Comparative Microbial Genomic Comparisons on Single DNA Molecules
Optical mapping is a technology developed by David Schwartz (University of Wisconsin) to directly image a “stretched-out” molecule of genomic DNA using the unique locations of restriction enzyme cut sites as orientation marks along the length of the DNA. Schwartz and collaborators have now used this powerful technology to directly compare single genomic DNA molecules from a series of different bacteria in order to identify and annotate DNA alterations between bacterial strains represented by several species. These results, published in the November issue of Journal of Bacteriology (v. 186 (22), pp. 7773-7782, 2004), suggest that genomic rearrangements and chromosomal breakpoints can be readily identified and annotated against a prototypic sequenced strain by using the tools of optical mapping. This will contribute to analysis of microbial genomes by comparative genomics which uses information derived from previously sequenced microbial species. To gain further insights, new sequencing efforts are now dealing with the variety of strains or isolates that gives a species definition and range; however, this number vastly outstrips our ability to sequence them.