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Isolation And Characterization Of A Rhodobacter Capsulatus Hemc Mutant., Karen Coleman Sullivan
Isolation And Characterization Of A Rhodobacter Capsulatus Hemc Mutant., Karen Coleman Sullivan
LSU Historical Dissertations and Theses
Rhodobacter capsulatus, a purple, nonsulfur photosynthetic bacterium, uses the tetrapyrrole pathway to synthesize four end products: heme, bacteriochlorophyll, vitamin B12, and siroheme. This laboratory has focused on the regulation of the common pathway leading from aminolevulinate to protoporphyrin IX in R. capsulatus. The common portion of the pathway is regulated up to 100-fold by changes in oxygen tension. Research on the regulation of this pathway has been hampered due to a lack of mutants. Until now, the only mutants isolated which block heme production are hemA mutants, which lack aminolevulinate synthase. Since R. capsulatus lacks a cytochrome-independent growth mechanism, mutations …
Epidemiology Of Salmonella In The Green Iguana (Iguana Iguana)., Mark Anthony Mitchell
Epidemiology Of Salmonella In The Green Iguana (Iguana Iguana)., Mark Anthony Mitchell
LSU Historical Dissertations and Theses
The incidence of iguana-associated salmonellosis reported in humans during the 1990's is a public health concern. This research is the first attempt to describe the epidemiology of Salmonella in the green iguana. Seasonal prevalence of Salmonella in green iguanas and their environment were estimated at a commercial iguana farm in El Salvador. The prevalence of Salmonella was lower in adult iguanas (44%) than in yearlings (50%) (Odds ratio (OR): 0.77, 95% Confidence Intervals (CI): 0.6--0.96) and higher in male iguanas (50%) than females (41%) (OR: 1.5, 95% CI: 1.2--1.8). Salmonella recovery was lower in the fall (41%) sampling period than …
Creation And Characterization Of 25 Kda Outer Membrane Protein (Omp25) Deletion Mutants In Brucella Species., Matthew David Edmonds
Creation And Characterization Of 25 Kda Outer Membrane Protein (Omp25) Deletion Mutants In Brucella Species., Matthew David Edmonds
LSU Historical Dissertations and Theses
The genus Brucella is composed of Gram-negative, facultative intracellular pathogens that impact man and animals. Brucella species express a 25 kDa major outer membrane protein termed Omp25. To determine the role of Omp25 in virulence, mutants were created in Brucella abortus (BA25), Brucella melitensis (BM25), and Brucella ovis (BO25) that contain disruptions in the omp25 gene (Deltaomp25 mutants). In the murine brucellosis model, each Deltaomp25 mutant was attenuated when compared to the virulent parental strain. To assess the ability of the B. abortus and B. melitensis mutants to colonize and induce abortions in the ruminant host, cattle and goats in …
Isolation And Characterization Of Newly Emerging Coronaviruses In Acute Respiratory Tract Diseases Of Cattle., Xiaoqing Lin
Isolation And Characterization Of Newly Emerging Coronaviruses In Acute Respiratory Tract Diseases Of Cattle., Xiaoqing Lin
LSU Historical Dissertations and Theses
A total of 411 G clone cell-dependent virus strains recently were isolated from nasal, trachea and lung samples in etiological investigations of acute respiratory tract diseases of vaccinated cattle, including shipping fever pneumonia. The virus infectivity titers reached up to 1.2 x 10 7 plaque forming units per gram of lung tissues of fatal cases. These viral agents were isolated in the 1st G clone cell passage without trypsin enhancement, and induced cell fusion. They have a restricted hemagglutination pattern, agglutinating only rat and mouse erythrocytes. Majority of them has receptor-destroying enzyme activities. They are round and enveloped with a …
Host And Parasite Interactions Among Three Symbionts: Pocket Gophers, Chewing Lice, And Endosymbiotic Bacteria., David Lee Reed
Host And Parasite Interactions Among Three Symbionts: Pocket Gophers, Chewing Lice, And Endosymbiotic Bacteria., David Lee Reed
LSU Historical Dissertations and Theses
This study investigates the patterns of cophylogeny documented between pocket gophers (Rodentia: Geomyidae) and their ectoparasitic chewing lice (Phthiraptera: Trichodectidae). The first two chapters investigate the mechanisms that reinforce cospeciation in this system. Chapter one examines whether mammalian hair diameter is a resource tracked by chewing lice, and thus reinforces the patterns of cospeciation. I found that hair diameter of pocket gophers is correlated with gopher body size and the body size of the ectoparasitic chewing lice. Hair diameter also is correlated with size of the rostral groove, which chewing lice use to grasp hair shafts of pocket gophers. In …
Biological And Molecular Properties Of Sweet Potato Leaf Curl Virus., Pongtharin Lotrakul
Biological And Molecular Properties Of Sweet Potato Leaf Curl Virus., Pongtharin Lotrakul
LSU Historical Dissertations and Theses
In 1994, a sweet potato sample showing leaf curl symptoms was collected from the field in Louisiana. When graft-inoculated, Ipomoea setosa reacted with mild upward leaf curling while I. aquatica reacted with a bright yellow mottle. The putative virus was transmitted by the sweet potato whitefly, Bemisia tabaci biotype B, and it was designated the United States isolate of Sweet potato leaf curl virus (SPLCV-US). Four independent Southern blot hybridizations using the DNA-A of different begomoviruses as probes confirmed the presence of begomovirus-like DNA in the infected plants. Fibrillar inclusions and granular aggregates of geminivirus-like particles were observed in the …
Association Of Environmental And Climatic Factors In The Epidemiology Of American Visceral Leishmaniasis In Northeast Brazil Using Remote Sensing And Geographical Information System Methods., Roland Alexander Thompson
Association Of Environmental And Climatic Factors In The Epidemiology Of American Visceral Leishmaniasis In Northeast Brazil Using Remote Sensing And Geographical Information System Methods., Roland Alexander Thompson
LSU Historical Dissertations and Theses
This study associated climatic and environmental factors with the incidence of visceral leishmaniasis (calazar) in Northeast Brazil. Remote sensing (RS) techniques permitted evaluation of spatial and temporal landscape features to stratify the region and define the target population for this vector-borne disease. The Municipality of Caninde, Ceara, Brazil was divided into 873-- 2 x 2 km2 squares centered on coordinates from a Universal Transverse Mercator projection (scale 1:100,000, 1994) and geo-referenced with 2 Landsat T.M. (TM) scenes (September 26, 1976 and July 2, 1996). The assignment of squares into foothills, plains or city strata was based on vegetative categories determined …
Biology And Ecology Of The Anopheles Quadrimaculatus Sibling Species Complex In Louisiana., Cynthia Roxanne Rutledge
Biology And Ecology Of The Anopheles Quadrimaculatus Sibling Species Complex In Louisiana., Cynthia Roxanne Rutledge
LSU Historical Dissertations and Theses
A polymerase chain reaction method for identifying individuals in the Anopheles quadrimaculatus Say sibling species complex was validated for wild mosquitoes from Louisiana and Mississippi. This method distinguished An. quadrimaculatus species A, B, C, and D by detecting species-specific differences in the 2nd internal transcribed spacer of ribosomal DNA and was 100% specific and 95% sensitive. A polymerase chain reaction assay that detects differences in the second internal transcribed spacer of ribosomal DNA was tested for its usefulness in identifying all immature stages of two representatives in the An. quadrimaculatus sibling species complex. The technique was successful in amplifying DNA …
Aflatoxin B(1) And Fumonisin B(1) Co-Contamination: Interactive Effects, Possible Mechanisms Of Toxicity, And Decontamination Procedures., Rebeca Lopez-Garcia
Aflatoxin B(1) And Fumonisin B(1) Co-Contamination: Interactive Effects, Possible Mechanisms Of Toxicity, And Decontamination Procedures., Rebeca Lopez-Garcia
LSU Historical Dissertations and Theses
The current study evaluated interactions between the mycotoxins aflatoxin B$\sb1$ (AFB$\sb1$) and fumonisin B$\sb1$ (FB$\sb1$) in pure systems as well as in corn. During storage at 25$\sp\circ$C with high moisture (ca. 50%), corn contaminated with Aspergillus flavus (L13) and/or Fusarium moniliforme (A00102) presented different aflatoxin and fumonisin levels. Toxin production/degradation varied over storage time (0-45 days). Evaluation of the mutagenicity of unifungal or bifungal corn extracts with the Salmonella/microsomal assay (tester strains TA-100 and TA-98) with metabolic activation (S9) showed positive mutagenic responses. Different ratios of pure AFB$\sb1$/FB$\sb1$ produced divergent mutagenic responses (tester strains TA-100 and TA-98) with S9. The …
Biological And Molecular Properties Of Potyviruses Isolated From Sweet Potato., Eliezer Rodrigues De Souto
Biological And Molecular Properties Of Potyviruses Isolated From Sweet Potato., Eliezer Rodrigues De Souto
LSU Historical Dissertations and Theses
Ten potyvirus isolates from sweet potato (Ipomoea batatas) cv. Beauregard showing russet crack symptoms and three other isolates associated with internal cork and feathery mottle symptoms were obtained from commercial fields in the United States. The biological properties of these isolates and those of a mechanically transmitted virus obtained from I. purpurea were compared with a previously characterized sweet potato feathery mottle virus strain (SPFMV-C) from North Carolina. The symptoms induced in a range of hosts indicated that two of the isolates were associated with russet crack symptoms in the cultivar Jersey; however, none of them could be associated with …
Antimycobacterial Natural Products From Higher Plants., Charles Lowell Cantrell
Antimycobacterial Natural Products From Higher Plants., Charles Lowell Cantrell
LSU Historical Dissertations and Theses
Two-hundred and thirty crude organic extracts from 118 plant species distributed among ten families of higher plants have been evaluated for antimycobacterial activity against Mycobacterium tuberculosis (H$\sb{37}$Rv) and M. avium using the BACTEC 460 radiorespirometric assay. At 100 $\mu$g/ml, twenty-four and ten of the extracts caused more than 95% inhibition of growth of M. tuberculosis and M. avium, respectively. Bioactive chromatographic fractions of Borrichia frutescens (Asteraceae) provided two new triterpenes and one known cycloartenol. In radiorespirometric bioassays against M. tuberculosis, the new (24R)-24,25-epoxycycloartan-3-one and the known (24R)-24,25-epoxycycloartan-3$\beta$-ol exhibited minimum inhibitory concentrations (MICs) of 8 $\mu$g/ml. In contrast, the new (23R)-3-oxolanosta-8,24-dien-23-ol …
Genetics And Functions Of Herpes Simplex Virus Type 1 (Hsv-1) Glycoprotein K (Gk) In Virus Envelopment And Egress., Sukhanya Jayachandra
Genetics And Functions Of Herpes Simplex Virus Type 1 (Hsv-1) Glycoprotein K (Gk) In Virus Envelopment And Egress., Sukhanya Jayachandra
LSU Historical Dissertations and Theses
HSV-1(KOS)$\Delta$gK, a virus lacking the UL53 gene coding for glycoprotein K(gK) was constructed, characterized and compared to the partially deleted gK-null virus HSV-1(F)-gK$\beta$. $\Delta$gK and F-gK$\beta$ viruses produced microscopic plaques on Vero cells at 48 hours post infection. F-gK$\beta$ plaques at 72 hours post infection contained fused cells (syn), while $\Delta$gK plaques resembled wild-type KOS plaques ($syn\sp+$). $\Delta$gK replicated efficiently in exponentially dividing Vero cells whereas F-gK$\beta$ yields were 10 and 1000-fold lower than $\Delta$gK yields in HEp-2 or log-phase Vero cells, respectively. Electron micrographs of $\Delta$gK-infected Vero cells revealed large numbers of capsids in the nuclei of Vero, but …
Rickettsia Felis, A Newly Discovered Rickettsia Associated With The Cat Flea (Ctenocephalides Felis Bouche)., Jimmy Wedincamp Jr
Rickettsia Felis, A Newly Discovered Rickettsia Associated With The Cat Flea (Ctenocephalides Felis Bouche)., Jimmy Wedincamp Jr
LSU Historical Dissertations and Theses
A study was performed to determine the life cycle of Rickettsia felis, a novel bacterium associated with cat fleas (Ctenocephalides felis Bouche). Cat flea populations maintain R. felis in successive generations by efficient transovarial transmission. Transovarial transmission was demonstrated in our study up to 12 generations. The mean infection rate for the progeny of fleas maintained on both cats and an artificial membrane system were comparable (64.3% and 58% respectively). Cats with no prior exposure to fleas were exposed to fleas infected with Rickettsia felis and monitored monthly for seroconversion via IFA. Blood samples were assayed for the presence of …
Cloning, Sequencing And Regulation Of The Rhodobacter Capsulatusheme Gene., Georgia Ineichen
Cloning, Sequencing And Regulation Of The Rhodobacter Capsulatusheme Gene., Georgia Ineichen
LSU Historical Dissertations and Theses
In Rhodobacter capsulatus, a purple nonsulfur bacterium, the tetrapyrrole pathway yields four end products: siroheme, vitamin B12, heme and bacteriochlorophyll. Growth of R. capsulatus under low oxygen tension increases carbon flow through the tetrapyrrole pathway up to 100 fold. The mechanism(s) for this regulation is currently unknown. One regulatory mechanism could be transcriptional control of one or more of the genes in the common portion of the tetrapyrrole pathway. The fifth gene in the pathway, hemE, has been cloned by complementation of an Escherichia coli hemE::miniTn10 mutant. Sequence data of hemE revealed the presence of an upstream palindrome that is …
Fluorescence Studies Of Ecori Restriction Endonuclease Structure And Dynamics., Wei Liu
Fluorescence Studies Of Ecori Restriction Endonuclease Structure And Dynamics., Wei Liu
LSU Historical Dissertations and Theses
Sequence specific protein-DNA interaction involves changes in protein conformation and dynamics. Research work involved in this thesis is the study of structure and dynamics of EcoRI restriction endonuclease N-termini. The N-termini of EcoRI endonuclease has been shown to be essential for DNA cleavage and also stabilize EcoRI-DNA complex. But they are not resolved in the X-ray crystal structure. An Asn3Cys mutation was made at the N-termini by site-directed mutagenesis and the mutant was subjected to cysteine crosslinking, pyrene labeling and fluorescence studies. Chemical crosslinking of Asn3Cys mutant and steady-state fluorescence studies of pyrene-labeled mutant indicated that the N-termini are in …
Expression Of A Designed Cecropin Analog Gene Using A Baculovirus Vector., Kyusam Choi
Expression Of A Designed Cecropin Analog Gene Using A Baculovirus Vector., Kyusam Choi
LSU Historical Dissertations and Theses
Cecropins are basic, amphipathic peptides with antibacterial activity against many Gram-positive and Gram-negative bacteria. By retaining the positively charged, amphipathic characteristic of cecropin B, a cecropin analog S1, in which 54% of amino acid residues were substituted, was synthesized and shown to possess a broad spectrum of antimicrobial activity. To determine expression of the cecropin analog S1 in Sf9 cells, two gene constructs were designed, and inserted into Autographa californica nuclear polyhedrosis virus under the control of the polyhedrin promoter. One construct, pBS1, consisted of a gene encoding the analog peptide, so that the gene was intended for expression in …
Reduction And Management Of Vibrio Vulnificus In Gulf Coast Oyster (Crassostrea Virginica)., Yu-Pin Chen
Reduction And Management Of Vibrio Vulnificus In Gulf Coast Oyster (Crassostrea Virginica)., Yu-Pin Chen
LSU Historical Dissertations and Theses
The AmeriPure Process (AmeriPure Oyster Company, New Orleans, Louisiana), which is a mild heat treatment for a specific time period, proved effective in eliminating Vibrio vulnificus from the Gulf Coast oysters (Crassostrea virginica), thus reducing the risk of possible V. vulnificus infections. The treatment was effective in the reduction of V. vulnificus in both $1.5\times10\sp5$ MPN/g (high artificially contaminated level) and $2.4\times10\sp3$ MPN/g (low artificially contaminated level) to undetectable level (MPN $<$ 3/g). The mild heat treatment also reduced naturally occurring V. vulnificus $(8.9\pm3.7\times10\sp4$ MPN/g) present in shellstock oysters harvested in warmer months to undetectable levels. The D value for V. vulnificus present in shellstock oyster averaged 45.6 $\pm$ 3.3 seconds at the AmeriPure Process temperature. Mild heat treatment can also control aerobic plate count numbers during refrigerated storage (0-2$\sp\circ$C) and extend the shelf-life of raw oysters for at least 7 days over unprocessed samples. Mild heat treated oysters need to be refrigerated (${<}4\sp\circ$C) to ensure the safety and quality, as well as shelf-life. Oysters treated according to the AmeriPure Process when exposed to an average room temperature of 27$\sp\circ$C were found unacceptable after 24 hours due to the high number of aerobic plate count (10$\sp7$ CFU/g) and were considered not safe to eat. Although there was a slight lightening in color, sensory panels, composed of both traditional raw oyster consumers and infrequent consumers, found the treated product to be comparable in flavor, texture and smell to untreated oysters. According to the result of sensory evaluation, the good oyster flavor of treated samples increased and the off-flavor and off-odor of the treated oysters were significantly lower than the control samples after 7 days of storage on ice. Possible temperature variations, which could occur during the transportation and storage were studied in a temperature abuse study. The result showed that no Vibrio vulnificus was recovered and no significant microbiological quality change was observed after 10 hours of exposure to the room temperature of $22\pm2\sp\circ$C.
Immobilization Of P. Digitatum And Bioconversion Of Limonene To Alpha-Terpineol., Qiang Tan
Immobilization Of P. Digitatum And Bioconversion Of Limonene To Alpha-Terpineol., Qiang Tan
LSU Historical Dissertations and Theses
The parameters of bioconversion of limonene to $\alpha$-terpineol by Penicillium digitatum were determined. This bioconversion was carried out stereo-specifically and selectively by this fungus. (R)-(+)-limonene was selectively converted to (R)-(+)-$\alpha$-terpineol by mycelia of this fungus during early growth phase. Immobilization of the fungal mycelia for use in continuous production of this product was possible. Aeration was critical to this bioconversion. The optimum aeration was about 1.6 mg/L for growing cells and immobilized cells. Substrate inhibition of the bioconversion was not observed when the substrate concentration was below 4% (v/v). End product inhibition was observed. The $\rm Ki\sb{app}$ was 12.08 mM. …
Biochemical And Microbiological Characteristics Of Ground Beef In Modified Atmosphere Packaging With Gas Exchange., Chung-Ping Ho
Biochemical And Microbiological Characteristics Of Ground Beef In Modified Atmosphere Packaging With Gas Exchange., Chung-Ping Ho
LSU Historical Dissertations and Theses
The shelf-life of ground beef in modified atmosphere packaging (MAP) with exchange of gases before retail display was compared with conventional vacuum packaging (VP) and overwrapping with polyvinylchloride film (PVC) for display. Ground beef patties in MAP with distribution gases of 20% $\rm N\sb2:80\%\ CO\sb2,\ 50\%\ N\sb2:50\%\ CO\sb2,\ or\ 80\%\ N\sb2:20\%\ CO\sb2$ and display gases of 80% $\rm O\sb2:20\%\ CO\sb2,\ 50\%\ O\sb2:20\%\ CO\sb2:30\%\ N\sb2,$ or 20% $\rm O\sb2:20\%\ CO\sb2:60\%\ N\sb2$ had decreased weight loss, microorganism growth rate, metmyoglobin formation, and color degradation compared with patties in VP-PVC. Increased CO$\sb2$ during distribution retarded microbial growth. Display gas mixtures with higher O$\sb2$ …
Differentiation Of Tobacco Etch Virus Strains Affecting Pepper., Indra Ariyaratne
Differentiation Of Tobacco Etch Virus Strains Affecting Pepper., Indra Ariyaratne
LSU Historical Dissertations and Theses
Tobacco etch virus (TEV) causes an important viral disease of pepper (Capsicum spp.) in the Western Hemisphere. In this study, 36 isolates of TEV from the United States, Mexico, the Caribbean, Central America, and South America were mechanically inoculated in the greenhouse to selected pepper lines reported to have resistance to one or more TEV isolates. Goals of the research were to evaluate reactions of the resistant pepper lines to the TEV isolates, and to determine if the TEV isolates could be grouped into pathotypes based on their reactions in pepper lines chosen as differentials during the course of the …
Role Of Curved Dna In Promoter Recognition With Bacillus Subtilis And Escherichia Coli Rna Polymerase., Cheryl Anne Nickerson
Role Of Curved Dna In Promoter Recognition With Bacillus Subtilis And Escherichia Coli Rna Polymerase., Cheryl Anne Nickerson
LSU Historical Dissertations and Theses
Intrinsically curved DNA upstream of the RNA polymerase binding site, the promoter, influences transcription in Bacillus subtilis. In this study, curved DNA upstream of the $-$35 region was examined for the ability to influence transcription in Escherichia coli and B. subtilis through the use of hybrid promoters. These promoters were constructed by substituting the curved DNA from two B. subtilis promoters, Bal129 and Alu156, for the DNA upstream of the $-$35 region in the lambda phage promoters $p\sb{\rm R}$ and $p\sb{\rm L}$. The hybrid promoters were designated Bal$p\sb{\rm R}$, Alu$p\sb{\rm R}$, Bal$p\sb{\rm L}$, and Alu$p\sb{\rm L}$. Using transcriptional fusions between …
Effect Of Temperature, Cell Concentration, And Split Dose Gamma Radiation On The Radiosensitivity Of Listeria Monocytogenes., Linda S. Andrews
Effect Of Temperature, Cell Concentration, And Split Dose Gamma Radiation On The Radiosensitivity Of Listeria Monocytogenes., Linda S. Andrews
LSU Historical Dissertations and Theses
Among food-borne pathogens, Listeria monocytogenes is one of the more resistant to food processing methods, including irradiation. USFDA approval for irradiation of processed meat and seafood products likely to contain Listeria spp. is $<$3 kGy gamma radiation. The incidence of L. monocytogenes in food products varies between 5-30% and at levels $<10\sp4$ CFU/g. With the capacity of this bacterium to multiply at refrigeration temperatures and the zero tolerance level mandated by the USFDA it becomes imperative to maximize the efficiency of the irradiation process. The first purpose of this study was to determine if initial cell concentration and/or temperature at time of irradiation influences the radiosensitivity of L. monocytogenes. Secondly, to determine whether split dose application would effect the radiation response of this bacterium. Concentrations of 10$\sp3,$ 10$\sp6$ and 10$\sp9$ cfu/ml of L. monocytogenes Scott A, were suspended in tryptic soy broth and exposed to 0-5 kGy gamma (1.25MeV) radiation at 20, 4, and -80$\sp\circ{\rm C}.$ Split doses were applied in equal portions to initial cell concentrations of 10$\sp6$ and 10$\sp9$ at the same temperatures. Surviving cells under the various conditions were enumerated and irradiation D-values were calculated from linear regression curves. At all temperatures, cell concentrations of 10$\sp3{\rm CFU/ml}$ were reduced to non recoverable levels with 2 kGy gamma radiation. The irradiation D-value of 0.43 kGy for frozen (-80$\sp\circ{\rm C})$ cultures of 10$\sp6$ CFU/ml was significantly lower (p $<$ 0.05) than the D-values (0.58 and 0.62 kGy) for the same cell concentration at the other two temperatures (20$\sp\circ$ and 4$\sp\circ{\rm C},$ respectively). For higher cell concentration of 10$\sp9$ cfu/ml, a D-value of 0.42 kGy was obtained for both 4$\sp\circ{\rm C}$ and -80$\sp\circ{\rm C}$ these were significantly lower (p $<$ 0.05) than 0.50 kGy for 20$\sp\circ{\rm C}$ suspensions. With both cell concentrations, the lowest D-values were obtained when cells were irradiated in the frozen state indicating a that primary cell damage was due to direct effects of irradiation. Split doses of 1 and 2 hours time between fractions approached the generation times for this bacterium and were significantly reduced at 20$\sp\circ{\rm C}.$ However, there was no consistent trend in reductions at 4$\sp\circ$ or -80$\sp\circ{\rm C}.$ Split dose application of irradiation to food pathogens should be further explored.
Effects Of Heat, Lactic Acid, And Modified Atmosphere Packaging On Listeria Monocytogenes On Cooked Crawfish Tail Meat., Warren Joseph Dorsa
Effects Of Heat, Lactic Acid, And Modified Atmosphere Packaging On Listeria Monocytogenes On Cooked Crawfish Tail Meat., Warren Joseph Dorsa
LSU Historical Dissertations and Theses
The generation time of L. monocytogenes was calculated to be 72.2, 28.5, 17.01, and 6.9 h on crawfish tail meat held at 0, 4, 6, and 12$\sp\circ$C, respectively. Potassium sorbate (PS) (0.3%) spray treatments on crawfish held at 4$\sp\circ$C, extended the lag phase of the bacterium. However, once exponential growth began, a generation time not significantly different (P $>$ 0.05) than that of untreated crawfish was observed. Samples sprayed with 0.3% citric acid (CA) and held at 4$\sp\circ$C supported growth of the bacterium equally well as that of untreated samples. Thermal inactivation of L. monocytogenes using a three neck …
The Role Of Flagellar Proteins In Adhesion Of Vibrio Parahaemolyticus, And Isolation Of The Corresponding Gene(S)., Ratchanee Hongprayoon
The Role Of Flagellar Proteins In Adhesion Of Vibrio Parahaemolyticus, And Isolation Of The Corresponding Gene(S)., Ratchanee Hongprayoon
LSU Historical Dissertations and Theses
Polar flagellar core protein was purified from Vibrio parahaemolyticus by differential centrifugation and cesium chloride isopycnic centrifugation. Twelve hybridomas secreting monoclonal antibodies against flagellar core protein (MAb-flc) were obtained from fusions. By chance, one purified flagellar core preparation retained flagellar sheath and as a consequence, two hybridomas were detected which secreted anti-sheath antibodies (MAb-fls). MAb-flc and MAb-fls reacted specifically with their corresponding antigens as demonstrated by immunogold labelling. Coagglutination reagents prepared with MAb-flc and MAb-fls were tested against 34 strains of V. parahaemolyticus and 34 heterologous Vibrio species. The coagglutination results revealed that the flagellar core was species-specific while the …
Acetylation Of Seaweed Alginate By Pseudomonas Syringae., Jin Woo Lee
Acetylation Of Seaweed Alginate By Pseudomonas Syringae., Jin Woo Lee
LSU Historical Dissertations and Theses
Acetylation of bacterial alginate by Pseudomonas syringae subsp. phaseolicola ATCC 19304 was independent of alginate biosynthesis. This allowed the development of a process for acetylating seaweed alginate using immobilized P. syringae ATCC 19304 cells. About 50% of the mannuronic acid residues of seaweed alginate were acetylated by carbon immobilized P. syringae cells in a fluidized bed, up-flow reactor system fed continuously with seaweed alginate and gluconic acid. O-Acetylation by this process was found to be specific for the C-2 and/or C-3 position(s) of mannuronate residues. Acetylated seaweed alginate showed altered properties including increased viscosity and changed affinities for some cations.
Antimicrobial Properties Of Glycerol Monolaurate Either Alone Or Combined With Selected Organic Acids Against Listeria Monocytogenes., Deog-Hwan Oh
LSU Historical Dissertations and Theses
The objective of this study was to evaluate the antimicrobial properties of glycerol monolaurate (monolaurin) either alone or in combination with organic acids against Listeria monocytogenes in model broth or food. The minimal inhibitory concentration (MIC) of monolaurin was reduced by decreasing the pH value of the medium. The contribution of temperature to monolaurin effectiveness showed that lethal effects of monolaurin increased at higher temperatures and lower pH values, whereas, bacteriostatic effects on growth increased as temperature and pH decreased. The inhibitory effect of ethanol on the growth of L. monocytogenes was slight up to 2.5% ethanol, but was significant …
In Vitro Studies On The Interactions Between Toxoplasma Gondii And Its Host Cell., Sandra Karen Halonen
In Vitro Studies On The Interactions Between Toxoplasma Gondii And Its Host Cell., Sandra Karen Halonen
LSU Historical Dissertations and Theses
Toxoplasma gondii is an obligate intracellular protozoan parasite of the Phylum Apicomplexa. The parasite resides in the cytoplasm of its host cells in a membrane bound compartment called the parasitophorous vacuole. All growth and development of the parasite occur within this compartment. In this thesis, the interactions between the Vero cells, a fibroblast-like cell line, and the parasite which occur during the intracellular growth of the parasite were addressed. The impact of infection on the host cell intermediate filaments and microtubular cytoskeletal elements was examined by immunofluorescence microscopy. Host cell intermediate filaments were found to overcoat the parasite vacuole beginning …
Characterization Of The Subunits Of The Mcrbc Restriction System In Escherichia Coli K12., Timothy Paul Beary
Characterization Of The Subunits Of The Mcrbc Restriction System In Escherichia Coli K12., Timothy Paul Beary
LSU Historical Dissertations and Theses
The McrBC (Modified Cytosine Restriction) restriction system has the ability to restrict DNA containing 5-hydroxymethylcytosine, N$\sp4$-methylcytosine, and 5-methylcytosine at specific sequences. The mcrB gene produces two gene products. The complete mcrB open reading frame produces a 53-kDa protein (McrB$\sb{\rm L}$) and a 35-kDa protein (McrB$\sb{\rm S}).$ The smaller McrB polypeptide is produced from an inframe, internal translational start in the mcrB gene. The mcrC gene produces a single 38-kDa protein. Evidence was presented that McrB$\sb{\rm S}$ regulates the activity of McrBC. When McrB$\sb{\rm S}$ was overproduced in a McrBC$\sp+$ background, there was dramatic loss of restriction. Underproduction of this protein …
Applicability Of Bioluminescence Assay And Aerobic Bacterial Counts For The Evaluation Of Raw Milk Quality., Abdul Ghafoor Mian
Applicability Of Bioluminescence Assay And Aerobic Bacterial Counts For The Evaluation Of Raw Milk Quality., Abdul Ghafoor Mian
LSU Historical Dissertations and Theses
Raw milk samples were analyzed to determine the bacteriological quality by the standard plate count (SPC), adenosine-5$\sp\prime$-triphosphate (ATP) assay, preliminary incubation counts, and the psychrotrophic bacteria count (PBC). In a comparison of SPC and ATP content, an overall correlation coefficient of 0.97 was found between the two methods. The correlations between ATP content and SPC of fresh raw milk samples at zero hour and after preliminary incubating these samples at 12.8 and 15.6$\sp\circ$C for 18 hours were.96,.97, and.97, respectively. The regression coefficients for all types of milk samples were highly significant ($P <$.01). High correlation coefficients demonstrated that the ATP measurement in combination with preliminary incubation practices could be a rapid technique for the determination of bacteriological quality of milk at receiving stations and milk processing plants. Median SPC for 175 fresh raw milk samples was 36,000/ml. The bioluminescence technique is reported previously to have a good correlation with SPC in the range of 1.0 $\times$ 10$\sp5$ to 1.0 $\times$ 10$\sp{10}$ bacteria/ml. The commingled milk coming at the receiving stations sometimes have a bacterial count that is less than 1.0 $\times$ 10$\sp{5}$ bacteria/ml. A correlation coefficient of.87 was calculated between the SPC and ATP values for the overall data while lowering the SPC range from 1.0 $\times$ 10$\sp5$ to 1.0 $\times$ 10$\sp4$ bacteria/ml. This range is more practical as a quick screening of raw milk at dairy processing facilities since 81 percent of all raw milk samples fell in this range. An equation (SPC = $-$1642213 + 6751(ATP)) was developed from the combined experimental data which could estimate the SPC of raw milk samples using their ATP content. Another phase of the experiment was to ascertain if the Petrifilm$\sp{\rm TM}$ technique could be effectively used in place of agar method to estimate PBC. The correlation coefficient between the Petrifilm$\sp{\rm TM}$ and the agar plate method for both the fresh and preliminary incubated raw milk samples was.99. A high linearity of relationship shows that one method can be substituted with the other. However, the Petrifilm$\sp{\rm TM}$ technique took longer than the usual time of 25 h to develop red colonies at 21$\sp\circ$C because of the slow reduction of the dye reagent triphenyl tetrazolium chloride (TTC) at this temperature.
Characterization Of Gentamicin Resistance In Enteric Bacteria Isolated From Pseudomys Scripta-Elegans From Commercial Turtle Farms., Michelle Anne Brassett
Characterization Of Gentamicin Resistance In Enteric Bacteria Isolated From Pseudomys Scripta-Elegans From Commercial Turtle Farms., Michelle Anne Brassett
LSU Historical Dissertations and Theses
Several genera of aminoglycoside resistant enteric bacteria were isolated from commercial turtle farms. Citrobacter freundii and Proteus vulgaris were the most prevalent organisms. Gentamicin resistance, measured by minimum inhibitory concentrations (MIC), ranged as high as 100 $\mu$g/ml. While resistance to other antibiotics was detected in gentamicin-resistant isolates, no correlation was observed between antibiotic resistance and plasmid content. Spontaneous mutation to gentamicin could not account for the high levels of gentamicin resistance found in the original isolates. Regions of chromosomal DNA encoding gentamicin resistance of 100 $\mu$g/ml were obtained from two Citrobacter freundii, two Proteus vulgaris, and two Salmonella enteritidis strains. …