Dataset Information

Cryptic contamination and phylogenetic nonsense.

ABSTRACT: Ancient human DNA has been treated cautiously ever since the problems related to this type of material were exposed in the early 1990s, but as sequential genetic data from ancient specimens have been key components in several evolutionary and ecological studies, interest in ancient human DNA is on the increase again. It is especially tempting to approach archaeological and anthropological questions through this type of material, but DNA from ancient human tissue is notoriously complicated to work with due to the risk of contamination with modern human DNA. Various ways of authenticating results based on ancient human DNA have been developed to circumvent the problems. One commonly used method is to predict what the contamination is expected to look like and then test whether the ancient human DNA fulfils this prediction. If it does, the results are rejected as contamination, while if it does not, they are often considered authentic. We show here that human contamination in ancient material may well deviate from local allele frequencies or the distributions to be found among the laboratory workers and archaeologists. We conclude that it is not reliable to authenticate ancient human DNA solely by showing that it is different from what would be expected from people who have handled the material.

SUBMITTER: Linderholm A

PROVIDER: S-EPMC2384008 | biostudies-literature | 2008 May

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Cryptic contamination and phylogenetic nonsense.

Linderholm Anna A Malmström Helena H Lidén Kerstin K Holmlund Gunilla G Götherström Anders A

PloS one 20080528 5

Ancient human DNA has been treated cautiously ever since the problems related to this type of material were exposed in the early 1990s, but as sequential genetic data from ancient specimens have been key components in several evolutionary and ecological studies, interest in ancient human DNA is on the increase again. It is especially tempting to approach archaeological and anthropological questions through this type of material, but DNA from ancient human tissue is notoriously complicated to wor ...[more]

PMID: 18509458

Similar Datasets

Project description:BackgroundAlthough Cryptococcus laurentii has been considered saprophytic and its taxonomy is still being described, several cases of human infections have already reported. This study aimed to evaluate molecular aspects of C. laurentii isolates from Brazil, Botswana, Canada, and the United States.MethodsIn this study, 100 phenotypically identified C. laurentii isolates were evaluated by sequencing the 18S nuclear ribosomal small subunit rRNA gene (18S-SSU), D1/D2 region of 28S nuclear ribosomal large subunit rRNA gene (28S-LSU), and the internal transcribed spacer (ITS) of the ribosomal region.ResultsBLAST searches using 550-bp, 650-bp, and 550-bp sequenced amplicons obtained from the 18S-SSU, 28S-LSU, and the ITS region led to the identification of 75 C. laurentii strains that shared 99-100% identity with C. laurentii CBS 139. A total of nine isolates shared 99% identity with both Bullera sp. VY-68 and C. laurentii RY1. One isolate shared 99% identity with Cryptococcus rajasthanensis CBS 10406, and eight isolates shared 100% identity with Cryptococcus sp. APSS 862 according to the 28S-LSU and ITS regions and designated as Cryptococcus aspenensis sp. nov. (CBS 13867). While 16 isolates shared 99% identity with Cryptococcus flavescens CBS 942 according to the 18S-SSU sequence, only six were confirmed using the 28S-LSU and ITS region sequences. The remaining 10 shared 99% identity with Cryptococcus terrestris CBS 10810, which was recently described in Brazil. Through concatenated sequence analyses, seven sequence types in C. laurentii, three in C. flavescens, one in C. terrestris, and one in the C. aspenensis sp. nov. were identified.ConclusionsSequencing permitted the characterization of 75% of the environmental C. laurentii isolates from different geographical areas and the identification of seven haplotypes of this species. Among sequenced regions, the increased variability of the ITS region in comparison to the 18S-SSU and 28S-LSU regions reinforces its applicability as a DNA barcode.

Project description:Analysis of the population genetic structure of microbial species is of fundamental importance to many scientific disciplines because it can identify cryptic species, reveal reproductive mode, and elucidate processes that contribute to pathogen evolution. Here, we examined the population genetic structure and geographic differentiation of the sexual, dimorphic fungus Blastomyces dermatitidis, the causative agent of blastomycosis.Criteria for Genealogical Concordance Phylogenetic Species Recognition (GCPSR) applied to seven nuclear loci (arf6, chs2, drk1, fads, pyrF, tub1, and its-2) from 78 clinical and environmental isolates identified two previously unrecognized phylogenetic species. Four of seven single gene phylogenies examined (chs2, drk1, pyrF, and its-2) supported the separation of Phylogenetic Species 1 (PS1) and Phylogenetic Species 2 (PS2) which were also well differentiated in the concatenated chs2-drk1-fads-pyrF-tub1-arf6-its2 genealogy with all isolates falling into one of two evolutionarily independent lineages. Phylogenetic species were genetically distinct with interspecific divergence 4-fold greater than intraspecific divergence and a high Fst value (0.772, P<0.001) indicative of restricted gene flow between PS1 and PS2. Whereas panmixia expected of a single freely recombining population was not observed, recombination was detected when PS1 and PS2 were assessed separately, suggesting reproductive isolation. Random mating among PS1 isolates, which were distributed across North America, was only detected after partitioning isolates into six geographic regions. The PS2 population, found predominantly in the hyper-endemic regions of northwestern Ontario, Wisconsin, and Minnesota, contained a substantial clonal component with random mating detected only among unique genotypes in the population.These analyses provide evidence for a genetically divergent clade within Blastomyces dermatitidis, which we use to describe a novel species, Blastomyces gilchristii sp. nov. In addition, we discuss the value of population genetic and phylogenetic analyses as a foundation for disease surveillance, understanding pathogen evolution, and discerning phenotypic differences between phylogenetic species.

Dataset Information

Cryptic contamination and phylogenetic nonsense.

Publications

Cryptic contamination and phylogenetic nonsense.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets