Book of Abstracts (PDF) - International Mycological Association

IMC7 Main Congress Theme III: PATHOGENS AND NUISANCES, FOOD AND MEDICINE Posters
propagules counts made by flow cytometry were compared
with counts by direct observation using epifluorescence
microscopy. Flow cytometric counts of laboratory
suspensions were performed by the use of forward angle
light scattering, a parameter related to particle size. Field
samples were stained with propidium iodide after
microwave irradiation, to discriminate the biological
particles, while forward angle light scattering was used for
identifying and counting fungal propagules population. A
close agreement was found between FCM and
epifluorescence microscopy counts.
874 - A 6 methylsalicylic acid synthase (6MSAS)
homologous gene isolated Byssochlamys nivea is
expressed during patulin production
O. Puel 1* , A. Foures 1 , R. Benaraba 1 , M. Delaforge 2 & P.
Galtier 1
1 I.N.R.A. Laboratoire de Pharmacologie et Toxicologie,
180 Chemin de Tournefeuille BP3 31931 Toulouse cedex 9,
France. - 2 CEA Saclay DSV/DRM/ SPI, Bat136, F91191
Gif sur Yvette Cedex, France. - E-mail:
opuel@toulouse.inra.fr
The Byssochlamys nivea NRRL 2615 strain can produce
mycophenolic acid and patulin. We used degenerate PCR
primers matching a ketosynthase nucleotide motif for a
RACE-PCR strategy and isolated a polyketide synthase
gene from B. nivea. The deduced amino acid sequence
(1778 residues) displays 74% identity with Penicillium
patulum 6-methylsalicylic acid synthase (6MSAS). Two
6MSAS homologous fragments located respectively on the
5 and 3 extremities were isolated from the mycophenolic
acid producer P. brevicompactum genome. After
translation, these fragments display 87 and 93% identity
with P. patulum 6MSAS. B. nivea and P. brevicompactum
cultures were monitored for PKS transcription kinetics by
RT-PCR. The B. nivea messenger is expressed throughout
the first 10 days of culture with a maximum observed level
between day 2 and 5. Using the HPLC/DAD and LC/MS,
the patulin precursor 6- methylsalicylic acid (day1-5),
patulin and mycophenolic acid (2-10) were detected in B.
nivea cultures. On the other hand, the mycophenolic acid
was detected in P. brevicompactum cultures, but not
patulin and 6-methylsalicylic acid. The P. brevicompactum
messenger was not expressed during culture. The B. nivea
amino acid sequence does not contain any methyl
transferase site required in the 5-methylorsellinic acid
synthesis (first precursor mycophenolic acid). The results
strongly support the identification of a new 6MSAS
involved in patulin and not in acid mycophenolic acid
synthesis in B. nivea.
875 - Comparison of genotypes and pathobiological
phenotypes of environmental and commensal isolates of
Candida albicans
M.G. Quick 1 , J. Xu 2 , T.G. Mitchell 2 & D.E. Padgett 1*
1
Biology Dept., Univ. of NC at Wilmington, 601 S. College
Rd. Wilmington, NC 28403, U.S.A. -
2
Dept. of
Microbiology and Immunology, Duke Univ., Medical
Center, Durham, NC 27710, U.S.A. - E-mail:
Padgett@uncwil.edu
The patterns of genetic variation, production of
phospholipase, and growth rate were analyzed among 129
isolates of the human pathogenic yeast, Candida albicans.
Two populations of C. albicans were studied: 71 strains
were collected from aquatic sources and 58 control strains
were isolated from oral samples of healthy human
volunteers. The phenotypes and genotypes were compared
to determine if environmental isolates represent a greater
risk to human health than commensal isolates. Genetic
analysis, which was performed by PCR fingerprinting,
revealed these two populations were genetically similar and
agree with previous studies based on codominant genetic
markers that the population structure of C. albicans is
predominately clonal. There was no difference in the
percent of phospholipase positive cultures between the two
populations. However, among the isolates that were
positive for enzyme production, the commensal isolates
secreted significantly more phospholipase than the
environmental isolates. Growth rate studies revealed that
the environmental isolates replicated at approximately the
same rate, as did commensal isolates. The DNA genotypes
and the phospholipase results also were similar for the
environmental and commensal isolates.
876 - Ultrastructure of pycnidial cells and
conidiogenesis of Septoria hyperici in dead tissues of
host plant
E. Rakhimova
Institute of Botany & Phytointroduction, 36 D Timiryazev
Str., Almaty, Kazakhstan. - E-mail: envirc@nursat.kz
The techniques of light and electron microscopy were used
to elucidate the details of pycnidial cells and conidium
ontogeny in Septoria hyperici Desm., causal agent of
foliage disease (leaf blotch) of common St. John's wort
(Hypericum perforatum L.). The pycnidia were present in
the intercellular spaces of host leaf tissues. The wall of
subspherical pycnidium, visible under the light microscope,
was composed of 1-3 layers of hyphae with normal
structure. The hyphal cell protoplast was highly vacuolated,
with well defined nucleus, numerous mitochondria,
ribosomes, short cisternae of ER, and concentric bodies.
Pycnidial wall septa had typical ascomycetous structure.
The conidiophores with electron-dense cytosol, numerous
mitochondria and large nucleus were found in inner layer
of pycnidial wall. Conidiophores were less vacuolated, than
Book of Abstracts 263