Comparison of gene expression and mutant fitness in Shewanella oneidensis MR-1
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ABSTRACT:
ORGANISM(S): Shewanella oneidensis MR-1
SUBMITTER: Morgan Price
PROVIDER: E-GEOD-39462 | biostudies-arrayexpress |
REPOSITORIES: biostudies-arrayexpress
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Project description:S. oneidensis MR-1 was grown with different electron acceptors: an electrode at 0.4 V vs. SHE, 50 mM Fe(III)citrate, and oxygen. The gene expression pattern for each experiment was analyzed and the differences in gene expression for the different experimental conditions were compared. For two samples S. oneidensis was grown with a graphite anode electrode (at 0.4 V. vs. SHE) as the only electron acceptor - one sample was directly fed with 20 mM lactate, one sample was fed with lactate produced during fermentation of glucose by Lactococcus lactis. Four samples were grown anaerobically with 50 mM Fe(III)citrate as the only electron acceptor, and 20 mM lactate for 20 h. Three samples were grown aerobically with 20 mM lactate for 20 h. The same modified M4 medium was used for all samples. For RNA extraction, the biofilm was scraped off the frozen (-80M-BM-0C) carbon electrode with a sterile razor blade. Biofilm-carbon sludge was combined with 7 mL ice-cold phosphate buffer saline (PBS), vortexed, sonicated at 7 W for 30 s on ice (3 repetitions), and centrifuged. For the liquid cultures, 2 mL of each culture were combined with 2 mL RNA protect, vortexed, and centrifuged at 5,500g for 10 min. The pellets were resuspended in NAES buffer (50 mM sodium acetate buffer, 10 mM EDTA and 1 % SDS at pH 5). RNA was isolated with a phenol:chloroform extraction protocol.
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Project description:Bioelectrochemical systems employing mixed microbial communities as biocatalysts are gaining importance as potential renewable energy, bioremediation, or biosensing devices. While we are beginning to understand how individual microorganism species interact with an electrode as electron donor, not much is known about the interactions between different microbial species in a community. Here, we compare the bioelectrochemical performance of Shewanella oneidensis in a pure-culture and in a co-culture with the homolactic acid fermenter Lactococcus lactis. While S. oneidensis alone can only use lactate as electron donor for current production, the co-culture is able to convert glucose into current with a similar coulombic efficiency of approximately 17%, respectively. With (electro)-chemical analysis and transcription profiling, we found that the BES performance and S. oneidensis physiology were not significantly different whether grown as a pure- or co-culture. These co-culture experiments represent a first step in understanding microbial interactions in BES communities with the goal to design complex microbial communities, which specifically convert target substrates into electricity. Further, for the first time, we elucidated S. oneidensis gene expression with an electrode as the only electron acceptor. The expression pattern confirms many previous studies regarding the enzymatic requirements for electrode respiration, and it generates new hypotheses on the functions of proteins, which are so far not known to be involved in electrode respiration. The BES was either operated with S. oneidensis alone, fed with lactate, or it was operated with S. oneidensis and L. lactis with glucose as primary substrate. The basic medium was a modified M4 medium containing 0.5 g/L yeast extract, 0.5 g/L trypton and 5 g/L glycerol phosphate, besides the commen M4 incredients. S. oneidensis oxidizes lactate to acetate and electrons in a BES - the latter generate a current at a graphite anode. The anode biofilm was harvested after about 4 weeks of continuous BES operation and subjected to total RNA extraction.
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