Brenda D. Wingfield

Killer Yeasts - Cause of Stuck Fermentations in a Wine Cellar

Sluggish fermentations in five fermenters in a wine cellar were investigated. Methylene blue-stains of yeast suspensions revealed that approximately 90% of the total yeast population in each of the fermenters were dead. The viable cells in each fermenter were killer yeasts. Polyacrylamide gel electrophoresis of total soluble cell proteins showed that the same killer yeast occurred in each of the five fermenters. The effect of killer yeast on viability and fermentation activity of the wine yeast was studied in an enriched grape juice medium at 20°C and 30°C. Death rate of the wine yeast was considerably higher in the presence of the killer yeast and fermentations were retarded at both temperatures. The killer yeast induced flocculation of the non-flocculent wine yeast.

Reclassification of Phialocephala based on conidial development

Leptographium and Phialocephala are separated based on conidial development. In Leptographium , conidia develop by apical wall building and sympodial or percurrent proliferation of the conidiogenous cells. Phialocephala includes species with ring wall building as well as species with apical wall building development. Some species of Phialocephala with ring wall building development are distinguished by their phialides with deep set cylindrical collarettes and conidia produced in chains with points of attachment at both ends resembling those in Chalara and allied genera. These are placed in Sporendocladia . The remaining Phialocephala spp. all have apical wall building with proliferation usually resulting in well-defined, and often ornate collarettes. In most cases these are distinct from the poorly-defined collarettes often found in Leptographium spp. These Phialocephala spp. apparently comprise a heterogeneous group probably affiliated with a number of teleomorph genera. In contrast Leptographium spp. are all anamorphs of Ophiostoma .

IMA Genome-F 2: Ceratocystis manginecans, Ceratocystis moniliformis, Diplodia sapinea: Draft genome sequences of Diplodia sapinea, Ceratocystis manginecans, and Ceratocystis moniliformis.

The draft nuclear genomes of Diplodia sapinea, Ceratocystis moniliformis s. str., and C. manginecans are presented. Diplodia sapinea is an important shoot-blight and canker pathogen of Pinus spp., C. moniliformis is a saprobe associated with wounds on a wide range of woody angiosperms and C. manginecans is a serious wilt pathogen of mango and Acacia mangium. The genome size of D. sapinea is estimated at 36.97 Mb and contains 13 020 predicted genes. Ceratocystis moniliformis includes 25.43 Mb and is predicted to encode at least 6 832 genes. This is smaller than that reported for the mango wilt pathogen C. manginecans which is 31.71 Mb and is predicted to encode at least 7 494 genes. The latter is thus more similar to C. fimbriata s.str., the type species of the genus. The genome sequences presented here provide an important resource to resolve issues pertaining to the taxonomy, biology and evolution of these fungi.

Ceratocystis eucalypticola sp. nov. from Eucalyptus in South Africa and comparison to global isolates from this tree.

Eucalyptus trees, mostly native to Australia, are widely planted in the tropics and Southern Hemisphere for the production of wood and pulp. Worldwide surveys of diseases on these trees have yielded a large collection of Ceratocystis isolates from dying trees or from wounds on their stems. The aim of this study was to characterise these isolates and to consider their relatedness to each other. Culture appearance, morphological features and a distinctive fruity odour in all cultures were typical of species in the Ceratocystis fimbriata sensu lato (s. lat.) complex. Phylogenetic analyses of sequences for the combined ITS, βt-1 and TEF1-α gene regions revealed a genetically diverse group of isolates residing in a single large clade, that were distinct from all other species in the C. fimbriata s. lat. complex. Based on morphology and phylogenetic inference, the Eucalyptus isolates are recognised as closely related. The South African isolates are described here as a new species, C. eucalypticola.

IMA Genome-F 1: Ceratocystis fimbriata: Draft nuclear genome sequence for the plant pathogen, Ceratocystis fimbriata

The draft nuclear genome of Ceratocystis fimbriata, the type species of Ceratocystis, is comprised of 29 410 862 bp. De novo gene prediction produced 7 266 genes, which is low for an ascomycete fungus. The availability of the genome provides opportunities to study aspects of the biology of this and other Ceratocystis species.

Ceratocystis larium sp. nov., a new species from Styrax benzoin wounds associated with incense harvesting in Indonesia

Styrax benzoin trees, native to the island Sumatra, Indonesia are wounded to produce resin that is collected and burned as incense. These wounds on trees commonly develop into expanding cankers that lead to tree death. The aim of this study was to consider whether Ophiostomatoid fungi, typically associated with wounds on trees might be associated with resin harvesting on S. benzoin. Samples were collected from the edges of artificially induced wounds, and particularly where cankers and staining of the vascular tissue was evident. Tissue samples were incubated in moist chambers and carrot baiting was also used to detect the presence of Ceratocystis spp. Fruiting structures with morphology typical of species in the C. fimbriata s.l. species complex and species in the anamorph genus Thielaviopsis were found, on both the incubated wood and the carrot baits. DNA sequences were generated for the Internal Transcribed Spacer regions 1 and 2 including the 5.8S rRNA gene, part of the β-tubulin and the Transcription Elongation Factor 1-α gene regions. These data were compared with those of other species in the C. fimbriata s.l. species complex and Thielaviopsis using phylogenetic analysis. Morphology of the isolates in culture as well as phylogenetic inference showed that the Thielaviopsis sp. present on the wounds was T. basicola. The Ceratocystis sp. from S. benzoin represents a new taxon in the C. fimbriata s.l. complex described here as C. larium sp. nov.

Plasmids in Leuconostoc oenos

A new procedure was used to isolate 11 plasmids from eight Leuconostoc oenos strains. Plasmid DNA was not detected in 34 other strains of this species. Plasmid sizes ranged from 2.47 to 4.61 kilobase pairs. This is the first report of extrachromosomal elements in L. oenos.

Size differentiation of M2 genomes among K2 killer yeasts

Viral double-stranded ribonucleic acid (dsRNA) genomes from killer yeasts isolated from wineries were extracted and compared with that of reference K2 and K3 killer strains. The sizes of the L genomes of all the strains were similar but the M genomes varied from 1·3 to 1·5 kilobase pairs (kb). This incorporates the sizes attributed to the M genomes of K2 and K3 killer yeasts.

Draft genome sequences for Ceratocystis fagacearum, C. harringtonii, Grosmannia penicillata, and Huntiella bhutanensis

Draft genomes for the fungi Ceratocystis fagacearum, C. harringtonii, Grosmannia penicillata, and Huntiella bhutanensis are presented. Ceratocystis fagacearum is a major causal agent of vascular wilt of oaks and other trees in the family Fagaceae. Ceratocystis harringtonii, previously known as C. populicola, causes disease in Populus species in the USA and Canada. Grosmannia penicillata is the causal agent of bluestain of sapwood on various conifers, including Picea spp. and Pinus spp. in Europe. Huntiella bhutanensis is a fungus in Ceratocystidaceae and known only in association with the bark beetle Ips schmutzenhorferi that infests Picea spinulosa in Bhutan. The availability of these genomes will facilitate further studies on these fungi.

K3 killer yeast is a mutant K2 killer yeast

The K 2 and K 3 killer yeast classes in Saccharomyces cerevisiae were compared. Sensitive strain 381 and the killer strains NCYC 232 NCYC 190, NCYC 738, NCYC 761 and KT28 were sensitive to the killer toxins produced by the K 2 and K 3 strains. However, these two strains were resistant to both toxins. Hybridization analysis showed that the M dsRNAs from the K 2 and K 3 strains had significant homology, but shared no homology with the dsRNAs from the K 1 and KT28 strains. The K 2 M dsRNA is larger than the K 3 M dsRNA, and electron micrographs showed an unmatched loop when these molecules were hybridized. This suggests that the K 3 M dsRNA is a mutant K 2 M genome. These results show that K 2 and K 3 strains belong in the same class, but separate from the K 1 and KT28 killer ty