Simultaneous analysis of microbial identity and function using NanoSIMS

Summary Identifying the function of uncultured microbes in their environments today remains one of the main challenges for microbial ecologists. In this article, we describe a new method allowing simultaneous analy- sis of microbial identity and function. This method is based on the visualization of oligonucleotide probe-conferred hybridization signal in single microbial cells and isotopic measurement using high- resolution ion microprobe (NanoSIMS). In order to characterize the potential of the method, an oligo- nucleotide containing iodized cytidine was hybridized on fixed cells of Escherichia coli cultured on media containing different levels of 13 Co r 15 N. Iodine signals could clearly be localized on targeted cells and the isotopic enrichment could be monitored at the single- cell level. The applicability of this new technique to the study of in situ ecophysiology of uncultured microorganisms within complex microbial communi- ties is illustrated.