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1 Centro de Recursos Microbiológicos (CREM), Biotechnology Unit, Faculty of Sciences and Technology, New University of Lisbon, 2829-516 Caparica, Portugal
2 National Center for Agricultural Utilization Research, Agricultural Research Service, US Department of Agriculture, Peoria, IL 61604, USA
3 Department of Biology, Syracuse University, NY 13244, USA
Correspondence
Isabel Spencer-Martins
ism{at}fct.unl.pt
| ABSTRACT |
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Published online ahead of print on 11 April 2003 as DOI 10.1099/ijs.0.02470-0.
The GenBank accession numbers for the D1/D2 26S rDNA sequences of strain PYCC 4650T and PYCC 4605T are AF017404 and AY080995, respectively.
| INTRODUCTION |
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In the present study, two novel species of Metschnikowia are proposed. These species, to be named Metschnikowia vanudenii and Metschnikowia lachancei, were isolated in North America from the common milkweed Asclepias syriaca and associated insects. M. vanudenii shares with Metschnikowia gruessii the formation of aeroplane cells, i.e. superimposed pairs of cells that form a cross-like configuration. The second species, M. lachancei, is characterized by clavate ascospores, which differentiates it from all other recognized species of Metschnikowia.
| METHODS |
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DNA base composition and DNADNA reassociations.
For thermal denaturation and reassociation experiments, DNA was purified by chromatography on hydroxylapatite columns following the protocol of Britten et al. (1970)
. The mean nuclear DNA (nDNA) G+C content from Metschnikowia strains was determined by thermal denaturation (Tm) (Marmur & Doty, 1962
) using a Gilford Response II Spectrophotometer and its thermal programming software. The G+C content was determined at least twice for each strain in 0·1x SSC (Owen et al., 1969
). The extent of DNA relatedness was determined spectrophotometrically as described by Seidler & Mandel (1971)
and modified by Kurtzman et al. (1980)
, using a Gilford Response II Spectrophotometer and its thermal kinetics program.
rDNA sequencing and sequence analysis.
Methods for nDNA isolation, amplification by PCR of the 26S rDNA domain D1/D2 and sequencing with the ABI TaqDyeDeoxy Terminator Cycle Sequencing kit and the ABI model 377 automated DNA sequencer (PE Biosystems) were previously described (Kurtzman & Robnett, 1998
). Sequence data were visually aligned with QEDIT 2.15 (SemWare, Marietta, GA, USA). Phylogenetic relationships were calculated with the maximum-parsimony program of PAUP*4.0b3a (Swofford, 1998
), as well as with the neighbour-joining program using the Kimura two-parameter distance measure. Schizosaccharomyces pombe was the designated outgroup species in all analyses. Confidence limits for phylogenetic trees were estimated from bootstrap analysis (1000 replications). The nucleotide sequences for the new species reported here, as well as for reference species, have been deposited with GenBank under the accession numbers given in Fig. 3
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| RESULTS AND DISCUSSION |
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,
-trehalosum (variabile), melezitosum, amylum solubile (variabile), D-xylosum (variabile), ethanolum (variabile), glycerolum (variabile), ribitolum (variabile), D-mannitolum (variabile), D-sorbitolum, salicinum (variabile), arbutinum, D-glucosaminum, glucono-
-lactonum (variabile), D-glutamatum (variabile), N-acetyl-glucosaminum (variabile) et 2-ketogluconatum ad non D-galactosum, lactosum, melibiosum, raffinosum, inulinum, L-arabinosum, D-arabinosum, D-ribosum, L-rhamnosum, erythritolum, D-glucitolum, methyl-
-D-glucosidum, acidum lacticum, acidum succinicum, acidum citricum, myo-inositolum, methanolum, acidum glucoronicum, acidum gluconicum, acidum tartaricum et acidum malicum. Assimilat L-lysini, ethylamini, cadaverini, D-glucosaminum (variabile), betanini, D-glutaminum ad non kallii nitratis, sodii nitrosi, creatino nec creatinino. Vitaminae externae ad crescentiam necessariae sunt. Crescit in 30 °C sed non in 35 °C. Materia amyloidea non formatur. Ureum non finditur. Ubiquinonum majus Q-9. Proportio molaris guanini plus cytosini in acidi deoxyribonucleati 44·4 mol%. Typus: PYCC 4650T, ex flore, exsicatus et vivus in collectione zymotica Centraalbureau voor Schimmelcultures (CBS 9134T), Trajectum ad Rhenum, praeservatus.
Description of Metschnikowia vanudenii Giménez-Jurado, Kurtzman & Spencer-Martins sp. nov.
Growth in glucose (2 %) yeast extract (0·5 %) peptone (1 %) broth.
After 3 days at 25 °C, vegetative cells are ovoid to cylindrical (35x79 µm) and occur mostly in pairs, tetrads or in short chains. Some cells develop into characteristic aeroplane or cross formations. Chlamydospores, when present, are globose to subglobose in shape (68x810 µm), highly refractile and contain several spherical lipid globules. Some strains produce few or no chlamydospores. No pseudohyphae or hyphae were observed in this medium. Cell division occurs by multilateral budding. After 1 week at 25 °C, abundant sediment is formed.
Growth on glucose (2 %) yeast extract (0·5 %) peptone (1 %) agar.
After 1 week at room temperature, strains form white to cream, smooth to papillate, glossy, butyrous colonies with entire margins.
Growth on malt extract agar.
After 1 week at room temperature, strains form copious amounts of subglobose chlamydospores with large, easily seen oil droplets. Cross or aeroplane configurations are present in strains PYCC 4606, PYCC 4648 and PYCC 4650T.
Dalmau plate cultures on corn-meal agar.
After 1 week at 25 °C, growth under semi-anaerobic conditions showed development of primitive pseudohyphae.
Formation of ascospores.
Asci with ascospores were formed by PYCC 4650T after incubation for 12 days at 17 °C on dilute (1 : 15) V8 agar (Fig. 1
). Asci initially developed from ellipsoid chlamydospores, which further elongated resulting in a cylindrical peduncle shape. Mature asci (68x2545 µm) contain two acicular to filiform ascospores, which are noticeably pointed at one end. Most asci are persistent, although a few become deliquescent.
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Physiological and biochemical characteristics
See Table 2
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Origin and deposits.
The type strain PYCC 4650T [UWO(PS) 86AW4.1] was isolated from a walk plate sampling of a muscoid fly collected from the common milkweed Asclepias syriaca in Guelph, Ontario, Canada. This strain has been deposited (living and dried) in the Portuguese Yeast Culture Collection (PYCC), Centro de Recursos Microbiológicos (CREM), Universidade Nova de Lisboa, Caparica, Portugal, and under number CBS 9134 in the Centraalbureau voor Schimmelcultures in Utrecht, The Netherlands.
Latin diagnosis of Metschnikowia lachancei Giménez-Jurado, Kurtzman, Starmer & Spencer-Martins sp. nov.
In medio liquido cum dextroso et peptono et extracto levedinis post dies 3 ad 25 °C cellulae sunt ellipsoideae aut cylindrateae (37x83 µm), singulae, binae vel aggregatae, gemmationem multipolarem reproducentes. Breves pseudohyphae formatur. Chlamydosporae non formatur. Post dies 7 ad 25 °C sedimentum parcum formatur. Cultura in medio agaro cum dextroso et peptono et extracto levedinis post dies 7, albida vel cremea cum margo crenatus. In agaro farinae Zea mays post dies 7 ad 25 °C pseudohyphae vera cum conidia globosa formatur. In agaro V8 dilutus post dies 34 ad 17 °C asci clavatispedunculati, pedunculi cylindrateae (36x1423 µm), 2-spori in quoque asco. Ascosporae clavatus vel pyriformis. Fermentatio glucosum. Assimilat glucosum, D-galactosum, D-glucosaminum, D-xylosum, sucrosum, maltosum,
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-trehalosum, cellobiosum, salicinum, arbutinum, melezitosum, glycerolum, xylitolum, D-sorbitolum, D-mannitolum, glucono-
-lactonum, 2-ketogluconatum, acidum gluconicum, D-glutamatum et N-acetyl-glucosaminum, et ad non L-sorbosum, D-ribosum, L-arabinosum, D-arabinosum, L-rhamnosum, ethanolum, methanolum, methyl-
-D-glucosidum, melibiosum, lactosum, raffinosum, inulinum, amylum solubile, erythritolum, ribitolum, D-glucitolum, myo-inositolum, acidum glucoronicum, acidum lacticum, acidum succinicum, acidum citricum, acidum malicum et acidum tartaricum. Assimilat L-lysini, ethylamini, cadaverini, betanini, D-glutaminum ad non kallii nitratis, sodii nitrosi, D-glucosaminum, creatino nec creatinino. Vitaminae externae ad crescentiam necessariae sunt. Crescit in 30 °C sed non in 35 °C. Materiae amyloidea non formatur. Ureum finditur. Ubiquinonum majus Q-9. Proportio molaris guanini plus cytosini in acidi deoxyribonucleati 46·9 mol%.
Typus: PYCC 4605T, ex flore, in collectione zymotica Centraalbureau voor Schimmelcultures (CBS 9131T), Trajectum ad Rhenum, praeservatus.
Description of Metschnikowia lachancei Giménez-Jurado, Kurtzman, Starmer & Spencer-Martins sp. nov.
Growth in glucose (2 %) yeast extract (0·5 %) peptone (1 %) broth.
After 3 days at 25 °C, vegetative cells are ellipsoidal to cylindrical (37x813 µm) and occur in pairs, tetrads or small chains. Cell division occurs by multilateral budding. Sparse slender pseudohyphae are formed. Chlamydospores are not formed. Some cells contain refractile globules. After 1 week at 25 °C sediment is formed.
Growth on glucose (2 %) yeast extract (0·5 %) peptone (1 %) agar.
After 1 week at room temperature, the streak culture is cream to off-white coloured, smooth, glossy and with a lobate margin.
Dalmau plate cultures on corn-meal agar.
After 1 week at 25 °C, growth under semi-anaerobic conditions shows the presence of slender pseudohyphae. Cells become elongated and eventually form branching pseudohyphae with terminal spherical conidia. Branching occurs from the quadrants of the parent cell with secondary branching occurring quite often. No crosswalls form between hyphal cells.
Formation of ascospores.
Asci with ascospores were observed in cultures of PYCC 4605T after 34 days incubation at 17 °C in dilute (1 : 15) V8 agar medium. Asci are clavate in shape and develop directly from vegetative cells. Some asci develop directly after conjugation of two cells followed by differentiation at one end of the conjugant giving rise to a long cylindrical peduncle. Mature asci (36x143 µm) usually contain two spindle-shaped ascospores, side by side, with their pointed ends oriented towards the peduncle or elongated portion of the ascus (Fig. 2
), but occasionally asci with one protruding ascospore are observed. Asci occur either in pairs or groups of short chains, show different stages of development and are usually persistent. Older asci show ascospores with swollen ends containing visible vacuolar and lipidic material. No ascospores were observed in strain PYCC 5767.
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Etymology.
The specific epithet lachancei, Latin gen. of Lachance, was chosen in honour of Professor Marc-André Lachance, in recognition of his important contribution to yeast taxonomy and the discovery of exotic species of the yeast genus Metschnikowia.
Origin and deposits.
The type strain PYCC 4605T [=UWO(PS) 7ASB2.3T] was isolated from nectar of the flower Asclepias syriaca in South Bombay, NY, USA. This strain has been deposited (living and dried) in the PYCC CREM, Universidade Nova de Lisboa, Caparica, Portugal, and under number CBS 9131 in the Centraalbureau voor Schimmelcultures, Utrecht, The Netherlands.
G+C content and nDNA relatedness
Initial characterization of the two new species was from mol% G+C content, which revealed that they separated into two groups, M. lachancei with 46·9 mol% and M. vanudenii with a strain mean of 43·5 mol%. This latter value is similar to the G+C content of M. reukaufii (Table 1
). nDNA reassociation experiments demonstrated M. vanudenii, M. lachancei and M. gruessii to be separate species (Table 3
), which is consistent with relationships determined from rDNA sequence analysis (Fig. 3
).
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| ACKNOWLEDGEMENTS |
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