Thèse de Doctorat

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Browsing Thèse de Doctorat by Author "BENAMMAR Leyla"

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    Study of the microbial biodiversity of terrestrial hydrothermal sources located in Eastern Algeria. Doctorat thesis,(2021) Université de Batna 2.
    (2022-01-10) BENAMMAR Leyla
    Northeastern regions of Algeria are known for their richness in hot springs. However, these hydrothermal sites are yet to be explored for their microbial ecology and biotechnology. This research work aims to analyze and characterize the diversity of prokaryotes from hot springs located in the North-East of Algeria and expand the knowledge of this biodiversity from a functional and biotechnological standpoint. In the first instance, we determine the diversity of culturable thermophilic bacteria isolated from eight terrestrial hot springs distributed over four cities (Batna, Biskra, Guelma, and Khenchela) using conventional methods, SDS-PAGE fingerprinting of whole-cell proteins, and 16S rRNA gene sequencing. In addition, their hydrolytic enzyme activities were also investigated. On the other hand, the abundance and diversity of bacterial and archaeal communities in two Algerian hot springs relatively physiochemically distinct; Debagh hot spring (Guelma) and Saïda hot spring (Batna), was analyzed through a metagenomic based approach with high throughput sequencing (Illumina, MiSeq) and correlating the prevailing bacteria with geochemical parameters. A total of 293 strains were isolated from the hot springs water and sediment samples using different culture media. Overall, five distinct bacterial groups were characterized by whole-cell protein pattern analysis. Based on the 16S rRNA gene sequencing of 100 selected strains, the isolates were assigned to three major phyla: Firmicutes (93%), Deinococcus-Thermus (5%), and Actinobacteria (2%), which included 27 distinct species belonging to 12 different phylotypes, Aeribacillus, Aneurinibacillus, Anoxybacillus, Bacillus, Brevibacillus, Geobacillus, Laceyella, Meiothermus, Saccharomonospora, Thermoactinomyces, Thermobifida, and Thermus. The screening for nine extracellular enzymes showed that 65.87% of the isolates presented at least five types of enzyme activities, and 6.48% of strains combined all tested enzymes (amylase, cellulase, pectinase, esculinase, protease, gelatinase, lipase, lecithinase, and nuclease). It was found that Bacillus, Anoxybacillus, Aeribacillus, and Aneurinibacillus were the genera showing the highest activities. Likewise, the study showed a large and diverse thermophilic community with probably seven novel taxa presenting a promising source of thermozymes with critical biotechnological applications. Metagenome sequence data revealed the dominance of Bacteria over Archaea. The most abundant phyla in Saïda hot spring were Proteobacteria, while Debagh hot spring showed a high relative abundance of Firmicutes. However, Bacteroidetes were nearly equally distributed over the two sites. Although other phyla were also present in both thermal sites with different variations such as Deinococcus-Thermus, Cyanobacteria, Chloroflexi, Acidobacteria, Chlorobi, Spirochaetes, Fibrobacteres, Verrucomicrobia, Nitrospirae, and Armatimonadetes. The physicochemical values obtained from the hot springs water samples when plotted on Piper and Schöeller-Berkaloff diagrams suggested that the water from Debagh hot spring was Ca-Cl-SO4 while Saïda hot spring was a sodium-sulfate type; these results revealed that the strong acidic anions (Cl- , SO4 2- ) dominant over the weak acidic anions (CO3 2- , HCO3 - ). The distribution of major genera and their statistical correlation analyses with the geochemistry of the springs predicted that the temperature, sodium, potassium, and alkalinity were the main environmental variables influencing the microbial community composition and diversity. This study on the diversity of thermophilic prokaryotes in Algerian hydrothermal environments revealed an abundant and diverse community, providing a valuable resource of novel taxa presenting potential sources of biocatalysts for important biotechnological applications.