Pigment production and isotopic fractionations in continuous culture: okenone producing purple sulfur bacteria Part II
- Creators
- Smith, D. A.
- Steele, A.
- Fogel, M. L.
Abstract
Okenone is a carotenoid pigment unique to certain members of Chromatiaceae, the dominant family of purple sulfur bacteria (PSB) found in euxinic photic zones. Diagenetic alteration of okenone produces okenane, the only recognized molecular fossil unique to PSB. The in vivo concentrations of okenone and bacteriochlorophyll a (Bchl a) on a per cell basis were monitored and quantified as a function of light intensity in continuous cultures of the purple sulfur bacterium Marichromatium purpuratum (Mpurp1591). We show that okenone-producing PSB have constant bacteriochlorophyll to carotenoid ratios in light-harvesting antenna complexes. The in vivo concentrations of Bchl a, 0.151 ± 0.012 fmol cell^(−1), and okenone, 0.103 ± 0.012 fmol cell^(−1), were not dependent on average light intensity (10–225 Lux) at both steady and non-steady states. This observation revealed that in autotrophic continuous cultures of Mpurp1591, there was a constant ratio for okenone to Bchl a of 1:1.5. Okenone was therefore constitutively produced in planktonic cultures of PSB, regardless of light intensity. This confirms the legitimacy of okenone as a signature for autotrophic planktonic PSB and by extrapolation water column euxinia. We measured the δ^(13)C, δ^(15)N, and δ^(34)S bulk biomass values from cells collected daily and determined the isotopic fractionations of Mpurp1591. There was no statistical relationship in the bulk isotope measurements or stable isotope fractionations to light intensity or cell density under steady and non-steady-state conditions. The carbon isotope fractionation between okenone and Bchl a with respect to overall bulk biomass (^(13)ε_pigment – biomass) was 2.2 ± 0.4‰ and −4.1 ± 0.9‰, respectively. The carbon isotopic fractionation (^(13)ε_pigment-CO_2) for the production of pigments in PSB is more variable than previously thought with our reported values for okenone at −15.5 ± 1.2‰ and −21.8 ± 1.7‰ for Bchl a.
Additional Information
© 2015 John Wiley & Sons Ltd. Received 8 September 2014; accepted 14 January 2015. Thanks to S. Scheller for constructive discussions, and W. Leavitt, R. Summons, and an anonymous reviewer for insightful comments that improved the manuscript. Dartmouth College and the Carnegie Institution of Washington (CIW) funded DAS. W. M. Keck Foundation (2007-6-29) to MLF and AS, NASA's NASA Astrobiology Institute (NNH08ZDA002C) and CIW supported the research.Attached Files
Supplemental Material - gbi12135-sup-0001-FigS1.pdf
Supplemental Material - gbi12135-sup-0002-FigS2.pdf
Supplemental Material - gbi12135-sup-0003-DataSet.xlsx
Supplemental Material - gbi12135-sup-0004-SupplementalText.docx
Files
Additional details
- Eprint ID
- 57353
- Resolver ID
- CaltechAUTHORS:20150507-162516382
- Dartmouth College
- Carnegie Institution of Washington
- 2007- 6-29
- W. M. Keck Foundation
- NNH08ZDA002C
- NASA
- Created
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2015-05-11Created from EPrint's datestamp field
- Updated
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2021-11-10Created from EPrint's last_modified field