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The genetic basis of energy conservation in the sulfate-reducing bacterium Desulfovibrio alaskensis G20.

Price MN, Ray J, Wetmore KM, Kuehl JV, Bauer S, Deutschbauer AM, Arkin AP - Front Microbiol (2014)

Bottom Line: Similarly, during the oxidation of malate or fumarate, the electron-bifurcating transhydrogenase NfnAB-2 (Dde_1250:1) is important and may generate reduced ferredoxin to allow additional ion pumping by Rnf.During formate oxidation, the periplasmic [NiFeSe] hydrogenase HysAB is required, which suggests that hydrogen forms in the periplasm, diffuses to the cytoplasm, and is used to reduce ferredoxin, thus providing a substrate for Rnf.During hydrogen utilization, the transmembrane electron transport complex Tmc is important and may move electrons from the periplasm into the cytoplasmic sulfite reduction pathway.

View Article: PubMed Central - PubMed

Affiliation: Physical Biosciences Division, Lawrence Berkeley Lab Berkeley, CA, USA.

ABSTRACT
Sulfate-reducing bacteria play major roles in the global carbon and sulfur cycles, but it remains unclear how reducing sulfate yields energy. To determine the genetic basis of energy conservation, we measured the fitness of thousands of pooled mutants of Desulfovibrio alaskensis G20 during growth in 12 different combinations of electron donors and acceptors. We show that ion pumping by the ferredoxin:NADH oxidoreductase Rnf is required whenever substrate-level phosphorylation is not possible. The uncharacterized complex Hdr/flox-1 (Dde_1207:13) is sometimes important alongside Rnf and may perform an electron bifurcation to generate more reduced ferredoxin from NADH to allow further ion pumping. Similarly, during the oxidation of malate or fumarate, the electron-bifurcating transhydrogenase NfnAB-2 (Dde_1250:1) is important and may generate reduced ferredoxin to allow additional ion pumping by Rnf. During formate oxidation, the periplasmic [NiFeSe] hydrogenase HysAB is required, which suggests that hydrogen forms in the periplasm, diffuses to the cytoplasm, and is used to reduce ferredoxin, thus providing a substrate for Rnf. During hydrogen utilization, the transmembrane electron transport complex Tmc is important and may move electrons from the periplasm into the cytoplasmic sulfite reduction pathway. Finally, mutants of many other putative electron carriers have no clear phenotype, which suggests that they are not important under our growth conditions, although we cannot rule out genetic redundancy.

No MeSH data available.


Related in: MedlinePlus

Growth of mutants in electron transport complexes Rnf, Hdr/flox-1, Nfn-2, Hmc, and Tmc, with sulfate as the electron acceptor and with a variety of electron donors. Growth of the parent strain (G20) on the same day is shown for comparison. Because results for the parent strain sometimes varied across days, we graph experiments done on different days separately. Y. E. is short for yeast extract. For each complex, we used transposon insertions in at least two different genes, and for each mutant and condition, we collected 2–4 replicates, except for floxD-1 (Dde_1210) growing on hydrogen.
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Figure 6: Growth of mutants in electron transport complexes Rnf, Hdr/flox-1, Nfn-2, Hmc, and Tmc, with sulfate as the electron acceptor and with a variety of electron donors. Growth of the parent strain (G20) on the same day is shown for comparison. Because results for the parent strain sometimes varied across days, we graph experiments done on different days separately. Y. E. is short for yeast extract. For each complex, we used transposon insertions in at least two different genes, and for each mutant and condition, we collected 2–4 replicates, except for floxD-1 (Dde_1210) growing on hydrogen.

Mentions: Among the electron transport systems, we identified phenotypes for mutants of qrc, rnf, hdr/flox-1, nfnAB-2, nox, tmc, and hmc (Figure 5). We validated the phenotypes for these (except qrc and nox) by growing mutant strains individually (Figure 6).


The genetic basis of energy conservation in the sulfate-reducing bacterium Desulfovibrio alaskensis G20.

Price MN, Ray J, Wetmore KM, Kuehl JV, Bauer S, Deutschbauer AM, Arkin AP - Front Microbiol (2014)

Growth of mutants in electron transport complexes Rnf, Hdr/flox-1, Nfn-2, Hmc, and Tmc, with sulfate as the electron acceptor and with a variety of electron donors. Growth of the parent strain (G20) on the same day is shown for comparison. Because results for the parent strain sometimes varied across days, we graph experiments done on different days separately. Y. E. is short for yeast extract. For each complex, we used transposon insertions in at least two different genes, and for each mutant and condition, we collected 2–4 replicates, except for floxD-1 (Dde_1210) growing on hydrogen.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4215793&req=5

Figure 6: Growth of mutants in electron transport complexes Rnf, Hdr/flox-1, Nfn-2, Hmc, and Tmc, with sulfate as the electron acceptor and with a variety of electron donors. Growth of the parent strain (G20) on the same day is shown for comparison. Because results for the parent strain sometimes varied across days, we graph experiments done on different days separately. Y. E. is short for yeast extract. For each complex, we used transposon insertions in at least two different genes, and for each mutant and condition, we collected 2–4 replicates, except for floxD-1 (Dde_1210) growing on hydrogen.
Mentions: Among the electron transport systems, we identified phenotypes for mutants of qrc, rnf, hdr/flox-1, nfnAB-2, nox, tmc, and hmc (Figure 5). We validated the phenotypes for these (except qrc and nox) by growing mutant strains individually (Figure 6).

Bottom Line: Similarly, during the oxidation of malate or fumarate, the electron-bifurcating transhydrogenase NfnAB-2 (Dde_1250:1) is important and may generate reduced ferredoxin to allow additional ion pumping by Rnf.During formate oxidation, the periplasmic [NiFeSe] hydrogenase HysAB is required, which suggests that hydrogen forms in the periplasm, diffuses to the cytoplasm, and is used to reduce ferredoxin, thus providing a substrate for Rnf.During hydrogen utilization, the transmembrane electron transport complex Tmc is important and may move electrons from the periplasm into the cytoplasmic sulfite reduction pathway.

View Article: PubMed Central - PubMed

Affiliation: Physical Biosciences Division, Lawrence Berkeley Lab Berkeley, CA, USA.

ABSTRACT
Sulfate-reducing bacteria play major roles in the global carbon and sulfur cycles, but it remains unclear how reducing sulfate yields energy. To determine the genetic basis of energy conservation, we measured the fitness of thousands of pooled mutants of Desulfovibrio alaskensis G20 during growth in 12 different combinations of electron donors and acceptors. We show that ion pumping by the ferredoxin:NADH oxidoreductase Rnf is required whenever substrate-level phosphorylation is not possible. The uncharacterized complex Hdr/flox-1 (Dde_1207:13) is sometimes important alongside Rnf and may perform an electron bifurcation to generate more reduced ferredoxin from NADH to allow further ion pumping. Similarly, during the oxidation of malate or fumarate, the electron-bifurcating transhydrogenase NfnAB-2 (Dde_1250:1) is important and may generate reduced ferredoxin to allow additional ion pumping by Rnf. During formate oxidation, the periplasmic [NiFeSe] hydrogenase HysAB is required, which suggests that hydrogen forms in the periplasm, diffuses to the cytoplasm, and is used to reduce ferredoxin, thus providing a substrate for Rnf. During hydrogen utilization, the transmembrane electron transport complex Tmc is important and may move electrons from the periplasm into the cytoplasmic sulfite reduction pathway. Finally, mutants of many other putative electron carriers have no clear phenotype, which suggests that they are not important under our growth conditions, although we cannot rule out genetic redundancy.

No MeSH data available.


Related in: MedlinePlus