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Small chromosomes among Danish Candida glabrata isolates originated through different mechanisms.

Ahmad KM, Ishchuk OP, Hellborg L, Jørgensen G, Skvarc M, Stenderup J, Jørck-Ramberg D, Polakova S, Piškur J - Antonie Van Leeuwenhoek (2013)

Bottom Line: 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).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".

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Lund University, Sölvegatan 35, 223 62 Lund, Sweden. khadija_mohamed.ahmad@biol.lu.se

ABSTRACT
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".

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Electrophoretic karyotyping of nine clinical isolates of C. glabrata with small chromosomes. S. cerevisiae S288C (Y1307) and CBS 138 were included as references to determine the size of the new chromosomes. Y624a is a daughter strain of KA000127 (Y624) which has lost its small chromosome but the position of the small chromosome, as it would be in Y624, is circled. Y624 and its small chromosome were described previously (Poláková et al. 2009). The sizes of small chromosomes determined by calculation of chromosomal migration on the gel were estimated to be between 280 and 420 kb (see also Table 2). Note, strains Y1640 and Y1641 are from the same patient taken at different time points and the two small chromosomes have a slightly different size
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Fig4: Electrophoretic karyotyping of nine clinical isolates of C. glabrata with small chromosomes. S. cerevisiae S288C (Y1307) and CBS 138 were included as references to determine the size of the new chromosomes. Y624a is a daughter strain of KA000127 (Y624) which has lost its small chromosome but the position of the small chromosome, as it would be in Y624, is circled. Y624 and its small chromosome were described previously (Poláková et al. 2009). The sizes of small chromosomes determined by calculation of chromosomal migration on the gel were estimated to be between 280 and 420 kb (see also Table 2). Note, strains Y1640 and Y1641 are from the same patient taken at different time points and the two small chromosomes have a slightly different size

Mentions: The karyotypes of 151 isolates of C. glabrata were determined in this study, but in addition 40 strains had been analyzed already before (Poláková et al. 2009) thus providing 191 different karyotypes. There was apparent variation among the obtained karyotypes, ranging in the number of detected bands from ten to fourteen (Fig. 3). CBS 138 fourteen chromosomes are illustrated in Supplementary materials Fig. S1. The variation in the intensity of the chromosomal bands was also observed, and it could be explained as that some of the more intensive bands were composed of two or even more chromosomes. For example, Y663 has likely two double bands (of higher intensity then expected from the equal stoichiometric distribution), one in the K-L-M chromosome group and another in the C-D-E group. Figure 3 shows karyotypes originating from a set of strains belonging to the same phylogenetic sub-group KA002574 (see Fig. 2, the arrowed group). These strains are very closely related, but they exhibited a clear chromosomal polymorphism, in chromosome band numbers, sizes and intensity vary. Only one strain in this group, KA002870 (Y663) (Poláková et al. 2009), has 14 chromosome bands because of its small chromosome, while the remaining 24 strains show 10–13 bands (Fig. 3). The polymorphism is especially apparent within the large chromosomes K, L and M. This is in agreement with the previously published observations explaining the large chromosome polymorphism as a consequence of variation within the gene copy numbers at the rDNA locus (Muller et al. 2009). Among those 25 related isolates, we also found some that were isolated the same year from patients who were treated at the same hospital (Fig. 3; Supplementary material Table S1). However, even in these cases the karyotypes showed some degree of rearrangements. Interestingly, two strains from the same patient, KA002940 (Y1640) and KA002941 (Y1641), taken at different times of treatment, showed different karyotypes with 10–11 chromosomal bands detected (Fig. 4).Fig. 3


Small chromosomes among Danish Candida glabrata isolates originated through different mechanisms.

Ahmad KM, Ishchuk OP, Hellborg L, Jørgensen G, Skvarc M, Stenderup J, Jørck-Ramberg D, Polakova S, Piškur J - Antonie Van Leeuwenhoek (2013)

Electrophoretic karyotyping of nine clinical isolates of C. glabrata with small chromosomes. S. cerevisiae S288C (Y1307) and CBS 138 were included as references to determine the size of the new chromosomes. Y624a is a daughter strain of KA000127 (Y624) which has lost its small chromosome but the position of the small chromosome, as it would be in Y624, is circled. Y624 and its small chromosome were described previously (Poláková et al. 2009). The sizes of small chromosomes determined by calculation of chromosomal migration on the gel were estimated to be between 280 and 420 kb (see also Table 2). Note, strains Y1640 and Y1641 are from the same patient taken at different time points and the two small chromosomes have a slightly different size
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3672514&req=5

Fig4: Electrophoretic karyotyping of nine clinical isolates of C. glabrata with small chromosomes. S. cerevisiae S288C (Y1307) and CBS 138 were included as references to determine the size of the new chromosomes. Y624a is a daughter strain of KA000127 (Y624) which has lost its small chromosome but the position of the small chromosome, as it would be in Y624, is circled. Y624 and its small chromosome were described previously (Poláková et al. 2009). The sizes of small chromosomes determined by calculation of chromosomal migration on the gel were estimated to be between 280 and 420 kb (see also Table 2). Note, strains Y1640 and Y1641 are from the same patient taken at different time points and the two small chromosomes have a slightly different size
Mentions: The karyotypes of 151 isolates of C. glabrata were determined in this study, but in addition 40 strains had been analyzed already before (Poláková et al. 2009) thus providing 191 different karyotypes. There was apparent variation among the obtained karyotypes, ranging in the number of detected bands from ten to fourteen (Fig. 3). CBS 138 fourteen chromosomes are illustrated in Supplementary materials Fig. S1. The variation in the intensity of the chromosomal bands was also observed, and it could be explained as that some of the more intensive bands were composed of two or even more chromosomes. For example, Y663 has likely two double bands (of higher intensity then expected from the equal stoichiometric distribution), one in the K-L-M chromosome group and another in the C-D-E group. Figure 3 shows karyotypes originating from a set of strains belonging to the same phylogenetic sub-group KA002574 (see Fig. 2, the arrowed group). These strains are very closely related, but they exhibited a clear chromosomal polymorphism, in chromosome band numbers, sizes and intensity vary. Only one strain in this group, KA002870 (Y663) (Poláková et al. 2009), has 14 chromosome bands because of its small chromosome, while the remaining 24 strains show 10–13 bands (Fig. 3). The polymorphism is especially apparent within the large chromosomes K, L and M. This is in agreement with the previously published observations explaining the large chromosome polymorphism as a consequence of variation within the gene copy numbers at the rDNA locus (Muller et al. 2009). Among those 25 related isolates, we also found some that were isolated the same year from patients who were treated at the same hospital (Fig. 3; Supplementary material Table S1). However, even in these cases the karyotypes showed some degree of rearrangements. Interestingly, two strains from the same patient, KA002940 (Y1640) and KA002941 (Y1641), taken at different times of treatment, showed different karyotypes with 10–11 chromosomal bands detected (Fig. 4).Fig. 3

Bottom Line: 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).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".

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Lund University, Sölvegatan 35, 223 62 Lund, Sweden. khadija_mohamed.ahmad@biol.lu.se

ABSTRACT
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".

Show MeSH
Related in: MedlinePlus