Comparison of the proteome of Mycobacterium tuberculosis strain H37Rv withclinical isolate CDC 1551

The genome sequences of two virulent strains of Mycobacterium tuberculosis (H37Rv and CDC 1551) are now available. CDC 1551 is a recent clinical isola te and H37Rv is a commonly used lab strain which has been subject to in vit ro passage. The two strains have been shown to display differing phenotypes both in vivo and in vitro. The proteome of the two strains grown in liquid culture were examined over time to determine whether there are any major d ifferences between them at the protein level and the differences were compa red to the genome data. Total cell lysates of the two strains were analysed by two-dimensional electrophoresis. Approximately 1750 protein spots were visualized by silver staining and the protein profiles of the two strains w ere found to be highly similar. Out of a total of 17 protein spot differenc es, seven were unique to CDC 1551 and three to H37Rv. Two further spots sho wed increased intensity in H37Rv, one spot showed differing vertical mobili ty between the strains and four showed differing spot intensities with time . Twelve of the spot differences were identified using mass spectrometry; h owever, no obvious association with phenotype could be deduced. When genome differences were analysed and related to the proteome differences, a mobil ity shift identified in the MoxR protein could be explained by a point muta tion at the gene level. This proteome analysis reveals that, despite having been maintained under vastly different conditions, namely in vitro passage and in vivo transmission, these two strains have remained highly similar.