Thesis (MSc)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: Leptospirillum ferriphilum is a moderately thermophilic, iron-oxidizing bacterium that was
isolated from a continuous-flow biooxidation plant used for the recovery of gold from
arsenopyrite ore concentrates. Over many years of continuous selection, L. ferriphilum and
other bacteria associated with this environment developed resistance to high concentrations of
arsenic. We investigated the arsenic resistance genes (ars) of Leptospirillum ferriphilum strain
Fairview and compared these genes to the ars genes from other Leptospirilli. An arsenic
resistance operon (ars operon) was isolated from a L. ferriphilum Fairview genebank. We
discovered that this ars operon was situated in between divergently transcribed transposase
(tnpA) and resolvase (tnpR) genes related to the Tn21 subfamily of transposons. Sequence
analysis of this transposon ars operon indicated the presence of arsRCDAB genes and an
additional CBS orf, located in between the arsA and arsB genes. The 8.5 kb L. ferriphilum
transposon ars operon (TnLfArs) was shown to be present only in L. ferriphilum strain
Fairview and none of the other Leptospirillum strains. The TnLfArs conferred resistance to
arsenate and arsenite in an Escherichia coli ars mutant. We also showed that the TnLfArs is
capable of transposition in Escherichia coli. / AFRIKAANSE OPSOMMING: Leptospirillum ferriphilum, ‘n matig termofilies, yster-oksiderende bakterium, is een van `n
konsortium bakterieë betrokke by die biologiese herwinning van goud uit arsenopiriet erts.
Oor vele jare het die selektiewe druk, weens hoë arseen konsentrasies teenwoordig in die erts,
veroorsaak dat L. ferriphilum en die ander bakteriee geassosieer met die omgewing, verhoogde
vlakke van weerstandbiedendheid teen die metaal opgebou het. Die doel van die studie was
om die aard van die aanpassing op die molukulere vlak vas te stel deur die gene wat in L.
ferriphilum (Fairview ras) hiervoor verantwoordelik is te identifiseer en te vergelyk met die
van ander Leptospirilli. `n Arseen weestandbiedendheids operon (ars operon) is met behulp
van `n L. ferriphilum geen-bank geisoleer. DNA-volgorde bepaling het aangedui dat die
operon arsRCDAB gene bevat, sowel as `n CBS orf, gelee tussen die arsA en arsB gene. Die
hele operon is gelee tussen `n tnpR- (resolvase) en tnpA (transposase) gene wat in
teenoorgestelde rigtings getranskribeer word. Hierdie gene behoort aan die Tn21 familie van
transposons. Daar is gevind dat die 8.5 kb L. ferriphilum transposon wat die ars operon bevat
(TnLfArs) slegs teenwoordig is in die Fairview ras van L. ferriphilum maar in geen van die
ander Leptospirillum rasse nie. Die TnLfArs het weerstanbiedendheid verleen, teen beide
arsenaat en arseniet, aan `n Escherichia coli arseen-sensitiewe mutant. Die vermoë van die
transposon (TnLfArs) om transposisie te ondergaan is ook in E. coli bevestig.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/16607 |
| Date | 10 1900 |
| Creators | Hector, Stanton Bevan Ernest |
| Contributors | Rawlings, D.E., 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 | iii, 112 leaves : ill. |
| Rights | University of Stellenbosch |
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