Transcription profiling of G sulfurreducens GGS nitrogen fixation

ABSTRACT: G. sulfurreducens (ATCC #51573) was obtained from the laboratory culture collection of Dr. Derek Lovley. Cells were grown under strict anaerobic conditions at 30 °C in chemostats, as previously described (for more information see Esteve-Núñez, A., M. M. Rothermich, M. Sharma, and D. R. Lovley. 2004. Growth of Geobacter sulfurreducens under nutrient-limiting conditions in continuous culture. Environ. Microbiol.:in press.), with acetate (5 mM) as the electron donor and fumarate (27.5 mM) as the electron acceptor. For growth in the absence of fixed nitrogen, the ammonium chloride (4.7 mM) was omitted from the medium and fumarate served as the electron acceptor. Therefore, cultures with ammonium chloride were limited by acetate while cultures without ammonium chloride were limited by nitrogen. Cultures were maintained at a dilution rate of 0.05 h-1 for 5 culture vessel volumes to ensure that cells were at steady-state prior to harvesting. Cells were harvested by centrifugation at 4 °C and the cell pellet was flash-frozen in liquid nitrogen and then stored at -80 °C prior to RNA extraction. Cells grown in the absence of ammonium had acetylene reduction rates of 0.012 nmol/hr compared to 0.003 nmol/hr in ammonium-grown cells, providing evidence that these cells were fixing nitrogen.. The steady-state concentration of cells in the nitrogen-fixing chemostats (0.178 mg/mL + 0.011; mean + standard deviation, n=3) was significantly lower than chemostats provided with ammonium (0.45 mg/mL + 0.007). Three cultures of acetate limited growth with fumarate as the electron acceptor and three cultures of nitrogen limited growth with fumarate as the electron acceptor were grown. Each culture vessel was harvested and extracted for total RNA separately to produce three biological replicates for this experiment.

ORGANISM(S): Geobacter sulfurreducens

SUBMITTER: Barb Methe 

PROVIDER: E-TIGR-82 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress