期刊
JOURNAL OF BACTERIOLOGY
卷 196, 期 6, 页码 1231-1237出版社
AMER SOC MICROBIOLOGY
DOI: 10.1128/JB.01299-13
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资金
- College of Arts and Science at Indiana University (IU)
- Office of Science (BER), U. S. Department of Energy grant [DE-SC0008131]
- Hutton Honors College Undergraduate Research Grant (IU)
- Biology Undergraduate Research Award (Cook Inc., Bloomington, IN)
- Fox Glen Research and Education Fund Award
- Microbiology Undergraduate Summer Research Award through the Department of Biology (IU)
- U.S. Department of Energy (DOE) [DE-SC0008131] Funding Source: U.S. Department of Energy (DOE)
Purple nonsulfur bacteria grow photoheterotrophically by using light for energy and organic compounds for carbon and electrons. Disrupting the activity of the CO2-fixing Calvin cycle enzyme, ribulose 1,5-bisphosphate carboxylase (RubisCO), prevents photoheterotrophic growth unless an electron acceptor is provided or if cells can dispose of electrons as H-2. Such observations led to the long-standing model wherein the Calvin cycle is necessary during photoheterotrophic growth to maintain a pool of oxidized electron carriers. This model was recently challenged with an alternative model wherein disrupting RubisCO activity prevents photoheterotrophic growth due to the accumulation of toxic ribulose-1,5-bisphosphate (RuBP) (D. Wang, Y. Zhang, E. L. Pohlmann, J. Li, and G. P. Roberts, J. Bacteriol. 193: 3293-3303, 2011, http://dx. doi. org/10.1128/JB. 00265-11). Here, we confirm that RuBP accumulation can impede the growth of Rhodospirillum rubrum (Rs. rubrum) and Rhodopseudomonas palustris (Rp. palustris) RubisCO-deficient (Delta RubisCO) mutants under conditions where electron carrier oxidation is coupled to H-2 production. However, we also demonstrate that Rs. rubrum and Rp. palustris Calvin cycle phosphoribulokinase mutants that cannot produce RuBP cannot grow photoheterotrophically on succinate unless an electron acceptor is provided or H-2 production is permitted. Thus, the Calvin cycle is still needed to oxidize electron carriers even in the absence of toxic RuBP. Surprisingly, Calvin cycle mutants of Rs. rubrum, but not of Rp. palustris, grew photoheterotrophically on malate without electron acceptors or H-2 production. The mechanism by which Rs. rubrum grows under these conditions remains to be elucidated.
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