Bacteria/Mass Spectrometry Table 1. cont. Isolates Israel Egypt Egypt Preparation procedure LBglc LBglc LBglc Identified microorganism ID score Specific mass signals (m/z) E.amylovora CFBP1232 E.amylovora CFBP1232 E.amylovora CFBP1232 2.7 2.6 2.5 8302, 8726, 8842, 9510 8302, 8726, 8842, 9510 8302, 8726, 8842, 9510 We could identify a number of bacteria from different locations and deriving from different biological samples: bacteria directly taken from infected pears, isolated bacteria grown on agar, or bacteria additionally grown in liquid medium (LB-glucose). Log scores over 2 were considered reliable for type strain identification using the pattern-matching approach. These identification scores could be easily replicated with the same strains analyzed several times. Specific mass signals were used to accurately identify sub-species by visual inspection of mass spectra or by software-supported weighted pattern matching as demonstrated in Figure 5 and in Tables 2 and 3. doi:10.1371/journal.pone.0002843.t001 Figure 4. Identification of E. amylovora from diseased pears. A typical mass spectrum of a bacterial sample taken from necrotic wood compared with a matching spectrum from the reference library. (Top) Original mass spectra, (Middle) respective pseudo gel-view showing a bar-code of masses and their intensities, (Bottom) identification by comparison of experimental and reference mass spectra using a pattern matching algorithm. In this example, a highly reliable identification score of 2.7 was obtained from the identification of E. amylovora (CFBP1232). doi:10.1371/journal.pone.0002843.g004 PLoS ONE | www.plosone.org 6 July 2008 | Volume 3 | Issue 7 | e2843