The yeast Saccharomyces cerevisiae is characterized by its ability to: (a) degrade glucose or fructose to ethanol, even in the presence of oxygen (Crabtree effect); (b) grow in the absence of oxygen; and (c) generate respiratory‐deficient mitochondrial mutants, so‐called petites. How unique are these properties among yeasts in the Saccharomyces clade, and what is their origin? Recent progress in genome sequencing has elucidated the phylogenetic relationships among yeasts in the Saccharomyces complex, providing a framework for the understanding of the evolutionary history of several modern traits. In this study, we analyzed over 40 yeasts that reflect over 150 million years of evolutionary history for their ability to ferment, grow in the absence of oxygen, and generate petites. A great majority of isolates exhibited good fermentation ability, suggesting that this trait could already be an intrinsic property of the progenitor yeast. We found that lineages that underwent the whole‐genome duplication, in general, exhibit a fermentative lifestyle, the Crabtree effect, and the ability to grow without oxygen, and can generate stable petite mutants. Some of the pre‐genome duplication lineages also exhibit some of these traits, but a majority of the tested species are petite‐negative, and show a reduced Crabtree effect and a reduced ability to grow in the absence of oxygen. It could be that the ability to accumulate ethanol in the presence of oxygen, a gradual independence from oxygen and/or the ability to generate petites were developed later in several lineages. However, these traits have been combined and developed to perfection only in the lineage that underwent the whole‐genome duplication and led to the modern Saccharomyces cerevisiae yeast.

RNase P from the mitochondria of Saccharomyces cerevisiae was purified to near homogeneity > 1800-fold with a yield of 1.6% from mitochondrial extracts. The most abundant protein in the purified fractions is, at 105 kDa, considerably larger than the 14-kDa bacterial RNase P protein subunits. Oligonucleotides designed from the amino-terminal sequence of the 105-kDa protein were used to identify and isolate the 105-kDa protein-encoding gene. Strains carrying a disruption of the gene for the 105-kDa protein are viable but respiratory deficient and accumulate mitochondrial tRNA precursors with 5' extensions. As this is the second gene known to be necessary for yeast mitochondrial RNase P activity, we have named it RPM2 (for RNase P mitochondrial).

A number of mutants with pleiotropic effects on mitochondrial metabolism have been isolated in yeast Saccharomyces cerevisiae, and for many the biochemical function that is impaired is not yet known. We report here the isolation and characterization of the LIP5 gene involved in lipoic acid metabolism which complements the g189 mutant (Tzagoloff, A., and Dieckmann, C. L. (1990) Microbiol. Rev. 54, 211-225). DNA sequence analysis of complementing yeast genomic DNA revealed an open reading frame predicting a protein of 414 amino acids. The protein sequence deduced from the gene shares 43% identical residues with the product of the Escherichia coli lip gene, which codes an enzyme involved in lipoic acid synthesis. The LIP5 mutant is not capable of synthesizing lipoic acid but still possesses the activity necessary for attachment of lipoic acid to protein. Relative to the E. coli lip gene product, the LIP5 protein has an amino-terminal extension with characteristics of mitochondrial targeting signals. Cells carrying a disrupted copy of the LIP5 gene show slow growth on ethanol-rich media and barely detectable growth on glycerol-rich media. Unlike other strains with defects in the tricarboxylic acid cycle, LIP5 mutants undergo a high frequency of mitochondrial DNA deletions.

Background: The aim of this work was to find a reliable nested PCR for the detection ofHelicobacter pyloriin biopsy, stool, and saliva specimens.Materials and Methods: Novel nested PCR was elaborated and validated on 81 clinical biopsy, stool, and saliva samples from the same individual and compared to availableH pyloriassays: histology, rapid urease test (RUT), stool antigen test (SAT),¹³C‐urea breath test (UBT).Results: The efficiency and selectivity of 17 published nested polymerase chain reactions (PCR) available forHelicobacter pyloridetection were re‐evaluated. Most of them had serious limitations and mistakes in primer design. Hence, we elaborated a nested PCR for the unambiguous identification ofH pyloriin biopsy, stool, and saliva, using primers targeted to variable regions of the 16S ribosomal RNA (rRNA) gene. Moreover, we determined the detection limit by adding a known number of cells. This number was as low as 0.5 cells in a PCR vial, but due to the DNA isolation procedures, it required 1‐5 × 10³cells/g or ml of specimen. The sensitivity for nested PCR from stomach biopsies was on the same scale as¹³C‐UBT (93.8%), but it was much lower in amplifications from stool (31.3%). Sequencing of all obtained PCR products exclusively confirmedH pylori‐specific DNA sequences.Conclusions: Elaborated nested PCR assay can serve as an auxiliary method for controversial samples (patients with bleeding or taking proton‐pump inhibitor) in laboratories with basic equipment. The sensitivity and specificity for the amplification from gastric biopsies was almost like¹³C‐UBT. Despite the good sensitivity, the threshold occurrence and the ability to survive in the oral cavity aside from and independent of the stomach is the reason whyH pyloriDNA cannot be reliably detected in saliva, stool, and some biopsy samples.

The yeast Saccharomyces are widely used to test ecological and evolutionary hypotheses. A large number of nuclear genomic DNA sequences are available, but mitochondrial genomic data are insufficient. We completed mitochondrial DNA (mtDNA) sequencing from Illumina MiSeq reads for all Saccharomyces species. All are circularly mapped molecules decreasing in size with phylogenetic distance from Saccharomyces cerevisiae but with similar gene content including regulatory and selfish elements like origins of replication, introns, free-standing open reading frames or GC clusters. Their most profound feature is species-specific alteration in gene order. The genetic code slightly differs from well-established yeast mitochondrial code as GUG is used rarely as the translation start and CGA and CGC code for arginine. The multilocus phylogeny, inferred from mtDNA, does not correlate with the trees derived from nuclear genes. mtDNA data demonstrate that Saccharomyces cariocanus should be assigned as a separate species and Saccharomyces bayanus CBS 380^T should not be considered as a distinct species due to mtDNA nearly identical to Saccharomyces uvarum mtDNA. Apparently, comparison of mtDNAs should not be neglected in genomic studies as it is an important tool to understand the origin and evolutionary history of some yeast species.