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M A Lachance

Publications and source records attributed to M A Lachance.

34 records · Page 2Linked to original sources
PubMed1995

Yeast communities associated with Drosophila species and related flies in an eastern oak-pine forest: a comparison with western communities.

Intestinal yeast mycobiota were studied in 14 species of Drosophila and in the drosophilid species Chymomyza amoena, captured at Pinery Provincial Park, Ontario. Over 56 yeast species, some undescribed, were isolated. These yeast communities were compared with those from two similar surveys conducted in western portions of North America. The community structures were influenced significantly by the habitat rather than phylogeny of the flies. Geographic separation was a factor affecting yeast taxa frequencies in the fly species, but it was largely overshadowed by ecological factors when the communities were described physiologically. The notion that habitats are filled by yeasts which add up to a suitable physiological potential, more or less independently of their taxonomic affinities, was thus confirmed.

Animals↗
PubMed1994

Mating in the heterothallic haploid yeast Clavispora opuntiae, with special reference to mating type imbalances in local populations.

Mating was studied in the haploid, heterothallic yeast Clavispora opuntiae to assess the importance of nutritional, genetic, and other factors that may favour mating and recombination. Local populations of this yeast generally exhibit dramatic inequalities in mating type distributions, suggesting that mating is rare in nature even though most isolates mate freely in the laboratory. The absence of assimilable nitrogen is prerequisite to mating competence, presumably by causing G1 arrest. Maximum mating competence is found in cells entering stationary phase in nitrogen-limited media. Unlike the vast majority of mating yeasts, C. opuntiae does not appear to produce diffusible mating factors (sex pheromones), and mating-competent cells do not undergo sexual agglutination. Pairwise cell contact appears to be the only signal that triggers the sexual process in this case. In order to determine if mating type imbalances in nature are caused by reduced fertility of 'consanguine' crosses, meiotic recombination was measured in pairs of strains that varied in their genetic distances as indicated by restriction mapping. That hypothesis was rejected, as recombination efficiency decreased with increasing genetic distance. We conclude that the rarity of mating in local populations is exacerbated by the stringent physical (pairwise cell contact) and nutritional (nitrogen depletion) conditions that will allow mating to proceed. Parallels are drawn with mating patterns observed in Clavispora lusitaniae.

Crosses, Genetic↗
PubMed1994

Candida caseinolytica sp. nov., a new species of yeast occurring in necrotic tissue of Opuntia and Stenocereus species in the southwestern United States and Baja California, Mexico.

We describe Candida caseinolytica, a new yeast species which occurs in rotting tissues of opuntias and other cacti in the North American Sonoran Desert and a few other localities. This small-celled, slowly growing yeast does not ferment any sugar and assimilates a limited number of carbon compounds, including 2- and 5-ketogluconic acids. It exhibits strong extracellular proteolytic activity on casein at pH 6.5, but gelatin is not hydrolyzed or is only weakly hydrolyzed by a few strains. The type strain of C. caseinolytica is strain UCD-FST 83-438.3 (= ATCC 90546 = CBS 7781).

Candida↗
PubMed1993

Phylogenetic study of ribosomal DNA of cactophilic Pichia species by restriction mapping.

The rDNAs of strains of the cactophilic Pichia species P. amethionina, P. antillensis, P. barkeri, P. cactophila, P. caribaea, P. deserticola, P. heedii, P. kluyveri, P. norvegenesis, P. opuntiae, P. pseudocactophila, P. thermotolerans and their varieties and anamorphs were mapped with 15 restriction endonucleases, and compared to P. membranaefaciens and P. salictaria as possible non-cactophilic relatives. The existence of species complexes among those taxa was confirmed. P. membranaefaciens was a plausible ancestral species, and its closest relative in the cactophilic group was P. deserticola. These two species appeared to be moderately related to P. heedii and to P. barkeri, but the latter was shown clearly to belong to the P. kluyveri complex, in spite of a 6 mol% G+C difference in their nuclear DNAs. P. cactophila and P. pseudocactophila ostensibly emerged from P. norvegensis, a facultatively cactophilic yeast. The P. amethionina, P. cactophila and P. opuntiae species complexes appeared independent from one another and from all other species studied. P. salictaria did not appear to be related to P. amethionina.

Amino Acid Sequence↗
PubMed1993

Kluyveromyces: systematics since 1970.

The taxonomy of Kluyveromyces has been the object of intense study since van der Walt's (1970) monograph. This is an account of the major developments and the classification to be adopted in the 4th edition of The Yeasts, a Taxonomic Study. The guiding principles that will be followed in eventual revisions of the genus are presented.

DNA, Fungal↗
PubMed1990

Metschnikowia hawaiiensis sp. nov., a heterothallic haploid yeast from Hawaiian morning glory and associated drosophilids.

A new haploid, heterothallic yeast species was isolated repeatedly from morning glory (Ipomoea acuminata) flowers and from two associated drosophilid species, Scaptomyza calliginosa and Drosophila floricola, in a Hawaiian kipuka. Haploid strains of this organism multiply asexually by budding and, under nutrient deprivation, by the formation of long germ tubes that develop into branching true mycelia. Mating compatibility is controlled by two alleles of a single locus. Plasmogamy between compatible strains is followed by the development of very large elongate asci bearing vestiges of the zygotes and the formation in each ascus of two unusually large aciculate ascospores similar to those formed by members of the genus Metschnikowia. Membership in the genus Metschnikowia is supported by the physiological profile of the yeast, which is typical of the genus but not identical to the profile of any previously described species. The name Metschnikowia hawaiiensis is proposed to emphasize the geographic origin of the new species, not its habitat, which has not been determined precisely. The holotype strain of M. hawaiiensis is strain UWO(PS) 87-2167.2 (= ATCC 76059 = CBS 7432), and the isotype strain is strain UWO(PS) 87-2203.2 (= ATCC 76058 = CBS 7433).

Animals↗
PubMed1989

Restriction mapping of rDNA and the taxonomy of Kluyveromyces van der Walt emend. van der Walt.

Ribosomal DNA from the type strains of 13 nomenspecies of Kluyveromyces and from other strains were mapped with 11 restriction endonucleases. The length of the repeating unit ranged from ca. 8.4 kb (in K. aestuarii) to ca. 10.9 kb (in K. phaffii). The length variation resided as expected in the nontranscribed spacer. The patterns confirmed some of the inferences articulated by various students of the genus. The closely related species K. marxianus and K. lactis constituted a core to which could be linked first K. wickerhamii and K. dobzhanskii and then K. aestuarii. The presumed relatedness between K. waltii and K. thermotolerans was endorsed by rDNA mapping as well, but evidence linking these two species to the rest of the genus is wanting. The restriction patterns suggest that the multispored species together with K. delphensis form a loose assemblage acting as a bridge between the "core" species and the species K. phaffii and K. lodderi.

DNA, Fungal↗
PubMed1987

The use of N,N,N',N'-tetramethylphenylenediamine to detect peroxidase activity on polyacrylamide electrophoresis gels.

N,N,N',N'-Tetramethylphenylenediamine (TMPD) acts as an effective indicator of peroxidase activity on polyacrylamide electrophoresis gels. The test is easy to perform, rapid, sensitive, and reliable. The procedure produces vivid bright blue bands (Wursters blue) on a clear background. TMPD and Wursters blue did not interfere with a number of other electrophoresis stains subsequently applied. These included total protein staining with Coomassie blue, and a number of pigment producing electrophoresis stains used to investigate melanogenesis-related enzymes in the black yeast Phaeococcomyces sp.

Chromogenic Compounds↗
PubMed1987

The ecological role of killer yeasts in natural communities of yeasts.

The killer phenomenon of yeasts was investigated in naturally occurring yeast communities. Yeast species from communities associated with the decaying stems and fruits of cactus and the slime fluxes of trees were studied for production of killer toxins and sensitivity to killer toxins produced by other yeasts. Yeasts found in decaying fruits showed the highest incidence of killing activity (30/112), while yeasts isolated from cactus necroses and tree fluxes showed lower activity (70/699 and 11/140, respectively). Cross-reaction studies indicated that few killer-sensitive interactions occur within the same habitat at a particular time and locality, but that killer-sensitive reactions occur more frequently among yeasts from different localities and habitats. The conditions that should be optimal for killer activity were found in fruits and young rots of Opuntia cladodes where the pH is low. The fruit habitat appears to favor the establishment of killer species. Killer toxin may affect the natural distribution of the killer yeast Pichia kluyveri and the sensitive yeast Cryptococcus cereanus. Their distributions indicate that the toxin produced by P. kluyveri limits the occurrence of Cr. cereanus in fruit and Opuntia pads. In general most communities have only one killer species. Sensitive strains are more widespread than killer strains and few species appear to be immune to all toxins. Genetic study of the killer yeast P. kluyveri indicates that the mode of inheritance of killer toxin production is nuclear and not cytoplasmic as is found in Saccharomyces cerevisiae and Kluyveromyces lactis.

Arizona↗
PubMed1985

Aerobic Fermentation of D-Xylose to Ethanol by Clavispora sp.

Eleven strains of an undescribed species of Clavispora fermented D-xylose directly to ethanol under aerobic conditions. Strain UWO(PS)83-877-1 was grown in a medium containing 2% D-xylose and 0.5% yeast extract, and the following results were obtained: ethanol yield coefficient (ethanol/D-xylose), 0.29 g g (57.4% of theoretical); cell yield coefficient (dry biomass/D-xylose), 0.25 g g; maximum ethanol concentration, 5.9 g liter; maximum volumetric ethanol productivity, 0.11 g liter h. With initial D-xylose concentrations of 40, 60, and 80 g liter, maximum ethanol concentrations of 8.8, 10.9, and 9.8 g liter were obtained, respectively (57.2, 57.1, and 48.3% of theoretical). Ethanol was found to inhibit the fermentation of D-xylose (K(p) = 0.58 g liter) more than the fermentation of glucose (K(p) = 6.5 g liter). The performance of this yeast compared favorably with that reported for some other D-xylose-fermenting yeasts.

Journal Article↗
PubMed1985

Isolation and Screening of Yeasts That Ferment d-Xylose Directly to Ethanol.

Natural habitats of yeasts were examined for the presence of strains able to produce ethanol from d-xylose. Black knots, insect frass, and tree exudates were screened by enrichment in liquid d-xylose-yeast extract medium. These and each d-xylose-assimilating yeast in a collection from cactus fruits and Drosophila spp. were tested for alcohol production from this sugar. Among the 412 isolates examined, 36 produced more than 1 g of ethanol liter from 20 g of d-xylose liter, all under aerated conditions. Closer examination of the strains indicated that their time courses of d-xylose fermentation followed different patterns. Some strains produced more biomass than ethanol, and among these, ethanol may or may not be assimilated rapidly after depletion of d-xylose. Others produced more ethanol than biomass, but all catabolized ethanol after carbohydrate exhaustion. Ethanol production appeared best at low pH values and under mild aeration. Possible correlations between the nutritional profiles of the yeasts and their ability to produce ethanol from d-xylose were explored by multivariate analysis. d-Xylose appeared slightly better utilized by yeasts which rate poorly in terms of fermentation. The fermentation of d-glucose had no bearing on d-xylose fermentation. No specific nutritional trait could discriminate well between better d-xylose fermentors and other yeasts.

Journal Article↗
PubMed1985

Current views on the yeast species.

The application of the biological species concept to the delineation of yeast species is becoming a reality. Studies centred on heterothallic Pichia and related species, and on homothallic species of Kluyveromyces have facilitated a better understanding of the concept of 'yeast species'.

Animals↗
PubMed1981

Hanseniaspora nodinigri, a new yeast species found in black knots (Dibotryon morbosum) of Prunus virginiana.

The new yeast species Hanseniaspora nodinigri is described to accommodate members of the genus Hanseniaspora that are unable to assimilate glucono-sigma-lactone and isolated from stromatal tissue of black knots (Dobotryon morbosum) of chokecherry, Prunus virginiana. The newly described taxon shows much resemblance, by other criteria, to H. vineae van der Walt et Tscheuschner and H. osmophila (Niehaus) Phaff, Miller et Shifrine.

Ascomycota↗
PubMed1977

Purification and partial characterization of an exo-beta-glucanase from the yeast Kluyveromyces aestaurii.

The intracellular-periplasmic exo-1,3-beta-glucanase (EC 3.2.1.58) has been extracted from the yeast Kluyveromyces aestuarii and purified to immunoelectrophoretic homogeneity by ion-exchange and gel-exclusion chromatography. The kinetic constants and activation energies for laminarin, p-nitrophenyl-beta-D-glucoside, and pustulan have been determined, along with the effect of pH. Evidence is presented indicating that the enzyme is composed of a single polypeptide chain, about 24% carbohydrates, and its molecular weight was estimated to be 43 000.

Ascomycota↗
PubMed1976

Dehiscence and active spore release in pathogenic strains of the yeast Metschnikowia bicuspidata var. australis: possible predatory implication.

Strains of Metschnikowia bicuspidata var. australis, pathogenic to brine shrimp (Artemia salina), were observed to form asci which, upon reaching maturity, forcibly expelled their needle-shaped spores. The mechanical force responsible apparently originates from the formation of an ectoplasmic mucilage capable of exerting pressure over all of the ascus contents; when the apex of the peduncle ruptures, the ascospores are violently released. Cytochemical analyses indicated that the gel is a substance highly resistant to chemical and enzymatic hydrolysis. Its chemical nature is not known as yet. The morphogenetic events of this process are described, and its ecological implication, the possibility of active mechanical predation in yeast, is discussed.

Aldehyde-Lyases↗