Salley Venda Law (2017) Characterization of bacterial communities associated with the dinoflagellate, Pyrodinium bahamense var. compressum. Masters thesis, Universiti Malaysia Sabah.
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Abstract
Toxic dinoflagellate, Pyrodinium bahamense var. compressum (PBVC) is the causative agent of paralytic shellfish poisoning (PSP) in Sabah harmful algal bloom (HAB) occurrence. Pure unialgal cultured strain CC-UHABS-040(M) harvested from the late exponential phase used for bacteria isolation. Study aims to characterize bacterial communities associated with PBVC by using two molecular approaches; the 165 rDNA culture-dependent and culture-independent 165 rRNA metagenomics analysis. The potential putative PST (Paralytic shellfish toxin)-producing bacterium, PBVC088 selected for whole genome sequencing analysis to produce draft genome of Ruegeria sp. and further identify the sxt (saxitoxin) genes in their genome. Colony morphology analysis revealed the 74 bacterial colonies were small punctiform or large circular, smooth-textured and non-pigmented. The culture-dependent analysis revealed bacteria diversity was limited to gamma-proteobacteria and alpha-proteobacteria, where it is predominated by Alteromonas sp. and Ruegeria sp. The taxonomic profile analysis using culture-independent approach showed high bacterial diversity in Sabah PBVC culture, which was classified into 20 classes, 43 orders, 60 families, and 105 genera. In addition, bacterium Ruegeria sp. (PBVC088) exhibited a draft genome size of 5, 784, 660 bp with a G+C content of 65 %, and containing 5, 640 protein coding sequences (CDSs). BLASTP sequence similarity search of saxitoxin proteins ( expectation value, E-value < le-5) against the 26 putative sxt genes of the toxic cyanobacterium, Cylindrospermopsis raciborskii T3 successfully identified eleven putative sxt candidate genes. The eleven sxt genes (sxtA, sxtB, sxtF/M, sxtH/T, sxtS, sxtU, sxtV, sxtW, and sxtZ ) found to contain similar conserved domains as in the cyanobacterial domain, C raciborskii T3. The finding suggesting, genes (enzymes) associated with the STX biosynthesis pathway exist in the bacterial genome PBVC088, which most likely involved either in the biosynthesis of the final compound or as the precursor of the biosynthesis pathway. High-throughput genome analysis of the associated bacterial communities helps elucidate the hypothesis that the associated bacteria may or may not be involve in the PST production and subsequently help reveal their potential function.
| Item Type: | Thesis (Masters) |
|---|---|
| Keyword: | Pyrodinium bahamense var. Compressum Paralytic shellfish poisoning, Saxitoxin, Harmful algal blooms, Marine microbiome, Ruegeria sp. |
| Subjects: | Q Science > QK Botany > QK1-989 Botany |
| Department: | INSTITUTE > Biotechnology Research Institute (BRI) |
| Depositing User: | DG MASNIAH AHMAD - |
| Date Deposited: | 13 Jun 2025 15:02 |
| Last Modified: | 13 Jun 2025 15:02 |
| URI: | https://eprints.ums.edu.my/id/eprint/44116 |
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