Thesis (MSc)--University of Stellenbosch, 2006. / ENGLISH ABSTRACT: It is known that many hyphomycetous fungi are dispersed by wind, water and
insects. However, very little is known about how these fungi may differ from each other
regarding their ability to be disseminated by different environmental vectors.
Consequently, to obtain an indication of the primary means of spore dispersal employed
by representatives of the genera Acremonium, Aspergillus and Penicillium, isolated from
soil and indoor environments, we monitored spore liberation of cultures representing
these genera in an airflow cell. The experimental data obtained, of plate counts
conducted of the air at the outlet of the airflow cell, were subjected to an appropriate
analysis of variance (ANOVA), using SAS statistical software. Intraspecific differences
occurred regarding aerial spore release. Under humid conditions, however, Penicillium
species were more successful in releasing their spores than Aspergillus and the
Acremonium strain. Under desiccated conditions the Aspergillus took longer to release
their spores than representatives of Acremonium and Penicillium. The taxa that were
investigated did not differ from each other regarding the release of spores in
physiological salt solution (PSS). Although not proven, indications are that water may
act as an important dispersion agent for these fungi, because washing of cultures with
PSS resulted in all cases in an immediate massive release of colony forming units.
Subsequently, using standard plate count techniques, conidial adhesion of the
fungi mentioned above to synthetic membranes, leaf cuttings and insect exoskeletons
differing in hydrophobicity and electrostatic charge were investigated. We found that the
different genera showed different adhesion profiles for the series of test surfaces,
indicating differences in physico-chemical characteristics of the fungal spore surfaces. In
general, the Penicillium strains showed a greater ability to adhere to the test surfaces,
than the aspergilli, while the representative of Acremonium showed the least adherence.
No significant difference in the percentage spore adhesion was found between
hydrophobic and hydrophilic materials. Furthermore, evidence was uncovered supporting the contention that, under dry
conditions, electrostatic surface charges play a role in the adherence of fungal spores to
surfaces, because adherence was positively correlated (Correlation coefficient = 0.70898,
p = 0.001) to positive electrostatic charges on the lamellar surfaces. In the next part of
the study, standard plate count methods were used to determine the relative adhesion of
the above mentioned hyphomycetous fungi, as well as a polyphyletic group of yeasts, to
the test surfaces submerged in 10 mM sodium phosphate buffer (pH 7.0).
As was found with the experiments with the dry surfaces, both intraspecific and
intergenus differences were uncovered. Overall, the fungi adhered better to hydrophilic
surfaces than to hydrophobic surfaces. This indicated that the fungal surfaces were
covered with relatively hydrophilic compounds such as carbohydrates. Subsequently, it
was demonstrated that all the fungi adhered to plasma membrane glycoprotein coated
polystyrene and the presence of fungal carbohydrates on the surfaces of the fungal
propagules was confirmed using epi-fluorescence microscopy. Differences in the
strategy of the fungal genera to release their airborne spores, as well as differences in
their adhesion profiles for the series of test materials, may be indicative of a unique
environmental niche for each genus. In future, this phenomenon should be investigated
further. / AFRIKAANSE OPSOMMING: Hifomisete fungi is daarvoor bekend om te versprei deur middel van wind, water,
en insek vektore. Maar nietemin, daar is bykans geen kennis m.b.t. hoe hierdie fungi van
mekaar verskil t.o.v. hul vermoë om versprei te word deur omgewings vektore nie.
Gevolglik was spoorvrystelling van kulture, verteenwoordigend van die genera
Acremonium, Aspergillus en Penicillium gemoniteer om ‘n aanduiding te kry van
primêre wyse van spoorverspreiding waardeur verteenwoordigers van die onderskeie
genera ingespan word. Eksperimentele data ingewin, vanaf plaat tellings wat uitgevoer
was op lug afkomstig vanuit die uitlaat-klep van die lugvloei kapsule, was onderwerp aan
‘n toepaslike analise van afwyking (ANOVA), deur gebruik te maak van ‘n SAS
statistiese pakket. Intraspesie verskille is waargeneem t.o.v. lug spoorvrystelling.
Desnieteenstaande was Penicillium meer suksesvol onder vogtige kondisies t.o.v.
spoorvrystelling in vergelyking met Aspergillus en die Acremonium stam. Onder droë
kondisies het verteenwoordigers van Aspergillus langer geneem om hul spore vry te stel
as verteenwoordigers van onderskeidelik, Penicillium en Acremonium. Geen verskille
was waargeneem m.b.t. spoorvrystelling in fisiologiese soutoplossing (FSO) tussen die
verskillende filogenetiese stamme nie. Alhoewel dit nie bewys is nie, wil dit voorkom
asof water as belangrike verspreidingsagent van die betrokke fungi dien, aangesien die
spoel van kulture met FSO tot ‘n oombliklike enorme vrystelling van kolonie-vormende
eenhede gelei het.
Gevolglik, deur gebruik te maak van standaard plaattellings tegnieke, was spoor
aanhegting van bogenoemde fungi aan sintetiese membrane, blaar snitte en insek
eksoskelette wat verskil in terme van hidrofobisiteit en elektriese lading, ondersoek.
Daar was gevind dat die aanhegtingsprofiele m.b.t. hierdie reeks toetsoppervlaktes van
die verskillende genera verskil, wat op sigself ‘n aanduiding was van verskille in fisieschemiese
eienskappe van die swamspoor oppervlaktes. Penicillium stamme het ‘n hoër
aanhegtings vermoë aan die toetsoppervlaktes getoon as die aspergilli, terwyl die
verteenwoordiger van Acremonium die laagste aanhegting getoon het.
Geen betekenisvolle verskille i.t.v. persentasie spoor aanhegting was gevind tussen
hidrofobiese en hidrofiliese oppervlakte nie. Daarbenewens was die argument dat spoorvrystelling onder droë kondisies
beïnvloed word deur elektrostatiese oppervlak ladings, bevestig deur ons bevindinge,
want aanhegting het positief gekoreleer (Korrelasie koëffisient = 0.70898, p = 0.001) met
positiewe ladings op die oppervlaktes. ‘n Standaard plaattellingstegniek was aangewend
in die volgende fasset van die studie om die relatiewe aanhegting van bogenoemde
hifomisete fungi, sowel as ‘n polifilitiese groep giste aan die toetsoppervlaktes, gedompel
in 10 mM natrium fosfaat buffer (pH 7.0) vas te stel.
Intraspesie en intragenus verskille was weereens waargeneem, net soos in die
geval van die eksperimente met die droë oppervlakte. In die algemeen het die swamme
baie beter geheg aan hidrofiliese oppervlaktes in vergelyking met hidrofobiese
oppervlakte. Dit was ‘n aanduiding dat die swamspoor oppervlaktes bedek was met
relatiewe hidrofiliese verbindings bv. koolhidrate. Verder was daar bewys dat alle
swamme ingesluit in hierdie studie die vermoë het om plasmamembraan glikoproteïn
bedekte polistireen te bind, en gevolglik was die teenwoordigheid van van koolhidrate op
die swamspore bevestig m.b.v epi-fluoresensie mikroskopie. Verskille in die strategie
van swamme om spore in die lug vry te stel, sowel as verskille in die aanhegtingsprofiele
vir ‘n reeks toetsmateriale, mag net ‘n aanduiding wees van ‘n unieke omgewings nis vir
elke genus wat in hierdie studie ondersoek is. Hierdie verskynsel moet dus in die nabye
toekoms nagevors word.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/17371 |
| Date | 04 1900 |
| Creators | Hart, Rodney S. (Rodney Sebastian) |
| Contributors | Botha, A., University of Stellenbosch. Faculty of Science. Dept. of Microbiology. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 116 leaves : ill. |
| Rights | University of Stellenbosch |
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