Thesis (MSc)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: The 14.2 kb plasmid pTC-FI4 was isolated from the moderately thermophilic (45°-
50°C), highly acidophilic (pH 1.5 to 2.5), chemolithotrophic bacterium
Acidithiobacil/us caldus and has a replicon that is closely related to the promiscuous,
broad host-range, IncQ-family of plasmids. The region containing the mobilization
genes was sequenced and encoded five Mob proteins and an origin of transfer, which
are related to the DNA processing (Tral) region of IncPI plasmids, rather than to the
three Mob protein systems of the IncQ-l-group plasmids (e.g. plasmids RSFIOIO or
R1162). Plasmid pTC-F14 is the third example of an IncQ family plasmid that has
five mob genes, with the others being pTF-FC2 and pRAS3.1. The minimal region
that was essential for mobilization included the mobA, mobB and the mobC genes as
well as the oriT. The mobD and mobE genes were non-essential, but together
enhanced the mobilization frequency by approximately 300-fold. The repB gene
increased the mobilization frequency but was not essential for mobilization.
Mobilization of pTC-F14 between Escherichia coli strains by a chromosomally
integrated RP4 plasmid was more than 3500-fold less efficient than the mobilization
ofpTF-FC2. When both plasmids were co-resident in the same E. coli host, pTC-FI4
was mobilized at almost the same frequency as pTF-FC2. This enhanced pTC-FI4
mobilization frequency was due to the presence of a combination of the pTF-FC2
mobD and mobE gene products, the functions of which are still unknown. pTF-FC2
could mobilize the oriT of pTC-FI4 whereas pTC-F14 could only mobilize the pTFFC2
oriT if provided with some of the mobilization genes from the pTC-FC2
mobilization region. Unexpectedly either the mobEDC genes or the mobAB genes
would allow the mobilization of the pTF-FC2 oriT by pTC-F14 even though there
was no common gene between the two subsets. No evidence for any negative effect
on the transfer of one plasmid by the related, potentially competitive plasmid was
obtained. / AFRIKAANSE OPSOMMING: Die 14.2 kb plasmied, pTC-F14, is uit die matig termofiliese (45°C tot 50°C), hoogs
asidofiliese (pH 1.5 tot 2.5), chemolitooutotrofiese bakterium Acidithiobaci/lus caldus
geisoleer en beskik oor 'n replikon wat verwant is aan die vanaf die IncQ-familie van
plasmiede. Hierdie plasmiede is alom bekend vir hulle promiskuïteit tydens
konjugasie asook hul vermoë om in 'n groot aantal verskillende gasheer organismes te
kan repliseer. DNA volgorde analise van die mobiliserings area het 'n oordrags
oorsprong asook vyf oop leesrame onthul wat nader verwant is aan die DNA
prosseserings gene van die Tral area op die IncP 1 plasmiede, as die van die
mobiliserings stelsel van die IncQ-l-groep plasmiede. Plasmied pTC-Fl4 is die derde
voorbeeld, saam met pTF-FC2 en pRAS3.1, van 'n IncQ-tipe plasmied met 'n vyfgeen
mobiliserings sisteem. Die kleinste area op die plasmied nodig vir mobilisering
van pTC-Fl4 is bepaal, en het die mobA, mobB en mobC gene sowel as die oordrags
oorsprong ingesluit. Saam, was die mobD en mobE gene verantwoordelik vir 'n 300-
voud toename in die mobilisasie frekwensie van pTC-Fl4 alhowel die gene nie
absoluut nodig was vir mobilisering van die plasmied nie. Die repB geen het ook
bygedra tot die frekwensie waarteen die volledige plasmied gemobiliseer was, maar
hierdie geen was ook nie nodig vir mobilisering van die pTC-F14 plasmied nie.
Die frekwensie waarteen pTC-Fl4 tussen Escherichia coli rasse beweeg het tydens
konjugasie, terwyl gebruik gemaak is van 'n chromosomaal geintegreerde RP4
plasmied, was ongeveer 3500-voud laer as die van pTF-FC2. Indien beide pTC-Fl4
en pTF-FC2 in dieselfde E. coli gasheer aangetref word, word beide plasmiede teen
ongeveer dieselfde frekwensie gemobiliseer. Die verhoogde frekensie vir pTC-Fl4
was as gevolg van die teenwoordigheid van beide die mobD en mobE gene van die
pTF-FC2 plasmied, waarvan die funksies nog onbekend is. Plasmied pTF-FC2 kon
die oordrags oorsprong van pTC-Fl4 mobiliseer waarteenoor plasmied pTC-FI4 die
oordrags oorsprong vanafpTF-FC2 slegs kon mobiliseer indien een van twee dele van
die pTF-FC2 mobiliserings gene voorsien word (al was daar geen oorvleuling tussen
die twee nie). Alhoewel die plasmiede moontlik kon kompeteer op die vlak van
plasmied oordrag is geen negatiewe kompetesie waargeneem tussen dié twee
verwante plasmiede nie.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/70109 |
| Date | 12 1900 |
| Creators | Van Zyl, Leonardo Joaquim |
| Contributors | Rawlings, D. E., Stellenbosch University. Faculty of Science. Dept. of Microbiology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | viii,117 p. : ill. |
| Rights | Stellenbosch University |
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