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Australian National University (2014)

Characterising and tracking Australian desert dust and its sources

Munday, Christopher Ian

Titre : Characterising and tracking Australian desert dust and its sources

Auteur : Munday, Christopher Ian

Université de soutenance : Australian National University

Grade : Doctor of Philosophy (PhD) 2014

Description
The Lake Eyre Region (LER) in Australia is the primary source of dust in the southern hemisphere. Little is known about the microbial ecology of this area, and its relationship if any to the bacteria found in dust and aerosols. Initially, sediment and adjacent aerosol samples were collected from a small lake in Victoria which routinely deflated. Bacterial populations in both samples were compared by culturing followed by Rep-PCR, and 16S rRNA high throughput sequencing (HTS). Bacillus subtilis isolates of the same Rep type, and sequences representing the same OTUs of Salinomicrobium and Delftia were present in both aerosols and sediment. These results indicated that bacteria could be tracked through the environment regardless of the vast microbial diversity observed using both techniques. Subsequently, bacterial communities in aerosols collected off the coast of Australia were characterised and two different sampling methods compared ; filtration and a high volume swirling liquid sampler (OMNI 3000). The weather conditions were calm during both voyages. The microflora of the OMNI samples showed less diversity than the filter samples. Delftia, Methylobacterium, and Stenotrophomonas were present in samples from both voyages. HTS was then used to compare the microbiology of LER sediment, aerosols, and samples collected from major dust storms which affected eastern Australia in September 2009. There was vast microbial diversity within and among LER sediments of different types, desert crusts, salt lake crusts and fluff, collected in the same location, collected over time, and collected in different locations. Comparison of the microflora of dust to LER sediments revealed similarities to samples collected from specific locations that broadly correlated to the proposed source of the dust storm determined by multidisciplinary analyses. Dominant OTUs, representing Delftia, Stenotrophomonas, Acidovorax, and other taxa, were present in dust and source samples, with many of these genera also found in aerosols collected from different locations. Our results highlight the vast microbial diversity across the different samples collected, and has identified some of the dominant taxa in the Australian environment

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