A clonal theory of parasitic protozoa: the population structures of Entamoeba, Giardia, Leishmania, Naegleria, Plasmodium, Trichomonas, and Trypanosoma and their medical and taxonomical consequences.

Tibayrenc, Michel; Kjellberg, Finn; Ayala, Francisco J.

doi:10.1073/pnas.87.7.2414

Cited by 498 publications

(388 citation statements)

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“…Clonal (asexual) population dated by cloning and sequencing of PCR products from structure for Giardia has been inferred from fixed heterogenomic DNA. We discovered only minor sequence difzygosity, deviation from Hardy-Weinberg expectations, ferences between our clones and draft sequences (see and absence of recombinant genotypes [33]. Finally, a the Supplemental Data available with this article online).…”

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confidence: 59%

A Phylogenomic Inventory of Meiotic GenesEvidence for Sex in Giardia and an Early Eukaryotic Origin of Meiosis

2005

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homologs of well-known meiotic genes. The direct implications are that Giardia is, or was recently, capable of sexual reproduction and, thus, does not represent an ancient eukaryotic lineage that diverged before meiosis arose. Instead, the origin of meiosis predates the diver- plemental Data), all indicate that these genes are comOne possible interpretation of these observations is that plete, bona fide homologs of meiotic genes. diplomonads such as Giardia represent an "intermedi- Table 2 shows that the Giardia genome encodes hoate" (i.e., premeiotic) stage in eukaryotic evolution [35]. mologs of key genes required for meiosis. Homologs of We have evaluated this compelling hypothesis and can five meiosis-specific genes are present in Giardia: now reject it.Dmc1, Spo11, Mnd1, Hop1, and Hop2. Proteins encoded by these genes are not known to function outside of meiosis among AFP species. Of meiosis-specific Genes and Their Functions at the Core of Meiosis We used a phylogenomic approach [36] to identify and genes surveyed, Giardia does not appear to encode mutS homologs Msh4 and Msh5. Whether this is due to validate a core group of meiotic genes as indicators for the presence or absence of meiosis. Our selection of the loss of these genes or later evolutionary origins is unclear; the sparse distribution of Msh4/5 genes indimeiotic genes was based on previous studies in eukaryotic model systems-mostly AFP. We chose genes havcates some losses. Five meiosis-specific genes in Giardia in conjunction with other known meiotic genes proing major meiotic functions in AFP and conservation in sequence and function [2]. Gene products with similar vide strong evolutionary evidence for meiosis in the putatively asexual diplomonads. The presence of meiimportant roles in meiosis among known models have the greatest potential as meiotic indicators in diverse otic genes in Giardia and in the other protists surveyed (see below) extends the diversity of eukaryotes known to eukaryotes. Readily detectable protein sequence conservation among these genes ‫%51ف(‬ amino acid idencontain these genes. The collective presence of multiple genes that work together in meiotic recombination tity) was needed to identify potential homologs in evolutionarily distant species. We included some "meiosis strongly suggests that Giardia has or very recently had the capacity to undergo meiosis and, thus, sexual reprospecific" genes-null mutations in all of these genes (in S. cerevisiae, at least) are defective only in meiosis, and duction. The possibility that Giardia undergoes meiosis warrants further investigation; experiments will be remost genes do not function outside of meiosis, with some possible exceptions in mammals (Hop2 processes, present either from the loss of meiosis (despecific gene present in Giardia requires independent loss or gain of meiotic functions in all other eukaryotes rived asexuality) or prior to its invention (ancestral asexuality). As the numbers of meiotic genes mount, these known. The strong inference of meiosis being present...

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A Phylogenomic Inventory of Meiotic GenesEvidence for Sex in Giardia and an Early Eukaryotic Origin of Meiosis

2005

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“…The following four probability values proposed by Tibayrenc et al (1990) were used: d1: the combinatorial probability of sampling the most frequent genotype as often as or more often than actually observed if there were random recombination; d2: the probability of observing any genotype as often as or more often than the most common genotype actually observed if there were random recombination; e: the probability of observing as few or fewer genotypes than actually observed if there were random recombination; and f: it gives the probability of observing linkage disequilibrium as high, or higher than actually observed in the sample if there were random recombination. If a probability is non significant (p > 5 X 10 -2 ), random recombination can not be rejected, but it is significant (p < 5 X 10 -2 ), it supports the nonrandom association of loci.…”

Section: Methodsmentioning

confidence: 99%

“…Early studies addressing this question (Tibayrenc et al 1991, Caugant & Sandven 1993) have recorded low levels of linkage disequilibrium (nonrandom association of genotypes occuring at different loci), by comparison with other pathogens such as Trypanosoma or Leishmania (Tibayrenc et al 1990). By constrast, other authors (Hellstein et al 1993, Pujol et al 1993, Xu et al 1999, Arnavielhe et al 2000 have found considerable levels of linkage in differents C. albicans populations and have concluded that these populations propagate clonally.…”

Section: Albicansmentioning

confidence: 99%

First characterization of Candida albicans by random amplified polymorphic DNA method in Nicaragua and comparison of the diagnosis methods for vaginal candidiasis in Nicaraguan women

Bello

González

Barnabé

et al. 2002

Mem. Inst. Oswaldo Cruz

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The genital candidiasis is one of the pathogenic demonstrations of yeast. Candida albicans is the most frequent species; it is usually isolated in 85 to 90% from the vaginal mycoses (Odds et al. 1988).Vaginal candidiasis affects females at least once during their lifetime, at an estimated rate of 70 to 75%, of whom 40 to 50% will experience a recurrence (Sobel 1999).In Nicaragua, we know very little about the prevalence and incidence of vaginal candidiasis and no study of the biology of C. albicans has been carried out. In this country, diagnosis of vaginal candidiasis is mainly based on the clinical presentation. Laboratories of the hospitals and health centres (peripheral laboratories) carry out only the microscopic diagnosis from the vaginal fluid. In the laboratory of the National Centre of Diagnosis and Reference of Nicaragua (CNDR), the yeast identification is based on the observation of the microscopic aspects, culture and biochemical tests.Most of the genetic studies revealed that C. albicans is predominantly clonal (Pujol et al. 1993, Helstein et al. 1993, Lockhart et al. 1995, Xu et al. 1999. Some authors have proposed that clonal propagation with a remaining capacity of recombination, shape the population structure of C. albicans (Caugant & Sandven 1993, Gräser et al. 1996, Tibayrenc 1997 Southern blot hybridization with the moderately repetitive DNA Ca3 probe, not only clustered moderately related isolates in a similar fashion but also afforded similar levels of resolution of microevolution within a clonal population.The goal of this study was to use the RAPD method to examine the patterns of yeast genetic diversity among women with vaginitis from a single geographic area. We were specifically interested to know the frequency of yeast in vulvovaginal secretions. We also compared the conventional methods of yeast diagnosis from vaginal samples used in Nicaragua and yeast culture method. MATERIALS AND METHODSThe vaginal swabs were taken from 106 women exhibiting symptoms of vulvovaginitis, who were attended in the outpatient ward of the CNDR in Managua, Nicaragua, between June and August 1997. Swabs were processed by the method routinely used for the detection of germinated yeast pathogens: microscopic examination of wet mount, with a 10% potassium hydroxide (KOH) preparation, and the Gram's stain. Samples were inoculated into Sabouraud-glucose agar, supplemented with chloramphenicol, and were incubated at 37°C for 48 h. For identification of C. albicans, isolates were placed in foetal calf serum for 4 h to test for the production of germ tubes and were incubated on Rice-Agar-Tween (RAT ® ) BioMérieux Laboratories, France for 48 h to induce chlamydospores. All yeast isolates were preliminary identified to the species level according to the CHROMagar Albicans® Test (Mycoplasme International, Toulon, France). This medium contains a chromogene substrate for immediate identification of C. albicans (green), C. tropicalis (metallic blue), C. glabrata (pink) and C. krusei (pale pink). Yeast species were conf...

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“…At the single locus level, clonality will lead to an excess of heterozygotes in diploid organisms, while at the multilocus level, clonality will produce widespread, identical genotypes, non-random associations between alleles at different loci (linkage disequilibrium) and congruence in different intraspecific gene phylogenies [53,54,55]. A clonal population structure does not imply that genetic exchange is absent in the species, only that it is too rare to erode the basic genetic patterns of clonality.…”

Section: Mode Of Reproductionmentioning

confidence: 99%

“…A clonal population structure does not imply that genetic exchange is absent in the species, only that it is too rare to erode the basic genetic patterns of clonality. Using these criteria, Tibayrenc et al [53,56] identified a number of species of parasitic protozoa, including Entamboeba histolytica, Giardia duodenalis, Lieshmania tropica, L. major, Trypanosoma brucei, T. cruzi and T. vivax, as having an essentially clonal population structure. Subsequent studies have shown that the situation is rather more complex and different populations of the same species often show different degrees of clonality [57].…”

Section: Mode Of Reproductionmentioning

confidence: 99%

The molecular epidemiology of parasite infections: Tools and applications

Lymbery

Thompson

2012

Molecular and Biochemical Parasitology

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Molecular epidemiology, broadly defined, is the application of molecular genetic techniques to the dynamics of disease in a population. In this review, we briefly describe molecular and analytical tools available for molecular epidemiological studies and then provide an overview of how they can be applied to better understand parasitic disease. A range of new molecular tools have been developed in recent years, allowing for the direct examination of parasites from clinical or environmental samples, and providing access to relatively cheap, rapid, high throughput molecular assays. At the same time, new analytical approaches, in particular those derived from coalescent theory, have been developed to provide more robust estimates of evolutionary processes and demographic parameters from multilocus, genotypic data. To date, the primary application of molecular epidemiology has been to provide specific and sensitive identification of parasites and to resolve taxonomic issues, particularly at the species level and below. Population genetic studies have also been used to determine the extent of genetic diversity among populations of parasites and the degree to which this diversity is associated with different host cycles or epidemiologically important phenotypes. Many of these studies have also shed new light on transmission cycles of parasites, particularly the extent to which zoonotic transmission occurs, and on the prevalence and importance of mixed infections with different parasite species or intraspecific variants (polyparasitism). A major challenge, and one which is now being addressed by an increasing number of studies, is to find and utilise genetic markers for complex traits of epidemiological significance, such as drug resistance, zoonotic potential and virulence.

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A clonal theory of parasitic protozoa: the population structures of Entamoeba, Giardia, Leishmania, Naegleria, Plasmodium, Trichomonas, and Trypanosoma and their medical and taxonomical consequences.

Cited by 498 publications

References 37 publications

A Phylogenomic Inventory of Meiotic GenesEvidence for Sex in Giardia and an Early Eukaryotic Origin of Meiosis

A Phylogenomic Inventory of Meiotic GenesEvidence for Sex in Giardia and an Early Eukaryotic Origin of Meiosis

First characterization of Candida albicans by random amplified polymorphic DNA method in Nicaragua and comparison of the diagnosis methods for vaginal candidiasis in Nicaraguan women

The molecular epidemiology of parasite infections: Tools and applications

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