Fig1. The cover of “Applied and Environmental Biology” –Laser Raman microspectrophotometer as a single-cell mass spectrometer. Montage showing a reflected bright-field micrograph (left) of a bacterial population (E. coli) being interrogated by a Raman microspectrophotometer (right) to measure ¹³C-assimilation into proteins from the media. “Red shifts” of spectral peaks (lower center) to lower frequencies reveal degree of ¹³C-enrichment of the essential amino acid pheylalanine (structures above). In time course experiments using stable isotope probing (SIP) and Raman microspectrophotometric detection of ¹³C-enrichment in individual bacteria, microbial growth rates were accurately calculated at both the single-cell and population levels.