Microbial community structure and biogeochemistry of Miocene subsurface sediments: implications for long‐term microbial survival

Abstract

Thirty closely spaced cores were obtained from Miocene-aged fluvial, lacustrine and palaeosol subsurface sediments ranging in depth from 173 to 197 m at a site in southcentral Washington to investigate the size and composition of the microbial community in relation to sediment geochemical and geophysical properties. Total phospholipid fatty acid (PLFA) analysis indicated that the greatest concentrations of microbial biomass were in low-permeability lacustrine sediments that also contained high concentrations of organic carbon. Community structure, based on lipid analyses and on in situ hybridization of bacterial cells with 16s RNA-directed DNA probes, also revealed the presence of metabolically active bacteria that respire sulphate and/or Fe(II1) in the lacustrine sediments. Concentrations of pore water sulphate were low (4-8 mg/L) and HClextractable Fe was predominantly Fe(I1) in the same samples where total biomass and organic carbon were highest. The low hydraulic conductivity (106 to < l V cm/s) of these sediments has likely contributed to the long term maintenance of both bacteria and organic carbon by limiting the supply of soluble electron acceptors for microbial respiration. These results suggest that the current subsurface microbial population was derived from organisms that were present during lake sedimentation = 6-8 million years ago.

Functional metaproteome analysis of protein extracts from contaminated soil and groundwater

“…Major goals of these efforts are to attribute key functions to specific community members and, in view of the ecosystem stability, to reveal cooperation between community members and functional redundancies. Besides measuring enzyme activities, respiration rates and metabolite concentrations (Landi et al, 2000;Moreno et al, 2001), nucleic acids (Eilers et al, 2000) and lipids (Fredrickson et al, 1995) are often used as markers for microbial identity, and to a certain extent, metabolic potential and its expression in environmental samples (Kanagawa, 2003;Fields et al, 2006). Structural data obtained from lipids are based on the occurrence of fatty acids or quinones that are specific for certain taxa.…”

Erratum: correction: Biodegradation of oil in uplifted basins prevented by deep-burial sterilization

“…Thus, in deep reservoirs where degradation does occur, microorganisms must have already been in place during slow burial, and have survived and probably evolved on geological timescales. This implies that the microbial¯ora of deep reservoirs may be isolated biospheres, descendants of ancient lineages responding in an isolated manner to evolution over millions of years, as suggested for other sediments 31 . Our reservoir palaeo-temperature estimates suggest that the base of the hydrocarbon-degrading biosphere is at temperatures lower than 90 8C, in agreement with much oil®eld data and the empirical rule used by petroleum geologists that biodegraded oils are only found in reservoirs cooler than 80 8C.…”

“…It now seems likely that most sediments cooler than the maximum temperature boundary of the deep biosphere contain microorganisms 3,7,31 . If`palaeosterilization' occurs, it appears that once destroyed, effective bacterial and archaeal communities (or at the very least hydrocarbon-degrading bacterial and archaeal communities) are not re-established in deep reservoirs.…”

Physiological Status and Community Composition of Microbial Mats of the Ebro Delta, Spain, by Signature Lipid Biomarkers

“…The lipid analysis has been applied to assess microbial communities (bacteria, fungi, protozoa, and metazoa) in mud, soil, rhizosphere, sediments, and bioreactors [32,34]. The signature lipid biomarkers (SLB) analysis provides a quantitative means of measuring viable microorganisms [1,11,13], microbial community composition [13,34], and community nutritional/ physiological status [15,31]. Extractable phospholipids have been proposed as indicators of microbial abundance.…”