt, carbon, and nitrogen contents) were determined by using Dutch NEN standards and laboratory procedures. Samples were grouped based on chemical characteristics by using principal-component analysis and cluster analysis (Systat 7).…”

The Significance of Microbe-Mineral-Biomarker Interactions in the Detection of Life on Mars and Beyond

“…The numbers of microorganisms associated with solid surfaces in subsurface environments on Earth are typically more than one order of magnitude higher than those of the free-living microorganisms in pore water, per volume unit (Albrechtsen and Winding, 1992;Holm et al, 1992). The identities and metabolic potentials of attached microorganisms differ from those in the nearby liquid phase (Albrechtsen et al, 1996;Crump et al, 1999;Röling et al, 2001).…”

Biological impact on mineral dissolution: Application of the lichen model to understanding mineral weathering in the rhizosphere

“…Recent surveys of subsurface aquifers show large microbial populations, Ϸ10 5 -10 8 cells͞cm 3 (15,(28)(29)(30). Cell concentrations ranging from 10 3 to 10 9 cells͞cm 3 have been reported from soils, sediments, and natural waters (15,(31)(32)(33). Greater than 10 8 cells͞cm 2 of surface area occur on metal sulfide minerals (25)(26)(27).…”