Abstract
Spontaneous photosynthetic mutants of the aerobic anoxygenic phototrophic bacterium Roseicyclus mahoneyensis, strain ML6 have been identified based on phenotypic differences and spectrophotometric analysis. ML6 contains a reaction centre (RC) with absorption peaks at 755, 800, and 870 nm, light harvesting (LH) complex 1 at 870 nm, and monomodal LH2 at 805 nm; the mutant ML6(B) has only the LH2; ML6(DB) has also lost the LH1; in ML6(BN9O), the LH2 is absent and concentrations of LH1 and RC are much lower than in the wild type. RCs were isolated and purified from ML6 and ML6(BN9O); LH1-RC from ML6; and LH2 from ML6, ML6(B), and ML6(DB). All protein subunits composing the complexes were found to be of typical size. Flash-induced difference spectra revealed ML6 has a fully functional photosynthetic apparatus under aerobic and microaerophilic conditions, and as is typical for AAP, there is no photosynthetic activity anaerobically. ML6(BN9O), while also functional photosynthetically aerobically, showed lower rates due to the lack of LH2 and decreased concentrations of LH1 and RC. ML6(B) and ML6(DB) showed no photoinduced electron transport. Action spectra of light-mediated reactions were also performed on ML6 and ML6(BN9O) to reveal that the majority of carotenoids are not involved in light harvesting. Finally, redox titrations were carried out on membranes of ML6 and ML6(BN9O) to confirm that midpoint redox potentials of the QA, RC-bound cytochrome, and P+ were similar in both strains. QA midpoint potential is + 65 mV, cytochrome is + 245 mV, and P+ is + 430 mV.
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References
Fraser NJ, Hashimoto H, Cogdell RJ (2001) Carotenoids and bacterial photosynthesis: the story so far…. Photosynth Res 70:249–256
Hartigan N, Tharia HA, Sweeney F, Lawless AM, Papiz MZ (2002) The 7.5-A ˚ electron density and spectroscopic properties of a novel low-light B800 LH2 from Rhodopseudomonas palustris. Biophys J 82:963–977
Joliot P, Béal D, Frilley B (1980) Une nouvelle méthode spectrophotométrique destinée à l’étude des reactions photosynthétiques. J Chim Phys 77:209–216
Noguchi TH, Hayashi H, Shimada K, Takaichi S, Tasumi M (1992) In vivo states and function of carotenoids in an aerobic photosynthetic bacterium, Erythrobacter longus. Photosynth Res 31:21–30
Prince RC, Dutton PL (1978) Protonation and the reducing potential of the primary electron acceptor. In: Clayton RK, Sistrom WR (eds) The photosynthetic bacteria. Plenum Press, New York, pp 439–453
Rathgeber C, Beatty JT, Yurkov V (2004) Aerobic phototrophic bacteria: new evidence for the diversity, ecological importance and applied potential of this previously overlooked group. Photosynth Res 81:113–128
Rathgeber C, Yurkova N, Stackebrandt E, Schumann P, Beatty JT, Yurkov V (2005) Rosiecyclus mahoneyensis gen. nov., sp. nov., an aerobic phototrophic bacterium isolated from a meromictic lake. IJSEM 55:1597–1603
Rathgeber C, Alric J, Hughes E, Vermeglio A, Yurkov V (2012) The photosynthetic apparatus and photoinduced electron transfer in the aerobic phototrophic bacteria Roseicyclus mahoneyensis and Porphyrobacter meromictius. Photosynth Res 110(3):193–203
Shiba T (1991) Roseobacter litoralis gen. nov., sp. nov. and Roseobacter denitrificans sp. nov., aerobic pink-pigmented bacteria which contain bacteriochlorophyll a. Syst Appl Microbiol 14:140–145
Suzuki T, Muroga Y, Takahama M, Nishimura Y (1999) Roseivivax halodurans gen. nov., sp. nov. and Roseivivax halotolerans sp. nov., aerobic bacteriochlorophyll-containing bacteria isolated from a saline lake. Int J Syst Bacteriol 49:629–634
Yurkov V, Beatty JT (1998) Aerobic anoxygenic phototrophic bacteria. Microbiol Mol Biol Rev 62:695–724
Yurkov V, Csotonyi J (2009) New light on aerobic anoxygenic photosynthesis. In: Hunter CN, Daldal F, Thurnauer MC, Beatty JT (eds) The purple phototrophic bacteria. Springer, New York, pp 31–55
Yurkov V, Hughes E (2013) Genes associated with the peculiar phenotypes of the aerobic anoxygenic phototrophs. In: Beatty JT, Jacquot JP, Gadal P (eds) Genome evolution of photosynthetic bacteria. Elsevier, Amsterdam, pp 327–358
Yurkov V, Gad’on N, Angerhofer A, Drews G (1994) Light harvesting complexes of aerobic bacteriochlorophyll-containing bacteria Roseococcus thiosulfatophilus, RB3 and Erythromicrobium ramosum, E5 and the transfer of excitation energy from carotenoids to bacteriochlorophyll. Z Naturforsch 49:579–586
Yurkova N, Rathgeber C, Swiderski J, Stackebrandt E, Beatty JT, Hall KJ, Yurkov V (2002) Diversity, distribution and physiology of the aerobic phototrophic bacteria in the mixolimnion of a meromictic lake. FEMS Microbiol Ecol 40:191–204
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This research was supported by an NSERC Discovery Grant and GETS Funds from the University of Manitoba, both held by Vladimir Yurkov.
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Hughes, E., Alric, J. & Yurkov, V. Photosynthetic complexes and light-dependant electron transport chain in the aerobic anoxygenic phototroph Roseicyclus mahoneyensis and its spontaneous mutants. Photosynth Res 144, 341–347 (2020). https://doi.org/10.1007/s11120-020-00744-9
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DOI: https://doi.org/10.1007/s11120-020-00744-9