Date of Defense
17-4-2025 12:00 AM
Location
F1-1004
Document Type
Thesis Defense
Degree Name
Master of Science in Molecular Biology and Biotechnology
College
COS
Department
Biology
First Advisor
Prof. Khaled M. A. Amiri
Keywords
Citrullus colocynthis, desert microbiome, plant-microbe interactions, stress tolerance.
Abstract
Desert ecosystems impose substantial plant growth and survival limitations, including high radiation, temperatures, and drought. To endure these extreme conditions, plants have developed a range of physiological and biochemical adaptations and established symbiotic partnerships with microbes that significantly enhance their resilience. Citrullus colocynthis, the wild relative of domesticated watermelon, has multiple applications in pharmacology and the biomedical field. Although many studies have examined this plant, few have investigated its microbiome, and those that did often focused on limited aspects. Understanding the microbes associated with this plant and their contributions to its survival can yield important insights into developing C. colocynthis as a valuable resource for various industries. With increasing interest in bioprospecting desert microbiomes, C. colocynthis could be a rich source of microbes capable of alleviating stress in crop plants. In this study, we explored the microbiome of C. colocynthis across two seasons and in two locations in the United Arab Emirates—in the city of Al Ain and Ras Al Khaimah emirate. We analyzed the microbial community using 16S rRNA amplicon and metagenomic sequencing. The most prevalent phyla identified from each kingdom/domain were Actinomycetota (bacteria), Ascomycota (fungi), Uroviricota (viruses), and Euryarchaeota (archaea). Although the microbiome appeared stable at higher taxonomic levels, we observed spatiotemporal variations at lower levels, including a rise in drought-adapted taxa during summer and an increase in taxa suited for milder conditions and nutrient acquisition in winter. To further investigate, we employed culture-based and molecular methods to assess the stress tolerance and plant growth-promoting traits of culturable endophytic bacteria and fungi isolated from the plant. We isolated six fungal species from the genera Aspergillus, Alternaria, Fusarium, Neoscytalidium, and Cystofilobasidium, along with 15 bacterial species, including Pseudomonas, Bacillus, Brevibacillus, Paenibacillus, Streptomyces, Pantoea, Plantibacter, and Arthrobacter. Notably, three of the bacterial isolates appeared to represent potential new species. These microbes exhibited various stress tolerance and PGP characteristics, some of which had the potential to be transferred to crop plants like tomatoes. This research provides the first detailed microbiome analysis of C. colocynthis, shedding light on how this plant thrives in arid desert environments. Our findings illustrate how microbiome composition shifts with environmental conditions and geographic location while highlighting the mechanisms through which the microbiome supports the plant’s survival. The cultured microbes demonstrate potential for agricultural applications, and their annotated genomes unveil the advantages they confer on their host. By revealing the microbial diversity of C. colocynthis and identifying microbes with beneficial traits, this study lays the groundwork for optimizing these microbes for agricultural, pharmaceutical, and biotechnological uses.
CHARACTERIZING THE HOST-MICROBE INTERACTIONS OF CITRULLUS COLOCYNTHIS
F1-1004
Desert ecosystems impose substantial plant growth and survival limitations, including high radiation, temperatures, and drought. To endure these extreme conditions, plants have developed a range of physiological and biochemical adaptations and established symbiotic partnerships with microbes that significantly enhance their resilience. Citrullus colocynthis, the wild relative of domesticated watermelon, has multiple applications in pharmacology and the biomedical field. Although many studies have examined this plant, few have investigated its microbiome, and those that did often focused on limited aspects. Understanding the microbes associated with this plant and their contributions to its survival can yield important insights into developing C. colocynthis as a valuable resource for various industries. With increasing interest in bioprospecting desert microbiomes, C. colocynthis could be a rich source of microbes capable of alleviating stress in crop plants. In this study, we explored the microbiome of C. colocynthis across two seasons and in two locations in the United Arab Emirates—in the city of Al Ain and Ras Al Khaimah emirate. We analyzed the microbial community using 16S rRNA amplicon and metagenomic sequencing. The most prevalent phyla identified from each kingdom/domain were Actinomycetota (bacteria), Ascomycota (fungi), Uroviricota (viruses), and Euryarchaeota (archaea). Although the microbiome appeared stable at higher taxonomic levels, we observed spatiotemporal variations at lower levels, including a rise in drought-adapted taxa during summer and an increase in taxa suited for milder conditions and nutrient acquisition in winter. To further investigate, we employed culture-based and molecular methods to assess the stress tolerance and plant growth-promoting traits of culturable endophytic bacteria and fungi isolated from the plant. We isolated six fungal species from the genera Aspergillus, Alternaria, Fusarium, Neoscytalidium, and Cystofilobasidium, along with 15 bacterial species, including Pseudomonas, Bacillus, Brevibacillus, Paenibacillus, Streptomyces, Pantoea, Plantibacter, and Arthrobacter. Notably, three of the bacterial isolates appeared to represent potential new species. These microbes exhibited various stress tolerance and PGP characteristics, some of which had the potential to be transferred to crop plants like tomatoes. This research provides the first detailed microbiome analysis of C. colocynthis, shedding light on how this plant thrives in arid desert environments. Our findings illustrate how microbiome composition shifts with environmental conditions and geographic location while highlighting the mechanisms through which the microbiome supports the plant’s survival. The cultured microbes demonstrate potential for agricultural applications, and their annotated genomes unveil the advantages they confer on their host. By revealing the microbial diversity of C. colocynthis and identifying microbes with beneficial traits, this study lays the groundwork for optimizing these microbes for agricultural, pharmaceutical, and biotechnological uses.
