CHARACTERIZATION AND QUANTIFICATION OF ENDOGENOUS PHAGES OF LACTICASEIBACILLUS RHAMNOSUS JB-1
| dc.contributor.advisor | MacNeil, Lesley | |
| dc.contributor.author | Jose, Tamina Angel | |
| dc.contributor.department | Biochemistry and Biomedical Sciences | en_US |
| dc.date.accessioned | 2025-06-05T14:38:12Z | |
| dc.date.available | 2025-06-05T14:38:12Z | |
| dc.date.issued | 2025 | |
| dc.description.abstract | Lacticaseibacillus rhamnosus JB-1 is a strain recognized for its beneficial effects on eukaryotic host. This study aims to identify and characterize dormant bacterial viruses or prophages with the JB-1 genome, determine their capacity to be released as bacteriophages. We also investigate the membrane vesicles released from JB-1 and detect bacteriophages within these preparations. Bioinformatic analysis of the JB-1 genome predicted the presence of three prophage regions. Experimental validation demonstrated spontaneous release of two of these phages, which were also detected along with membrane vesicles and found systemically circulating. Genomic characterization included sequence annotation, determination of exact start/end points, analysis of gene function and comparison with other related bacteriophages. The JB-1 CRISPR-Cas system was also identified and characterized which will contribute to a deeper understanding of the potential for future manipulation of this probiotic microorganism. Morphological characterization was conducted using transmission electron microscopy to determine capsid shape, size, tail length, to classify the phages based on these features. To overcome limitations in quantifying phages lacking suitable hosts for propagation, a qPCR-based method was developed and validated. Furthermore, the stability of JB-1 phages was studied under a range of temperature and pH conditions relevant to the gastrointestinal tract. | en_US |
| dc.description.degree | Master of Science (MSc) | en_US |
| dc.description.degreetype | Thesis | en_US |
| dc.description.layabstract | The human digestive system is home to trillions of bacteria, collectively known as the gut microbiota, which play a pivotal role in our health. Probiotics, which are ‘good bacteria’, are live microorganisms that can provide health benefits when consumed. One such microorganism is Lacticaseibacillus rhamnosus JB-1, known for its beneficial effects in mice. In this study, we investigate the presence of dormant bacteriophages integrated within the JB-1 genome and genomically characterize it. We confirm that some of these viral blueprints can be induced as phages. This raises questions to how probiotics might exert their beneficial effects and highlights the importance of understanding bacteriophages associated with probiotic microorganisms. Additionally, JB-1 bacteriophages do not have a suitable host to propagate, so we study the potential of qPCR as a tool to quantify the phages. We investigated the stability of JB-1 phages to temperature and pH conditions relevant to the gastric environment, using qPCR. This study also highlights the use of qPCR for the quantification of phages lacking a host to propagate and provides valuable insights into the stability of JB-1 bacteriophages under conditions relevant to their passage through the host, which are crucial considerations for understanding their potential impact within the gastrointestinal environment. | en_US |
| dc.identifier.uri | http://hdl.handle.net/11375/31777 | |
| dc.language.iso | en | en_US |
| dc.subject | Phages | en_US |
| dc.subject | Prophages | en_US |
| dc.subject | Lacticaseibacillus | en_US |
| dc.title | CHARACTERIZATION AND QUANTIFICATION OF ENDOGENOUS PHAGES OF LACTICASEIBACILLUS RHAMNOSUS JB-1 | en_US |
| dc.type | Thesis | en_US |