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1. Isotope discrimination by form IC RubisCO from Ralstonia eutropha and Rhodobacter sphaeroides , metabolically versatile members of ‘ Proteobacteria ’ from aquatic and soil habitats

   https://doi.org/10.1111/1462-2920.14423  

   Thomas, Phaedra J. ; Boller, Amanda J. ; Satagopan, Sriram ; Tabita, F. Robert ; Cavanaugh, Colleen M. ; Scott, Kathleen M. ( November 2018 , Environmental Microbiology)

   RubisCO, the CO₂fixing enzyme of the Calvin–Benson–Bassham (CBB) cycle, is responsible for the majority of carbon fixation on Earth. RubisCO fixes¹²CO₂faster than¹³CO₂resulting in¹³C‐depleted biomass, enabling the use of δ¹³C values to trace CBB activity in contemporary and ancient environments. Enzymatic fractionation is expressed as anεvalue, and is routinely used in modelling, for example, the global carbon cycle and climate change, and for interpreting trophic interactions. Although values for spinach RubisCO (ε= ~29‰) have routinely been used in such efforts, there are five different forms of RubisCO utilized by diverse photolithoautotrophs and chemolithoautotrophs andεvalues, now known for four forms (IA, B, D and II), vary substantially withε =11‰ to 27‰. Given the importance ofεvalues in δ¹³C evaluation, we measured enzymatic fractionation of the fifth form, form IC RubisCO, which is found widely in aquatic and terrestrial environments. Values were determined for two model organisms, the ‘Proteobacteria’ Ralstonia eutropha (ε= 19.0‰) andRhodobacter sphaeroides(ε =22.4‰). It is apparent from these measurements that all RubisCO forms measured to date discriminate less than commonly assumed based on spinach, and that enzymeεvalues must be considered when interpreting and modelling variability of δ¹³C values in nature.

    

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2. Influence of Hydrogen Bonds on the Electron–Phonon Coupling Strength/Marker Mode Structure and Charge Separation Rates in Reaction Centers from Rhodobacter sphaeroides

   https://doi.org/10.1021/acs.jpcb.9b08388  

   Khmelnitskiy, Anton ; Williams, JoAnn C. ; Allen, James P. ; Jankowiak, Ryszard ( September 2019 , The Journal of Physical Chemistry B)
3. Analysis of Growth Characteristics and Differentially Expressed Homologous Genes in Rhodobacter sphaeroides under Normal and Simulated Microgravity Conditions

   https://doi.org/10.4236/aim.2023.1311035  

   Ranasinghe, Weerakkody ; Gutierrez, Eduardo ; Alyson, Zelaya ; Vazquez, Sabrina ; Ogg, Ashleigh ; Balaraman, Rajesh Prabhu ; Cho, Hyuk ; Choudhary, Madhusudan ( November 2023 , Advances in Microbiology)

   The term “microgravity” is used to describe the “weightlessness” or “zero-g” circumstances that can only be found in space beyond earth’s atmosphere. Rhodobacter sphaeroides is a gram-negative purple phototroph, used as a model organism for this study due to its genomic complexity and metabolic versatility. Its genome has been completely sequenced, and profiles of the differential gene expression under aerobic, semi-aerobic, and photosynthetic conditions were examined. In this study, we hypothesized that R. sphaeroides will show altered growth characteristics, morphological properties, and gene expression patterns when grown under simulated microgravity. To test that, we measured the optical density and colony-forming units of cell cultures grown under both microgravity and normal gravity conditions. Differences in the cell morphology were observed using scanning electron microscopy (SEM) images by measuring the length and the surface area of the cells under both conditions. Furthermore, we also identified homologous genes of R. spheroides using the differential gene expression study of Acidovorax under microgravity in our laboratory. Growth kinetics results showed that R. sphaeroides cells grown under microgravity experience a shorter log phase and early stationary phase compared to the cells growing under normal gravity conditions. The length and surface area of the cells under microgravity were significantly higher confirming that bacterial cells experience altered morphological features when grown under microgravity conditions. Differentially expressed homologous gene analysis indicated that genes coding for several COG and GO functions, such as metabolism, signal-transduction, transcription, translation, chemotaxis, and cell motility are differentially expressed to adapt and survive microgravity. 

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4. Identification of amino acid residues in a proton release pathway near the bacteriochlorophyll dimer in reaction centers from Rhodobacter sphaeroides

   https://doi.org/10.1007/s11120-022-00968-x  

   Allen, J. P. ; Chamberlain, K. D. ; Williams, J. C. ( January 2023 , Photosynthesis Research)
5. Influence of hydrogen bonds on the electron-phonon coupling strength/marker mode structure and charge separation rates in reaction centers from Rhodobacter sphaeroides

   A. Khmelnitskiy, J C. ( January 2019 , Journal of physical chemistry)

   Low-temperature persistent and transient hole-burning (HB) spectra are presented for the triple hydrogen-bonded L131LH + M160LH + M197FH mutant of Rhodobacter sphaeroides. These spectra expose the heterogeneous nature of the P-, B-, and H-bands, consistent with a distribution of electron transfer (ET) times and excitation energy transfer (EET) rates. Transient P+Q − holes are observed for A fast (tens of picoseconds or faster) ET times and reveal strong coupling to phonons and marker mode(s), while the persistent holes are bleached in a fraction of reaction centers with long-lived excited states characterized by much weaker electron−phonon coupling. Exposed differences in electron−phonon coupling strength, as well as a different coupling to the marker mode(s), appear to affect the ET times. Both resonantly and nonresonantly burned persistent HB spectra show weak blue- (∼150 cm−1) and large, red-shifted (∼300 cm−1) antiholes of the P band. Slower EET times from the H- and B-bands to the special pair dimer provide new insight on the influence of hydrogen bonds on mutation-induced heterogeneity. 

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