This study examined the effectiveness of UV radiation in reducing numbers of naturally occurring aerobic psychotrophic bacteria, lactic acid bacteria, Campylobacter and surface inoculated E. coli on split, boneless, skinless chicken breasts and the effects the UV treatments had on the taste of the chicken. The objective of the study was to determine the UV dosage that gave the largest amount of microbial kill without adversely affecting the taste of the chicken. Two groups of 12 breasts were individually vacuum packaged. One group was surface inoculated with 1ml of a 2.0 X 106 CFU/ml culture of generic E. coli. The other group received no inoculation. Two breasts from each group were treated with one of six different UV radiation doses, 0 mW s/cm2 (control-no exposure), 34mW s/cm2, 101mW s/cm2, 202mW s/cm2, 504mW s/cm2 and 1008mW s/cm2. Within 24 hr of the treatments and again after seven days, one breast from each group and each treatment was enumerated for bacterial load. The results showed that bacterial load on the inoculated UV treated breasts were significantly reduced (p <0.05) at every treatment level by an average of 1.5 logs compared to the inoculated controls. There were however, no significant differences (p >0.05) between the inoculated breasts at any of the five different UV treatment dosages. The non-inoculated breasts showed no significant differences in the numbers of bacteria on the controls, as compared to the breasts treated with any of the five UV doses (p >0.05). Another set of 50 breasts were individually vacuum packaged and divided into six groups. Five groups contained five breasts each. Each group was treated with UV doses of 202mW s/cm2, 504mW s/cm2, 1008mW s/cm2, 2016mW s/cm2 and 3024mW s/cm2 respectively. The control group (n=25) received no exposure. Within 48 hr, and again seven days after treatments, triangle tests for difference were conducted to see if the taste of the chicken had been affected by the treatments. A sensory panel detected a significant taste difference between the untreated chicken and chicken treated at 504mW s/cm2 (p <0.05) two days after treatment, and between the control and chicken treated at 2016mW s/cm2 seven days after treatment (p <0.05). / Master of Science

abstract: Emerging infectious diseases (EIDs) in vulnerable populations are a proposed cause of reduced global biodiversity due to local and regional extinctions. Chytridiomycosis, a fungal disease caused by Batrachochytrium dendrobatidis (Bd), is affecting amphibian populations worldwide. Chapter 1 of this thesis reports using lab-raised larval tiger salamanders (Ambystoma tigrinum nebulosum), collected as eggs, to test if Bd infects them. Bd infects metamorphosed tiger salamanders; however, it is currently unknown if larvae can be infected by Bd. Adult frogs tend to host Bd on ventral surfaces and hind legs while tadpoles host Bd in keratinized mouthparts. No research has considered differences in infection between life stages of salamanders. It was hypothesized that Bd can colonize larvae in the same manner as metamorphosed animals. Larval salamanders were inoculated to test if Bd concentrations differ among body regions in larvae compared to metamorphosed salamanders. Larvae can carry Bd with the concentration of Bd varying between body region. Chapter 2 report using native tiger salamanders (Ambystoma tigrinum nebulosum), from northern Arizona and Bd as a study system to test if Bd is native or introduced to Arizona. It was hypothesized that Bd is not endemic to Arizona, but is introduced. There are multiple hypotheses regarding potential routes Bd may have traveled through Arizona and into Mexico. These hypotheses were tested using the Kaibab Plateau in Coconino County, Arizona, as a study site. The plateau is isolated from surrounding areas by the Grand Canyon to the south and the Vermillion Cliffs to the north serving as major biogeographical barriers. It is hypothesized that tiger salamanders are not dispersing into or out of the Kaibab Plateau due to geological restrictions. Bd, therefore, should not be present on salamanders on the Kaibab Plateau due to geological restriction. Tiger salamanders in stock tanks located on the Kaibab as well as preserved museum specimens housed in the Arizona State University Natural History Collection were sampled. The results indicate that Bd occurs at low levels on Kaibab Plateau tiger salamanders. / Dissertation/Thesis / Masters Thesis Biology 2019

No description available.

No description available.

No description available.

Staphylococcus aureus is a major pathogen, which causes a wide range of infections. Despite its obvious clinical importance, little is known about the mechanisms of pathogenesis. An in vitro model mimicking infection was developed in order to identify putative virulence determinants. The model involves the growth of S. aureus in serum under microaerobic conditions. All known virulence factors tested were shown not to be required for growth, or preferentially expressed, in serum. Tn917 transposon libraries of S. aureus were screened to identify genes preferentially expressed in serum, compared to a nutrient-rich growth medium. 73 clones were identified and the transposon insertion site was characterised for 23 of these clones. Analysis of sequence flanking the transposon insertion revealed the identity of the mutated loci. 10 out of 23 sequenced clones, contained transposons inserted within genes involved in the biosynthesis of the aspartate family of amino acids (lysine. threonine, methionine and isoleucine). These were: the two common pathway enzymes; aspartokinase (lysC) , and aspartate semi aldehyde dehydrogenase (asd) , along with; dihydrodipicolinate dehydrogenase (dapA), and cystathionine y-synthase (yjcf) , involved in the biosynthesis oflysine and methionine respectively. Analysis of methionine biosynthesis indicated that S. aureus possesses only a single pathway, which proceeds via cystathionine. Several genes encoding methionine biosynthetic enzymes were found clustered on the S. aureus chromosome. The genes lyse, asd and dapA were found to be encoded by the first three genes of an eight gene operon, which also contains three other genes involved in lysine biosynthesis. This operon named the dap operon, is the major lysine biosynthetic operon of S. aureus. lysC, asd and dapA were all found to be repressed at the transcriptional level primarily by lysine, although factors other than the availability of lysine may be responsible for the regulation of lysine biosynthetic gene expression in serum. lysC, asd and dapA were all found to be expressed in vivo, in a murine pyelonephritis model using both RT-PCR and TaqMan techniques. However, these genes were not found to be important in three murine pathogenicity models. Finally, in addition to the development of a model mimicking infection, and the identification of genes with a potentially important role in vivo, this thesis has enhanced our understanding of both methionine and lysine biosynthesis in S. aureus.

Brassica napus (L.) contributes over $19 billion dollars each year to the Canadian economy. However, yields are constantly threatened by Sclerotinia sclerotiorum (Lib) de Bary, the fungus responsible for Sclerotinia stem rot. To date, there are no global RNA profiling data or gene regulatory analyses of plant tissues directly at the main site of foliar infection in the B. napus-S. sclerotiorum pathosystem. Using RNA sequencing and a gene regulatory analysis, I discovered putative transcriptional regulators of biological processes associated with the tolerant phenotype of B. napus cv. Zhougyou821 including subcellular localization of proteins, pathogen detection, and redox homeostasis. Functional characterization of Arabidopsis mutants identified a number of genes that contribute directly to plant defense to S. sclerotiorum. Together this research amounts to the expansion of our understanding of the B. napus-S. sclerotiorum pathosystem and a valuable resource to help protect B. napus crops from virulent pathogens such as S. sclerotiorum. / October 2016

Streptococcus pneumoniae is a nasopharyngeal commensal in most healthy individuals. However, it can translocate from this niche to deeper tissues, causing diseases such as otitis media, meningitis, sepsis and pneumonia, which are responsible for significant morbidity and mortality worldwide. At the commencement of this work, inherent difficulties in harvesting sufficient bacterial numbers from experimental animals restricted the examination of pneumococcal gene expression during pathogenesis, and thus virulence gene transcription patterns were largely unknown outside of an in vitro environment. This thesis aimed to investigate such transcriptional patterns in vivo, and to hence gain a better understanding of pneumococcal behaviour during colonisation and disease. This work describes refinement of an intranasal S. pneumoniae infection model in CD-1 mice that enables pneumococci to be harvested from multiple niches with low contamination by nasopharyngeal microflora or host tissue, and minimal crosscontamination with circulating pneumococci in the vascular system. The challenge route simulates the acquisition of S. pneumoniae in the human population, and progression to IPD occurs naturally. RNA extraction, enrichment and linear amplification procedures were optimised so that RNA could be obtained from in vivo site in sufficient quantities and with sufficient integrity to be used in semi-quantitative assays. Linear amplification allowed the examination of gene expression in niches where low bacterial numbers had previously prevented such analyses. Real-time RT-PCR and microarray analyses were used to examine bacterial RNA samples recovered from the nasopharynx, lungs, blood and brains of CD-1 mice, providing the first comparative transcriptional data for pneumococci during carriage and disease, within the same animal model. Two pneumococcal serotypes were examined; a type 2 (D39) and a type 6A (WCH16) strain. CbpA, Ply, and SpxB were shown to be important for carriage in both strains, with pneumococci up-regulating the expression of the genes encoding these virulence proteins in the nasopharynx. This provides in vivo evidence supporting the ascribed roles of these proteins in reducing the level of competing microflora and promoting nasopharyngeal adherence. Similarly, D39 nanA and pspA transcription levels were up-regulated in the nasopharynx. The level of pspA mRNA was also higher in the blood than the lungs, suggesting an increased requirement in the bloodstream, where PspA is involved in reducing complement-mediated opsonisation. Despite the antiphagocytic role of the pneumococcal polysaccharide capsule in the bloodstream, D39 cpsA mRNA was present in similar quantities in the nasopharynx, lungs and blood, which may support previous studies indicating post-transcriptional regulation of capsule expression. However, cpsA expression was up-regulated in the blood for WCH16. These results may indicate the existence of strain-specific differences in virulence gene regulation. Microarray analysis of in vivo-harvested S. pneumoniae D39 found that mRNAs encoding components of phosphotransferase systems, CbpA, a putative neuraminidase, and v-type sodium ATP synthase subunits were significantly higher in bacteria involved in carriage than bacteraemia. Conversely, the expression of genes involved in competence, and dinF (present on a competence-induced operon), were up-regulated in the blood compared to the nasopharynx, providing evidence that competence is induced during bacteraemia. Pneumococci also showed increased expression of genes involved in fatty acid metabolism, pgdA, lytB and cbpG in the blood compared to the nasopharynx. This study used a single pneumococcal strain and infection model and, therefore, overcomes inherent issues of serotype/strain- and animal model- specific gene expression that may have complicated interpretation of data in previous studies. This thesis reports some of the first in vivo pneumococcal gene expression data gained using a single animal model and pneumococcal strain. The data reinforce the putative roles of several virulence factors, and provides novel transcription data for pneumococci during carriage. Results suggest the existence of core genes that are essential for infection in multiple pneumococcal serotypes, whereas other genes appear to have strain-specific roles. / http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1287056 / Thesis (Ph.D.)-- University of Adelaide, School of Molecular and Biomedical Science, 2007

Salmonella and Escherichia coli O157:H7 (EC) contamination continues to be one of the major concerns for the microbiological safety of raw poultry and beef products. Application of more than one decontamination agent as a multi-hurdle intervention to carcasses in a processing line might produce greater reductions than one treatment alone due to different modes of action of individual antimicrobials. In this study, sequential spray applications of e-polylysine (EPL), lauric arginate and acidic calcium sulfate (ACS) solutions were evaluated against Salmonella Enteritidis (SE) and Salmonella Typhimurium (ST) on artificially inoculated broiler carcasses and against ST and EC on beef rounds and ground beef derived from the rounds. All possible 2-way combinations and individual applications of 20 % ACS (ACS20), 300 mg/liter EPL (EPL300) and 200 mg/liter LAE (LAE200) were evaluated using a sterile membrane filter model system. The combinations that provided higher Salmonella reductions were further evaluated on inoculated chicken carcasses using either response surface methodology (RSM) or in various concentrations applied in a sequential manner. Sequential spray applications of EPL300 - ACS 30 % (ACS30) or LAE200-ACS30 produced the highest Salmonella reductions on inoculated chicken carcasses. In a subsequent experiment, treatment of Salmonella inoculated carcasses with EPL300-ACS30 or LAE200-ACS30 combinations were found effective for reducing initial Salmonella counts by 1.5 and 1.8 log CFU/ml, respectively, immediately after treatment and by 1.2 and 1.8 log CFU/ml, respectively, following 6 days of storage at 4.4 °C. Evaluation of the resident microflora including aerobic plate counts (APC), E. coli, coliforms and psychrotrophs on uninoculated chicken carcasses after treatment with EPL300-ACS30 or LAE200-ACS30 and during storage indicated that these treatments have the potential to increase the shelf-life of poultry carcasses. Furthermore, application of warm (55 °C) EPL300-ACS30 or LAE200-ACS30 onto inoculated beef rounds reduced both ST and EC counts over 6 days of storage at 4.4 °C by 4.5 and 4.3 log CFU/cm2, respectively. Ground beef manufactured with EPL300-ACS30 or LAE200- ACS30 treated rounds had lower ST and EC counts initially and stayed lower over 4 days of storage at 4.4 °C when compared to control.

Thesis (doctoral)--Swedish University of Agricultural Sciences, 2001. / Includes bibliographical references.