Samson, Heidi E. (Heidi Estrelita) (2001-03)
Thesis (MSc)--University of Stellenbosch, 2001.
these fungi from a wide diversity of geographical areas in southern Africa.
However, it is known that psychrotolerant mucoralean fungi, able to grow at
25°C as well as at 5°C, occur in pristine Alti Mountain Grassland. Nothing is
known about the diversity of these psychrotolerant soil fungi in other vegetation
types of South Africa.
Consequently, in this study, the psychrotolerant fungal taxa and numbers in soil
from a vineyard and from pristine Mountain Fynbos were determined using an
incubation temperature of 4°C and a complex isolation medium. The latter
contained agar, malt extract, peptone, yeast extract, penicillin and streptomycin
sulphate. Soil samples were analysed in late summer, autumn and mid-winter.
It was found that, for the samples taken in late summer and autumn, the
diversity of mucoralean species in the soil differed between fynbos and
vineyard. In winter however, no significant difference was detected between the
Shannon's diversity indices of mucoralean species in the soil samples taken
from the two habitats. It was found that in both soil types, the percentage
mucoralean fungi on the plates increased from summer to winter. In addition,
the numbers of detectable Morlierella subgenus Morlierella on the plates were
higher in winter than in late summer. The diversity of mucoralean species
obtained during winter in fynbos and vineyard soil was significantly less than the
diversity of these species in Alti Mountain Grassland soil.
To determine if the Morlierella subgenus Morlierella isolates from the fynbos
and vineyard soil, and those obtained from Alti Mountain Grassland, differ in the
ability to grow at low temperatures, the radial growth rate on malt extract agar at
4°C and BOC was determined for each isolate. The results indicate that not only
did seasonal changes occur in the taxa within Morlierella subgenus Morlierella,
but that the isolates dominating the soil in different seasons also differed in the
ability to grow at low temperatures. The percentage of isolates that had
reached greater colony diameters after B days of incubation at 4°C, was higher for the isolates obtained in the cold wet month of July than for those obtained in
the warmer dryer month of February. Similar results were obtained with the
radial growth experiments conducted at BOC. The Morlierella subgenus
Morlierella isolates obtained in winter from fynbos and vineyard soil showed
less variation in low temperature growth rate than the isolates of this taxon
obtained in winter from Alti Mountain Grassland soil during a previous study.
This variation corresponds to the greater number (20) of Morlierella subgenus
Morlierella species found in the grassland soil. Altogether only seven species
of this subgenus was detected during the present study in the fynbos and
vineyard soil samples. It was speculated that this difference in diversity
between the fynbos and vineyard isolates, and the grassland isolates obtained
in a previous study, might have been as a result of differences in the habitat or
the enumeration methods used.
The phylogenetic relationship between different psychrotolerant isolates of
Morlierella subgenus Morlierella originating from the soil of the fynbos, vineyard
and Alti Mountain Grassland, was subsequently determine through comparison
of ITS regions, within ribosomal RNA repeats. Consequently, 45
psychrotolerant Morlierella subgenus Morlierella isolates originating from the
three soil habitats was compared on the basis ITS 1 nucleotide sequence
composition and radial growth rate at 4°C. Phylogenetic analyses showed that
the isolates could be grouped into two clusters correlating with the ability to
grow at low temperatures. Each cluster was further subdivided into two
subgroups. It was found that except for one subgroup and the reference strain
occurring in another subgroup, all the subgroups contain isolates originating
from a single soil habitat. Therefore, the ITS 1 sequence of these fungi seems
to indicate the original habitat and ability to grow at low temperatures. This
correlation of the ITS sequence with the ecological habitat of a fungus has also
been observed by other workers for other fungal groups.
AFRIKAANSE OPSOMMING: Mucoraliese fungi is meestal saprotrofe wat dikwels in grondhabitatte aangetref
word. Deur gebruik te maak van 'n isolasietemperatuur van circa 25°C, het
ander werkers dié fungi van 'n wye verskeidenheid geografiese gebiede in
suidelike Afrika verkry. Dit is egter bekend dat die psigrotolerante mucoraliese
fungi, wat in staat is om by 2SoC en ook by SaC te groei, in ongeskonde Alti
Berg-Grasland voorkom. Niks is egter bekend oor die diversiteit van dié
psigrotolerante grondfungi in ander veldtipes van suidelike Afrika nie.
Die psigrotolerante fungustaksa en -getalle in grond van 'n wingerd en van
ongeskonde Berg Fynbos is gevolglik in dié studie bepaal deur gebruik te maak
van 'n inkubasietemperatuur van 4"C en 'n komplekse isolasiemedium.
Laasgenoemde het agar, moutekstrak, peptoon, gisekstrak, penisillien en
streptomisiensulfaat bevat. Grondmonsters is in die laatsomer, herfs en
midwinter geanaliseer. Daar is 'n verskil gevind tussen die diversiteit van die
mucoraliese spesies in die grond van fynbos en dié van wingerd in die monsters
wat in die laatsomer en midwinter geneem is. In die winter is daar egter geen
beduidende verskil gevind tussen die Shannon diversiteitsindekse van
mucoraliese spesies in die grondmonsters wat uit die twee habitatte getrek is
nie. In albei grondtipes is daar gevind dat die persentasie mucoraliese fungi op
die plate toegeneem het van somer tot winter. Daarby was die aantal
waarneembare Morlierella subgenus Morlierella op die plate meer in die winter
as in die laatsomer. Die diversiteit van mucoraliese spesies wat in die winter uit
fynbos- en wingerdgrond verkry is, was beduidend minder as die diversiteit van
dié spesies in Alti Berg-Grasland grond.
Om te bepaal of die Morlierella subgenus Morlierella isolate van die fynbos- en
wingerdgrond en dié van Alti Berg-Grasland van mekaar verskil ten opsigte van
hul vermoë om by lae temperature te groei, is die radiale groeitempo op
moutekstrak by 4"C en aoc vir elke isolaat bepaal. Die resultate dui aan dat
daar nie alleen seisoenale veranderinge in die taksa binne Morlierella subgenus
Morlierella voorkom nie, maar dat die isolate wat tydens verskillende seisoene
uit die grond verkry is, ook ten opsigte van hul groeivermoë by lae temperature van mekaar verskil. Die persentasie isolate wat groter kolonie diameters bereik
het ná B dae inkubasie by 4°C, was hoër vir die isolate van die koue, nat
Juliemaand as vir dié wat in die warmer en droër Februariemaand verkry is.
Soortgelyke resultate is verkry met radiale groei-eksperimente wat by BOC
gedoen is. Die MortierelIa subgenus MortierelIa isolate wat in die winter uit
fynbos- en wingerdgrond verkry is, het In kleiner variasie in hul groeitempo by
lae temperature getoon as die isolate in dié takson wat tydens 'n vorige studie
in die winter uit Alti Berg-Grasland grond verkry is. Dié variasie stem ooreen
met die groter aantal (20) MortierelIa subgenus MortierelIa spesies wat in die
graslandgrond gevind is. Slegs sewe spesies van dié subgenus is gedurende
die huidige studie in die fynbos- en wingerdgrondmonsters waargeneem. Daar
is gespekuleer dat dié verskil in diversiteit tussen die fynbos- en wingerdisolate
en die graslandisolate van die vorige studie die gevolg mag wees van verskille
tussen die habitat of die enumerasiemetodes wat gebruik is.
Die filogenetiese verwantskap tussen verskillende psigrotolerante isolate van
MortierelIa subgenus MortierelIa uit die grond van die fynbos, wingerd en Alti
Berg-Grasland, is vervolgens bepaal deur 'n vergelyking van interne
getranskribeerde spasieerder (ITS) areas, binne ribosomale RNS herhalings.
Daar is gevolglik 45 psigrotolerante MortierelIa subgenus MortierelIa isolate uit
die drie grondhabitatte met mekaar vergelyk op grond van die basis ITS 1
nukleotied opeenvolgingsamestelling en radiale groeitempo by 4°C.
Filogenetiese analises het die isolate in twee groepe verdeel op grond van hul
vermoë om by lae temperature te groei. Elke groep is verder in twee subgroepe
verdeel. Daar is gevind dat behalwe vir een subgroep en die verwysingstam
wat in 'n ander subgroep voorgekom het, elkeen van die subgroepe bestaan het
uit isolate wat van 'n enkele grond habitat verkry is. Dit wil dus voorkom of die
ITS 1 opeenvolging van dié fungi 'n aanduiding gee van die oorspronklike
habitat en die vermoë om by lae temperature te groei. Dié korrelasie tussen die
ITS opeenvolging en die ekologiese habitat van 'n fungus is ook deur ander
werkers vir ander fungusgroepe waargeneem.
Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/52423
This item appears in the following collections: Masters Degrees (Microbiology)102