Survival during long-term starvation: global proteomics analysis of Geobacter sulfurreducens under prolonged electron-acceptor limitation.

The bioavailability of terminal electron acceptors (TEAs) and other substrates affects the efficiency of subsurface bioremediation. While it is often argued that microorganisms exist under "feast or famine", in the laboratory most organisms are studied under "feast" conditions, whereas they typically encounter "famine" in nature. The work described here aims to understand the survival strategies of the anaerobe Geobacter sulfurreduces under TEA-starvation conditions.

Growth advantage in stationary-phase (GASP) phenotype in long-term survival strains of Geobacter sulfurreducens.

Geobacter sulfurreducens exists in the subsurface and has been identified in sites contaminated with radioactive metals, consistent with its ability to reduce metals under anaerobic conditions. The natural state of organisms in the environment is one that lacks access to high concentrations of nutrients, namely electron donors and terminal electron acceptors (TEAs). Most studies have investigated G.

Molybdenum isotope fractionation by cyanobacterial assimilation during nitrate utilization and N₂ fixation.

We measured the δ⁹⁸Mo of cells and media from molybdenum (Mo) assimilation experiments with the freshwater cyanobacterium Anabaena variabilis, grown with nitrate as a nitrogen (N) source or fixing atmospheric N₂. This organism uses a Mo-based nitrate reductase during nitrate utilization and a Mo-based dinitrogenase during N₂ fixation under culture conditions here. We also demonstrate that it has a high-affinity Mo uptake system (ModABC) similar to other cyanobacteria, including marine N₂-fixing strains.

The effect of methanogen growth on mineral substrates: will Ni markers of methanogen-based communities be detectable in the rock record?

Methanogens, thought to be present on early Earth, have a high requirement for Ni, suggesting that Ni utilization could be a potential biosignature for methanogens if enhanced Ni extraction from surrounding minerals accompanies methanogenic growth. To test the potential for such Ni extraction from minerals by methanogens, Ni release from Ni-containing silicate glass was measured in Ni-free growth medium in the presence of the methanogen Methanothermobacter thermoautotrophicus (average pH ∼7.0) and observed to be higher than an abiotic control (average pH ∼6.

Mechanical disruption of Escherichia coli for plasmid recovery.

Five different mechanical cell disruption processes were evaluated as methods to extract plasmids from bacterial cells. The methods used were sonication, nebulization homogenization, microfluidization, and bead milling. The recovery yields of intact plasmids from the various methods were measured by quantitative gel electrophoresis.