Premium
Expression of form I and form II Rubisco in chemoautotrophic symbioses: Implications for the interpretation of stable carbon isotope values
Author(s) -
Robinson Jonathan J.,
Cavanaugh Colleen M.
Publication year - 1995
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1995.40.8.1496
Subject(s) - rubisco , isotopes of carbon , symbiosis , biology , ribulose , bacteria , enzyme , pyruvate carboxylase , isotope , stable isotope ratio , carbon fibers , botany , biochemistry , ecology , paleontology , physics , quantum mechanics , total organic carbon , materials science , composite number , composite material
Invertebrate‐chemoautotroph symbioses, in which the bacterial partner provides an internal source of autotrophically fixed carbon for its host, fall into two main groups based on previously reported stable carbon isotope ratios: those with δ 13 C = ‒27 to ‒35‰ (referred to as the ‒30‰ group) and those with δ 13 C = ‒9 to ‒16‰ (referred to as the ‒11‰ group). The δ 13 C values of the ‒30‰ group resemble those of free‐living chemoautotrophic bacteria, suggesting the role of the symbionts in the nutrition of the bivalves; there is presently no satisfactory explanation for the δ 13 C values of the ‒11 ‰ group. Immunological and enzyme inhibition data are presented demonstrating that the CO 2 ‐fixing enzyme expressed in representatives of the ‒11‰group is a form II ribulose‐1,5‐bisphosphate carboxylase/oxygenase (Rubisco), while a form I Rubisco is expressed in the ‒30% symbioses. Previously reported in vitro determinations on purified Rubisco show that the form II enzyme from free‐living bacteria has a smaller kinetic isotope effect with respect to CO 2 than does form I. Thus, the 13 C‐enriched stable carbon isotope signature observed in the intact ‒11% symbioses appears to be at least partially due to this diminished enzymatic discrimination.