Browsing by Author "Tilahun, Lulit"

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    Diversity of Culturable Alkaliphilic Denitrifying Bacteria in Four Soda Lakes of Ethiopia
    (Addis Ababa University, 2010-12) Tilahun, Lulit; Gessesse, Amare(PhD)
    Denitrifying bacteria (95 in number) were isolated from the four Soda Lakes of Ethiopia namely, Lake Abijata, Lake Arenguade, Lake Chitu and Lake Shalla. Similar species of denitrifying bacteria were identified from the four lakes. The sequence and phylogeny relation of the isolates show that Halomonas campisalis, Halomonas salina, Halomonas nitritophilus, Bacillus cohnii as well as Bacillus pseudofirmus exhibited high similarities with the isolates studied. In addition, 9 isolates from the four lakes show similarity with the novel bacterial group, Nitricola lacisaponesis. Fast denitrifyers were among the isolates that are capable of producing N2 gas only in 2 hours after inoculation. Molecular, morphological and some biochemical studies conducted on the DN-C18 isolate from L. Chitu, showed high similarity on all accounts with previously obtained isolate BACC180 from L. Chitu. These two isolates showed high denitrification activity and tolerance to high pH and salt concentration. Both isolates were found to be closely related the Halomonas sp. Key words: denitrification; alkaliphilic denitrifiers; soda lakes; Lake Abijata; Lake Arenguade; Lake Chitu; Lake Shalla; Halomonas; Bacillus; Nitricola lacisaponesis
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    Metagenomic Analysis of Microorganisms in Hyper Saline Aquatic and Acidic Habitats of Danakil Depression of the Afar Region of Ethiopia and their Biotechnological Potential
    (Addis Ababa University, 2021-12-04) Tilahun, Lulit; Simachew, Addis (PhD); Asrat, Asfawossen (Professor); Wessel, Gary M. (PhD)
    The Danakil Depression is one of the hottest place on Earth and is considered as an exceptional place where different extreme environments are found. Five locations in the Danakil Depression were studied for the presence of extremophiles and their biotechnological potentials. The sample sites for this study are the Hyper-saline Acid Ponds [HsAP] (Dallol [DAL], Black Water [BLA], Gaet’ale [GAL]) as well as the Hyper-saline Aquatic Systems [HsAqS] (coastal parts of Lake Asale [LA, LADP5, LADP6], Mud’ara pond [MUP]). All the sites were located South to Mount Dallol at less than -100 m below sea level. In our investigation, we tested for the presence of DNAbased life in the studied sites using Whole Metagenome Shotgun (WMS) DNA sequencing approaches. Bioinformatic tools that adopt techniques of assembly free (Bowtie, MetaPhlAn2) and assembly (MetaSpades, DIAMOND and MEGAN 6-CE) were used to identify the microbial communities and predict the major nutrient metabolic networks. Accordingly, the HsAqS were found to be mainly dominated by archaea Operational Taxonomic Units (OTUs), while the HsAP were dominated by bacteria OTUs. More than 95% of the total OTUs of HsAqS was grouped under phylum Euryarchaea, while more than 90% of the OTUs of HsAP was classified in the phyla Proteobacteria, Actinobacteria and Firmicutus. Halonotius sp J07HN6 and unclassified Salinibacter ruber were the two abundant archaeal and bacterial OTUs in the HsAqS, respectively. On the other hand, unclassified strain of Paraburkholderia fungorum was profiled as the most abundant OTU for DAL and BLA, while unclassified Escherichia and unclassified Burkholderia were top two abundant OTUs for GAL. Insilico prediction of gene functions and metabolic pathways using SEED and KEGG indicated presence of carbon fixation, sulfate oxidation, assimilative nitrogen and sulfate reduction reactions in DAL and BLA samples. Carbon fixation was also predicted in the HsAqS while methanogenesis was exclusively predicted in GAL. Based on the investigation of the sources of the genes of interest, it is clear that syntrophic metabolism is the main strategy adapted to utilize the nutrients in the studied sampling sites. Moreover, the predicted genes from DAL’s and BLA’s nitrogen metabolism helped to discover new protein sequences of cysteine desulfurase and [4Fe-4S] ferredoxin with less than 80% similarity to the homologous reference protein sequence. Images of DAL extremophiles obtained from Transmission Electron Microscopy (TEM) showed high production of nano sized Extracellular Membrane Vesicles (EMV). Further investigation on resistance of DAL’s extremophiles to phenolic compounds under lysing conditions indirectly signified their bio-remediation capability. In general, this preliminary investigation indicates great biotechnological and bioremediation potentials of extremophiles of Danakil Depression.