Multilocus microsatellite analysis of European and African Candida glabrata isolates

This study aimed to elucidate the genetic relatedness and epidemiology of 127 clinical and environmental Candida glabrata isolates from Europe and Africa using multilocus microsatellite analysis. Each isolate was first identified using phenotypic and molecular methods and subsequently, six unlinked microsatellite loci were analyzed using automated fluorescent genotyping. Genetic relationships were estimated using the minimum-spanning tree (MStree) method. Microsatellite analyses revealed the existence of 47 different genotypes. The fungal population showed an irregular distribution owing to the over-representation of genetically different infectious haplotypes. The most common genotype was MG-9, which was frequently found in both European and African isolates. In conclusion, the data reported here emphasize the role of specific C. glabrata genotypes in human infections for at least some decades and highlight the widespread distribution of some isolates, which seem to be more able to cause disease than others.This research was supported in part by the EU Mare Nostrum (EUMN-III Call) program of the European Union, grant agreement number 2011-4050/001-EMA2. Dr Sanae Rharmitt was the recipient of a scholarship (10 months) signed within the EUMN program for PhD students (F.S. 1.04.11.01 UORI) under the supervision of Prof Orazio Romeo.info:eu-repo/semantics/publishedVersio

Glucose uptake in Kluyveromyces lactis: role of the HGT1 gene in glucose transport.

A gene for high-affinity glucose transport, HGT1, has been isolated from the lactose-assimilating yeast Kluyveromyces lactis. Disruption strains showed much-reduced uptake of glucose at low concentrations and growth was particularly affected in low-glucose medium. The HGT1 nucleotide sequence implies that it encodes a typical transmembrane protein with 12 hydrophobic domains and with 26 to 31% amino acid identity with the Hxtp family of glucose transport elements in Saccharomyces cerevisiae. Expression is constitutive (in contrast to RAG1, the major gene for low-affinity glucose uptake in K. lactis) and is controlled by several genes also known to affect expression of RAG1. These include RAG5 (which codes for the single hexokinase of K. lactis), which is required for HGT1 transcription, and RAG4, which has a negative effect. The double mutant deltahgt1deltarag1 showed further reduced glucose uptake but still grew quite well on 2% glucose and was not completely impaired even on 0.1% glucose

Mitochondrial effects of the pleiotropic proteasomal mutation mpr1/rpn11: uncoupling from cell cycle defects in extragenic revertants

We have previously characterized a Saccharomyces cerevisiae mutant which contains a mutation in the essential rpn11/mpr1 gene coding for the proteasomal regulatory subunit Rpn11. The mpr1-1 mutation shows the phenotypic characteristics generally associated with proteasomal mutations, such as cell cycle defects and accumulation of polyubiquitinated proteins. However, for the first time, mitochondrial defects have also been found to be a consequence of a mutation in a proteasomal gene (Mol. Biol. Cell 9 (1998) 2917–2931). Since the mutant strain is thermosensitive both on glucose and on glycerol, we searched for revertants in order to shed light on the Rpn11/Mpr1 functions. Spontaneous revertants able to grow on glucose but not on glycerol at 368C were isolated, and, only from them, revertants able to grow at 368C on glycerol were selected. Revertants of the two classes were found to be extragenic. The detailed characterization of these extragenic suppressors demonstrates that the phenotypes related to cell cycle defects can be dissociated from those concerned with mitochondrial organization

Identification of nuclear genes which participate to mitochondrial translation in Saccharomyces cerevisiae.

The mitochondrial protein synthesis presents specific features and uses specific components different from their cytoplasmic counterparts. Since most genes which code for these components are localized in the chromosomes and only a small number are encoded by the mitochondrial DNA, it is important to identify and characterize the nuclear genes involved in this process. In order to do this, we have used a genetic screening which implies the selection and study of nuclear suppressors of mitochondrial mutations (or the reverse situation) which affect the mitochondrial protein synthesis. Three mutations have been used for this purpose. Two of them (ts 1398, cs 909) impair the mitochondrial ribosome; they were used to characterize new interacting components as well as two genes, MBR1 and MBR2, which control the assembly or the regulation of other genes involved in mitochondrial protein synthesis. The third mutation (ts 932), blocks the 3'-end maturation of the mitochondrial aspartyl tRNA. A nuclear suppressor has been obtained which presents all the characteristics of a mutation in the gene encoding the enzyme responsible for this process