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D-Lactate metabolism and the obligate requirement for CO2 during growth on nitrite by the facultative lithoautotroph Nitrobacter hamburgensis Public Deposited

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https://ir.library.oregonstate.edu/concern/articles/0v838125d

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  • Nitrobacter hamburgensis X14 is a facultative lithoautotroph that conserves energy from the oxidation of nitrite (NO 2 ) and fixes carbon dioxide (CO2) as its sole source of carbon. The availability of the N. hamburgensis X14 genome sequence initiated a re-examination of its mixotrophic and organotrophic potential, as genes encoding three flavin-dependent oxidases were identified that may function to oxidize lactate, providing energy and carbon for growth. The response of N. hamburgensis to D- and L-lactate in the presence (mixotrophy) and absence (organotrophy) of NO 2 was examined. L-Lactate did not support organotrophic growth or stimulate mixotrophic growth. In contrast, D-lactate enhanced the growth rate and yield of N. hamburgensis in the presence of NO 2 , and served as the sole carbon and energy source for growth in the absence of NO 2 with ammonium as the sole nitrogen source. Lithoautotrophically grown cells immediately consumed D-lactate, suggesting that a lactate metabolic pathway is constitutively expressed. Nevertheless, a physiological adaptation to lactate occurred, as Dlactate- grown cells consumed and assimilated lactate at a faster rate than NO 2 -grown cells, and the D-lactate-dependent O2 uptake rate was significantly greater in cells grown either organotrophically or mixotrophically compared with cells grown lithoautotrophically. Although D-lactate was assimilated and metabolized to CO2 in the presence or absence of NO 2 , exposure to atmospheric CO2 or the addition of 0.75 mM sodium carbonate was required for mixotrophic growth and for optimum organotrophic growth on D-lactate.
  • Keywords: Nitrobacter hamburgensis
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  • Starkenburg, S. R., Arp, D. J., & Bottomley, P. J. (2008, August). D-Lactate metabolism and the obligate requirement for CO2 during growth on nitrite by the facultative lithoautotroph Nitrobacter hamburgensis. Michrobiology, 154(8), 2473-2481. doi:10.1099/mic.0.2008/018085-0
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  • 154
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  • S. R. S. by the Subsurface Biosphere Integrative Graduate Education and Research Traineeship (IGERT) grant 0114427-DGE.
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