In recent years, Clostridiodes difficile has caused a sharp increase in hospital-acquired infections. Patients on multiple courses of antibiotics experience a general clearing of normal gut microbiota, leading to dysbiosis and an opportunity for C. difficile to colonize the colon. Understanding which nutrients produce optimal respiratory metabolism in C. difficile will help to determine the reasoning behind whether the microbe invests its energy into various cellular processes, such as motility. Different C. difficile strains were first cultured in BHIS broth (brain-heart infusion, supplemented) and CDMM broth (C. difficile minimal media) before being used to inoculate soft agar wells. The culture growth in the wells was observed to record the motility of each strain in each condition. Initial analysis demonstrated that motility was observed to a greater extent in less viscous, minimal media. This trend pointed to the bioenergetic need of C. difficile to expend limited energy resources in exhibiting a chemotactic response towards more distant nutrient sources after metabolizing nearby nutrient stores. Additional studies were performed to elucidate the motility patterns of various mutants in both rich and minimal media in the least viscous agar condition. In this study, the motility of two wild type strains, R20291 and JIR8094, were examined along with several mutant strains that lack selenoproteins. Motility was observed in JIR8094 in defined minimal medium after several days of incubation, and this result was surprising based on the published literature. Some reduction in motility was observed in a selD mutant in both rich and defined minimal medium. These results suggest that energy derived from selenoenzymes may contribute to motility. Additional research could be conducted to test this hypothesis.

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This study was designed to determine the survival of Vibrio parahaemolyticus in salted oysters as prepared in Korea. Three levels of salt concentration were included; 3.0%, 6.8%, and 10.6% of the weight of the raw oysters. Two methods were used to inoculate the products, surface-inoculation and injection into the oysters, which were then held at 18°C. Multiplication of V. parahaemolyticus (Japanese strain T-3765-1) did not occur in the salted oysters, except for a slight increase in numbers after 24 hours from surface-inoculated samples with 3.0% salt and all samples of injected oysters. The samples with the higher salt concentrations showed longer survival of the organisms. Numbers of survivors in surface-inoculated oysters were markedly reduced within three days; the samples of injected oysters did not show reduced numbers in this period. There were more survivors from the injected samples over the storage period than from the surface-inoculated samples. No viable cells were observed after seven days from the surface-inoculated samples with 3.0% salt and the injected samples with 3.0% salt, after eight days from the surface-inoculated samples with 6.8% salt, after nine days from the injected samples with 6.8% salt, and after 11 days from the injected samples with 10.6% salt. A small number of V. parahaemolyticus were recovered from the surface-inoculated samples with 10.6% salt after eight days, the last testing period for these samples. The results of pH measurement suggested that the samples with higher salt concentration may have prolonged survival of V. parahaemolyticus through the effect of the higher pH value. An analysis of variance revealed a significant difference (5% level) in recovery between a modified isolation medium (Twedt and Novelli) and thiosulfate-citrate-bile salts-sucrose agar. Salt concentrations of 3.0%, 6.8%, and 10.6% slightly reduced the total bacterial counts after three days from the two lots of oysters used for the surfaceinoculated samples and further reduction was observed after seven days; reduction in numbers was not detected within 8 or 11 days from the two lots used for the injected samples. The latter two lots had much lower plate counts at the beginning of the experiment. No relationship was found between pH and total bacterial counts on the salted oysters. / Graduation date: 1973

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Five strains of lactic cultures and their homologous bacteriophage races were examined for response in a whey-based medium under pH control and fortified with zero to two percent levels of added orthophosphates. One percent each of culture and phage was inoculated into each medium, which was incubated at 25 C and continuously neutralized at pH 6.3 with 20 percent NH4OH. Growth response in media was compared against growth in non fat dry milk and a commercial phage inhibitory medium (Marstar). The whey-based medium which had been frozen and thawed provided more effective growth response and greater phage protection than freshly prepared whey-based medium. Strain #3 grew optimally and was protected against phage inhibition with an added phosphate concentration of 0.5 percent whereas 0.7 percent was the required concentration in fresh whey-based medium. One strain grew optimally and was protected against inhibition in only 0.5 percent added phosphate in the fresh whey-based medium. Two strains required 0.7 to 0.75 percent and two required 1 percent. All five produced acid more rapidly in whey-based medium than in the milk or phage inhibitory medium controls. Phage inhibitory medium which was stored for four years at 25 C supported culture growth as effectively as two month old medium.

<p><strong><p>The <em>Enterococcus genus consists of natural members of the gastrointestinal tract but they are also opportunistic pathogens. They are a common cause of urinary tract infections but can also cause sepsis and other infections. <em>Enterococcus faecalis and <em>Enterococcus faecium are the most abundant in clinical specimens. Enterococci are a leading cause of nosocomial infections and they have developed resistance against a number of antibiotics e.g. vancomycin. <em>E. faecalis V583 was the first vancomycin resistant isolate reported in the U.S. Movable genetic elements such as pathogenicity islands, PAI, are important for bacterial evolution. PAI:s are large chromosomal fragments mostly seen in pathogenic strains and carry regions such as transposons and insertion elements along with virulence factors and transfer genes. A PAI has been detected in the chromosome of <em>E. faecalis. Excision of PAI:s has been studied for uropathogenic <em>E. coli and frequencies of 10-5 and 10-6 have been reported. In this study the excision rate and excision patterns of <em>E. faecalis V583 was studied using the counterselectable marker <em>pheS*, causing <em>p-Cl-phe sensitivity, and a chloramphenicol resistance gene, <em>cat, inserted at two different positions of the PAI and selecting for excisions by growth on <em>p-Cl-phe. Excision rates of 10-6 and 10-8 were seen based on the <em>p-Cl-phe resistance and chloramphenicol sensitivity. Mutation rate in the <em>pheS* gene was high compared to excision rate which made the method difficult to work with. No obvious excision patterns were detected but the excisions seemed to be limited to the close surroundings of the <em>pheS*/cat insertion. </em></em></em></em></em></em></em></em></em></em></em></em></em></em></p></strong></p> / <p>Bakterier finns överallt i vår omgivning och hos oss människor, exempelvis på huden och i vår mag-tarmkanal. Flertalet av dessa är apatogena, d.v.s. orsakar inte sjukdom. Vissa normalt goda bakterier kan dock orsaka sjukdom när de hamnar på fel plats och får tillfälle att orsaka sjukdom s.k. opportunistiska patogener. Ett exempel på detta är bakterien</p><p>Genetiska egenskaper hos såväl människor som bakterier styrs av arvsmassan, DNA. Hos människor är arvsmassan samlad i 46 kromosomer medan bakterier har en. På senare år har vi lärt oss hur man kan klippa och klistra i exempelvis bakteriers DNA för att introducera egenskaper eller ta bort. Detta används inom forskning för att studera t.ex. bakteriers förmåga att orsaka sjukdom eller anpassning till sin omgivning. Bakterier är mycket duktiga på just anpassning vilket beror på deras förmåga att snabbt förändra sitt DNA ofta genom utbyte med andra bakterier, detta kan bl.a. leda till utveckling av antibiotikaresistens eller nyvunnen förmåga att orsaka sjukdom. Största delen av en bakteries arvsmassa består av konserverade regioner medan andra är mycket föränderliga exempelvis s.k. isertions element, tansposoner och patogenicitetsöar, som har visat sig kunna lämna kromosomen via excision. En patogenicitetsö har hittas hos</p><p>I den här studien klistras en gen in i patogenicitetsön hos</p><p>Bakteriekloner där excision förekommit erhölls och excisionsfrekvensen bestämdes till 10</p><p>bakterier. Inga kloner där hela patogenicitetsön lämnat kromosomen kunde detekteras, dock visade det sig att områden precis intill området där genen klistrats in hade försvunnit. Inga tydliga excisionsmönster kunde bestämmas. En hög frekvens av mutationer i den insatta genen gjorde metoden svår att arbeta med.</p><p><em>Enterococcus faecalis som finns i mag-tarmkanalen hos friska människor men som när den hamnar på fel plats kan orsaka bl.a. urinvägsinfektion, sårinfektioner och i svåra fall blodförgiftning, s.k. sepsis. <em>E. faecalis. Patogenicitetsöar är delar av kromosomen som ofta innehåller virulensfaktorer, som gör bakterien patogen och hos vissa bakterier har man påvisat gener för antibiotikaresistens på sådana öar. <em>E. faecalis som gör att bakterien inte kan växa på ett speciellt selektivt media. Detta gör det möjligt att välja bakterier där ön lämnat kromosomen för vidare studier och en excisionsfrekvens bestämmas. -6 till 10-8. Detta är låga frekvenser jämfört med vad man kommit fram till hos andra 3 </em></em></em></p>