Molecular cloning and sequence analysis of the Zygosaccharomyces rouxiiLEU2 gene encoding a beta-isopropylmalate dehydrogenase

Transcriptome profiling in response to Kanamycin B reveals its wider non-antibiotic cellular function in Escherichia coli

Aminoglycosides are not only antibiotics but also have wider and diverse non-antibiotic cellular functions. To elucidate the understanding of non-antibiotic cellular functions, here we report transcriptome-profiling analysis of Escherichia coli in the absence or presence of 0.5 and 1 μM of Kanamycin B, concentrations that are neither lethal nor inhibit growth, and identified the differentially expressed genes (DEGs) at two given concentrations of Kanamycin B. Functional classification of the DEGs revealed that they were mainly related to microbial metabolism including two-component systems, biofilm formation, oxidative phosphorylation and nitrogen metabolism in diverse environments. We further showed that Kanamycin B and other aminoglycosides can induce reporter gene expression through the 5′ UTR of napF gene or narK gene (both identified as DEG) and Kanamycin B can directly bind to the RNA. The results provide new insights into a better understanding of the wider aminoglycosides cellular function in E. coli rather than its known antibiotics function.

Osmoresistant yeastZygosaccharomyces rouxii: the two most studied wild-type strains (ATCC 2623 and ATCC 42981) differ in osmotolerance and glycerol metabolism

The yeast Zygosaccharomyces rouxii is known for its high tolerance to osmotic stress, which is thought to be caused by sets of specific genes. Relatively few Z. rouxii genes have been identified so far, all of them having homologues in Saccharomyces cerevisiae; none of them was Z. rouxii-specific. Most of the known Z. rouxii genes were isolated from two wild-type strains, ATCC 2623 and ATCC 42981. In this study, we compared these two strains with regard to some of their morphological, physiological and genomic properties. Important differences were found in their salt tolerance and assimilation of glycerol and karyotype; slight differences were also present in their cell morphology. The ATCC 42981 strain showed a higher resistance to salts, higher glycerol production and, unlike ATCC 2623, was able to assimilate glycerol. Under conditions of osmotic stress, the glycerol production in both Z. rouxii strains was much lower than in a S. cerevisiae S288c culture, which suggested the presence of a system that efficiently retains glycerol inside Z. rouxii cells. The karyotype analysis revealed that ATCC 42981 cells contain more chromosomes and have a bigger genome size than those of ATCC 2623.

Cloning, sequencing and application of the LEU2 gene from the sour dough yeast Candida milleri

We have cloned by complementation in Saccharomyces cerevisiae and sequenced a LEU2 gene from the sour dough yeast Candida milleri CBS 8195 and studied its chromosomal location. The LEU2 coding sequence was 1092 nt long encoding a putative beta-isopropylmalate dehydrogenase protein of 363 amino acids. The nucleotide sequence in the coding region had 71.6% identity to S. cerevisiae LEU2 sequence. On the protein level, the identity of C. milleri Leu2p to S. cerevisiae Leu2p was 84.1%. The CmLEU2 DNA probe hybridized to one to three chromosomal bands and two or three BamHI restriction fragments in C. milleri but did not give any signal to chromosomes or restriction fragments of C. albicans, S. cerevisiae, S. exiguus or Torulaspora delbrueckii. Using CmLEU2 probe for DNA hybridization makes it easy to quickly identify C. milleri among other sour dough yeasts.

Efficient transformation of the osmotolerant yeast Zygosaccharomyces rouxii by electroporation

A rapid and simple electroporation method to transform osmotolerant yeast Zygosaccharomyces rouxii has been developed and conditions for efficient transformation of mutants derived from different Z. rouxii wild-type strains optimized.

The ALEU2 gene--a new component for an Arxula adeninivorans-based expression platform

The ALEU2 gene, encoding beta-isopropylmalate dehydrogenase, was isolated from the non-conventional yeast Arxula adeninivorans. The isolated gene harbours an open reading frame of 1086 bp, encoding a putative protein of 362 amino acids. The derived protein sequence shares a high degree of homology with other fungal beta-isopropylmalate dehydrogenases thus confirming the identity of the gene. The isolated ALEU2 gene was tested for its suitability to complement the auxotrophy of an A. adeninivorans aleu2 host. For this purpose the plasmid pAL-ALEU2m which contains the ALEU2 gene as a selection marker and the 25S rDNA for targeting was employed in transformation experiments. Transformants harboured a single copy of the heterologous DNA and were found to be mitotically stable. For assessment of heterologous gene expression, two model genes were incorporated into the vector: the GFP gene, encoding intracellular green fluorescent protein, and the HSA gene, encoding the secreted human serum albumin. For expression control, both gene sequences were fused to the constitutive A. adeninivorans-derived TEF1 promoter and the Saccharomyces cerevisiae-derived PHO5 terminator. In the respective recombinant strains the GFP was localised in the cytoplasm, whereas more than 95% of the HSA accumulated in the culture medium. In initial fermentation trials using a 200-ml shake flask, maximal HSA product levels were observed after 96 h of cultivation.