Salmonella enterica is a foodborne pathogen of major significance, and as such it has been extensively studied by researchers around the world. However, despite the numerous scientific publications on Salmonella, there are still many gaps in our understanding of its biology. One such gap is in the bacteria's interactions with invertebrate hosts, and in particular, oysters. Nearly 70 million pounds of oysters are consumed in the United States each year, and previous work in the Joens' laboratory found Salmonella in roughly 7% of the market oysters they sampled, with the majority of the isolates being the Newport serovar. The majority of oysters are consumed raw, which makes the presence of Salmonella within oysters a potentially significant food safety problem.To more closely examine the interactions between Salmonella and oysters, the Present Study developed a method to consistently and reproducibly raise oysters in a controlled laboratory environment in order to systematically expose them to enteric bacteria and quantify the amount of surviving bacteria at various time points after the initial exposure. Use of this model system throughout the Present Study led to four main conclusions.The first is that Salmonella enterica serovar Newport is capable of surviving in oysters for at least 60 days, from an average concentration of 3.7x103 CFU/g of oyster meat after 10 days, to over 102 CFU/g of oyster meat after 60 days. The second main conclusion is that the Newport serovar of Salmonella, which was found in such predominance in the earlier Joens' laboratory study, does not appear to have any special adaptations for survival within oysters, as other strains of Newport and other serovars of Salmonella survived equally well within our model. The third main conclusion, based on the results of immunohistochemistry, is that the relationship between Salmonella and oysters is not a transient interaction that is limited to the outside of the oyster's gut epithelium, but involves a long-term colonization inside the oysters' connective tissues. Because the survival of Salmonella in oysters could be of a pathogenic nature, the Present Study knocked out two key type III secretion systems (T3SS) found in two distinct Salmonella pathogenicity islands (SPI-1 and SPI-2) known to be critical for pathogenesis in mammalian hosts and examined their role in the bacteria's ability to survive within oysters. The results revealed that neither the SPI-1 nor the SPI-2 T3SS were necessary for Salmonella's survival in oysters, which led to the final conclusion of the Present Study that the nature of Salmonella's infection of oysters is fundamentally different than the pathogenesis that occurs in mammalian hosts and that further study of the mechanisms of the survival of Salmonella in oysters is needed to better understand the important and interesting relationship between a significant source of food and this common, and occasionally deadly, foodborne pathogen.

Thesis (M.Sc.) -- Hawkesbury Agricultural College, 1985. / "A thesis submitted to Hawkesbury Agricultural College in partial fulfilment for the Degree of Master of Applied Science."

Thesis (MAppSc) -- Auckland University of Technology, 2004. / Also held in print (104 leaves, ill., 30 cm.) in Wellesley Theses Collection. (T 639.41 PER)

Thesis (Ph.D.) - James Cook University, 2004. / Typescript (photocopy) Appendices: leaves 136-141. Bibliography: leaves 119-135.

Thesis (Ph.D.) -- Australian National University, 2007.

A rapid assay kit for Vibrio cholerae (Vc) was developed to detect and quantify Vc cells in oyster samples within 24 h. The kit, formulated within a two -phase (liquid and solid) 96-well plate, can detect biomarker expression of Vc when the enrichment broth and incubation temperature are optimized. The kit showed 91 % selectivity and 92 % specificity when tested with 23 inclusive Vc and 106 exclusive non-Vc strains. The kit was further optimized using 47 samples of oysters, clams, and soil. There was no significant difference in most probable number between the kit, conventional PCR and BAX PCR regardless of agar heating method (autoclaved vs. boiled). The kit’s limit of detection was below 5 cfu/g. The kit is a reliable method for the detection of V. cholerae in bivalve samples.

Eastern Oysters, or Crassostrea virginica, are an important dietary component in the Chesapeake region and have supported a major fishery in the Chesapeake for more than 100 years. Virginia oysters do not always receive attention in up-scale markets. It is possible that the lack of information on sensory characteristics of Chesapeake oysters may contribute to this problem. In order to differentiate Chesapeake oysters from other oysters, a descriptive sensory test (n=8) was conducted and chemical composition attributes were measured, including glycogen content, proximate analysis, sodium chloride content, and fatty acid analysis. Statistical differences were found for the attributes: volume of liquor, gray/brown and tan colors, roundness of shell, plumpness and salty taste when comparing eastern oysters from Chesapeake to oysters from Rhode Island and New Brunswick, Canada. The glycogen contents in eastern oysters followed the reproductive cycle and glycogen increased from September to December, and started to decrease by April. There were small but significant (p<.05) differences in the contents of moisture, ash, protein and fat of oysters from Chesapeake and other areas. Oysters from Chesapeake had higher percentages of long-chain n-3 fatty acids, which were about 4 times higher than Beau Soleil, an oyster from New Brunswick, Canada. The high percentage of long chain n-3 fatty acids in Chesapeake oysters may be valuable for marketing. / Master of Science

Thesis (M. Phil.)--University of Hong Kong, 1975. / Typewritten.

Pearl oysters of the genus Pinctada include some economically important species. The taxonomy of some of the species is problematic. Phylogenetic relationship of the species in the genus is also poorly studied. In the present study, phylogenetic relationships of P. chemnitzi, P. fucata, P. margaritifera, P. maxima, P. nigra, P. radiata (from China), P. fucata martensii (from Japan), P. albina and P. imbricata (from Australia) were studied with Pteria penguin as an outgroup, and genetic variation of Chinese P. fucata, Japanese P. fucata martensii and Australian P. imbricata populations were investigated (1) to address the taxonomic confusion and phylogeny of pearl oysters, (2) to understand the genetic connections between the Chinese P. fucata, Japanese P. fucata martensii and Australian P. imbricata in west Pacific and (3) to provide information for the genetic improvement program initiated in China. / Since P. fucata, P. fucata martensii and P. imbricata are synonymous, to study the genetic differentiation and genetic variation of such widely distributed populations is helpful in understanding their genetic connections. For this purpose, five populations, three from China (Daya Bay, Sanya Bay and Beibu Bay), one from Japan (Mie Prefecture) and one from Australia (Port Stephens) were studied using AFLP technique. Three primer pairs generated 184 loci among which 91.8-97.3% is polymorphic. An overall genetic among populations and an average of 0.37 within populations (ranging from 0.35 in Japanese population to 0.39 in Beibu Bay population) were observed. Genetic differentiation among the five populations is low but significant as indicated by pairwise GST (0.0079-0.0404). AMOVA further shows that differentiation is significant among the five populations but is not significant at a broader geographical scale, among the three groups of Chinese. Japanese and Australian populations or among the two groups of Australian and north Pacific populations. The low level of genetic differentiation indicated that P. fucata populations in the west Pacific are genetically linked. Among the five populations, the Australian one is more differentiated from the others, based on both pairwise AMOVA and GST analyses, and is genetically isolated by distance as indicated by Mantel test. However, genetic differences among the three Chinese populations are not correlated with the geographic distances, suggesting that Hainan Island and Leizhou Peninsula may act as barriers blocking gene flow. / The above three wild Chinese populations in southern China were compared with the three adjacent cultured populations using AFLP markers. Three pairs of primers generated 184 loci among 179 individuals in populations from Beibu Bay, Daya Bay and Sanya Bay. A high level of genetic diversity, ranging from 0.363 in a wild population in Sanya Bay to 0.388 in a wild population in Beibu Bay, was observed within both wild and cultured populations, indicating an absence of strong bottleneck effects in the history of cultured P. fucata populations. Yet cultured populations in Sanya Bay and Beibu Bay had more fixed loci than the corresponding wild populations. Genetic differentiation in most pairwise comparisons of populations was significant. AMOVA indicated that genetic variation among populations were very low (1.77%) though significant, while more than 98% variation resided among individuals within population. These findings provide no evidence to show that hatchery practice of pearl oyster in China to date has significantly affected the genetic diversity of the cultured populations, and suggest that all populations are competent for selection. Yet the significant genetic differentiation among populations implies that any translocation of individuals for genetic improvement program should be managed with caution for the preservation of genetic diversity in natural populations. / The internal transcribed spacers (ITS1 and ITS2) of nuclear ribosomal DNA were compared among the above nine taxa, based on sequences determined by the present study and those available from Genl3ank. The phylogenetic analysis indicates that the pearl oysters studied constitute three clades: clade I with the small oysters P. fucata, P. fucata martensii and P. imbricata, clade II with P. albina, P. nigra, P. chemnitzi and P. radiata, and clade III and clade III with the big pearl oysters P. margaritifera and P. maxima forming the basal clade. Clade II is made up two subclades: clade IIA consisting of P. albina and P. nigra and clade IIB consisting of P. chemnitzi and P. radiata. The topology of the phylogenetic tree and substitution pattern of ITS sequences suggest that P. margaritifera and P. maxima are primitive species and P. chemnitzi is a recent species. The genetic divergences between clades ranged from 28% to 76.5%, and between subclades, 8.7-10.2%. In clade I, the interspecific genetic divergences ranged from 0.6% to 1.4%, and overlapped with interspecific divergences (0.6-1.1%), indicating that P. fucata, P. fucata martensii and P. imbricata may be conspecific. Based on amplified fragment length polymorphism (AFLP) markers and ITS sequences from more individuals, analyses of the populations of these three taxa also support the conclusion that Chinese P. fucata, Japanese P. fucata martensii and Australian P. imbricata are the same species, with P. fucata being the correct name. The genetic divergence between P. albina and P. nigra was also very low (1.2%), suggesting that they may represent two subspecies that can only be distinguished by shell color. The genetic divergences between P. maxima and P. margaritifera, and between clade IIA and clade IIB ranged from 8.3% to 10.2%, suggesting that they are closely related, respectively. The ITS1 sequence of P. radiata from GenBank is almost identical to that of P. chemnitzi determined in the present study, suggesting that the specimen used for the P. radiata sequence was possibly misidentified. / Yu Dahui. / "August 2005." / Adviser: Ka Hou Chu. / Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6125. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (p. 100-124). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

Heavy metals present in high concentrations in aquatic habitats are bioaccumulated within the tissues of intertidal organisms. The chemical analyses of animal tissues and sediments provide an indication of bioavailability of heavy metals in the environment. Monitoring of the coastal pollution using organisms is widely practiced all over the world.Chemical analysis of the tissues of Pacific oyster, Crassostrea gigas, and river sediments were used in this study to monitor the environmental concentrations, of cadmium, copper, lead and zinc of shallow coastal areas near to the river mouths of Mahurangi, Awaruku, Waiake, Taiorahi and Wairau. All of these river mouths are situated along the northeastern coast of Auckland. Each month, during the period of November 2002 to October 2003, three replicate samples of oysters, and sediments were collected from each of the river mouths for analysis. Three additional replicate samples of oysters were collected separately, in each month in order to calculate the condition index of oysters. Oyster tissues and sediments were analysed with Inductively Coupled Atomic Plasma Emission Spectrometer to detect the concentration levels of cadmium, copper, lead and zinc.The highest level of copper and zinc concentrations in the oyster tissues was observed in the river mouth of Wairau. Wairau river mouth receives water from heavily urbanised and industrialised catchments. A higher concentration of cadmium was observed in the oysters of the river mouth of Mahurangi than in the oysters in the other sites. The reason for this difference could be due to the heavy use of cadmium contaminated fertilizers at the pasture lands situated around the Mahurangi estuary. Therefore, the relationship between the land use of the catchments and the degree of pollution of the estuarine habitats could be established from the data obtained from this study. Higher concentrations of heavy metals were found in the sediments of Waiake, Taiorahi and Wairau compared to the sediments of Mahurangi and Awaruku. Significantly higher level of copper was observed in the sediments of Awaruku. However no clear co-relation was found between heavy metal concentration in oysters and in sediments. Variations of the condition of oysters were closely related to seasonal changes of the life cycle of the oysters. No clear relationship was found between the condition of the oysters and the heavy metal concentration of the river mouth habitats.This study provides evidence that Pacific oysters are good organisms to use as bioindicators of environmental heavy metal levels in shallow coastal waters. The results of this study suggest a clear relationship between the heavy metal concentration in river waters and the land use of the catchment areas of those rivers. The results may be useful in management strategies of the northeastern coastal areas of Auckland.