@article {38290,
	title = {Genome assortment, not serogroup, defines Vibrio cholerae pandemic strains},
	journal = {NatureNature},
	year = {2009},
	abstract = {Vibrio cholerae, the causative agent of cholera, is a bacterium autochthonous to the aquatic environment, and a serious public health threat. V. cholerae serogroup O1 is responsible for the previous two cholera pandemics, in which classical and El Tor biotypes were dominant in the 6th and the current 7th pandemics, respectively. Cholera researchers continually face newly emerging and re-emerging pathogenic clones carrying combinations of new serogroups as well as of phenotypic and genotypic properties. These genotype and phenotype changes have hampered control of the disease. Here we compare the complete genome sequences of 23 strains of V. cholerae isolated from a variety of sources and geographical locations over the past 98 years in an effort to elucidate the evolutionary mechanisms governing genetic diversity and genesis of new pathogenic clones. The genome-based phylogeny revealed 12 distinct V. cholerae phyletic lineages, of which one, designated the V. cholerae core genome (CG), comprises both O1 classical and EI Tor biotypes. All 7th pandemic clones share nearly identical gene content, i.e., the same genome backbone. The transition from 6th to 7th pandemic strains is defined here as a {\textquoteright}shift{\textquoteright} between pathogenic clones belonging to the same O1 serogroup, but from significantly different phyletic lineages within the CG clade. In contrast, transition among clones during the present 7th pandemic period can be characterized as a {\textquoteright}drift{\textquoteright} between clones, differentiated mainly by varying composition of laterally transferred genomic islands, resulting in emergence of variants, exemplified by V.cholerae serogroup O139 and V.cholerae O1 El Tor hybrid clones that produce cholera toxin of classical biotype. Based on the comprehensive comparative genomics presented in this study it is concluded that V. cholerae undergoes extensive genetic recombination via lateral gene transfer, and, therefore, genome assortment, not serogroup, should be used to define pathogenic V. cholerae clones.},
	keywords = {59, CHOLERA, genes, Genetics, GENOTYPE, ISLANDS, ORIGIN, PHENOTYPE, PUBLIC HEALTH, recombination, STRAINS, Toxins},
	author = {Brettin, Thomas S. and Bruce, David C. and Challacombe, Jean F. and Detter, John C. and Han, Cliff S. and Munik, A. C. and Chertkov, Olga and Meincke, Linda and Saunders, Elizabeth and Choi, Seon Y. and Haley, Bradd J. and Taviani, Elisa and Jeon, Yoon-Seong and Kim, Dong Wook and Lee, Jae-Hak and Walters, Ronald A. and Hug, Anwar and Rita R. Colwell}
}
@article {38415,
	title = {An optimized system for expression and purification of secreted bacterial proteins},
	journal = {Protein Expression and PurificationProtein Expression and Purification},
	volume = {46},
	year = {2006},
	type = {10.1016/j.pep.2005.09.003},
	abstract = {In this report, we describe an optimized system for the efficient overexpression, purification, and refolding of secreted bacterial proteins. Candidate secreted proteins were produced recombinantly in Escherichia coli as Tobacco Etch Virus protease-cleavable hexahistidine-c-myc eptiope fusion proteins. Without regard to their initial solubility, recombinant fusion proteins were extracted from whole cells with guanidium chloride, purified under denaturing conditions by immobilized metal affinity chromatography, and refolded by rapid dilution into a solution containing only Tris buffer and sodium chloride. Following concentration on the same resin under native conditions, each protein was eluted for further purification and/or characterization. Preliminary studies on a test set of 12 secreted proteins ranging in size from 13 to 130\&$\#$xa0;kDa yielded between 10 and 50\&$\#$xa0;mg of fusion protein per liter of induced culture at greater than 90\% purity, as judged by Coomassie-stained SDS{\textendash}PAGE. Of the nine proteins further purified, analytical gel filtration chromatography indicated that each was a monomer in solution and circular dichroism spectroscopy revealed that each had adopted a well-defined secondary structure. While there are many potential applications for this system, the results presented here suggest that it will be particularly useful for investigators employing structural approaches to understand protein function, as attested to by the crystal structures of three proteins purified using this methodology (B.V. Geisbrecht, B.Y. Hamaoka, B. Perman, A. Zemla, D.J. Leahy, J. Biol. Chem. 280 (2005) 17243{\textendash}17250).},
	keywords = {Pathogens, Secreted proteins, Toxins, Virulence factors},
	isbn = {1046-5928},
	author = {Geisbrecht, Brian V. and Bouyain, Samuel and M. Pop}
}
