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Influence of light and anoxia on chemiosmotic energy conservation in Dinoroseobacter shibae.

ABSTRACT: In the present study we have investigated the influence of light and anoxia on the energetic state of the aerobic anoxygenic phototroph (AAP) Dinoroseobacter shibae. Respiration, chemiosmotic proton translocation and the adenylate energy charge (AEC) of the cells were measured comparing light versus dark and oxic versus anoxic conditions. Light caused a decrease of the respiration rates of washed cells. This might be a substitution rather than a direct inhibitory effect, because both photosynthesis and respiration contribute to the proton-motive force. As known from other AAPs, light alone did not induce proton translocation if applied to anoxic cell suspensions. However, additions of small oxygen pulses to anoxic cell suspensions caused two times more proton translocation in the light than in the dark. The AEC of the cells was measured by means of a modified luciferin-luciferase method. Growing cells of D. shibae kept an AEC of 0.93, indicating that the adenylate pool was highly phosphorylated. After harvesting and storing the cells under anoxic conditions for 2 h, the AEC dropped to 0.12. However, the cells remained reactive. Upon addition of oxygen, the AEC increased to its original value within 40 s by the formation of about 12 mM of intracellular ATP. There were no differences whether this recovery experiment was carried out in the dark or in the light. We conclude that D. shibae is able to change its energetic state not only in response to the light regime but also during oxic-anoxic transitions. Both responses appear suited to save in situ organic substrates and endogenous electron donors, thus enhancing the role of photosynthetic energy conservation.

SUBMITTER: Holert J

PROVIDER: S-EPMC3064978 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Chemiosmotic Energy Conservation in Dinoroseobacter shibae: Proton Translocation Driven by Aerobic Respiration, Denitrification, and Photosynthetic Light Reaction.

Project description:Dinoroseobacter shibae is an aerobic anoxygenic phototroph and able to utilize light energy to support its aerobic energy metabolism. Since the cells can also grow anaerobically with nitrate and nitrite as terminal electron acceptor, we were interested in how the cells profit from photosynthesis during denitrification and what the steps of chemiosmotic energy conservation are. Therefore, we conducted proton translocation experiments and compared O2-, NO3-, and NO2- respiration during different light regimes and in the dark. We used wild type cells and transposon mutants with knocked-out nitrate- and nitrite- reductase genes (napA and nirS), as well as a mutant (ppsR) impaired in bacteriochlorophyll a synthesis. Light had a positive impact on proton translocation, independent of the type of terminal electron acceptor present. In the absence of an electron acceptor, however, light did not stimulate proton translocation. The light-driven add-on to proton translocation was about 1.4 H+/e- for O2 respiration and about 1.1 H+/e- for NO3- and NO2-. We could see that the chemiosmotic energy conservation during aerobic respiration involved proton translocation, mediated by the NADH dehydrogenase, the cytochrome bc1 complex, and the cytochrome c oxidase. During denitrification the last proton translocation step of the electron transport was missing, resulting in a lower H+/e- ratio during anoxia. Furthermore, we studied the type of light-harvesting and found that the cells were able to channel light from the green-blue spectrum most efficiently, while red light has only minor impact. This fits well with the depth profiles for D. shibae abundance in the ocean and the penetration depth of light with different wavelengths into the water column.

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Boosted Membrane Potential as Bioenergetic Response to Anoxia in <i>Dinoroseobacter shibae</i>.

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Light enhances survival of Dinoroseobacter shibae during long-term starvation.

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Transcriptome of Dinoroseobacter shibae under changeing light regimes

Project description:D. shibae was cultivated under changing light regimes and samples for transcriptome and metabolome were taken.

2014-07-01 | GSE57164 | GEO

Effect of changing light regimes on Dinoroseobacter shibae DFL12 growth

Project description:This SuperSeries is composed of the SubSeries listed below.

2010-12-03 | GSE25591 | GEO

Transcriptome of Dinoroseobacter shibae under changeing light regimes

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