Microbial Diversity and Ecology in the Interfaces of the Deep-sea Anoxic Brine Pools in the Red Sea
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Tyas Hikmawan Dissertation.pdf
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Tyas Hikmawan Dissertation
Type
DissertationAuthors
Hikmawan, Tyas I.
Advisors
Stingl, Ulrich
Committee members
Moran, Xose Anxelu G.
Pain, Arnab

Jebbar, Mohamed

Program
Marine ScienceDate
2015-05Embargo End Date
2016-05-21Permanent link to this record
http://hdl.handle.net/10754/552806
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At the time of archiving, the student author of this dissertation opted to temporarily restrict access to it. The full text of this dissertation became available to the public after the expiration of the embargo on 2016-05-21.Abstract
Deep-sea anoxic brine pools are one of the most extreme ecosystems on Earth, which are characterized by drastic changes in salinity, temperature, and oxygen concentration. The interface between the brine and overlaying seawater represents a boundary of oxic-anoxic layer and a steep gradient of redox potential that would initiate favorable conditions for divergent metabolic activities, mainly methanogenesis and sulfate reduction. This study aimed to investigate the diversity of Bacteria, particularly sulfate-reducing communities, and their ecological roles in the interfaces of five geochemically distinct brine pools in the Red Sea. Performing a comprehensive study would enable us to understand the significant role of the microbial groups in local geochemical cycles. Therefore, we combined culture-dependent approach and molecular methods, such as 454 pyrosequencing of 16S rRNA gene, phylogenetic analysis of functional marker gene encoding for the alpha subunits of dissimilatory sulfite reductase (dsrA), and single-cell genomic analysis to address these issues. Community analysis based on 16S rRNA gene sequences demonstrated high bacterial diversity and domination of Bacteria over Archaea in most locations. In the hot and multilayered Atlantis II Deep, the bacterial communities were stratified and hardly overlapped. Meanwhile in the colder brine pools, sulfatereducing Deltaproteobacteria were the most prominent bacterial groups inhabiting the interfaces. Corresponding to the bacterial community profile, the analysis of dsrA gene sequences revealed collectively high diversity of sulfate-reducing communities. Desulfatiglans-like dsrA was the prevalent group and conserved across the Red Sea brine pools. In addition to the molecular studies, more than thirty bacterial strains were successfully isolated and remarkably were found to be cytotoxic against the cancer cell lines. However, none of them were sulfate reducers. Thus, a single-cell genomic analysis was used to study the metabolism of uncultured phyla without having them in culture. We analysed ten single-cell amplified genomes (SAGs) of the uncultivated euryarchaeal Marine Benthic Group E (MBGE), which contain a key enzyme for sulfate reduction. The results showed the possibility of MBGE to grow autotrophically only with carbon dioxide and hydrogen. In the absence of adenosine 5’-phosphosulfate reductase, we hypothesized that MBGE perform sulfite reduction rather than sulfate reduction to conserve energy.ae974a485f413a2113503eed53cd6c53
10.25781/KAUST-C8949