title: Kinetic15N-isotope effects on algal growth.
abstract: Stable isotope labeling is a standard technique for tracing material transfer in molecular, ecological and biogeochemical studies. The main assumption in this approach is that the enrichment with a heavy isotope has no effect on the organism metabolism and growth, which is not consistent with current theoretical and empirical knowledge on kinetic isotope effects. Here, we demonstrate profound changes in growth dynamics of the green alga Raphidocelis subcapitata grown in15N-enriched media. With increasing15N concentration (0.37 to 50 at%), the lag phase increased, whereas maximal growth rate and total yield decreased; moreover, there was a negative relationship between the growth and the lag phase across the treatments. The latter suggests that a trade-off between growth rate and the ability to adapt to the high15N environment may exist. Remarkably, the lag-phase response at 3.5 at%15N was the shortest and deviated from the overall trend, thus providing partial support to the recently proposed Isotopic Resonance hypothesis, which predicts that certain isotopic composition is particularly favorable for living organisms. These findings confirm the occurrence of KIE in isotopically enriched algae and underline the importance of considering these effects when using stable isotope labeling in field and experimental studies.
authors.affiliation: Faculty of Chemistry and Geosciences, Department of Physical Chemistry, Vilnius University, Vilnius, Lithuania.|Laboratory of Bio-Nanotechnology, Center for Physical Sciences and Technology, Vilnius, Lithuania.
authors.forename: Eivydas
authors.initials: E
authors.lastname: Andriukonis
authors.affiliation: Department of Environmental Science and Analytical Chemistry, Stockholm University, Stockholm, Sweden.
authors.forename: Elena
authors.initials: E
authors.lastname: Gorokhova
mesh_terms: D007553:Isotope Labeling; D009587:Nitrogen Isotopes / Q000737:chemistry / Q000378:metabolism*; D000461:Rhodophyta / Q000254:growth & development*
chemical_list: D009587:Nitrogen Isotopes