| dc.contributor.author | Pan, Youlian. | en_US |
| dc.date.accessioned | 2014-10-21T12:35:39Z | |
| dc.date.available | 1994 | |
| dc.date.issued | 1994 | en_US |
| dc.identifier.other | AAINN98919 | en_US |
| dc.identifier.uri | http://hdl.handle.net/10222/55455 | |
| dc.description | Pseudonitzschia pungens f. multiseries Hasle is the first diatom to have been implicated in an episode of shellfish poisoning. In 1987, 150 people became sick and 3 died after consuming mussels, Mytilus edulis, from Cardigan Bay, Prince Edward Island (Addison and Stewart, 1989). It was discovered that the mussels had been feeding on a monospecific bloom of P. pungens f. multiseries, and the toxin involved was domoic acid (DA, Subba Rao et al., 1988a). This thesis reports an investigation of the physiology of the diatom, with particular emphasis on factors that lead to DA production. | en_US |
| dc.description | Photosynthesis, phosphate (P) and silicate (Si) uptake, and domoic acid production were studied in batch and chemostat continuous cultures. The photosynthetic carbon assimilation rate of P. pungens f. multiseries was low compared to other diatoms, especially when the cultures progressed into stationary phase and were nutrient limited. Luxury uptake of P and Si occurred when the culture populations were perturbed with these nutrients after being starved of them. Domoic acid was produced both in dividing and non-dividing populations and the production rates correlated with the severity of P or Si limitation. Production of DA was significantly enhanced when overall cell metabolism declined due to nutrient limitation. In the batch cultures, there were two stages of DA production. The first stage corresponded to the decline of population growth, and the second stage to nutrient limitation. These two stages are believed to be controlled by self-limiting factors and external stress respectively. In continuous culture, the same two stages were detected. Under severe limitation of either P or Si, DA production rose to maximum levels around 200 $\mu$g 1$\sp{-1}$ d$\sp{-1}$ (3.17 pg DA cell$\sp{-1}$ d$\sp{-1}$) and the maximum DA levels attained were 11.9 pg DA cell$\sp{-1}$ in cells and 1118 $\mu$g 1$\sp{-1}$ in whole culture. The main conclusions are (i) the self-limiting control associated with decline of population growth is an essential prerequisite to DA production, but the main control is external nutrient stress; (ii) the major cell mechanism regulating DA production is a change in partitioning of energy and precursors between primary and secondary metabolism; (iii) the domoic acid poisoning episodes in Cardigan Bay were likely caused by abnormal nutrient ratios in the sea water. | en_US |
| dc.description | Thesis (Ph.D.)--Dalhousie University (Canada), 1994. | en_US |
| dc.language | eng | en_US |
| dc.publisher | Dalhousie University | en_US |
| dc.publisher | | en_US |
| dc.subject | Health Sciences, Toxicology. | en_US |
| dc.subject | Biology, Oceanography. | en_US |
| dc.subject | Biology, Animal Physiology. | en_US |
| dc.subject | Health Sciences, Public Health. | en_US |
| dc.subject | Environmental Sciences. | en_US |
| dc.title | Production of domoic acid, a neurotoxin, by the diatom Pseudonitzchia pungens f. multiseries Hasle under phosphate and silicate limitation. | en_US |
| dc.type | text | en_US |
| dc.contributor.degree | Ph.D. | en_US |
