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Isotope discrimination by form IC RubisCO from Ralstonia eutropha and Rhodobacter sphaeroides , metabolically versatile members of ‘ Proteobacteria ’ from aquatic and soil habitats
Author(s) -
Thomas Phaedra J.,
Boller Amanda J.,
Satagopan Sriram,
Tabita F. Robert,
Cavanaugh Colleen M.,
Scott Kathleen M.
Publication year - 2019
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/1462-2920.14423
Subject(s) - rhodobacter sphaeroides , ralstonia , biology , rubisco , rhodobacter , proteobacteria , rhodospirillaceae , rhodospirillales , stable isotope probing , microbiology and biotechnology , morita therapy , botany , photosynthesis , bacteria , biochemistry , genetics , 16s ribosomal rna , gene , mutant , psychology , microorganism , psychoanalysis
Summary RubisCO, the CO 2 fixing enzyme of the Calvin–Benson–Bassham (CBB) cycle, is responsible for the majority of carbon fixation on Earth. RubisCO fixes 12 CO 2 faster than 13 CO 2 resulting in 13 C‐depleted biomass, enabling the use of δ 13 C values to trace CBB activity in contemporary and ancient environments. Enzymatic fractionation is expressed as an ε value, 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 and ε values, now known for four forms (IA, B, D and II), vary substantially with ε = 11‰ to 27‰. Given the importance of ε values in δ 13 C 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‰) and Rhodobacter 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 enzyme ε values must be considered when interpreting and modelling variability of δ 13 C values in nature.