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<p>Phosphate is of central importance in cellular metabolism and since bacteria are often exposed to various concentration of phosphorous in their environment, they have acquired various Pi transport systems for its uptake. <em>Sinorhizobium</em> <em>meliloti</em> has three Pi-uptake systems: a low affinity system encoded by <em>pap</em>-<em>pit</em> and two ABC type systems encoded by the <em>phnCDET</em> and <em>pstSCAB</em> operons. It is currently known that PstSCAB₂, a high affinity, high velocity transporter is induced under Pi limiting conditions and its transcription is controlled mainly in a PhoB-P dependent manner. During excess phosphate conditions, the negative regulation of the Pho regulon seems to involve PstSCAB₂ and PhoU. PhoU appears to be a negative regulator of the Pho regulon however; the mechanism by which PhoU accomplishes this task is currently unknown. In <em>Escherichia</em> <em>coli</em> and some other bacteria, mutations in <em>phoU</em> result in constitutive Pho regulon expression as do mutations in the <em>pstSCAB</em> genes. In order to address the function of PhoU in <em>Sinorhizobium</em> <em>meliloti</em>, we report the creation of a <em>Sinorhizobium</em> <em>meliloti</em> <em>ΔphoU</em> mutant strain. Results from the analysis of the <em>S. meliloti ΔphoU</em> strain suggest that this mutant behaves similarly to <em>E. coli phoU </em>mutant where one observes constitutive expression of the Pho regulon.</p> / Master of Science (MSc)

Although there are many laboratory manuals in microbiology for differenct professions (e.g., A General Microbiology Manual for Nurses, Laboratory Manual for Professional Students in the Medical Sciences, etc.), there has been no laboratory manual in this area for Turkish High School Biology Teachers.The author anticipates that the present manual will be successful in accomplishing the objective of better preparing Turkish High School Biology Teachers.In summer courses, teachers from all of Turkey gather to learn new science ideas, and gain new skills by studying in the laboratories. This manual is intended for use as a study guide in these summer courses.The author has conducted all experiments in the laboratory manual and has attempted to assure that fundamental principles of bacteriology and diagnostic microbiology are interwoven in a functional pattern.

<p>Microbes are ubiquitous in the biosphere and play important roles in natural ecosystems. They are typically present as diverse, complex communities, and in humans these communities are present on all exposed surfaces and mucosal tissues. The human upper respiratory tract harbors a complex microbiome and the composition includes what are traditionally considered commensal organisms, including a significant proportion of anaerobic bacteria. It is generally assumed that most of the bacteria from any particular environment cannot be readily cultivated, including the human microbiome. Some<em> in vitro </em>microfluidic and <em>in vivo </em>models are available to study the airway microbial communities, however these methods are expensive, limited and are not practical for experiments manipulating the community. A robust culture-based approach that can propagate these polymicrobial communities has been developed in this study to investigate spatial-temporal changes in bacterial populations <em>in vitro</em>. Matrix embedded synthetic bacterial communities, comprised of aerobes and anaerobes, were cultivated in continuous flow cell systems. The structure of communities propagated in these systems was compared to those in static and shaken batch cultures. The data shows that reproducible stable bacterial communities can be propagated with these culture methods, however the community composition varies considerably with the approach used. Only matrix embedded communities, cultured under continuous flow conditions, could successfully retain obligate anaerobes when flow cell systems were operated in an aerobic environment. This optimized method was used for culturing complex and diverse natural communities from clinical samples (sputum). The majority of bacteria present in the original sample were recovered in flow cell cultures and the methodology was consistent. This study provides an experimental system that can be used for examining microbial community dynamics and community structure-function relationship.</p> / Master of Science (MSc)

Call number: LD2668 .T4 1961 S64

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Tripartite rhizosphere (host, fungus, and rhizobacterial) interactions were studied to determine the mechanism(s) associated with lack of oospore germination and host colonization by Pythium aphanidermatum at soil temperatures below 27°C. Results indicate that rhizobacterial competition for nutrients was responsible for the general supression of pathogen activity at low soil temperature. In general less than 25% host colonization occurred at 20°C whereas greater than 90% colonization recorded at 27°C. However, when bacterial competition was reduced or eliminated by the addition of vancomycin, host colonization at 20°C increased to 83%. Competition between the fungus and the resident rhizobacterial population was also shown to occur prior to any significant increase in bacterial multiplication. The generation time of bacteria in undisturbed rhizosphere soil was estimated at about 8 hrs at both 20 and 27°C. Whereas both the rate and percentage germination of oospores were increased significantly at both 20 and 27°C in the rhizosphere soil if bacterial competition was inhibited by the addition of vancomycin.