No description available.

Bacteriophages, regarded today as viruses parasitic on bacteria, are characterized by a number of well-defined properties, one of these being the specificity exhibited by some varieties of phages, not only for a single species of bacteria, but also for certain strains or types of that single species. A practical application of this property has been the use of bacteriophage for the identification or phage typing of certain strains of a given species. Fisk (1942) introduced a method of phage typing of staphylococci which has been successfully used for tracing sources of infection in epidemic outbreaks of staphylococcal enterotoxin food-poisoning and of staphylococcal infections of the skin in babies in maternity hospitals. Although this method is relatively simple and rapid, many strains of staphyloccoi are resistant to the action of the available phages and the absolute specificity of the phage types is questionable. The purpose of this work is to investigate the growth and multiplication requirements and the stability of the staphylococcus bacteriophages now available, and to use anti-bacteriophage sera (prepared by immunizing rabbits with selected phage strains) as a means for recognition of specificity. If the phages could be divided into a few representative groups, it is hoped that by a careful selection of these phages, a simpler method of phage typing applicable in every laboratory may be developed.

Call number: LD2668 .T4 1951 B5 / Master of Science

The TonB-ExbB-ExbD complex is essential for the siderophore mediated acquisition of iron by Gram negative bacteria. The system provides energy from the proton motive force to the outer membrane in order for the iron siderophore complex to enter into the cell. The main protein involved in energy transduction, TonB, has been extensively studied in the species Escherichia Coli. It has been determined that the protein consists of 239 amino acids. In comparison, however, the TonB of Rhizobium leguminosarum consists of 457 amino acids with the same conserved regions. What is in question, therefore, is how the additional amino acids effect the structure of the C-terminal region of the protein and how such information can give insight into the way in which the proton motive force functions to provide energy to the outer membrane receptor. The protein regions of R. leguminosarum TonB chosen for study were 120 and 248 amino acids from the C-terminal end. Genomic DNA was isolated, primers were designed for each fragment, and polymerase chain reactions were performed. After appropriate restriction enzyme digestion, each DNA fragment was ligated into the plasmid pET-17b and then transformed into Escherichia Coli BL21 (DE3). Successful transformation of the 120 amino acid fragment was followed by expression via IPTG induction & extraction of protein. Afterwards, a T7-tag affinity column was attempted to collect the protein for analysis; however, a sufficient amount of protein was not eluted. The procedure will be repeated for obtaining sufficient protein for crystallization or NMR spectrometric analysis.

Obligate intracellular bacteria are significant causes of morbidity and mortality with over two hundred and fifty million infections worldwide annually. One such bacterium, Anaplasma phagocytophilum is the etiologic agent of human granulocytic anaplasmosis (HGA), a tick-transmitted febrile illness. Previous studies have shown that A. phagocytophilum lacks genes for cholesterol biosynthesis and solely relies on Niemann Pick protein type C (NPC)1-mediated low density lipoprotein (LDL)-derived cholesterol to complete its infection cycle.Acid sphingomyelinase (ASMase) is a lysosomal enzyme that is essential for diverse cellular processes including liberation of LDL-derived cholesterol from the lysosome. By first studying A. phagocytophilum, we found that functional inhibitors of acid sphinogmyelinase (FIASMAs) arrest the bacterium’s infection cycle in a dose-dependent manner. FIASMAs inhibit vacuole maturation, conversion to the infectious form, and eliminate the production of infectious progeny. NPC1-mediated LDL-derived cholesterol traffic to the ApV is abrogated in the presence of FIASMAs. Similar to the in vitro model, A. phagocytophilum cannot establish a productive infection in both ASMase-/-and FIASMA treated mice. Furthermore, we extended our studies to Coxiella burnetti (Q fever), and Chlamydia spp. (STD, infectious blindness, pneumonia). FIASMA treatment has a rapid bacteriocidal effect on C. burnettiwithin host cells. Additionally, FIASMA treatment inhibits C. trachomatis and C. pneumoniae inclusion expansion and infectious progeny generation, with C. pneumoniae being more severely impacted. These data highlight the critical, yet distinct roles that ASMase plays in these pathogens’ infection cycles. Furthermore, these results signify the therapeutic potential of FIASMAs for treating diseases caused by these pathogens.

Thesis (M.Phil.)-University of Hong Kong, 1995. / Includes bibliographical references (p. 133-141). Also available in print.

No description available.

Recently much information has accumulated indicating specific functions of inorganic ions, especially Na⁺ in the nutrition and metabolism of marine bacteria. A number of marine bacteria have been reported to have a specifie Na+ requirement for growth and for optimal metabolism. The function of the ions has been considered to be more than a simple osmotic effect, since evidence has been obtained, indicating that inorganic ions play a major part in the maintenance of the integrity of the cell wall. It has also been shown, recently, that Na⁺ is involved in the penetration of substrates into cells of marine bacteria. Since marine bacteria appear to have special requirements for inorganic ions for growth, transport and the maintenance of cell wall integrity, the knowledge of intracellular ion concentrations are of particular importance to an understanding of the relation of marine bacterial cells to their environment. Only one marine bacterium has so far been examined in any detail in this connection. The aim of this investigation has been to study ion distributions and the conditions affecting ion uptake in three other marine bacterial species. In this study the actual intracellular Na⁺, K⁺ and Cl⁻ concentrations have been determined directly and the penetration and the exchange of Na²² isotope into the cells has been measured. [...]

Since the advent of improved tissue culture techniques the study of animal viruses has made rapid progress. The effect of a virus infection on the host cells has been studied from many aspects. One aspect is the alteration of the protein synthetic capacities of the infected cells. Many studies have been performed on the proteins of the virus particle such as the antigens and the haemagglutinins, or the proteins of the cells, such as the enzymes used to synthesize the virus particles. Little attention has been paid to the cellular proteins which were not involved in the synthesis of the virus particle. Such a protein is antibody. The following report shows how the metbod was establisbed for the quantitation of antibody produced in vitro. It will examine the effect of Newcastle disease virus on the immunologically competent cells in spleen cell suspensions. [...]

The survival of bacteria at low temperatures has been a subject of study for many years. Bretz and Hartsell (1969) pointed out that many variables affect the survival of micro-organisms following exposure to sub-freezing temperatures. The variables were listed as the freezing and suspending medium, initial cell concentration, species of micro-organism, age of the culture or stage of growth of the cells, the rate of freezing and thawing, the period of time which elapses between thawing and plating and the composition of the diluent and of the plating medium. All these variables have been shown to affect the apparent numbers of viable micro-organisms after exposure to freezing temperatures. [...]