Small chromosomes among Danish Candida glabrata isolates originated through different mechanisms

We analyzed 192 strains of the pathogenic yeast Candida glabrata from patients, mainly suffering from systemic infection, at Danish hospitals during 1985-1999. Our analysis showed that these strains were closely related but exhibited large karyotype polymorphism. Nine strains contained small chromosomes, which were smaller than 0.5 Mb. Regarding the year, patient and hospital, these C. glabrata strains had independent origin and the analyzed small chromosomes were structurally not related to each other (i.e. they contained different sets of genes). We suggest that at least two mechanisms could participate in their origin: (i) through a segmental duplication which covered the centromeric region, or (ii) by a translocation event moving a larger chromosome arm to another chromosome that leaves the centromere part with the shorter arm. The first type of small chromosomes carrying duplicated genes exhibited mitotic instability, while the second type, which contained the corresponding genes in only one copy in the genome, was mitotically stable. Apparently, in patients C. glabrata chromosomes are frequently reshuffled resulting in new genetic configurations, including appearance of small chromosomes, and some of these resulting "mutant" strains can have increased fitness in a certain patient "environment"

Formation of new chromosomes as a virulence mechanism in yeast Candida glabrata

In eukaryotes, the number and rough organization of chromosomes is well preserved within isolates of the same species. Novel chromosomes and loss of chromosomes are infrequent and usually associated with pathological events. Here, we analyzed 40 pathogenic isolates of a haploid and asexual yeast, Candida glabrata, for their genome structure and stability. This organism has recently become the second most prevalent yeast pathogen in humans. Although the gene sequences were well conserved among different strains, their chromosome structures differed drastically. The most frequent events reshaping chromosomes were translocations of chromosomal arms. However, also larger segmental duplications were frequent and occasionally we observed novel chromosomes. Apparently, this yeast can generate a new chromosome by duplication of chromosome segments carrying a centromere and subsequently adding novel telomeric ends. We show that the observed genome plasticity is connected with antifungal drug resistance and it is likely an advantage in the human body, where environmental conditions fluctuate a lot

First molecular phylogeny of Laevicaudata (Crustacea: Branchiopoda) with description of a new species of Lynceus from Chile and an updated key to species in the Americas

Este artículo contiene 22 páginas, 9 figuras, 2 tablas.The first molecular phylogeny of Lynceus (Crustacea: Branchiopoda: Laevicaudata) is presented together with a description of anewspecies of laevicaudatan branchiopod from Chile, Lynceus huentelauquensis, sp. nov.DNAsequences were obtained from six species of Lynceus using freshly collected specimens from Europe, North America, South America, and Australia and combined with GenBank sequences from previous studies. Specimens of the new species were collected from a pool on the Huentelauquén Plains near Huentelauquén City. Our molecular analyses placed L. huentelauquensis, sp. nov. within Lynceus and close to a cluster of Australian species, and revealed morphological misidentifications, crosscontamination, or incorrect upload in earlier GenBank sequences. L. huentelauquensis, sp. nov. is separated from other Lynceus primarily by the morphology of the rostrum and the male claspers. L. huentelauquensis, sp. nov. is thefirst described laevicaudatan from Chile, the sixth from South America, and the 13th from the Americas. The morphology of laevicaudatans from the Americas is reviewed and an updated key to the (male) Lynceidae of the region is provided. Our study highlights the necessity of a revision of Laevicaudata using multiple genetic markers as well as thorough morphological studies on a greater number of taxa.The sample collection was financed by projects MECESUP UCT 0804 (PDLR), DIDULS PR17121, and FPA-NAC-I-032-2014.A visit by ZS and JO to BMNH was supported by a SYNTHESYS grant from the European Union. FP acknowledges project CHALLENGEN (CTM2013-48163) of the Spanish Government and a postdoctoral contract funded by the Beatriu de Pinos Program of the Generalitat de Catalunya (2014-BPB-00038). JO acknowledges financial support from the Villum Foundation for sequencing. The study is part of ZS’s PhD project financed by the Faculty of Science, University of Copenhagen.Peer reviewe