The association of historical plague pandemics with Yersinia pestis remains controversial, partly because the evolutionary history of this largely monomorphic bacterium was unknown. The microevolution of Y. pestis was therefore investigated by three different multilocus molecular methods, targeting genomewide synonymous SNPs, variation in number of tandem repeats, and insertion of IS100 insertion elements. Eight populations were recognized by the three methods, and we propose an evolutionary tree for these populations, rooted on Yersinia pseudotuberculosis. The tree invokes microevolution over millennia, during which enzootic pestoides isolates evolved. This initial phase was followed by a binary split 6,500 years ago, which led to populations that are more frequently associated with human disease. These populations do not correspond directly to classical biovars that are based on phenotypic properties. Thus, we recommend that henceforth groupings should be based on molecular signatures. The age of Y. pestis inferred here is compatible with the dates of historical pandemic plague. However, it is premature to infer an association between any modern molecular grouping and a particular pandemic wave that occurred before the 20th century.insertion element ͉ SNP ͉ variable number tandem repeats ͉ pandemic ͉ molecular clock

Circulating tumor cells (CTCs) disseminated into peripheral blood from a primary, or metastatic, tumor can be used for early detection, diagnosis and monitoring of solid malignancies. CTC isolation by size exclusion techniques have long interested researchers as a simple broad based approach, which is methodologically diverse for use in both genomic and protein detection platforms. Though a variety of these microfiltration systems are employed academically and commercially, the limited ability to easily alter microfilter designs has hindered the optimization for CTC capture. To overcome this problem, we studied a unique photo-definable material with a scalable and mass producible photolithographic fabrication method. We use this fabrication method to systematically study and optimize the parameters necessary for CTC isolation using a microfiltration approach, followed by a comparison to a “standard” filtration membrane. We demonstrate that properly designed microfilters can capture MCF-7 cancer cells at rate of 98 ± 2% if they consist of uniform patterned distributions, ≥160 000 pores, and 7 μm pore diameters.