Thesis (MSc (Microbiology))--University of Stellenbosch, 2009. / Biomining organisms are generally found in metal-rich, inorganic environments such as iron and sulfur
containing ores; where they play a vital role in mineralization and decomposition of minerals. They are
typically obligatory acidophilic, mesophilic or thermophilic, autotrophic, usually aerobic, iron-or sulfur
oxidizing chemolithotrophic bacteria. The most prominent biomining organisms used in bioleaching of
metal sulfides are Acidithiobacillus ferrooxidans, At. thiooxidans, At. caldus, Sulfobacillus spp. and
Leptospirillum spp. Biomining enables us to utilize low grade ores that would not have been utilized
by conventional methods of mining. Research has focused on the backbone features of plasmids
isolated from bacteria of biomining environments. The aim of this study is to sequence and analyze an
18 kb region of the 66 kb plasmid pTcM1 isolated from At. caldus MNG, focusing on accessory genes
carried by this plasmid.
Fifteen putative genes / open reading frames were identified with functions relating to metabolism and
transport systems. The genes are located in two divergently located operons. The first operon carries
features related to general metabolism activities and consists of a transcriptional regulator (ORF 2), a
succinate / fumarate dehydrogenase-like subunit (ORF 3), two ferredoxin genes (ORF 4 and ORF 7), a
putative HEAT-like repeat (ORF 6) which is interrupted by an insertion sequence (ORF 5) and a
GOGAT-like subunit (ORF 8). The second operon contains an ABC-type nitrate / sulfonate
bicarbonate-like gene (ORF 9), a binding protein-dependent inner membrane component-like gene,
another ABC sulfonate / nitrate-like gene (ORF 12i and 12ii) which is interrupted by an insertion
sequence (ORF 13) and two hypothetical proteins with unknown functions (ORF 14 and ORF 15).
Southern hybridization analysis have shown that most of the genes from the two operons are found in
other At caldus strains #6, âfâ, C-SH12 and BC13 from different geographical locations. Expression of
the GOGAT-like subunit and the succinate / fumarate-like subunit was demonstrated in At. caldus
MNG showing that these genes are functional and actively transcribed. The transcriptional regulator
(ORF 2) has been shown to repress the downstream genes of putative operon 1. The persistence of
these genes on plasmids together with the fact that they are being expressed, represents a potential
metabolic burden, which begs the question why they have been maintained on the plasmid from
geographically separated strains (and perhaps also growing under very different nutrient availability
conditions) and therefore what possible role they may play.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/1667 |
| Date | 03 1900 |
| Creators | Louw, Lilly-Ann |
| Contributors | Rawlings, Douglas E., University of Stellenbosch. Faculty of Science. Dept. of Microbiology. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Rights | University of Stellenbosch |
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