Heterotrimeric G-protein subunit function in Candida albicans: both the alpha and beta subunits of the pheromone response G protein are required for mating.

A pheromone-mediated signaling pathway that couples seven-transmembrane-domain (7-TMD) receptors to a mitogen-activated protein kinase module controls Candida albicans mating. 7-TMD receptors are typically connected to heterotrimeric G proteins whose activation regulates downstream effectors. Two Galpha subunits in C.

Comparative phylogenetic analysis of microbial communities in pristine and hydrocarbon-contaminated Alpine soils.

A molecular characterization of pristine and petroleum hydrocarbon-contaminated Alpine soils sampled in Tyrol (Austria) was performed. To identify predominant bacteria, PCR-amplified 16S rRNA gene fragments from five pristine and nine contaminated soils were analysed using denaturing gradient gel electrophoresis (DGGE). Sequencing and phylogenetic analyses demonstrated that the majority of the DGGE bands represented bacteria in the Actinobacteria and Proteobacteria phyla: 18 and 73%, respectively, in pristine soils, compared with 20 and 76%, respectively, in contaminated soils.

Identification and characterization of MFA1, the gene encoding Candida albicans a-factor pheromone.

In the opaque state, MTLa and MTLalpha strains of Candida albicans are able to mate, and this mating is directed by a pheromone-mediated signaling process. We have used comparisons of genome sequences to identify a C. albicans gene encoding a candidate a-specific mating factor.

Stress-induced gene expression in Candida albicans: absence of a general stress response.

We used transcriptional profiling to investigate the response of the fungal pathogen Candida albicans to temperature and osmotic and oxidative stresses under conditions that permitted >60% survival of the challenged cells. Each stress generated the transient induction of a specific set of genes including classic markers observed in the stress responses of other organisms. We noted that the classical hallmarks of the general stress response observed in Saccharomyces cerevisiae are absent from C.

Identification and phylogenetic analysis of a glucose transporter gene family from the human pathogenic yeast Candida albicans.

We have identified a large family of glucose transporter genes (HGT1 to HGT20) from the human pathogenic yeast Candida albicans by screening of genomic sequences, reverse-transcription PCR assays, and phylogenetic analyses. The putative glucose transporter ORF sequences share among themselves 10-93% pairwise sequence identity and, in comparative analyses of predicted amino acid sequences, exhibit similarities to human and yeast transporters of the major facilitator superfamily (MFS): the predicted 12-transmembrane domains and sugar transporter signatures align closely to those of HXT transporters of Saccharomyces cerevisiae and GLUT transporters of humans, with amino acid residues at certain positions highly conserved throughout the families. Reverse-transcription PCR analyses demonstrated that the majority of the glucose transporters was transcribed in culture medium containing 2% glucose, while several were transcribed in the presence of low (0.

Physiological adaptations involved in alkane assimilation at a low temperature by Rhodococcus sp. strain Q15.

We examined physiological adaptations which allow the psychrotroph Rhodococcus sp. strain Q15 to assimilate alkanes at a low temperature (alkanes are contaminants which are generally insoluble and/or solid at low temperatures). During growth at 5 degrees C on hexadecane or diesel fuel, strain Q15 produced a cell surface-associated biosurfactant(s) and, compared to glucose-acetate-grown cells, exhibited increased cell surface hydrophobicity.

Biodegradation of variable-chain-length alkanes at low temperatures by a psychrotrophic Rhodococcus sp.

The psychorotrophic Rhodococcus sp. strain Q15 was examined for its ability to degrade individual n-alkanes and diesel fuel at low temperatures, and its alkane catabolic pathway was investigated by biochemical and genetic techniques. At 0 and 5 degrees C, Q15 mineralized the short-chain alkanes dodecane and hexadecane to a greater extent than that observed for the long-chain alkanes octacosane and dotriacontane.

Biodegradation of petroleum hydrocarbons by psychrotrophic Pseudomonas strains possessing both alkane (alk) and naphthalene (nah) catabolic pathways.

Three hydrocarbon-degrading psychrotrophic bacteria were isolated from petroleum-contaminated Arctic soils and characterized. Two of the strains, identified as Pseudomonas spp., degraded C5 to C12 n-alkanes, toluene, and naphthalene at both 5 and 25 degrees C and possessed both the alk catabolic pathway for alkane biodegradation and the nah catabolic pathway for polynuclear aromatic hydrocarbon biodegradation.

Pheromone signalling and polarized morphogenesis in yeast.

Yeast cells respond to mating pheromones by activating a signal transduction pathway involving a seven transmembrane receptor/G protein complex linked to a mitogen-activated protein kinase module. Regulation of the G protein signal is controlled by the receptor and Sst2p; Sst2p may function as a GTPase-activating protein for the G protein alpha subunit. The Ste20 kinase acts in the linkage between the G protein and the MAP kinase module.

Cloning and characterization of the SKI3 gene of Saccharomyces cerevisiae demonstrates allelism to SKI5.

We have identified a mutant strain of the yeast Saccharomyces cerevisiae which overproduces killer toxin. This strain contains a single mutation which fails to complement defects in both the SKI3 and SKI5 genes, while a cloned copy of this gene complements both the ski3 and ski5 defects. The level of secreted toxin from a cDNA based plasmid is not increased in a ski3 strain, showing that the overproduction phenotype is dependent upon an increased level of M1 dsRNA.

The STE4 and STE18 genes of yeast encode potential beta and gamma subunits of the mating factor receptor-coupled G protein.

The STE4 and STE18 genes are required for haploid yeast cell mating. Sequencing of the cloned genes revealed that the STE4 polypeptide shows extensive homology to the beta subunits of mammalian G proteins, while the STE18 polypeptide shows weak similarity to the gamma subunit of transducin. Null mutations in either gene can suppress the haploid-specific cell-cycle arrest caused by mutations in the SCG1 gene (previously shown to encode a protein with similarity to the alpha subunit of G proteins).

Expression of MF alpha 1 in MATa cells supersensitive to alpha-factor leads to self-arrest.

MATa cells of Saccharomyces cerevisiae defective in both the SST1 and SST2 gene products exhibit self-arrest when they express the MF alpha 1 gene under the control of the GAL1 promoter. This response to endogenously produced pheromone can be alleviated by mutations which prevent the production of, or response to, alpha-factor. Suppressors of the self-arrest phenotype include a class of mutants which remain responsive to low levels of pheromone, but are resistant to high levels of alpha-factor.