<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Rich, S M</style></author><author><style face="normal" font="default" size="100%">Sawyer, S A</style></author><author><style face="normal" font="default" size="100%">Barbour, A G</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Antigen polymorphism in Borrelia hermsii, a clonal pathogenic bacterium.</style></title><secondary-title><style face="normal" font="default" size="100%">Proc Natl Acad Sci U S A</style></secondary-title><alt-title><style face="normal" font="default" size="100%">Proc. Natl. Acad. Sci. U.S.A.</style></alt-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Antigens, Bacterial</style></keyword><keyword><style  face="normal" font="default" size="100%">Base Sequence</style></keyword><keyword><style  face="normal" font="default" size="100%">Borrelia</style></keyword><keyword><style  face="normal" font="default" size="100%">DNA, Bacterial</style></keyword><keyword><style  face="normal" font="default" size="100%">Polymorphism, Genetic</style></keyword><keyword><style  face="normal" font="default" size="100%">Repetitive Sequences, Nucleic Acid</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2001</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2001 Dec 18</style></date></pub-dates></dates><volume><style face="normal" font="default" size="100%">98</style></volume><pages><style face="normal" font="default" size="100%">15038-43</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The relapsing fever spirochete, Borrelia hermsii, escapes immune selection by alternating expression of surface lipoprotein alleles. The switch results from a duplicative transposition of one of several surface lipoprotein-encoding nucleotide sequences into the singular expression site. These nucleotide sequences constitute a large gene family whose diversity originated, in some cases, before the major divergences of Borrelia species. We have examined the B. hermsii vsp subfamily of alleles, which are carried on linear plasmids within each cell and maintained in several diverse copies as an antigenic archive. Each encodes a distinct serotype-specific protein. We sequenced more than 90% of the alleles within a single strain-B. hermsii strain HS1. A preponderance of allelic mosaicism suggests that intragenic recombination, coupled with selection imposed by host immune response, has driven diversification of the archived ensemble of vsp alleles. The recombinational diversification of vsp alleles generates change in the associated serotypes of the magnitude (30-40% amino acid differentiation) necessary for overcoming cross-reactivity of neutralizing antibodies. We conclude that evolution of vsp has occurred by punctuated occurrence of allelic differentiation, rather than by gradual selection of incremental point mutations that do not meet the threshold for antigenic diversity.</style></abstract><issue><style face="normal" font="default" size="100%">26</style></issue><custom1><style face="normal" font="default" size="100%">http://www.ncbi.nlm.nih.gov/pubmed/11742066?dopt=Abstract</style></custom1></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Feng, X</style></author><author><style face="normal" font="default" size="100%">Rich, S M</style></author><author><style face="normal" font="default" size="100%">Akiyoshi, D</style></author><author><style face="normal" font="default" size="100%">Tumwine, J K</style></author><author><style face="normal" font="default" size="100%">Kekitiinwa, A</style></author><author><style face="normal" font="default" size="100%">Nabukeera, N</style></author><author><style face="normal" font="default" size="100%">Tzipori, S</style></author><author><style face="normal" font="default" size="100%">Widmer, G</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Extensive polymorphism in Cryptosporidium parvum identified by multilocus microsatellite analysis.</style></title><secondary-title><style face="normal" font="default" size="100%">Appl Environ Microbiol</style></secondary-title><alt-title><style face="normal" font="default" size="100%">Appl. Environ. Microbiol.</style></alt-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Animals</style></keyword><keyword><style  face="normal" font="default" size="100%">Base Sequence</style></keyword><keyword><style  face="normal" font="default" size="100%">Cattle</style></keyword><keyword><style  face="normal" font="default" size="100%">Cryptosporidiosis</style></keyword><keyword><style  face="normal" font="default" size="100%">Cryptosporidium parvum</style></keyword><keyword><style  face="normal" font="default" size="100%">DNA, Protozoan</style></keyword><keyword><style  face="normal" font="default" size="100%">Humans</style></keyword><keyword><style  face="normal" font="default" size="100%">Karyotyping</style></keyword><keyword><style  face="normal" font="default" size="100%">Mice</style></keyword><keyword><style  face="normal" font="default" size="100%">Mice, Knockout</style></keyword><keyword><style  face="normal" font="default" size="100%">Microsatellite Repeats</style></keyword><keyword><style  face="normal" font="default" size="100%">Molecular Sequence Data</style></keyword><keyword><style  face="normal" font="default" size="100%">Polymerase Chain Reaction</style></keyword><keyword><style  face="normal" font="default" size="100%">Polymorphism, Genetic</style></keyword><keyword><style  face="normal" font="default" size="100%">Sequence Analysis, DNA</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2000</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2000 Aug</style></date></pub-dates></dates><volume><style face="normal" font="default" size="100%">66</style></volume><pages><style face="normal" font="default" size="100%">3344-9</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Restriction fragment length polymorphism and DNA sequence analysis discern two main types of Cryptosporidium parvum. We present a survey of length polymorphism at several microsatellite loci for type 1 and type 2 isolates. A total of 14 microsatellite loci were identified from C. parvum DNA sequences deposited in public databases. All repeats were mono-, di-, and trinucleotide repeats of A, AT, and AAT, reflecting the high AT content of the C. parvum genome. Several of these loci showed significant length polymorphism, with as many as seven alleles identified for a single locus. Differences between alleles ranged from 1 to 27 bp. Karyotype analysis using probes flanking three microsatellites localized each marker to an individual chromosomal band, suggesting that these markers are single copy. In a sample of 19 isolates for which at least three microsatellites were typed, a majority of isolates displayed a unique multilocus fingerprint. Microsatellite analysis of isolates passaged between different host species identified genotypic changes consistent with changes in parasite populations.</style></abstract><issue><style face="normal" font="default" size="100%">8</style></issue><custom1><style face="normal" font="default" size="100%">http://www.ncbi.nlm.nih.gov/pubmed/10919789?dopt=Abstract</style></custom1></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Ayala, F J</style></author><author><style face="normal" font="default" size="100%">Rich, S M</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Genetic variation and the recent worldwide expansion of Plasmodium falciparum.</style></title><secondary-title><style face="normal" font="default" size="100%">Gene</style></secondary-title><alt-title><style face="normal" font="default" size="100%">Gene</style></alt-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Animals</style></keyword><keyword><style  face="normal" font="default" size="100%">Antigens, Protozoan</style></keyword><keyword><style  face="normal" font="default" size="100%">Base Sequence</style></keyword><keyword><style  face="normal" font="default" size="100%">Genetic Variation</style></keyword><keyword><style  face="normal" font="default" size="100%">Merozoite Surface Protein 1</style></keyword><keyword><style  face="normal" font="default" size="100%">Molecular Sequence Data</style></keyword><keyword><style  face="normal" font="default" size="100%">Phylogeny</style></keyword><keyword><style  face="normal" font="default" size="100%">Plasmodium</style></keyword><keyword><style  face="normal" font="default" size="100%">Plasmodium falciparum</style></keyword><keyword><style  face="normal" font="default" size="100%">Polymorphism, Genetic</style></keyword><keyword><style  face="normal" font="default" size="100%">Protozoan Proteins</style></keyword><keyword><style  face="normal" font="default" size="100%">Repetitive Sequences, Nucleic Acid</style></keyword><keyword><style  face="normal" font="default" size="100%">RNA, Ribosomal</style></keyword><keyword><style  face="normal" font="default" size="100%">Sequence Homology, Nucleic Acid</style></keyword><keyword><style  face="normal" font="default" size="100%">Species Specificity</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2000</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2000 Dec 30</style></date></pub-dates></dates><volume><style face="normal" font="default" size="100%">261</style></volume><pages><style face="normal" font="default" size="100%">161-70</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Plasmodium falciparum, the agent of human malignant malaria, diverged from Plasmodium reichenowi, the chimpanzee parasite, about the time the human and chimpanzee lineages diverged from each other. The absence of synonymous nucleotide variation at ten loci indicates that the world populations of P. falciparum derive most recently from one single strain, or 'cenancestor,' which lived a few thousand years ago. Antigenic genes of P. falciparum (such as Csp, Msp-1, and Msp-2) exhibit numerous polymorphisms that have been estimated to be millions of years old. We have discovered in these antigenic genes short repetitive sequences that distort the alignment of alleles and account for the apparent old age of the polymorphisms. The processes of intragenic recombination that generate the repeats occur at rates about 10(-3) to 10(-2), several orders of magnitude greater than the typical mutational process of nucleotide substitutions. We conclude that the antigenic polymorphisms of P. falciparum are consistent with a recent expansion of the world populations of the parasite from a cenancestor that lived in tropical Africa a few thousand years ago.</style></abstract><issue><style face="normal" font="default" size="100%">1</style></issue><custom1><style face="normal" font="default" size="100%">http://www.ncbi.nlm.nih.gov/pubmed/11164047?dopt=Abstract</style></custom1></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Rich, S M</style></author><author><style face="normal" font="default" size="100%">Ferreira, M U</style></author><author><style face="normal" font="default" size="100%">Ayala, F J</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">The origin of antigenic diversity in Plasmodium falciparum.</style></title><secondary-title><style face="normal" font="default" size="100%">Parasitol Today</style></secondary-title><alt-title><style face="normal" font="default" size="100%">Parasitol. Today (Regul. Ed.)</style></alt-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Amino Acid Sequence</style></keyword><keyword><style  face="normal" font="default" size="100%">Animals</style></keyword><keyword><style  face="normal" font="default" size="100%">Antigens, Protozoan</style></keyword><keyword><style  face="normal" font="default" size="100%">Base Sequence</style></keyword><keyword><style  face="normal" font="default" size="100%">Genes, Protozoan</style></keyword><keyword><style  face="normal" font="default" size="100%">Genetic Variation</style></keyword><keyword><style  face="normal" font="default" size="100%">Merozoite Surface Protein 1</style></keyword><keyword><style  face="normal" font="default" size="100%">Molecular Sequence Data</style></keyword><keyword><style  face="normal" font="default" size="100%">Plasmodium falciparum</style></keyword><keyword><style  face="normal" font="default" size="100%">Protozoan Proteins</style></keyword><keyword><style  face="normal" font="default" size="100%">Sequence Homology</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2000</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2000 Sep</style></date></pub-dates></dates><volume><style face="normal" font="default" size="100%">16</style></volume><pages><style face="normal" font="default" size="100%">390-6</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Most studies of genetic variability of Plasmodium falciparum have focused on protein antigens and the genes that encode them. The consensus is that populations exhibit high levels of genetic polymorphism, most notably the genes encoding surface proteins of the merozoite (Msp1, Msp2) and the sporozoite (Csp). The age and derivation of this variation is a subject that warrants further careful consideration, as discussed here by Stephen Rich, Marcelo Ferreira and Francisco Ayala.</style></abstract><issue><style face="normal" font="default" size="100%">9</style></issue><custom1><style face="normal" font="default" size="100%">http://www.ncbi.nlm.nih.gov/pubmed/10951599?dopt=Abstract</style></custom1></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Rich, S M</style></author><author><style face="normal" font="default" size="100%">Ayala, F J</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Population structure and recent evolution of Plasmodium falciparum.</style></title><secondary-title><style face="normal" font="default" size="100%">Proc Natl Acad Sci U S A</style></secondary-title><alt-title><style face="normal" font="default" size="100%">Proc. Natl. Acad. Sci. U.S.A.</style></alt-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Amino Acid Sequence</style></keyword><keyword><style  face="normal" font="default" size="100%">Animals</style></keyword><keyword><style  face="normal" font="default" size="100%">Base Sequence</style></keyword><keyword><style  face="normal" font="default" size="100%">Biological Evolution</style></keyword><keyword><style  face="normal" font="default" size="100%">Genes, Protozoan</style></keyword><keyword><style  face="normal" font="default" size="100%">Genetics, Population</style></keyword><keyword><style  face="normal" font="default" size="100%">Molecular Sequence Data</style></keyword><keyword><style  face="normal" font="default" size="100%">Plasmodium falciparum</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2000</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2000 Jun 20</style></date></pub-dates></dates><volume><style face="normal" font="default" size="100%">97</style></volume><pages><style face="normal" font="default" size="100%">6994-7001</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Plasmodium falciparum is the agent of malignant malaria, one of mankind's most severe maladies. The parasite exhibits antigenic polymorphisms that have been postulated to be ancient. We have proposed that the extant world populations of P. falciparum have derived from one single parasite, a cenancestor, within the last 5, 000-50,000 years. This inference derives from the virtual or complete absence of synonymous nucleotide polymorphisms at genes not involved in immune or drug responses. Seeking to conciliate this claim with extensive antigenic polymorphism, we first note that allele substitutions or polymorphisms can arise very rapidly, even in a single generation, in large populations subject to strong natural selection. Second, new alleles can arise not only by single-nucleotide mutations, but also by duplication/deletion of short simple-repeat DNA sequences, a process several orders of magnitude faster than single-nucleotide mutation. We analyze three antigenic genes known to be extremely polymorphic: Csp, Msp-1, and Msp-2. We identify regions consisting of tandem or proximally repetitive short DNA sequences, including some previously unnoticed. We conclude that the antigenic polymorphisms are consistent with the recent origin of the world populations of P. falciparum inferred from the analysis of nonantigenic genes.</style></abstract><issue><style face="normal" font="default" size="100%">13</style></issue><custom1><style face="normal" font="default" size="100%">http://www.ncbi.nlm.nih.gov/pubmed/10860962?dopt=Abstract</style></custom1></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Ayala, F J</style></author><author><style face="normal" font="default" size="100%">Escalante, A A</style></author><author><style face="normal" font="default" size="100%">Rich, S M</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Evolution of Plasmodium and the recent origin of the world populations of Plasmodium falciparum.</style></title><secondary-title><style face="normal" font="default" size="100%">Parassitologia</style></secondary-title><alt-title><style face="normal" font="default" size="100%">Parassitologia</style></alt-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Amino Acid Sequence</style></keyword><keyword><style  face="normal" font="default" size="100%">Animals</style></keyword><keyword><style  face="normal" font="default" size="100%">Base Sequence</style></keyword><keyword><style  face="normal" font="default" size="100%">DNA, Protozoan</style></keyword><keyword><style  face="normal" font="default" size="100%">Evolution, Molecular</style></keyword><keyword><style  face="normal" font="default" size="100%">Hominidae</style></keyword><keyword><style  face="normal" font="default" size="100%">Humans</style></keyword><keyword><style  face="normal" font="default" size="100%">Merozoite Surface Protein 1</style></keyword><keyword><style  face="normal" font="default" size="100%">Molecular Sequence Data</style></keyword><keyword><style  face="normal" font="default" size="100%">Plasmodium</style></keyword><keyword><style  face="normal" font="default" size="100%">Plasmodium falciparum</style></keyword><keyword><style  face="normal" font="default" size="100%">Polymorphism, Genetic</style></keyword><keyword><style  face="normal" font="default" size="100%">Sequence Alignment</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1999</style></year><pub-dates><date><style  face="normal" font="default" size="100%">1999 Sep</style></date></pub-dates></dates><volume><style face="normal" font="default" size="100%">41</style></volume><pages><style face="normal" font="default" size="100%">55-68</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We have investigated the evolution of Plasmodium parasites by analyzing DNA sequences of several genes. We reach the following conclusions: (1) The four human parasites, P. falciparum, P. malariae, P. ovale, and P. vivax are very remotely related to each other, so that their evolutionary divergence predates the origin of the hominids; several of these parasites became associated with the human lineage by lateral transfer from other hosts. (2) P. falciparum diverged from P. reichenowi about 8 million years ago, consistently with the time of divergence of the human lineage from the apes; a parsimonious inference is that falciparum has been associated with humans since the origin of the hominids. (3) P. malariae is genetically indistinguishable from P. brasilianum, a parasite of New World monkeys; and, similarly. (4) P. vivax is genetically indistinguishable from the New World monkey parasite P. simium. We infer in each of these two cases a very recent lateral transfer between the human and monkey hosts, and explore alternative hypotheses about the direction of the transfer. We have also investigated the population structure of P. falciparum by analyzing 10 genes and conclude that the extant world populations of this parasite have evolved from a single strain within the last several thousand years. The extensive polymorphisms observed in the highly repetitive central region of the Csp gene, as well as the apparently very divergent two classes of alleles at the Msa-1 gene, are consistent with this conclusion.</style></abstract><issue><style face="normal" font="default" size="100%">1-3</style></issue><custom1><style face="normal" font="default" size="100%">http://www.ncbi.nlm.nih.gov/pubmed/10697834?dopt=Abstract</style></custom1></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Rich, S M</style></author><author><style face="normal" font="default" size="100%">Rosenthal, B M</style></author><author><style face="normal" font="default" size="100%">Telford, S R</style></author><author><style face="normal" font="default" size="100%">Spielman, A</style></author><author><style face="normal" font="default" size="100%">Hartl, D L</style></author><author><style face="normal" font="default" size="100%">Ayala, F J</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Heterogeneity of the internal transcribed spacer (ITS-2) region within individual deer ticks.</style></title><secondary-title><style face="normal" font="default" size="100%">Insect Mol Biol</style></secondary-title><alt-title><style face="normal" font="default" size="100%">Insect Mol. Biol.</style></alt-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Animals</style></keyword><keyword><style  face="normal" font="default" size="100%">Base Sequence</style></keyword><keyword><style  face="normal" font="default" size="100%">Deer</style></keyword><keyword><style  face="normal" font="default" size="100%">DNA</style></keyword><keyword><style  face="normal" font="default" size="100%">DNA, Ribosomal</style></keyword><keyword><style  face="normal" font="default" size="100%">Genetic Heterogeneity</style></keyword><keyword><style  face="normal" font="default" size="100%">Ixodes</style></keyword><keyword><style  face="normal" font="default" size="100%">Molecular Sequence Data</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1997</style></year><pub-dates><date><style  face="normal" font="default" size="100%">1997 May</style></date></pub-dates></dates><volume><style face="normal" font="default" size="100%">6</style></volume><pages><style face="normal" font="default" size="100%">123-9</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">To determine whether nuclear rDNA sequences provide a useful means for assessing the structure of populations of Ixodes ticks, we compared variability among copies of an internal transcribed spacer (ITS-2) sequence within individual ticks to the variability between ticks. At least 4% of the nucleotides comprising this sequence vary among the copies present within individual ticks. ITS-2 diversity in each of two ticks is nearly half as great as that reported between ticks from geographically disparate populations. Because individual ticks retain ancestral polymorphism, ITS-2 variation does not accurately reflect descent relationships among these ticks. Sequencing single copies of PCR-amplified ITS-2 therefore does not permit assessment of the phylogenetic relationships among the I. ricinus-like ticks in eastern North America. We recommend caution in future analyses, and emphasize the importance of procedures designed to ensure that the many paralogous copies of the rDNA cistron have been sufficiently homogenized by concerted evolutionary processes. Such precautionary measures will make certain that phylogenetic trees based on these gene sequences reflect the phyletic relatedness of the biological species.</style></abstract><issue><style face="normal" font="default" size="100%">2</style></issue><custom1><style face="normal" font="default" size="100%">http://www.ncbi.nlm.nih.gov/pubmed/9099576?dopt=Abstract</style></custom1></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Boyd, E F</style></author><author><style face="normal" font="default" size="100%">Hill, C W</style></author><author><style face="normal" font="default" size="100%">Rich, S M</style></author><author><style face="normal" font="default" size="100%">Hartl, D L</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Mosaic structure of plasmids from natural populations of Escherichia coli.</style></title><secondary-title><style face="normal" font="default" size="100%">Genetics</style></secondary-title><alt-title><style face="normal" font="default" size="100%">Genetics</style></alt-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Bacterial Proteins</style></keyword><keyword><style  face="normal" font="default" size="100%">Base Sequence</style></keyword><keyword><style  face="normal" font="default" size="100%">DNA Helicases</style></keyword><keyword><style  face="normal" font="default" size="100%">DNA, Bacterial</style></keyword><keyword><style  face="normal" font="default" size="100%">DNA-Binding Proteins</style></keyword><keyword><style  face="normal" font="default" size="100%">Escherichia coli</style></keyword><keyword><style  face="normal" font="default" size="100%">Escherichia coli Proteins</style></keyword><keyword><style  face="normal" font="default" size="100%">Evolution, Molecular</style></keyword><keyword><style  face="normal" font="default" size="100%">Membrane Proteins</style></keyword><keyword><style  face="normal" font="default" size="100%">Molecular Sequence Data</style></keyword><keyword><style  face="normal" font="default" size="100%">Mosaicism</style></keyword><keyword><style  face="normal" font="default" size="100%">Nucleic Acid Hybridization</style></keyword><keyword><style  face="normal" font="default" size="100%">Phylogeny</style></keyword><keyword><style  face="normal" font="default" size="100%">Plasmids</style></keyword><keyword><style  face="normal" font="default" size="100%">Polymorphism, Genetic</style></keyword><keyword><style  face="normal" font="default" size="100%">Proteins</style></keyword><keyword><style  face="normal" font="default" size="100%">Recombination, Genetic</style></keyword><keyword><style  face="normal" font="default" size="100%">Repressor Proteins</style></keyword><keyword><style  face="normal" font="default" size="100%">RNA-Binding Proteins</style></keyword><keyword><style  face="normal" font="default" size="100%">Trans-Activators</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1996</style></year><pub-dates><date><style  face="normal" font="default" size="100%">1996 Jul</style></date></pub-dates></dates><volume><style face="normal" font="default" size="100%">143</style></volume><pages><style face="normal" font="default" size="100%">1091-100</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The distribution of plasmids related to the fertility factor F was examined in the ECOR reference collection of Escherichia coli. Probes specific for four F-related genes were isolated and used to survey the collection by DNA hybridization. To estimate the genetic diversity of genes in F-like plasmids, DNA sequences were obtained for four plasmid genes. The phylogenetic relationships among the plasmids in the ECOR strains is very different from that of the strains themselves. This finding supports the view that plasmid transfer has been frequent within and between the major groups of ECOR. Furthermore, the sequences indicate that recombination between genes in plasmids takes place at a considerably higher frequency than that observed for chromosomal genes. The plasmid genes, and by inference the plasmids themselves, are mosaic in structure with different regions acquired from different sources. Comparison of gene sequences from a variety of naturally occurring plasmids suggested a plausible donor of some of the recombinant regions as well as implicating a chi site in the mechanism of genetic exchange. The relatively high rate of recombination in F-plasmid genes suggests that conjugational gene transfer may play a greater role in bacterial population structure than previously appreciated.</style></abstract><issue><style face="normal" font="default" size="100%">3</style></issue><custom1><style face="normal" font="default" size="100%">http://www.ncbi.nlm.nih.gov/pubmed/8807284?dopt=Abstract</style></custom1></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Armstrong, P M</style></author><author><style face="normal" font="default" size="100%">Rich, S M</style></author><author><style face="normal" font="default" size="100%">Smith, R D</style></author><author><style face="normal" font="default" size="100%">Hartl, D L</style></author><author><style face="normal" font="default" size="100%">Spielman, A</style></author><author><style face="normal" font="default" size="100%">Telford, S R</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">A new Borrelia infecting Lone Star ticks.</style></title><secondary-title><style face="normal" font="default" size="100%">Lancet</style></secondary-title><alt-title><style face="normal" font="default" size="100%">Lancet</style></alt-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Animals</style></keyword><keyword><style  face="normal" font="default" size="100%">Base Sequence</style></keyword><keyword><style  face="normal" font="default" size="100%">Borrelia</style></keyword><keyword><style  face="normal" font="default" size="100%">Borrelia Infections</style></keyword><keyword><style  face="normal" font="default" size="100%">Deer</style></keyword><keyword><style  face="normal" font="default" size="100%">Disease Vectors</style></keyword><keyword><style  face="normal" font="default" size="100%">DNA Primers</style></keyword><keyword><style  face="normal" font="default" size="100%">Maryland</style></keyword><keyword><style  face="normal" font="default" size="100%">Molecular Sequence Data</style></keyword><keyword><style  face="normal" font="default" size="100%">Ticks</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1996</style></year><pub-dates><date><style  face="normal" font="default" size="100%">1996 Jan 6</style></date></pub-dates></dates><volume><style face="normal" font="default" size="100%">347</style></volume><pages><style face="normal" font="default" size="100%">67-8</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><issue><style face="normal" font="default" size="100%">8993</style></issue><custom1><style face="normal" font="default" size="100%">http://www.ncbi.nlm.nih.gov/pubmed/8531586?dopt=Abstract</style></custom1></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Caporale, D A</style></author><author><style face="normal" font="default" size="100%">Rich, S M</style></author><author><style face="normal" font="default" size="100%">Spielman, A</style></author><author><style face="normal" font="default" size="100%">Telford, S R</style></author><author><style face="normal" font="default" size="100%">Kocher, T D</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Discriminating between Ixodes ticks by means of mitochondrial DNA sequences.</style></title><secondary-title><style face="normal" font="default" size="100%">Mol Phylogenet Evol</style></secondary-title><alt-title><style face="normal" font="default" size="100%">Mol. Phylogenet. Evol.</style></alt-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Animals</style></keyword><keyword><style  face="normal" font="default" size="100%">Arachnid Vectors</style></keyword><keyword><style  face="normal" font="default" size="100%">Base Sequence</style></keyword><keyword><style  face="normal" font="default" size="100%">Dermacentor</style></keyword><keyword><style  face="normal" font="default" size="100%">DNA Primers</style></keyword><keyword><style  face="normal" font="default" size="100%">DNA, Mitochondrial</style></keyword><keyword><style  face="normal" font="default" size="100%">Genes</style></keyword><keyword><style  face="normal" font="default" size="100%">Humans</style></keyword><keyword><style  face="normal" font="default" size="100%">Ixodes</style></keyword><keyword><style  face="normal" font="default" size="100%">Molecular Sequence Data</style></keyword><keyword><style  face="normal" font="default" size="100%">Phylogeny</style></keyword><keyword><style  face="normal" font="default" size="100%">Polymerase Chain Reaction</style></keyword><keyword><style  face="normal" font="default" size="100%">RNA, Ribosomal, 16S</style></keyword><keyword><style  face="normal" font="default" size="100%">Species Specificity</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1995</style></year><pub-dates><date><style  face="normal" font="default" size="100%">1995 Dec</style></date></pub-dates></dates><volume><style face="normal" font="default" size="100%">4</style></volume><pages><style face="normal" font="default" size="100%">361-5</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Ticks of the genus Ixodes have recently assumed prominence because they frequently serve as vectors of important zoonoses, including Lyme disease and babesiosis. The morphological characteristics that have been used in their identification often are ambiguous and are useful solely at a particular stage of development. Here we report the DNA sequence of the mitochondrially encoded 16S rRNA gene of nine different Ixodes ticks and an outgroup from another genus, Dermacentor. The sequences readily discriminate between these ticks. Samples of I. dammini from the northeastern and upper midwestern United States differ from southeastern I. scapularis at about 2% of the nucleotides. This difference is about half that separating other members of the I. ricinus group of species, but exceeds typical levels of intraspecific variation. Two major clades exist within the I. ricinus complex. One includes I. cookei, I. hexagonus, and I. angustus. The other includes I. persulcatus, I. pacificus, I. muris, I. ricinus, I. scapularis, and I. dammini. We conclude that mtDNA sequences are useful for unravelling the systematics of these important vectors of human disease.</style></abstract><issue><style face="normal" font="default" size="100%">4</style></issue><custom1><style face="normal" font="default" size="100%">http://www.ncbi.nlm.nih.gov/pubmed/8747292?dopt=Abstract</style></custom1></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Rich, S M</style></author><author><style face="normal" font="default" size="100%">Caporale, D A</style></author><author><style face="normal" font="default" size="100%">Telford, S R</style></author><author><style face="normal" font="default" size="100%">Kocher, T D</style></author><author><style face="normal" font="default" size="100%">Hartl, D L</style></author><author><style face="normal" font="default" size="100%">Spielman, A</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Distribution of the Ixodes ricinus-like ticks of eastern North America.</style></title><secondary-title><style face="normal" font="default" size="100%">Proc Natl Acad Sci U S A</style></secondary-title><alt-title><style face="normal" font="default" size="100%">Proc. Natl. Acad. Sci. U.S.A.</style></alt-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Animals</style></keyword><keyword><style  face="normal" font="default" size="100%">Base Sequence</style></keyword><keyword><style  face="normal" font="default" size="100%">Demography</style></keyword><keyword><style  face="normal" font="default" size="100%">DNA Primers</style></keyword><keyword><style  face="normal" font="default" size="100%">DNA, Mitochondrial</style></keyword><keyword><style  face="normal" font="default" size="100%">DNA, Ribosomal</style></keyword><keyword><style  face="normal" font="default" size="100%">Geography</style></keyword><keyword><style  face="normal" font="default" size="100%">Mitochondria</style></keyword><keyword><style  face="normal" font="default" size="100%">Molecular Sequence Data</style></keyword><keyword><style  face="normal" font="default" size="100%">Phylogeny</style></keyword><keyword><style  face="normal" font="default" size="100%">Polymerase Chain Reaction</style></keyword><keyword><style  face="normal" font="default" size="100%">Population</style></keyword><keyword><style  face="normal" font="default" size="100%">RNA, Ribosomal, 16S</style></keyword><keyword><style  face="normal" font="default" size="100%">Ticks</style></keyword><keyword><style  face="normal" font="default" size="100%">United States</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1995</style></year><pub-dates><date><style  face="normal" font="default" size="100%">1995 Jul 3</style></date></pub-dates></dates><volume><style face="normal" font="default" size="100%">92</style></volume><pages><style face="normal" font="default" size="100%">6284-8</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We analyzed the geographic distribution of the Ixodes ricinus-like ticks in eastern North America by comparing the mitochondrial 16S rDNA sequences of specimens sampled directly from the field during the 1990s. Two distinct lineages are evident. The southern clade includes ticks from the southeastern and middle-eastern regions of the United States. The range of the northern clade, which appears to have been restricted to the northeastern region until the mid-1900s, now extends throughout the northeastern and middle-eastern regions. These phyletic units correspond to northern and southern taxa that have previously been assigned specific status as Ixodes dammini and Ixodes scapularis, respectively. The expanding range of I. dammini appears to drive the present outbreaks of zoonotic disease in eastern North America that include Lyme disease and human babesiosis.</style></abstract><issue><style face="normal" font="default" size="100%">14</style></issue><custom1><style face="normal" font="default" size="100%">http://www.ncbi.nlm.nih.gov/pubmed/7603983?dopt=Abstract</style></custom1></record></records></xml>