1993 - Mycological Society of America

had been colonized with Pestalotia sp. for 3 weeks and dipped in a
spore suspension containing conidia of Trichoderma sp., Cladosporium
sp. and Penicillium sp.. Commercial bleach was the most effective of
these treatments. ~ h t i oof n fungal taxa associated with f. Bsus
involved the collection of standing dead senescent leaves from random
sites within the wetland. Leaves were cut into 2 an long pieces; 100
leaf pieces were surface sterilized for 5 min. in 50/50 v/v commercial
bleach ahd 100 were left untreated. Fifty leaf pieces of each treatment
were plated onto 1/2 strength corn meal agar and the remaining 50
onto mineral water agar (damp chamber). Frequency of fungal taxa
from surface sterilized leaves indicated that the most common genera
were Cuymqma sp. (56%), Drechslera sp. (52"/0), Phoma sp. (30%) and 2
unidentified Deuteromycetes in the Moniliales (58%) and the Melanconiales
(44%). Untreated leaf material supported similar fungal taxa,
but with much higher frequencies of Cladospwium sp. (68% vs. 4% in
surface sterilized treatments), Rhinodadielln sp. (42% vs. 12%), Altermria
sp. (34% vs. 14%) and Acremaium sp. (24% vs. 0%).
Poster D5; Sunday pm
Double-stranded RNA from Phytophthora
megaspma as a probe for the initiation of
the parasexual cycle
David N. Kuhn, Benjamin Allen, and Jose Soto. Dept. of
Biological Sciences, Florida International Univ., Miami, FL
33199.
We plan to produce a cDNA to a portion of the double-stranded RNA
(dsRNA) we have observed in three Phytopkfhura megaspemu isolates.
With this cDNA as a hybridization probe, we will monitor the transfer
of dsRNA into uninfeded cultures. DsRNA transfer requires hyphal
fusion, the first step in the parasexual cycle, but may occur without
formation of a stable heterokaryon or karyogamy, later stages in the
parasexual cycle. Previously, we could only observe stable hetero-
karyons. Now, detection of dsRNA transfer by hybridization should
prove a more sensitive measure of the initiation of the parasexual
cyde. We characterized the dsRNA by electrophoresis, hybridization,
and in vitro translation prior to cDNA cloning.
DsRNA was isolated from three P. megaspenna cultures (kindly supplied
by Dr. Everett Hansen, Oregon State Univ.) from two different
regions and pathogenic on different hosts. Each culture had the identi-
. cal four molecules of dsRNA: 14.8 kb, 5.8 kb, 1.9 kb, and 0.8 kb. The
smaller molecules all hybridized with the largest (14.8 kb) molecule.
Total dsRNA showed no hybridization to P. megasperma DNA or RNA.
Interestingly, total dsRN~from P. megasperma hybridized with dsRNA
from P. infestans. In etro translation of total P. megasperma dsRNA
resulted in nine dsRNA-specific protein products ranging from 235 to
89 kDa. The largest dsRNA molecule encoded six of these proteins. In
vivo labelling experiments suggest that expression of dsRNAspecific
proteins are synthesized at an early growth stage in the host cell.
Poster E17; Sunday pm
The systematics of the Ramalina americana group
Scott. Dept. of Botany, Box 90339, Bio. Sci. Bldg., Duke
Univ., Durham, NC 277084339.
In a systematic investigation of the chemotypes of the lichen Ramalina
mnericmra, a pilot study utilizing PCR fragment banding patterns suggests
that the chemotypes are a monophyletic group. RFLP patterns
obtained by digesting the PCR fragments with four-cutter restriction
enzymes demonstrate that genetic variability exists within chemotypes.
The breeding system of these fungi will be elucidated by the
chemical analysis of the progeny of maternal individuals of known
chemotype. ~reliminar~wo;k has resulted in the rediscovery of the
sekikaic/homosekikaic acid race of R. a m ' m and has yielded the
first report of meta-depside production in a lichen fungus culture.
Symposium; Monday pm
Use of white-rot fungi in bioremediation of
contaminated soil
Richard T. lamar. Institute for Microbial and Biochemical
Technology, USDA-Forest Service, Forest Products Laboratory,
Madison, WI.
The ability of lignindegrading fungi to transform and in many cases
completely - - mineralize a wide variety of hazardous organic compounds
in aqueous culture has generated inkrest in using the& organisms in a
varietv of bioremediation and biotreatment activities. We have focused
our wbrk on the development of a technology for the bioremediation
of contaminated soils, initially targeting soils contaminated with the
wood preservative pentachlorophenol (PCP). This technology involves
inoculation of contaminated soil with selected species of lignindegrading
fungi that colonize the soil and transform the contaminants
to innocuous products.
We have evaluated the utility of lignindegrading fungi in soil remedi-
ation in several independent field investigations. In the first study, the
ability of two lignin>egrading fungi to deplete PCP from a stro&ly
alkaline (pH 9.6) sandy gravel soil, that was contaminated with a com-
mercial wood preservative, was examined. Inoculation of soil contain-
ing 250 to 400 ppm PCP with either Phanerochaete duysosporium or
P. sordida resulted in overall decreases of 88% to 91% of PCP in the
soil in 6.5 weeks. Inocula consisted of aspen (Populus tremuloides
Michx.) wood chips thoroughly grown through with P. chrysosporium
or P. wdida. The demease was achieved under suboptimal tempera-
hues for the growth and activity of these organisms and without the
addition of inorganic nutrients. However, because the soil had a very
low organic matter content, peat was included as an additional source
of organic carbon for fungal growth and activity.
The second study was a treatability study conducted at the former
Brookhaven Wood Preserving facility in Brookhaven, MS. While the
facility was in operation both PCP and creosote we^ used to treat
poles. the abilities of the lignin-degrading fungi P. chrysospmium, P.
sordida, and Trmnetes hissuta to remove PCP and polynuclear aromatic
(PAH) components of creosote from a strongly acidic (pH 3.8) day soil
from a waste sludge pile were evaluated. Inoculation of soil that was
contaminated with PCP (672 ppm) and creosote (total of 15 measured
PAWS ca 4017 PPM) with P. sordida resulted in an 89% depletion of
PCP and a 75% depletion of total measured PAWS after 8 weeks.
Inocula consisted of pure cultur& of each organism grown on a
nutrient foMed sawdust-grain mixture used in the commercial
,cultivation of mushrooms.
Results from these field trials demonstrate that the development of a
technology that employs lignin-degrading fungi to remediate contami-
nated soils is promising. Actual implementation of the technology on a
commercial scale will require the development of an economical and
effective inoculum and improvement in the efficiency of contaminant
removal.
SymposiumTuesday, 1020 am
Current trends in the molecular
epidemiology of fungal infections
Brent J a*. Mycotic Diseases Branch, Centers for Disease
Control, Atlanta, GA 30333.
Poster 15; Sunday pm
The Lactatius species of Minnesota, systematics
and biogeography of section Dapetes Fr. ex Burl.
Patrick R. Jeacock. Dept. of Plant Biology, Univ. of Minnesota,
St. Paul, MN 55108.
The Lactarius flora of Minnesota is strongly affiliated with that of the
Great Lakes region. The biomes of boreal forest, eastern deciduous