1. ¹Department of Biological Sciences, University of Warwick, Coventry, UK
2. ²Department of Microbial Ecology, Vienna Ecology Center, University of Vienna, Vienna, Austria

Correspondence: Professor JC Murrell, Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, UK. E-mail: j.c.murrell@warwick.ac.uk

³Address from 1 July 2007: Department of Biology, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1.

Received 26 March 2007; Revised 28 March 2007; Accepted 28 March 2007; Published online 17 May 2007.

Abstract

Isotope-labelling experiments have changed the way microbial ecologists investigate the ecophysiology of microbial populations and cells in the environment. Insight into the 'uncultivated majority' accompanies methodology that involves the incorporation of stable isotopes or radioisotopes into sub-populations of environmental samples. Subsequent analysis of labelled biomarkers of sub-populations with stable-isotope probing (DNA-SIP, RNA-SIP, phospholipid-derived fatty acid-SIP) or individual cells with a combination of fluorescence in situ hybridization and microautoradiography reveals linked phylogenetic and functional information about the organisms that assimilated these compounds. Here, we review some of the most recent literature, with an emphasis on methodological improvements to the sensitivity and utility of these methods. We also highlight related isotope techniques that are in continued development and hold promise to transform the way we link phylogeny and function in complex microbial communities.