Does metabolic water control the phosphate oxygen isotopes of microbial cells?

The oxygen isotopes ratio (δO) of microbial cell water strongly controls the δO of cell phosphate and of other oxygen-carrying moieties. Recently it was suggested that the isotopic ratio in cell water is controlled by metabolic water, which is the water produced by cellular respiration. This potentially has important implications for paleoclimate reconstruction, and for measuring microbial carbon use efficiency with the O-water method.

A simple method for rapid removal of the memory effect in cavity ring-down spectroscopy water isotope measurements.

Rationale: The accuracy determined in the routine analysis of water isotopes (δ O, δ O, δ H) using cavity ring-down spectroscopy is greatly affected by the memory effect (ME), a sample-to-sample carryover that biases measurements. This study aims to develop a simple method that rapidly removes the ME.

Methods: We developed a method, designed for the Picarro L2140-i, that removes the ME by injecting small amounts of water with an extreme isotopic value ("kick") in the opposite direction of the ME.