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- Title
- Breaking biofilms : regulation of Type II secretion system in V. cholerae and the formation of the hyper-pseudopilus
- Creator
- Sloup, Rudolph E.
- Date
- 2016
- Collection
- Electronic Theses & Dissertations
- Description
-
Vibrio cholerae is the causative agent of the human disease cholera, it resides in aquatic resevoirs and forms biofilms, which are closely associated communities of bacteria embedded in polysaccharides, DNA, and proteins. In V. cholerae biofilm formation is regulated by the second messenger molecule cyclic di-GMP (c-di-GMP). A genetic screen for promoters regulated by the c-di-GMP revealed a novel promoter (PepsG) in the eps operon encoding the V. cholerae Type 2 secretion system (T2SS). The...
Show moreVibrio cholerae is the causative agent of the human disease cholera, it resides in aquatic resevoirs and forms biofilms, which are closely associated communities of bacteria embedded in polysaccharides, DNA, and proteins. In V. cholerae biofilm formation is regulated by the second messenger molecule cyclic di-GMP (c-di-GMP). A genetic screen for promoters regulated by the c-di-GMP revealed a novel promoter (PepsG) in the eps operon encoding the V. cholerae Type 2 secretion system (T2SS). The T2SS, which exports proteins from the periplasm to the extracellular space, is phylogenetically related to Type 4 pili. The major pseudopilin is encoded by epsG which forms a short piston like structure necessary for secretion. I hypothesized that differential regulation of the eps operon extends the pseudopilin forming a structure called a hyper-pseudopilus outside the cell where it promotes biofilm development. In Chapter 2, I determined that the promoter upstream of the operon (PepsC1) is induced four fold by c-di-GMP and this induction is mediated by the c-di-GMP binding transcription factor VpsR directly. High levels of c-di-GMP were found to decrease the activity of extra cellular proteases secreted by the T2SS, however this effect was not a direct result of regulation of the T2SS as determined by mutation of the VpsR binding site in PepsC1. I was unable to establish a phenotype for the transcriptional control of the eps operon. This work establishes T2S as a new phenotype which is transcriptionally controlled by c-di-GMP and the biofilm associated transcription factor VpsR. In Chapter 3, I show that overexpression of epsG in a continuous flow cell system increased V. cholerae biofilms while a ΔepsG strain showed no biofilm formation. However, there was no change in activity of T2S dependent serine proteases while epsG was over expressed indicating increased biofilms is not likely due to increased secretion. Polyclonal antibody stained EpsG was also detectable on the surface of WT cells and long pseudopili were visualized with over expression of epsG. This evidence suggests the T2SS forms a hyper-pseudopilus important for biofilm formation. In Chapter 4, I present my work identifying novel anti-biofilm compounds. In 2011 Escherichia coli O104:H4 caused the deadliest E. coli outbreak in modern times resulting in 54 deaths and the highest rate of hemolytic uremic syndrome ever recorded. Subsequently, we showed a correlation between biofilm gene expression and virulence factor expression. I sought to identify small molecule compounds effective at inhibiting O104:H4 biofilms. I discovered at a concentration of 0.01% the nonionic surfactants polysorbate 80 (PS80) and polysorbate 20 (PS20) were found to inhibit biofilm formation by 90% and 91% respectively. These compounds were able to disperse preformed biofilms. Treatment of mice infected with E. coli O104:H4 resulted in high bacterial loads and inflammation. While addition of PS80 in the drinking water of the mice did not reduce bacterial loads, it completely abolished inflammation symptoms. PS80 is an FDA approved compound, well studied and effective at low nanomolar concentrations that reduces symptoms of infection in mice. which establishes it as an excellent candidate for further study as an anti-infective agent with anti-biofilm capabilities
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- Title
- The relationship between substrate concentration, respiration rate, and growth rate of Escherichia coli in continuous flow culture
- Creator
- Lipe, Robert Sterling
- Date
- 1961
- Collection
- Electronic Theses & Dissertations
- Title
- Mechanism of forelimb skin and skeletal muscle glucose uptake during Escherichia coli endotoxin shock in the dog
- Creator
- Karlstad, Michael Donald
- Date
- 1982
- Collection
- Electronic Theses & Dissertations
- Title
- Studies of Escherichia coli RNA-DNA hybrid and of methylation of RNA in T-4 infected cells / by
- Creator
- Armstrong, Robert Lee
- Date
- 1966
- Collection
- Electronic Theses & Dissertations
- Title
- Assessment of E. coli and total coliforms in surface irrigation water sources in Michigan blueberry farms
- Creator
- Alraqibah, Sultan Ali
- Date
- 2016
- Collection
- Electronic Theses & Dissertations
- Description
-
Fresh produce that is consumed raw can be a source of pathogens that cause human illness. This is particularly true for produce that is irrigated with untreated surface water at times close to harvest. Michigan has many blueberry farms, and these farms often irrigate their crops using untreated water drawn from irrigation ponds. This research was conducted to quantify E. coli levels in irrigation water sources at six blueberry farms in Michigan, and associate these levels with factors such as...
Show moreFresh produce that is consumed raw can be a source of pathogens that cause human illness. This is particularly true for produce that is irrigated with untreated surface water at times close to harvest. Michigan has many blueberry farms, and these farms often irrigate their crops using untreated water drawn from irrigation ponds. This research was conducted to quantify E. coli levels in irrigation water sources at six blueberry farms in Michigan, and associate these levels with factors such as, rainfall, pH and conductivity of the water, and susceptibility of the water sources to runoff. Samples of water and blueberries were collected during summer 2015. Water samples were obtained twice weekly and blueberry samples once weekly. The Colilert Quanti-Tray/2000 method was used to quantify E. coli. Among the water samples (n=111), 95% contained detectable E. coli, and 17% of samples had E. coli levels greater than 126 MPN/100 ml, - the maximum geometric mean (GM) of E. coli level allowed in agricultural water under the FDA Produce Safety Regulation. The maximum detected level of E. coli was 4,611 MPN. Among the blueberry samples assayed (n=68), only 4.4% tested positive for E. coli, with the maximum level detected being 12 MPN E. coli per 100 grams of blueberries. These results indicate a high likelihood of detecting E. coli in surface irrigation water sources used on selected Michigan blueberry farms, and will be useful in establishing initial water quality profiles for these farms as required under the new FDA Produce Safety Regulation.
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- Title
- Membrane structural transitions modulate growth limits of Escherichia coli
- Creator
- Janoff, Andrew Stuart
- Date
- 1980
- Collection
- Electronic Theses & Dissertations
- Title
- Investigation of bacterial fecal indicators and coliphage virus in sediment and surface water of parks and beaches along the Grand River (MI) and Lake Michigan (MI)
- Creator
- Singh, Shikha
- Date
- 2007
- Collection
- Electronic Theses & Dissertations
- Title
- Piliated Escherichia coli and porcine enteric disease in Michigan
- Creator
- Evans, Mark G.
- Date
- 1983
- Collection
- Electronic Theses & Dissertations
- Title
- Local immune responses following in utero vaccination of the bovine fetus with Escherichia coli
- Creator
- Wamukoya, Joseph Pius Otieno
- Date
- 1975
- Collection
- Electronic Theses & Dissertations
- Title
- Resistance of the newborn calf to oral challenge with a septicemia-producing Escherichia coli
- Creator
- Johnston, Noel Edgar
- Date
- 1975
- Collection
- Electronic Theses & Dissertations
- Title
- The nature of DNA-protein interactions studied by polyacrylamide gel electrophoresis
- Creator
- Ceglarek, John Anthony
- Date
- 1987
- Collection
- Electronic Theses & Dissertations
- Title
- Pathologic effects of Escherichia coli 083:K.:NM in gnotobiotic pigs
- Creator
- Britt, Alfred Lenneth, 1924-
- Date
- 1967
- Collection
- Electronic Theses & Dissertations
- Title
- Sedimentation characteristics of the T₃ bacteriophage of Escherichia coli B
- Creator
- De Long, Richard James
- Date
- 1956
- Collection
- Electronic Theses & Dissertations
- Title
- The gol site : a bacteriophage T4 regulatory region that can affect expression of all the T4 late genes
- Creator
- Champness, Wendy Cooley
- Date
- 1982
- Collection
- Electronic Theses & Dissertations
- Title
- Studies of two iron-containing enzymes from Escherichia coli : pyruvate formate-lyase activating enzyme and AlkB
- Creator
- Henshaw, Timothy F.
- Date
- 2004
- Collection
- Electronic Theses & Dissertations
- Title
- Physical properties of gram negative membranes and lipopolysaccharide
- Creator
- Coughlin, Richard Thomas
- Date
- 1982
- Collection
- Electronic Theses & Dissertations
- Title
- Mutagenic properties of cis-platinum(II) diamminodichloride in Escherichia coli
- Creator
- Beck, Doris Jean, 1938-
- Date
- 1974
- Collection
- Electronic Theses & Dissertations
- Title
- Purification of the human basal transcription factor TFIIE produced in bacteria
- Creator
- Chavez, David P.
- Date
- 1993
- Collection
- Electronic Theses & Dissertations
- Title
- Bioavailability of tetracycline in water and soil to Escherichia coli for expression of antibiotic resistance
- Creator
- Zhang, Yingjie
- Date
- 2013
- Collection
- Electronic Theses & Dissertations
- Description
-
Tetracyclines are a class of antimicrobials extensively used as human and veterinary medicine, and in livestock production since they were discovered in the 1940s. A large portion of tetracyclines administered to humans and animals are excreted and subsequently released into the environment, where they pose potential risks to ecosystem and human health. There is a growing concern that the presence of antibiotics such as tetracycline at trace levels in the environment is related to the...
Show moreTetracyclines are a class of antimicrobials extensively used as human and veterinary medicine, and in livestock production since they were discovered in the 1940s. A large portion of tetracyclines administered to humans and animals are excreted and subsequently released into the environment, where they pose potential risks to ecosystem and human health. There is a growing concern that the presence of antibiotics such as tetracycline at trace levels in the environment is related to the emergence and ever-increasing abundance of antibiotic resistance genes in natural and engineered microbial populations. However, basic knowledge at the molecular scale of bacterial access to tetracyclines present in environmental matrices and expression of antibiotic resistance genes remain nearly unknown. In this study, we used the E. coli MC4100/pTGM whole-cell bioreporter as an effective tool to investigate bioavailability of tetracycline in water and soil to bacteria for expression of antibiotic resistance genes. Our hypothesis was that the speciation of tetracycline dissolved in water and sorption by soil minerals controls the bioavailabilities for bacterial uptake and subsequent activation of antibiotic resistance genes. The results revealed that activation of antibiotic resistance in the E. coli bioreporter responded linearly to intracellular tetracycline concentration. The extent of tetracycline uptake by E. coli was modulated by tetracycline speciation. We have identified that zwitterionic tetracycline as the primary species favorable for bacterial uptake. Geochemical factors such as pH, salt composition and concentration influenced the fractional distributions of tetracycline species in aqueous solution and hence altered uptake by E. coli. In addition, the presence of organic ligands could also alter tetracycline speciation by releasing tetracycline from its metal complexes in aqueous solution. For tetracycline associated with Mg-smectite, desorption of tetracycline from clay to solution was the major exposure pathway for bacterial uptake and subsequent activation of antibiotic resistance in the diluted clay suspensions. In clay film cultivation, clay-sorbed tetracycline was still bioaccessible to E. coli evoking strong expression of antibiotic resistance. Direct contact of the E. coli bioreporters with clay surfaces and further formation of biofilms plausibly facilitated tetracycline transfer to bacteria. Overall, this study greatly advances the fundamental understanding of bioavailability of tetracycline in the environment to bacteria for expression of antibiotic resistance genes.
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- Title
- Cell division in cis-platinum(II)diamminodichloride-induced filaments of Escherichia coli : dependence upon completion of deoxyribonucleic acid repair and a protease activity
- Creator
- Markham, Bruce Edward
- Date
- 1980
- Collection
- Electronic Theses & Dissertations