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1دورية أكاديمية
المؤلفون: Li, Zhenchi
المصدر: Open Access Theses and Dissertations
مصطلحات موضوعية: RNA, Metagenomics, Puffers (Fish), Tetrodotoxin, Metabolites, Bacteria
الوصف: Tetrodotoxin (TTX) is a lethal neurotoxin isolated mainly from the organs of wild puffer fishes. Although the neurotoxicity mechanisms of TTX are well known, the TTX origin and the biosynthetic mechanisms inside its hosts remain unresolved. In recent decades, the numerous reports of TTX-producing bacteria strongly suggested its bacterial origin. However, this origin is currently being challenged by the low and inconsistent TTX productions in vitro by the previously reported TTX-producing bacteria. Culturable TTX-producing bacteria were frequently isolated and reported from the guts of TTX-bearing animals including puffer fishes, however, these bacteria were estimated to account for 0.1% of the total gut bacteria. Moreover, the identification and functions of the non-culturable gut bacteria participating in TTX biosynthesis have never been reported. I hypothesize that the puffer fish gut bacteria and the entire gut environment serve as a functional integrality responsible for TTX biosynthesis. In this study, 16S rRNA amplicon metagenomics pipeline was established to profile the entire gut bacterial structures of both toxic and non-toxic puffer fishes respectively. UniFrac based principal coordinate analysis showed that bacterial diversities were significantly different (P-value < 0.001) between the gut environments of toxic puffer fishes and the non-toxics. Vibrio and Cyanobacteria were identified as centralities of gut bacteria co-occurrence network in toxic puffer fishes, implying their key roles in TTX biosynthesis. The results of metagenome prediction and gene set enrichment indicated that arginine biosynthesis was significant enriched (P-value < 0.05) in the toxic group. To further investigate the roles of key bacteria and arginine biosynthesis in producing TTX, metabolomics pipeline was established along with 16S rRNA amplicon metagenomics to monitor the dynamics of metabolites and bacterial compositions in guts of toxic puffer fishes during their detoxification process. The average TTX concentrations ...
وصف الملف: application/pdf
العلاقة: https://repository.hkbu.edu.hk/etd_oa/832Test; https://repository.hkbu.edu.hk/cgi/viewcontent.cgi?article=1835&context=etd_oaTest
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2دورية أكاديمية
المؤلفون: Xiao, Zhe
المصدر: Open Access Theses and Dissertations
مصطلحات موضوعية: Antineoplastic agents, Synthesis, Tetrodotoxin
الوصف: In this study, the synthesis of TTX by three species of TTX-producing bacteria (Vibrio alginolyticus, Microbacterium arabinogalactanolyticum and Serratia marcescens) was conducted in a 10-L fermentor under the same controlled fermentation conditions for each of a period of 60 hours. The bacterial growth curves were monitored and the TTX synthesized in the culture medium was determined by HPLC. The TTX biosynthesis was found limited at the microgram level per L of culture medium with toxicities 14.7 MU (mouse unit) and 13.0 MU per mL in the partially purified culture medium of V. alginolyticus and M. arabinogalactanolyticum respectively by mouse bioassay. In the studies on SW480 and SW620 colorectal carcinoma cell lines, the expression, distribution, invasion and proliferation of voltage-gated sodium channels (VGSCs) were investigated by MTT assay (24-48 hours) and wound healing assay (0-120 hours). The different subtypes of VGSCs were expressed by semiquantitative RT-PCR and the locations of Nav1.5 and Nav 1.7 were detected by immunofluorescence microscopy. In the MTT assay, 40μmol/L of TTX showed significant inhibitory effect on both cell lines, with maximum inhibition rate, 33% and 40%, in SW480 and SW620 respectively. In the wound-healing assay, the inhibitory rate of 80μmol/L of TTX on SW480 reached 22% after 120 hours, compared with 30% in the control group. Moreover, VGSCs were highly expressed in both SW480 and SW620, with the main subtypes of Nav1.5 and Nav1.7 located on the cell surface, which might increase the metastatic rate of the cell lines. Keywords: Tetrodotoxin (TTX), Bacterial synthesis, Anticancer, VGSCs
وصف الملف: application/pdf
العلاقة: https://repository.hkbu.edu.hk/etd_oa/56Test; https://repository.hkbu.edu.hk/cgi/viewcontent.cgi?article=1055&context=etd_oaTest
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3رسالة جامعية
المؤلفون: Li, Zhenchi
المصدر: Open Access Theses and Dissertations.
مصطلحات موضوعية: RNA, Metagenomics, Puffers (Fish), Tetrodotoxin, Metabolites, Bacteria
الوصف: Tetrodotoxin (TTX) is a lethal neurotoxin isolated mainly from the organs of wild puffer fishes. Although the neurotoxicity mechanisms of TTX are well known, the TTX origin and the biosynthetic mechanisms inside its hosts remain unresolved. In recent decades, the numerous reports of TTX-producing bacteria strongly suggested its bacterial origin. However, this origin is currently being challenged by the low and inconsistent TTX productions in vitro by the previously reported TTX-producing bacteria. Culturable TTX-producing bacteria were frequently isolated and reported from the guts of TTX-bearing animals including puffer fishes, however, these bacteria were estimated to account for 0.1% of the total gut bacteria. Moreover, the identification and functions of the non-culturable gut bacteria participating in TTX biosynthesis have never been reported. I hypothesize that the puffer fish gut bacteria and the entire gut environment serve as a functional integrality responsible for TTX biosynthesis. In this study, 16S rRNA amplicon metagenomics pipeline was established to profile the entire gut bacterial structures of both toxic and non-toxic puffer fishes respectively. UniFrac based principal coordinate analysis showed that bacterial diversities were significantly different (P-value < 0.001) between the gut environments of toxic puffer fishes and the non-toxics. Vibrio and Cyanobacteria were identified as centralities of gut bacteria co-occurrence network in toxic puffer fishes, implying their key roles in TTX biosynthesis. The results of metagenome prediction and gene set enrichment indicated that arginine biosynthesis was significant enriched (P-value < 0.05) in the toxic group. To further investigate the roles of key bacteria and arginine biosynthesis in producing TTX, metabolomics pipeline was established along with 16S rRNA amplicon metagenomics to monitor the dynamics of metabolites and bacterial compositions in guts of toxic puffer fishes during their detoxification process. The average TTX concentrations in the liver after a 60-day culture (6.41 ± 3.00 µg/g) was found significantly lower (P-value < 0.01) than that of the same species from the wild (31.86 ± 22.20 µg/g). The relative abundance of Vibrio was found positively correlated with the liver TTX concentrations. With the increase of culture periods, the relative abundance of Vibrio and Cyanobacteria decreased. In addition, both the metabolites and functional genes in arginine biosynthesis metabolic pathway were found significantly down-regulated (P-value < 0.05). These results indicated that both Vibrio and Cyanobacteria bacterial symbionts participated in TTX biosynthesis using arginine as a potential precursor in the gut environment of toxic puffer fishes.
وصف الملف: application/pdf
الإتاحة: https://repository.hkbu.edu.hk/etd_oa/832Test
https://repository.hkbu.edu.hk/cgi/viewcontent.cgi?article=1835&context=etd_oaTest -
4رسالة جامعية
المؤلفون: Li, Zhenchi
المصدر: Open Access Theses and Dissertations.
مصطلحات موضوعية: RNA, Metagenomics, Puffers (Fish), Tetrodotoxin, Metabolites, Bacteria
الوصف: Tetrodotoxin (TTX) is a lethal neurotoxin isolated mainly from the organs of wild puffer fishes. Although the neurotoxicity mechanisms of TTX are well known, the TTX origin and the biosynthetic mechanisms inside its hosts remain unresolved. In recent decades, the numerous reports of TTX-producing bacteria strongly suggested its bacterial origin. However, this origin is currently being challenged by the low and inconsistent TTX productions in vitro by the previously reported TTX-producing bacteria. Culturable TTX-producing bacteria were frequently isolated and reported from the guts of TTX-bearing animals including puffer fishes, however, these bacteria were estimated to account for 0.1% of the total gut bacteria. Moreover, the identification and functions of the non-culturable gut bacteria participating in TTX biosynthesis have never been reported. I hypothesize that the puffer fish gut bacteria and the entire gut environment serve as a functional integrality responsible for TTX biosynthesis. In this study, 16S rRNA amplicon metagenomics pipeline was established to profile the entire gut bacterial structures of both toxic and non-toxic puffer fishes respectively. UniFrac based principal coordinate analysis showed that bacterial diversities were significantly different (P-value < 0.001) between the gut environments of toxic puffer fishes and the non-toxics. Vibrio and Cyanobacteria were identified as centralities of gut bacteria co-occurrence network in toxic puffer fishes, implying their key roles in TTX biosynthesis. The results of metagenome prediction and gene set enrichment indicated that arginine biosynthesis was significant enriched (P-value < 0.05) in the toxic group. To further investigate the roles of key bacteria and arginine biosynthesis in producing TTX, metabolomics pipeline was established along with 16S rRNA amplicon metagenomics to monitor the dynamics of metabolites and bacterial compositions in guts of toxic puffer fishes during their detoxification process. The average TTX concentrations in the liver after a 60-day culture (6.41 ± 3.00 µg/g) was found significantly lower (P-value < 0.01) than that of the same species from the wild (31.86 ± 22.20 µg/g). The relative abundance of Vibrio was found positively correlated with the liver TTX concentrations. With the increase of culture periods, the relative abundance of Vibrio and Cyanobacteria decreased. In addition, both the metabolites and functional genes in arginine biosynthesis metabolic pathway were found significantly down-regulated (P-value < 0.05). These results indicated that both Vibrio and Cyanobacteria bacterial symbionts participated in TTX biosynthesis using arginine as a potential precursor in the gut environment of toxic puffer fishes.
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5رسالة جامعية
المؤلفون: Xiao, Zhe
المصدر: Open Access Theses and Dissertations.
مصطلحات موضوعية: Antineoplastic agents, Synthesis, Tetrodotoxin
الوصف: In this study, the synthesis of TTX by three species of TTX-producing bacteria (Vibrio alginolyticus, Microbacterium arabinogalactanolyticum and Serratia marcescens) was conducted in a 10-L fermentor under the same controlled fermentation conditions for each of a period of 60 hours. The bacterial growth curves were monitored and the TTX synthesized in the culture medium was determined by HPLC. The TTX biosynthesis was found limited at the microgram level per L of culture medium with toxicities 14.7 MU (mouse unit) and 13.0 MU per mL in the partially purified culture medium of V. alginolyticus and M. arabinogalactanolyticum respectively by mouse bioassay. In the studies on SW480 and SW620 colorectal carcinoma cell lines, the expression, distribution, invasion and proliferation of voltage-gated sodium channels (VGSCs) were investigated by MTT assay (24-48 hours) and wound healing assay (0-120 hours). The different subtypes of VGSCs were expressed by semiquantitative RT-PCR and the locations of Nav1.5 and Nav 1.7 were detected by immunofluorescence microscopy. In the MTT assay, 40μmol/L of TTX showed significant inhibitory effect on both cell lines, with maximum inhibition rate, 33% and 40%, in SW480 and SW620 respectively. In the wound-healing assay, the inhibitory rate of 80μmol/L of TTX on SW480 reached 22% after 120 hours, compared with 30% in the control group. Moreover, VGSCs were highly expressed in both SW480 and SW620, with the main subtypes of Nav1.5 and Nav1.7 located on the cell surface, which might increase the metastatic rate of the cell lines. Keywords: Tetrodotoxin (TTX), Bacterial synthesis, Anticancer, VGSCs
وصف الملف: application/pdf
الإتاحة: https://repository.hkbu.edu.hk/etd_oa/56Test
https://repository.hkbu.edu.hk/cgi/viewcontent.cgi?article=1055&context=etd_oaTest
