336 research outputs found
Identification of new epidemiological molecular markers by comparative proteomics of serogroup A meningococcal isolates from three pandemic waves
No full textWe previously described the first reference map for the proteome of one strain of serogroup A Neisseria meningitidis (MenA), a major cause of epidemic meningitis in humans. As a preliminary finding, in that work we noted that 2-DE protein maps of closely related MenA isolates from different epidemics spreads could be easily compared to detect minor differences and that 2-DE phenotypes attributable to the well-known epidemiological marker tbpB agreed with the genoclouds model of MenA epidemiological variation during pandemic waves. We explored here the possibility that an extended comparative study of 2-DE maps of isolates representative of the nine genoclouds described by Achtman and collaborators could be used to discriminate between strains otherwise undistinguishable. We showed the example of 14 proteins with different 2-DE spot patterns in different genoclouds that could be considered as putative tracers for alike-strains discrimination. We introduce the novel concept that comparative proteomics can be useful in identifying new epidemiological markers for N. meningitidis
Presence/absence of IS<i>100</i> loci described in Achtman et al (2004).
No full text1<p>CO92 profile from Achtman et al (2004).</p
Genealogical typing of Neisseria meningitidis
No full textDespite the increasing popularity of multilocus sequence typing (MLST), the most appropriate method for characterizing bacterial variation and facilitating epidemiological investigations remains a matter of debate. Here, we propose that different typing schemes should be compared on the basis of their power to infer clonal relationships and investigate the utility of sequence data for genealogical reconstruction by exploiting new statistical tools and data from 20 housekeeping loci for 93 isolates of the bacterial pathogen Neisseria meningitidis. Our analysis demonstrated that all but one of the hyperinvasive isolates established by multilocus enzyme electrophoresis and MLST were grouped into one of six genealogical lineages, each of which contained substantial variation. Due to the confounding effect of recombination, evolutionary relationships among these lineages remained unclear, even using 20 loci. Analyses of the seven loci in the standard MLST scheme using the same methods reproduced this classification, but were unable to support finer inferences concerning the relationships between the members within each complex
Evolutionary relationships of wild hominids recapitulated by gut microbial communities
No full textMultiple factors over the lifetime of an individual, including diet, geography, and physiologic state, will influence the microbial communities within the primate gut. To determine the source of variation in the composition of the microbiota within and among species, we investigated the distal gut microbial communities harbored by great apes, as present in fecal samples recovered within their native ranges. We found that the branching order of host-species phylogenies based on the composition of these microbial communities is completely congruent with the known relationships of the hosts. Although the gut is initially and continuously seeded by bacteria that are acquired from external sources, we establish that over evolutionary timescales, the composition of the gut microbiota among great ape species is phylogenetically conserved and has diverged in a manner consistent with vertical inheritance. © 2010 Ochman et al
The mating phenomenon in Escherichia Coli
No full textMating between Escherichia coli was first demonstrated in the 1940’s and somewhat defined during the 1950’s and early 1960’s (for review see 7). These results were obtained using primarily donor cells carrying the sex factor F (see below) and recipient cells not carrying it. Under laboratory conditions matings are performed by mixing actively growing donor and recipient cultures at 37° and allowing DNA transfer to occur for one to two hours. Early observations on mating mixtures led to the general concept, still accepted today, that mating consists of pairing between donor and recipient cells in a form sensitive to mild shear forces. The results presented here indicate that this concept is inadequate and a modified definition of mating will be presented below
A broad brush, global overview of bacterial sexuality
No full textBacterial sexuality is confusing, even for experts! I used to be such an expert on one mechanism of sexuality, conjugation, but that was over 30 years ago. At that time, extra-chromosomal elements, so-called plasmids, were known to encode multiple proteins that together enabled cell-to-cell contacts, which were then used to transfer single-stranded DNA from donor to recipient, thus providing the plasmid with a new host. Transfer of the plasmid resulted in concomitant transfer of any genes that it happened to include, such as genes encoding resistance to antibiotics or virulence factors. On unusual and rare occasions, the plasmid integrated into the chromosome, resulting in the conjugative transfer of chromosomal DNA. What was particularly confusing was the plethora of plasmids that encoded genes for conjugation, each apparently different from the other, and the corresponding large variety of differences between mechanisms of conjugation associated with different plasmids. Some plasmids didn't even encode genes for conjugation, but simply hitch-hiked with the help of conjugation proteins expressed by other plasmids, a phenomenon called mobilization
population structure, asymptomatic carriage and host association
No full textSerovare von Salmonella enterica subspecies enterica sind im allgemeinen pathogen für Mensch und andere Säugetiere. In dieser Arbeit habe ich anhand eines “Multilocus Sequences Typing” Typisierungsschemas die Populationsstruktur einer der am häufigsten auftretenden Serovaren dieser Subspecies, das aus Menschen und Schlachttieren isolierte Serovar Newport charakterisiert. Dieses Schema wurde auch für die Charakterisierung von Isolaten derselben Subspecies aus humanen Dauerträgern und Reptilien verwandt, um zu bestimmen, ob Isolate aus diesen Quellen sich in ihrer Populationstruktur von denjenigen unterscheiden, die aus anderen Quellen isoliert wurden. Multilocus Sequences Typing ist eine weitgehend für die Untersuchung der Evolution und Populationsstruktur von einen breiten Spektrum von Organismen verwendete Technik. 400 - 600 bp lange Fragmente von 7 Haushaltsgenen wurden sequenziert, und jede einzelne Sequenz jedes einzelnen Gens wurde eine Allelnummer zugeordnet. Jede einzelne Allelkombination wurde einem Sequenztyp zugeordnet. Die so gewonnenen Daten wurden weiter analysiert. Drei “Lineages”, Newport-I, Newport-II und Newport-III, wurden innerhalb dieses Serovars identifiziert, die jeweils aus Menschen in Europa, Tieren und Menschen in Nordamerika isoliert wurden. Der Multiresistenz-Phänotyp wurde häufiger in Newport II gefunden, während die meisten Newport III Isolate pan-sensitiv waren. Verglichen mit anderen Serovaren war die Anzahl von “Lineages” innerhalb Newport höher als bei Enteritidis, Kentucky und Typhimurium, aber niedriger als bei Paratyphi B. Das heisst, die Serovare von S. enterica subspecies enterica variieren stark in ihrer Populationsstruktur. Die Sequenztypen in Isolaten aus humanen Dauerträgern waren im allgemeinen am häufigsten in Isolaten von klinischen Patienten und Tieren vorhanden. In der Mehrheit der Serovaren waren die meisten Isolate aus Patienten und Tieren genetisch identisch mit solchen, die aus gesunden Trägern isoliert wurden. Die genetische Variabilität war zwischen Isolaten aus diesen Quellen vergleichbar. Diese Ergebnissen deuten daraufhin, dass Salmonellen aus Dauerträgern sowie Isolate aus Patienten und Tieren derselben Population angehören. Die meisten Serovare aus Reptilienisolaten waren genetisch identisch mit denen von Menschen und warmblütigen Tieren. In den Serovaren Bovismorbificans, Decatur, Miami und Oranienburg hingegen waren die meisten Isolate aus Reptilien genetisch anders als Isolate aus anderen Wirten. Allerdings wurden nur wenige Isolate der Serovaren Bovismorbificans, Decatur und Miami aus Reptilien und nur wenige Isolate der Serovaren Oranienburg aus anderen Quellen getestet; eine grössere Anzahl von Isolaten müsste daher untersucht werden, um festzustellen ob diese genetischen Unterschiede statistich signifikant sind oder nicht.Serovars of Salmonella enterica subspecies enterica are generally pathogenic to humans and other mammals. In this study, I examined the population structure of one of the most common serovars of this subspecies isolated from humans and food animals, serovar Newport, using a multilocus sequence typing scheme. This scheme was also used to analyze isolates of this subspecies from chronic human carriers and reptiles to determine whether isolates from these sources represent distinct populations than those from other hosts. Multilocus sequence typing has extensively been used to study evolution and population structure of a wide range of organisms. 400-600 bp fragments of 7 housekeeping genes were sequenced and every unique sequence of each gene fragment was given a distinct allele number. Each unique combination of alleles was assigned a distinct sequence type number. The data were used in further analyses. Three lineages, namely Newport-I, Newport-II and Newport-III were identified within serovar Newport which were associated to European humans, animals and humans in North America, respectively. Multidrug resistance phenotypes were most common in Newport-II whereas most isolates in Newport-III were pan-susceptible. When compared to other serovars, the numbers of lineages within Newport were higher than for Enteritidis, Kentucky and Typhimurium but lower than for Paratyphi B. Therefore, serovars of S. enterica subspecies enterica vary greatly in their population structures. The sequence types observed for isolates from chronic human carriers were generally the most common among human-clinical and animal isolates. Most isolates from non-carrier humans plus animals were genetically identical to the carried isolates within most serovars. Genetic diversity was also comparable between isolates from these sources. These results suggest that salmonellae from chronic human carriers belong to the same population as isolates from non-carrier humans and animals. For most serovars, most isolates from reptiles were genetically identical to those from humans or other warm blooded animals. However, in serovars Bovismorbificans, Decatur, Miami and Oranienburg, most reptile isolates were genetically distinct from isolates from other hosts. Only few reptile isolates were tested from Bovismorbificans, Decatur and Miami and only few non-reptile isolates were tested from Oranienburg, and in larger numbers of such isolates would be needed to determine whether these differences are statistically significant
<i>Bacterial Population Genetics in Infectious Disease</i>. Edited by D. Ashley Robinson, Daniel Falush, and Edward J. Feil. Hoboken (New Jersey): Wiley-Blackwell. $130.00. xviii + 420 p. + 8 pl.; ill.; index. ISBN: 978-0-470-42474-2. 2010.
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