Allium sativum Extract Chemical Composition, Antioxidant Activity and Antifungal Effect against Meyerozyma guilliermondii and Rhodotorula mucilaginosa Causing Onychomycosis

Onychomycosis is a major health problem due to its chronicity and resistance to therapy. Because some cases associate paronychia, any therapy must target the fungus and the inflammation. Medicinal plants represent an alternative for onychomycosis control. In the present work the antifungal and antioxidant activities of Alium sativum extract against Meyerozyma guilliermondii (Wick.) Kurtzman & M. Suzuki and Rhodotorula mucilaginosa (A. Jörg.) F.C. Harrison, isolated for the first time from a toenail onychomycosis case, were investigated. The fungal species were confirmed by DNA molecular analysis. A. sativum minimum inhibitory concentration (MIC) and ultrastructural effects were examined. At the MIC concentration (120 mg/mL) the micrographs indicated severe structural alterations with cell death. The antioxidant properties of the A. sativum extract were evaluated is a rat turpentine oil induced inflammation, and compared to an anti-inflammatory drug, diclofenac, and the main compound from the extract, allicin. A. sativum reduced serum total oxidative status, malondialdehyde and nitric oxide production, and increased total thiols. The effects were comparable to those of allicin and diclofenac. In conclusion, the garlic extract had antifungal effects against M. guilliermondii and R. mucilaginosa, and antioxidant effect in turpentine-induced inflammation. Together, the antifungal and antioxidant activities support that A. sativum is a potential alternative treatment in onychomycosis.

The half-bridge component Kar1 promotes centrosome separation and duplication during budding yeast meiosis

The budding yeast centrosome, often called the spindle pole body (SPB), nucleates microtubules for chromosome segregation during cell division. An appendage, called the half bridge, attaches to one side of the SPB and regulates SPB duplication and separation. Like DNA, the SPB is duplicated only once per cell cycle. During meiosis, however, after one round of DNA replication, two rounds of SPB duplication and separation are coupled with homologue segregation in meiosis I and sister-chromatid segregation in meiosis II. How SPB duplication and separation are regulated during meiosis remains to be elucidated, and whether regulation in meiosis differs from that in mitosis is unclear. Here we show that overproduction of the half-bridge component Kar1 leads to premature SPB separation during meiosis. Furthermore, excessive Kar1 induces SPB overduplication to form supernumerary SPBs, leading to chromosome missegregation and erroneous ascospore formation. Kar1--mediated SPB duplication bypasses the requirement of dephosphorylation of Sfi1, another half-bridge component previously identified as a licensing factor. Our results therefore reveal an unexpected role of Kar1 in licensing meiotic SPB duplication and suggest a unique mechanism of SPB regulation during budding yeast meiosis.

Characterization of Septin Ultrastructure in Budding Yeast Using Electron Tomography

Septins are essential for the completion of cytokinesis. In budding yeast, Saccharomyces cerevisiae, septins are located at the bud neck during mitosis and are closely connected to the inner plasma membrane. In vitro, yeast septins have been shown to self-assemble into a variety of filamentous structures, including rods, paired filaments, bundles, and rings (Bertin et al. Proc Natl Acad Sci U S A, 105(24):8274-8279, 2008; Garcia et al. J Cell Biol, 195(6):993-1004, 2011; Bertin et al. J Mol Biol, 404(4):711-731, 2010). Using electron tomography of freeze-substituted sections and cryo-electron tomography of frozen sections, we determined the three-dimensional organization of the septin cytoskeleton in dividing budding yeast with molecular resolution (Bertin et al. Mol Biol Cell, 23(3):423-432, 2012; Bertin and Nogales. Commun Integr Biol 5(5):503-505, 2012). Here, we describe the detailed procedures used for our characterization of the septin cellular ultrastructure.

The centrosome and its duplication cycle

The centrosome was discovered in the late 19th century when mitosis was first described. Long recognized as a key organelle of the spindle pole, its core component, the centriole, was realized more than 50 or so years later also to comprise the basal body of the cilium. Here, we chart the more recent acquisition of a molecular understanding of centrosome structure and function. The strategies for gaining such knowledge were quickly developed in the yeasts to decipher the structure and function of their distinctive spindle pole bodies. Only within the past decade have studies with model eukaryotes and cultured cells brought a similar degree of sophistication to our understanding of the centrosome duplication cycle and the multiple roles of this organelle and its component parts in cell division and signaling. Now as we begin to understand these functions in the context of development, the way is being opened up for studies of the roles of centrosomes in human disease.

Biophysical characterization of the centromere-specific nucleosome from budding yeast

The centromeric DNA of all eukaryotes is assembled upon a specialized nucleosome containing a histone H3 variant known as CenH3. Despite the importance and conserved nature of this protein, the characteristics of the centromeric nucleosome are still poorly understood. In particular, the stoichiometry and DNA-binding properties of the CenH3 nucleosome have been the subject of some debate. We have characterized the budding yeast centromeric nucleosome by biochemical and biophysical methods and show that it forms a stable octamer containing two copies of the Cse4 protein and wraps DNA in a left-handed supercoil, similar to the canonical H3 nucleosome. The DNA-binding properties of the recombinant nucleosome are identical to those observed in vivo demonstrating that the octameric structure is physiologically relevant.

Pyrenochaeta keratinophila sp. nov., isolated from an ocular infection in Spain

The new coelomycete Pyrenochaeta keratinophila, isolated from corneal scrapings of a case of keratitis in Spain, is described and illustrated. This fungus is morphologically characterized by grey-olivaceous to greenish olivaceous colonies, scarce pycnidial setae placed mainly near the ostiole and production of phialoconidia from the aerial mycelium. The latter feature is unknown in any other species of the genus Pyrenochaeta. Sequencing of the ITS rDNA region of this clinical strain confirmed this proposal and revealed its close genetic relationship with the Leptosphaeriaceae.

Lab-on-Chip for fast 3D particle tracking in living cells

We present a novel Lab-on-Chip technology for 3D particle tracking in living cells based on V-shaped micro-mirrors, which are used to observe fluorescent specimens from multiple vantage points, providing simultaneous stereo-images that can be recombined for 3D reconstruction. Our technology can be readily used with standard fluorescence microscopes, and we apply it to study chromatin dynamics using yeast strains with one or two GFP-tagged gene loci. Using an Andor EMCCD camera, loci are followed in 3D with inter-frame intervals of up to 10 ms and with an error of 27 nm per axis, yielding quantitative information on their dynamics with exquisite temporal spatial resolution.

Easily fabricated magnetic traps for single-cell applications

We describe a simple and inexpensive method of fabricating single cell magnetic traps within a polydimethylsiloxane (PDMS) device. These traps were developed as part of an automated system that captures individual yeast cells in a microfluidic device and analyzes each cell as it buds. To make the traps, PdCl(2) catalyst is rubbed with vinyl foam onto plasma-patterned PDMS, and then Co-Ni-B alloy is electrolessly deposited onto the catalyst at a moderate temperature. We demonstrate individual yeast cell capture and estimate the capture force (1.9-4.4 pN) by measuring the flow speed required to remove the cell from its trap in a microfluidic channel.

Isolation of Issatchenkia occidentalis from the esophagus of a leukemic patient

Issatchenkia occidentalis was isolated from an esophageal biopsy of a young leukemic male patient who underwent bone marrow transplantation. At the time the specimen was collected, the patient was also suffering from esophageal herpetic lesions. The identification of the isolate was not possible by the use of the available commercial methods. Thus, its identification was done by PCR and DNA sequencing using panfungal primers.

The release of elongated, sheathed ascospores from bottle-shaped asci inDipodascus geniculatus

Yeasts use different mechanisms to release ascospores of different lengths from bottle-shaped asci. Round to oval-shaped ascospores are enveloped in oxylipin-coated compressible sheaths, enabling ascospores to slide past each other when they reach the narrowing ascus neck. However, more elongated ascospores do not contain sheaths, but are linked by means of oxylipin-coated interlocked hooked ridges on the surfaces of neighboring ascospores, thereby keeping them aligned while they are pushed towards the ascus tip by turgor pressure. In this study, we found elongated, oxylipin-coated sheathed ascospores in Dipodascus geniculatus that are released effectively from bottle-shaped asci without alignment. This is possible because the ascus neck and opening have a diameter that is the same as the length of the ascospore, thus allowing the ascospores to turn sideways without blocking the ascus when they are released. We found that increased concentrations of acetylsalicylic acid inhibit both ascospore release and 3-hydroxy oxylipin production in this yeast, thereby implicating this oxylipin in sexual reproduction.

Negative regulation of yeast Eps15-like Arp2/3 complex activator, Pan1p, by the Hip1R-related protein, Sla2p, during endocytosis

Control of actin assembly nucleated by the Arp2/3 complex plays a crucial role during budding yeast endocytosis. The yeast Eps15-related Arp2/3 complex activator, Pan1p, is essential for endocytic internalization and proper actin organization. Pan1p activity is negatively regulated by Prk1 kinase phosphorylation after endocytic internalization. Phosphorylated Pan1p is probably then dephosphorylated in the cytosol. Pan1p is recruited to endocytic sites approximately 25 s before initiation of actin polymerization, suggesting that its Arp2/3 complex activation activity is kept inactive during early stages of endocytosis by a yet-to-be-identified mechanism. However, how Pan1p is maintained in an inactive state is not clear. Using tandem affinity purification-tagged Pan1p, we identified End3p as a stoichiometric component of the Pan1p complex, and Sla2p, a yeast Hip1R-related protein, as a novel binding partner of Pan1p. Interestingly, Sla2p specifically inhibited Pan1p Arp2/3 complex activation activity in vitro. The coiled-coil region of Sla2p was important for Pan1p inhibition, and a pan1 partial loss-of-function mutant suppressed the temperature sensitivity, endocytic phenotypes, and actin phenotypes observed in sla2DeltaCC mutant cells that lack the coiled-coil region. Overall, our results establish that Sla2p's regulation of Pan1p plays an important role in controlling Pan1p-stimulated actin polymerization during endocytosis.

Acetylsalicylic acid as antifungal in Eremothecium and other yeasts

Interesting distribution patterns of acetylsalicylic acid (ASA, aspirin) sensitive 3-hydroxy (OH) oxylipins were previously reported in some representatives of the yeast genus Eremothecium--an important group of plant pathogens. Using immunofluorescence microscopy and 3-OH oxylipin specific antibodies in this study, we were able to map the presence of these compounds also in other Eremothecium species. In Eremothecium cymbalariae, these oxylipins were found to cover mostly the spiky tips of narrowly triangular ascospores while in Eremothecium gossypii, oxylipins covered the whole spindle-shaped ascospore with terminal appendages. The presence of these oxylipins was confirmed by chemical analysis. When ASA, a 3-OH oxylipin inhibitor, was added to these yeasts in increasing concentrations, the sexual stage was found to be the most sensitive. Our results suggest that 3-OH oxylipins, produced by mitochondria through incomplete beta-oxidation, are associated with the development of the sexual stages in both yeasts. Strikingly, preliminary studies on yeast growth suggest that yeasts, characterized by mainly an aerobic respiration rather than a fermentative pathway, are more sensitive to ASA than yeasts characterized by both pathways. These data further support the role of mitochondria in sexual as well as asexual reproduction of yeasts and its role to serve as a target for ASA antifungal action.

Two new species of Kazachstania that form ascospores connected by a belt-like intersporal body: Kazachstania zonata and Kazachstania gamospora

Four strains of ascomycetous yeasts were isolated from samples collected at two locations in southern Japan. The strains formed two warty ascospores that were joined together by an intersporal body appearing as a belt. Phylogenetic analysis of rRNA gene nucleotide sequences indicated that the strains represented two new and closely related species of the genus Kazachstania. Isolates of one of the species were from Miyazaki Prefecture and those of the other species were from the Iriomote Islands. Genetic separation of the two species was further confirmed by DNA-DNA reassociation, which gave values of 63.3-78.1%, and from interspecific crosses, which gave nonviable ascospores. On the basis of these data, the isolates from Miyazaki Prefecture are described as Kazachstania zonata sp. nov. [type strain NBRC 100504=CBS 10326, mating types NBRC 101821 (+), NBRC 101822 (-)], and the isolates from the Iriomote Islands are described as Kazachstania gamospora sp. nov. [type strain NBRC 11056=CBS 10328, mating types NBRC 101825 (+), NBRC 101826 (-)].

Mapping the distribution of 3-hydroxy oxylipins in the ascomycetous yeast Saturnispora saitoi

The distribution of 3-hydroxy oxylipins in Saturnispora saitoi was mapped using immunofluorescence microscopy. Fluorescence was observed on aggregating ascospores, indicating the presence of 3-hydroxy oxylipins on the surface or between ascospores. The oxylipin was identified as 3-hydroxy 9:1 using gas chromatography mass spectrometry. Furthermore, ultrastructural studies using scanning and transmission electron microscopy on ascospores revealed a clear equatorial ledge surrounding oval-shaped ascospores.

Exit from mitosis triggers Chs2p transport from the endoplasmic reticulum to mother-daughter neck via the secretory pathway in budding yeast

Budding yeast chitin synthase 2 (Chs2p), which lays down the primary septum, localizes to the mother–daughter neck in telophase. However, the mechanism underlying the timely neck localization of Chs2p is not known. Recently, it was found that a component of the exocyst complex, Sec3p–green fluorescent protein, arrives at the neck upon mitotic exit. It is not clear whether the neck localization of Chs2p, which is a cargo of the exocyst complex, was similarly regulated by mitotic exit. We report that Chs2p was restrained in the endoplasmic reticulum (ER) during metaphase. Furthermore, mitotic exit was sufficient to cause Chs2p neck localization specifically by triggering the Sec12p-dependent transport of Chs2p out of the ER. Chs2p was “forced” prematurely to the neck by mitotic kinase inactivation at metaphase, with chitin deposition occurring between mother and daughter cells. The dependence of Chs2p exit from the ER followed by its transport to the neck upon mitotic exit ensures that septum formation occurs only after the completion of mitotic events.

Oxylipin covered ascospores of Eremothecium coryli

Eremothecium coryli is known to produce intriguing spindle-shaped ascospores with long and thin whip-like appendages. Here, ultra structural studies using scanning electron microscopy, indicate that these appendages serve to coil around themselves and around ascospores causing spore aggregation. Furthermore, using immunofluorescence confocal laser scanning microscopy it was found that hydrophobic 3-hydroxy oxylipins cover the surfaces of these ascospores. Using gas chromatography-mass spectrometry, only the oxylipin 3-hydroxy 9:1 (a monounsaturated fatty acid containing a hydroxyl group on carbon 3) could be identified. Sequential digital imaging suggests that oxylipin-coated spindle-shaped ascospores are released from enclosed asci probably by protruding through an already disintegrating ascus wall.

Ascospore release from bottle-shaped asci in

Yeasts utilize different mechanisms to release ascospores of different lengths from bottle-shaped asci. Using electron microscopy, confocal laser scanning microscopy, gas chromatography-mass spectrometry and digital live imaging, the individual release of oval ascospores from tight-fitting narrow bottle-necks, is reported in the yeast Dipodascus albidus. These ascospores are surrounded by compressible, oxylipin-coated sheaths enabling ascospores to slide past each other when forced by turgor pressure and by possible sheath contractions towards the narrowing ascus-neck. In this paper, the release mechanisms of ascospores of various lengths from bottle-shaped asci and produced by different yeasts are compared. We suggest that different release mechanisms, utilizing compressible sheaths or geared-alignment, have possibly evolved to compensate for variation in ascospore length. Alternatively, sheaths and ridges might be two evolutionary solutions to the same biomechanical problem, i.e. to release ascospores irrespective of length from bottle-shaped asci.

Uncovering the first double brimmed hat-shaped ascospores in Ambrosiozyma platypodis Van der Walt

Using transmission electron microscopy with glutaraldehyde and osmium tetroxide as chemical fixatives, hat-shaped ascospores with two brims each were uncovered in the yeast Ambrosiozyma platypodis. This is the first report on such structures.

Actin and septin ultrastructures at the budding yeast cell cortex

Budding yeast has been a powerful model organism for studies of the roles of actin in endocytosis and septins in cell division and in signaling. However, the depth of mechanistic understanding that can be obtained from such studies has been severely hindered by a lack of ultrastructural information about how actin and septins are organized at the cell cortex. To address this problem, we developed rapid-freeze and deep-etch techniques to image the yeast cell cortex in spheroplasted cells at high resolution. The cortical actin cytoskeleton assembles into conical or mound-like structures composed of short, cross-linked filaments. The Arp2/3 complex localizes near the apex of these structures, suggesting that actin patch assembly may be initiated from the apex. Mutants in cortical actin patch components with defined defects in endocytosis disrupted different stages of cortical actin patch assembly. Based on these results, we propose a model for actin function during endocytosis. In addition to actin structures, we found that septin-containing filaments assemble into two kinds of higher order structures at the cell cortex: rings and ordered gauzes. These images provide the first high-resolution views of septin organization in cells.

CLIP-170 family members: a motor-driven ride to microtubule plus ends

CLIP-170 family proteins regulate microtubule plus end dynamics. Two reports published in this issue of Developmental Cell show that Bik1 and tip1p, the CLIP-170-like proteins of budding and fission yeast, are carried to microtubule plus ends by kinesin motor proteins. These findings indicate a complex interplay between microtubule-associated proteins and suggest a novel mechanism by which kinesin proteins stabilize microtubules.

Variation in functional ascospore parts in the ascomycetous yeast Dipodascopsis uninucleata

A variation in functional ascospore morphology was detected using electron microscopy (EM) in two varieties of the yeast Dipodascopsis uninucleata, i.e., D. uninucleata var. uninucleata and D. uninucleata var. wickerhamii. It was found that the latter produces ascospores characterized by the absence of small surface hooks which have been implicated in the release and re-assembly of ascospores in D. uninucleata var. uninucleata. These varieties are closely related on the basis of their mode of sexual reproduction, ascospore morphology as observed under the light microscope, physiological characteristics as well as the extent of divergence in the variable D1/D2 domain of the large subunit 26S ribosomal DNA.

Metschnikowia bicuspidata and Enterococcus faecium co-infection in the giant freshwater prawn Macrobrachium rosenbergii

In May 2001, an epizootic yeast and bacterial co-infection in the giant freshwater prawn Macrobrachium rosenbergii occurred in Taiwan causing a cumulative mortality of 25%. The diseased prawns had a yellowish-brown body color, milky hemolymph, opaque, whitish muscles, and were approximately 7 mo old with total lengths ranging from 8 to 10 cm. Histopathological examination showed marked edema, yeast infiltration, and necrotic lesions with inflammation in the muscles, hepatopancreas and other internal organs. We isolated 2 pathogens from the diseased prawns, one was a yeast (AOD081MB) and the other a gram-positive coccus (AOD081EF). The gram-positive coccus was identified as Enterococcus faecium by the API 20 Strepsystem, conventional biochemical tests, and it had 99% 16S rDNA sequence identity (GenBank Accession Number AJ276355) to E. faecium (GenBank Accession Number AF529204). The sequence of a PCR product from the D1/D2 domain of 26S rDNA (GenBank Accession Number AF529297) from the yeast gave 99% sequence identity to Metschnikowia bicuspidata (GenBank Accession Number U44822). Experimental infections with these isolates produced gross signs and histopathological changes similar to those observed in the naturally infected prawns. The lethal doses (LD50) for isolate E. faecium AOD081EF, M. bicuspidata AOD081MB and the co-infection were 4.7 x 10(4), 2.6 x 10(2), and 2.4 x 10(2) colony-forming units prawn(-1), respectively. This is the first report of a confirmed co-infection of M. bicuspidata and E. faecium in prawn aquaculture.

Oxylipins and ascospore morphology in the ascomycetous yeast genus Dipodascus

Immunofluorescence microscopy was used to assess members of the yeast genus Dipodascus for the presence of 3-hydroxy oxylipins. Fluorescence was associated with the aggregating ascospores in all species tested, thus suggesting the association of 3-hydroxy oxylipins with these cells, especially the surrounding slime sheaths. An ultrastructural study of the ascospores revealed sheaths with indentations, probably caused by the close packing of the ascospores to form clusters. In addition, an increase in the neutral and glycolipid fractions as well as a decrease in the phospholipid fraction during ascosporogenesis in D. ambrosiae was found.

Role for lipid signaling and the cell integrity MAP kinase cascade in yeast septum biogenesis

Polarized deposition of chitin at the bud neck is essential for cell separation in yeast. Chitin septum biogenesis is catalyzed by two distinct chitin synthase activities encoded by the CHS2 and CHS3 genes. The phosphoinositide phosphatase Sac1p is required for proper trafficking of the Chs3p chitin synthase. sac1 mutants also display a severe synthetic growth defect, with mutations in the SLT2 gene which encodes a MAP kinase involved in cell integrity. We characterized the defect that underlies this genetic interaction and found that sac1 Delta slt2 Delta cells arrest as large-budded cells because they fail to separate at the end of mitosis. This inability to complete cell division appears to be caused by an increased deposition of chitin at the septum area and correlates with a mislocalized accumulation of the Chs2p chitin synthase at the cell periphery. Our data therefore indicate that Sac1p and Slt2p have synergistic roles in regulating chitin septum biogenesis.

Ascospores of large-spored Metschnikowia species are genuine meiotic products of these yeasts

The asci of Metschnikowia species normally contain two ascospores (never more), raising the question of whether these spores are true meiotic products. We investigated this problem by crossing genetically-marked strains of the haploid, heterothallic taxa Metschnikowia hawaiiensis, Metschnikowia continentalis var. continentalis, and M. continentalis var. borealis. Asci were dissected and the segregation patterns for various phenotypes analyzed. In all cases (n = 47) both mating types (h+ and h-) were recovered in pairs of sister spores, casting further uncertainty as to whether normal meiosis takes place. However, the segregation patterns for cycloheximide resistance and several auxotrophic markers were random, suggesting that normal meiosis indeed occurs. To explain the lack of second-division segregation of mating types, we concluded that crossing-over does not occur between the mating-type locus and the centromere, and that meiosis I is tied to spore formation, which explains why the number of spores is limited to two. The latter assumption was also supported by fluorescence microscopy. The second meiotic division takes place inside the spores and is followed by the resorption of two nuclei, one in each spore.

Centromeres and kinetochores: from epigenetics to mitotic checkpoint signaling

The centromere is a chromosomal locus that ensures delivery of one copy of each chromosome to each daughter at cell division. Efforts to understand the nature and specification of the centromere have demonstrated that this central element for ensuring inheritance is itself epigenetically determined. The kinetochore, the protein complex assembled at each centromere, serves as the attachment site for spindle microtubules and the site at which motors generate forces to power chromosome movement. Unattached kinetochores are also the signal generators for the mitotic checkpoint, which arrests mitosis until all kinetochores have correctly attached to spindle microtubules, thereby representing the major cell cycle control mechanism protecting against loss of a chromosome (aneuploidy).

Considering nuclear compartmentalization in the light of nuclear dynamics

Many proteins are concentrated in compartments within the nucleus. Chromatin is also compartmentalized at different nuclear sites. However, nuclear proteins have now been shown to be highly mobile. This review considers the formation and function of nuclear compartments in a situation in which proteins are rapidly moving through the nuclear volume.

Effects of low electric treatment on yeast microflora

AIMS

To contribute to the understanding of phenomena related to different intensity electric current treatments on the growth and metabolism of selected micro-organisms using laboratory samples of pure and co-cultures (Saccharomyces cerevisiae strain 404 and Hanseniaspora guilliermondii strain 465).

METHODS AND RESULTS

Low electric current (10, 30, 50 and 100 mA) was applied to prepared samples. Parameters, such as polarity, treatment duration (18-48 h) and type of inoculum yeast, were varied one at a time to highlight their cause-effect relationships. The effects on cell activity as well as microflora viability were assessed. Bioindicators capable of describing the phenomena caused by the electric current on the microflora were identified.

CONCLUSIONS

Results demonstrated that a low voltage treatment using graphite electrodes had a greater effect on the viable S. cerevisiae strain 404 microflora. There was less bactericidal activity in the S. cerevisiae strain 404 than in the H. guilliermondii strain 465.

SIGNIFICANCE AND IMPACT OF THE STUDY

These results may be of significant importance in the development of new technological processes in the fields of agriculture and food, particularly new fermenting process controls.

Cross-linked cell aggregates of Trigonopsis variabilis: D-amino acid oxidase catalyst for oxidation of cephalosporin C

Trigonopsis variabilis CBS 4095 was treated with alkali (pH 11, 30 min), heated (65 degrees C, 60 s) and immobilized. Glutaraldehyde, polyethyleneimine and a cross-linking reagent formed by reaction of polyethyleneimine with glutaraldehyde were used for stabilization of D-amino acid oxidase in the cells, as well as for aggregation and binding of the cells. A specific activity of 82-98 U of D-amino acid oxidase per g dry mass was produced with a yield of about 20%. The half-life time of 142 repeated conversion cycles corresponds to a productivity of 130 kg cephalosporin C oxidized per kg catalyst dry mass.

Colocalization of cortical microtubules and F-actin in Dipodascus magnusii using confocal laser scanning microscopy

Distribution of microtubules and F-actin in aerobically growing cells of Dipodascus magnusii, belonging to the class Saccharomycetes was analyzed using immunofluorescence microscopy and labeling with rhodamine-tagged phalloidin. A conspicuous system of permanent cytoplasmic microtubules was observed in association with multiple nuclei. In elongating cells, helices of cytoplasmic microtubules appeared at the cell cortex. In cells approaching cytokinesis transversely oriented microtubules were revealed at incipient division sites. Confocal laser scanning microscopy showed a continuity of these transverse microtubules with the remaining microtubule network. The actin system of D. magnusii consisted of patches and filaments. Patches were found to accumulate at the tips of growing cells. Bands of fine actin filaments were usually observed before F-actin rings were established. A close cortical association of microtubules with the F-actin ring was documented on individual optical sections of labeled cells. Cells with developing septa showed medial F-actin discs associated at both sides with microtubules. Colocalization of cytoplasmic microtubules with actin filaments at the cortex of dividing cells supports a role of both cytoskeletal components in controlling cell wall growth and septum formation in D. magnusii.

Budding yeast Cdc5 phosphorylates Net1 and assists Cdc14 release from the nucleolus

Polo-like kinase Cdc5 and Cdc14 phosphatase are essential for mitotic exit in budding yeast. Cdc14 sequestered in the nucleolus by forming a complex with Net1, a nucleolar inhibitor of Cdc14, is activated after the release from the nucleolus and Cdc5 is essential for this release. Here we show that Cdc5 affects the phosphorylation state of Net1. Tab6 is a dominant active form of Cdc14. We found that Tab6 was released from the nucleolus of cdc5 mutant cells in a cell cycle dependent manner and that the release of Tab6 (or Cdc14) was not sufficient for the cdc5 mutant to grow at a higher temperature. Altogether, we propose that Cdc5 acts to reduce affinity between Cdc14 and Net1 and that the timing of Cdc14 release is independent of Cdc5. We also provide evidence that the critical function of Cdc5, other than Cdc14 liberation, exists in late mitotic events.

Mitochondrial dynamics and division in budding yeast

Mitochondria adopt a variety of different shapes in eukaryotic cells, ranging from multiple, small compartments to elaborate tubular networks. The establishment and maintenance of different mitochondrial morphologies depends, in part, on the equilibrium between opposing fission and fusion events. Recent studies in yeast, flies, worms and mammalian cells indicate that three high-molecular-weight GTPases control mitochondrial membrane dynamics. One of these is a dynamin-related GTPase that acts on the outer mitochondrial membrane to regulate fission. Recently, genetic approaches in budding yeast have identified additional components of the fission machinery. These and other new findings suggest a common mechanism for membrane fission events that has been conserved and adapted during eukaryotic evolution.

Chromosome associations in budding yeast caused by integrated tandemly repeated transgenes

The binding of GFP-tagged tetracycline repressor (TetR) molecules to chromosomally integrated tetracycline operator (tetO) sequence repeats has been used as a system to study chromosome behaviour microscopically in vivo. We found that these integrated transgenes influence the architecture of yeast interphase nuclei, as chromosomal loci with tandem repeats of exogenous tetO sequences are frequently associated. These associations occur only if TetR molecules are present. tetO tandem repeats associate regardless of their chromosomal context. When they are present at a proximal and a distal chromosomal position, they perturb the normal polarized Rabl-arrangement of chromosome arms by recruiting chromosome ends to the centromeric pole of the nucleus. Associations are established at G1 and are reduced during S-phase and mitosis. This system may serve as a model for the role of DNA sequence-specific binding proteins in imposing nonrandom distribution of chromosomes within the nucleus.

Metschnikowia koreensis sp. nov., a novel yeast species isolated from flowers in Korea

A novel ascomycetous yeast was isolated from flowers of Lilium sp. and Ipomoea sp. in Korea. The name Metschnikowia koreensis sp. nov. (type strain SG99-34T = CBS 8854T = KCTC 7998T) is proposed for this novel species based on comparative sequence analyses of the D1/D2 domain of 26S rDNA and phenotypic characteristics.

Ascospore aggregation and oxylipin distribution in the yeast Dipodascopsis tothii

Upon cultivation of the yeast Dipodascopsis tothii in its sexual stage, small ascospores are released individually from the ascus tip, which then assemble in sheathed cluster balls. In contrast to Dipodascopsis uninucleata, this yeast produced smooth bean shaped ascospores with sheath-like appendages that assemble in a disordered sheathed ball of ascospores outside the ascus. Strikingly, upon release, the ascus tip contained 3-hydroxy oxylipins, while the released ascospore clusters contained little or no 3-hydroxy oxylipins as indicated by immunofluorescence microscopy. In D. uninucleata, these oxylipins are concentrated on the spore surface and interspore matrix, but not on the ascus tip.

trans-dominant mutations in the GPR1 gene cause high sensitivity to acetic acid and ethanol in the yeast Yarrowia lipolytica

Acetate non-utilizing strains harbouring trans-dominant mutations in the GPR1 gene (GPR1(d)) of the dimorphic yeast Yarrowia lipolytica have been selected and characterized. These mutants are highly sensitive to low concentrations of acetic acid and ethanol, even in presence of glucose. The toxic effect of acetic acid is pH-dependent and has the strongest effect at low pH. In contrast, the action of ethanol is pH-independent. One GPR1(d) mutant has been detected that was highly sensitive to acetic acid but could still grow on ethanol, which indicates putative differences in the function of the GPR1 gene product in the sensitivity to acetic acid and ethanol. The GPR1(d) mutants exhibit a complex pleiotropic phenotype. The mutations cause changed colony morphology as well as dimorphism of cells, and induce early cell death during growth on glucose, even without the presence of dicarbon compounds. Composition of intracellular membranes, as well as morphology of vacuole and mitochondria, were strongly changed. Back-crosses with wild-type strains and analysis of recombinant strains have shown that the expression of the pleiotropic phenotype depends on the site of mutation in the GPR1 gene, as well as on the genetic background of the strain harbouring the responsive mutation. Our data suggest that Gpr1p is involved in a general response of cells to the toxic action of dicarbon compounds like acetic acid and ethanol.

Candida albicans and Yarrowia lipolytica as alternative models for analysing budding patterns and germ tube formation in dimorphic fungi

The site for bud selection and germ tube emission in two yeasts, Candida albicans and Yarrowia lipolytica, was analysed. Both dimorphic organisms display different patterns of budding, which also differ from those described for Saccharomyces cerevisiae. C. albicans, which is diploid and (until now) lacks a known sexual cycle, buds in an axial budding pattern. During the yeast-hypha transition induced by pH, serum, N-acetylglucosamine (GlcNAc) or temperature, germ tube emergence occurs at approximately 50% in a polar manner, while the other 50% of cells show non-polar germ tube emission. Y. lipolytica, in which most of the natural isolates are haploid and which has a well characterized sexual cycle, buds with a polar budding pattern independently of the degree of ploidy. Germ tube emission during the yeast-hypha transition in both haploid and diploid cells generally occurs at the pole distal from the division site (bipolar). The addition of hydroxyurea (HU), an inhibitor of DNA synthesis, also produces different effects. In its presence, and therefore in the absence of DNA synthesis, the yeast-hypha transition is completely abolished in Y. lipolytica. By contrast, in C. albicans germ tube emission in the presence of HU is similar to that observed in control cultures for at least 90 min under induction conditions. These results demonstrate that, rather than a single developmental model, several models of development should be invoked to account for the processes involved in the morphological switch in yeasts (the yeast-hypha transition).

Isocitrate lyase of Ashbya gossypii--transcriptional regulation and peroxisomal localization

The isocitrate lyase-encoding gene AgICL1 from the filamentous hemiascomycete Ashbya gossypii was isolated by heterologous complementation of a Saccharomyces cerevisiae icl1d mutant. The open reading frame of 1680 bp encoded a protein of 560 amino acids with a calculated molecular weight of 62584. Disruption of the AgICL1 gene led to complete loss of AgIcl1p activity and inability to grow on oleic acid as sole carbon source. Compartmentation of AgIcl1p in peroxisomes was demonstrated both by Percoll density gradient centrifugation and by immunogold labeling of ultrathin sections using specific antibodies. This fitted with the peroxisomal targeting signal AKL predicted from the C-terminal DNA sequence. Northern blot analysis with mycelium grown on different carbon sources as well as AgICL1 promoter replacement with the constitutive AgTEF promoter revealed a regulation at the transcriptional level. AgICL1 was subject to glucose repression, derepressed by glycerol, partially induced by the C2 compounds ethanol and acetate, and fully induced by soybean oil.

Time-lapse microscopy reveals unique roles for kinesins during anaphase in budding yeast

The mitotic spindle is a complex and dynamic structure. Genetic analysis in budding yeast has identified two sets of kinesin-like motors, Cin8p and Kip1p, and Kar3p and Kip3p, that have overlapping functions in mitosis. We have studied the role of three of these motors by video microscopy of motor mutants whose microtubules and centromeres were marked with green fluorescent protein. Despite their functional overlap, each motor mutant has a specific defect in mitosis: cin8Delta mutants lack the rapid phase of anaphase B, kip1Delta mutants show defects in the slow phase of anaphase B, and kip3Delta mutants prolong the duration of anaphase to the point at which the spindle becomes longer than the cell. The kip3Delta and kip1Delta mutants affect the duration of anaphase, but cin8Delta does not.

Organelle purification and selective permeabilisation of the plasma membrane: two different approaches to study vacuoles of the filamentous fungus Ashbya gossypii

Two different approaches to prepare and characterise vacuoles from the filamentous fungus Ashbya gossypii are described, i.e. the isolation of vacuoles from hyphal cells and the controlled permeabilisation of the plasma membrane. By mechanical lysis of protoplasts and separation of the organelles on a stepped density gradient, we obtained a vacuolar fraction virtually free of contamination by other organelles, unlysed protoplasts and cell debris. The integrity of the isolated organelles was characterised by vital-staining, the presence of alpha-mannosidase, and retained accumulation of basic amino acids. In a second approach, the cell membrane of the fungus was selectively permeabilised by use of the saponin digitonin leaving the vacuoles in their physiological surrounding, i.e. protected by the rigid cell wall. The permeabilisation was monitored by the latency of predominantly cytosolic amino acids and the ATP status of the cells. Functional intactness of the vacuoles within the permeabilised hyphae was demonstrated by maintenance of the pH gradient across the vacuolar membrane as detected by accumulation of the fluorescent dye, Acridine orange. These two methods are well-suited tools for the in situ assay of intracellular compartmentation of metabolites, for vacuolar transmembrane fluxes in Ashbya gossypii, as well as for the direct access to vacuolar membranes and enzymes of this fungus.

Wickerhamiella australiensis, Wickerhamiella cacticola, Wickerhamiella occidentalis, Candida drosophilae and Candida lipophila, five new related yeast species from flowers and associated insects

Five new yeast species, Wickerhamiella australiensis, Wickerhamiella cacticola, Wickerhamiella occidentalis, Candida drosophilae and Candida lipophila, are described to accommodate isolates recovered from flowers and floricolous insects of Australian Hibiscus trees, cosmopolitan morning glories (Ipomoea spp.) and Brazilian cereoid cacti. The new Wickerhamiella species are heterothallic, occur in the haploid condition and are clearly separated reproductively from one another. Although they exhibit little physiological variation, they are easily delineated from Wickerhamiella domercqiae, the only species known previously, by their resistance to cycloheximide and the production of strong extracellular lipases. C. drosophilae and C. lipophila share the latter property, but unlike the Wickerhamiella species, they fail to utilize nitrate as sole nitrogen source. PFGE indicates that these yeasts have an unusually low number of chromosomes. The large-subunit rDNA (D1/D2) sequences demonstrate a close relationship between the five species and Candida vanderwaltii and Candida azyma. Their relationship with W. domercqiae is more distant, but all share, with some other Candida species, a single monophyletic clade. The type and isotype strains are as follows: W. australiensis strains UWO(PS)95-604.3T (h+; CBS 8456T) and UWO(PS)95-631.3I (h-; CBS 8457I); W. cacticola strains UFMG96-267T (h+; CBS 8454T) and UFMG96-381I (h-; CBS 8455I); W. occidentalis strains UWO(PS)91-698.4T (h+; CBS 8452T) and UFMG96-212I (h-; CBS 8453I); C. drosophilae UWO(PS)91-716.3T (CBS 8459T); and C. lipophila UWO(PS)91-681.3T (CBS 8458T).

Mutants of the yeast Yarrowia lipolytica defective in protein exit from the endoplasmic reticulum are also defective in peroxisome biogenesis

Mutations in the SEC238 and SRP54 genes of the yeast Yarrowia lipolytica not only cause temperature-sensitive defects in the exit of the precursor form of alkaline extracellular protease and of other secretory proteins from the endoplasmic reticulum and in protein secretion but also lead to temperature-sensitive growth in oleic acid-containing medium, the metabolism of which requires the assembly of functionally intact peroxisomes. The sec238A and srp54KO mutations at the restrictive temperature significantly reduce the size and number of peroxisomes, affect the import of peroxisomal matrix and membrane proteins into the organelle, and significantly delay, but do not prevent, the exit of two peroxisomal membrane proteins, Pex2p and Pex16p, from the endoplasmic reticulum en route to the peroxisomal membrane. Mutations in the PEX1 and PEX6 genes, which encode members of the AAA family of N-ethylmaleimide-sensitive fusion protein-like ATPases, not only affect the exit of precursor forms of secretory proteins from the endoplasmic reticulum but also prevent the exit of the peroxisomal membrane proteins Pex2p and Pex16p from the endoplasmic reticulum and cause the accumulation of an extensive network of endoplasmic reticulum membranes. None of the peroxisomal matrix proteins tested associated with the endoplasmic reticulum in sec238A, srp54KO, pex1-1, and pex6KO mutant cells. Our data provide evidence that the endoplasmic reticulum is required for peroxisome biogenesis and suggest that in Y. lipolytica, the trafficking of some membrane proteins, but not matrix proteins, to the peroxisome occurs via the endoplasmic reticulum, results in their glycosylation within the lumen of the endoplasmic reticulum, does not involve transport through the Golgi, and requires the products encoded by the SEC238, SRP54, PEX1, and PEX6 genes.

Phytopathogenic filamentous (Ashbya, Eremothecium) and dimorphic fungi (Holleya, Nematospora) with needle-shaped ascospores as new members within the Saccharomycetaceae

Phylogenetic relationships between species from the genera Kluyveromyces and Saccharomyces and representatives of the Metschnikowiaceae (Holleya, Metschnikowia, Nematospora) including the two filamentous phytopathogenic fungi Ashbya gossypii and Eremothecium ashbyii were studied by comparing the monosaccharide pattern of purified cell walls, the ubiquinone system, the presence of dityrosine in ascospore walls, and nucleotide sequences of ribosomal DNA (complete 18S rDNA, ITS1 and ITS2 region). Based on sequence information from both ITS regions, the genera Ashbya, Eremothecium, Holleya and Nematospora are closely related and may be placed in a single genus as suggested by Kurtzman (1995; J Industr. Microbiol. 14, 523-530). In a phylogenetic tree derived from the ITS1 and ITS2 region as well as in a tree derived from the complete 18S rDNA gene, the genus Metschnikowia remains distinct. The molecular evidence from ribosomal sequences suggests that morphology and ornamentation of ascospores as well as mycelium formation and fermentation should not be used as differentiating characters in family delimitation. Our data on cell wall sugars, ubiquinone side chains, dityrosine, and ribosomal DNA sequences support the inclusion of plant pathogenic, predominantly filamentous genera like Ashbya and Eremothecium or dimorphic genera like Holleya and Nematospora with needle-shaped ascospores within the family Saccharomycetaceae. After comparison of sequences from the complete genes of the 18S rDNA the genus Kluyveromyces appears heterogeneous. The type species of the genus, K. polysporus is congeneric with the genus Saccharomyces. The data of Cai et al. (1996; Int. J. Syst. Bacteriol. 46, 542-549) and our own data suggest to conserve the genus Kluyveromyces for a clade containing K. marxianius, K. dobzhanskii, K. wickerhamii and K. aestuarii, which again can be included in the family Saccharomycetaceae. The phylogenetic age of the Metschnikowiaceae and Saccharomycetaceae will be discussed in the light of coevolution.

Enlarged peroxisomes are present in oleic acid-grown Yarrowia lipolytica overexpressing the PEX16 gene encoding an intraperoxisomal peripheral membrane peroxin

Pex mutants of the yeast Yarrowia lipolytica are defective in peroxisome assembly. The mutant strain pex16-1 lacks morphologically recognizable peroxisomes. Most peroxisomal proteins are mislocalized to a subcellular fraction enriched for cytosol in pex16 strains, but a subset of peroxisomal proteins is localized at, or near, wild-type levels to a fraction typically enriched for peroxisomes. The PEX16 gene was isolated by functional complementation of the pex16-1 strain and encodes a protein, Pex16p, of 391 amino acids (44,479 D). Pex16p has no known homologues. Pex16p is a peripheral protein located at the matrix face of the peroxisomal membrane. Substitution of the carboxylterminal tripeptide Ser-Thr-Leu, which is similar to the consensus sequence of peroxisomal targeting signal 1, does not affect targeting of Pex16p to peroxisomes. Pex16p is synthesized in wild-type cells grown in glucose-containing media, and its levels are modestly increased by growth of cells in oleic acid-containing medium. Overexpression of the PEX16 gene in oleic acid- grown Y. lipolytica leads to the appearance of a small number of enlarged peroxisomes, which contain the normal complement of peroxisomal proteins at levels approaching those of wild-type peroxisomes.