Giessen, Universiẗat, Diss., 2002. / Erscheinungsjahr an der Haupttitelstelle: 2001.

Serratia marcescens is a microorganism that constitutes one of the primary causes of nosocomial outbreaks in hospitals. One characteristic of S. marcescens clinical isolates is the high resistance to antimicrobials used in the clinic. Recent reports have attributed antibiotic resistance to altered porin expression. In this study, S. marcescens Db11 isogenic porin mutants were generated using the generalized transducing phage IF3 to move marked target-genes between isogenic strain backgrounds, prior to removal of the antibiotic resistance cassette by Flp-FRT strategy. Mutants for three classical porins were obtained and the effect of ompF and ompC deletion on antimicrobial resistance was evaluated by MIC. The use of this method avoided the incorporation of additional resistance markers and is an alternative strategy to create clean unmarked Serratia mutant strains. The lack of OmpF, but not OmpC, significantly increased MIC values to the β-lactam drugs such as ampicillin and cefoxitin as well as to nitrofurantoin. Genetic deletion of both ompF and ompC did not compromise the integrity of the bacterial cell envelope in optimal growth conditions, suggesting that other outer-membrane porins may function in a compensatory role to facilitate nutrient uptake and cell envelope integrity. S. marcescens is a pathogen of C. elegans and can be used to study host response to bacterial infections. The host model Caenorhabditis elegans was used in this study to investigate if porin deficits affected bacterial virulence. When porin mutants were evaluated in the C. elegans host model, the virulence of the single porin mutant strains increased in comparison to the wild-type. This study demonstrated that mutations of ompF and ompC did not attenuate S. marcescens virulence, but rather demonstrated a hypervirulent phenotype when they were assessed in C. elegans. The absence of OmpF and OmpC porins in S. marcescens appeared to increase the bacterial invasion of C. elegans nematode tissue. Further studies are required to fully investigate the hypervirulent phenotype of these mutant strains. This study reveals that decrease of outer membrane permeability due to porin mutation alters antimicrobial resistance and does not generate virulence attenuation in S. marcescens Db11. / May 2015

In Fulfilment for the requirements for the degree of Doctor of Philosophy University of the Witwatersrand Johannesburg, South Africa Thesis Defended 23 September 2015 / The phylum nematoda has a variety of functional groups. The parasitic functional group comprise various nematodes some which are parasitic to insects and are known as entomopathogenic nematodes (EPNs). The two most studied genera of EPNs are Steinernema and Heterorhabditis. These EPNs are associated symbiotically with the two enterobacteria genera; Xenorhabdus and Photorhabdus, respectively. The explanation of EPNs has been recently expanded to include the genus Oscheius which have been found to be associated with Serratia species. The bacteria synthesize a range of insecticidal and antimicrobial metabolites which may be useful in various ways as agricultural pest control and medical disease control. An insight into the genome of the nematode-bacterium duo will provide us with information about the symbiosis between the two and parasitism against insect pests. Here in I discuss the isolation and identification of a South African EPN and its symbiotic bacterium. In addition I highlight the production of indole derivatives which are common metabolites produced by entomopathogenic bacteria. The thesis eventually describes and discusses the methods for whole genome sequencing of both the isolated nematode and its symbiotic bacterium, and the genomic content indicate similar genes with other known EPN genera and protein-coding genes involved in symbiosis and parasitism. / MT2016

Serratia marcescens is an opportunistic pathogen involved in predominantly nosocomial infections, however, it is also implicated as a common cause of microbial keratitis. Since many S. marcecens strains are also resistant to multiple antibiotics, this organism represents a growing public health problem. S. marcescens MG1 utilises a regulatory system for regulation of swarming motility and exo-enzyme secretion that relies on the production of a diffusible signal identified as N-butanoyl-L-homoserine lactone (C4-HSL). The aim of this study was to determine the role of C4-HSL in surface colonisation (adhesion and biofilm formation). In this thesis, the development of a novel biofilm in S. marcescens MG1 is described. The biofilm comprises of an intricate and complex structure consisting of long filamentous cells, cell aggregates and cell chains. Two C4-HSL controlled genes (bsmA and bsmB) are shown to be crucial for biofilm formation. It is proposed that C4-HSL regulated bsmA and bsmB gene products are engaged in fine tuning aggregation at a specific time point in late biofilm development. Since adhesion is the first stage of colonisation, the role of C4-HSL in adhesion to a hydrophilic abiotic surface (HAS) and a human corneal epithelial (HCE) cell line was assessed. While adhesion to the HAS was found to be C4-HSL controlled, this was not the case for adhesion to the HCE cells. In adhesion to the HAS, mutations in the following C4-HSL regulated genes resulted in reduced adhesion; a sensor kinase gene (rssA), a type I transporter gene (lipB), bsmA and bsmB. These four genes were found to effect the expression of type I fimbriae which is proposed to be the adhesin affecting C4-HSL regulated adhesion. While C4-HSL is not involved in adhesion to the HCE cell line, the genes bsmA and bsmB are important. It is proposed that bsmA and bsmB dependent HCE adhesion is due to the requirement of these genes for type I fimbriae production. Furthermore, C4-HSL was found to regulate capsule polysaccharide and OmpX production and repress cytotoxic activity against HCE cells and erythrocytes. It is proposed that cytotoxicity is mediated by ShlA haemolysin.

Alkylphenol polyethoxylates (APEOs) are commonly present in both industrial and municipal wastewaters. They belong to the nonionic surfactants which have been widely used for years. APEOs themselves are nontoxic to organisms. When released into the environment, the EO chain of APEOs are degraded chemically and biologically. Some of the products, such as nonylphenol and octylphenol, are persistant. According to the partition coefficient constant, the alkylphenols are adsorpted in the sediments and accumulated in the environment. Nonylphenol (NP) is an analog of 17£]-estradiol, a sex hormone. It is one of the environmental hormones which can get into the organisms through the food chain and may interfere with the reproduction function. Previous studies showed the Love River in Kaohsiung was polluted with APEOs considerably. Bacteria capable of using nonylphenol as the sole carbon source were isolated by the enrichment procedures. Some of the bacterial isolates were identified as Serratia marcescens (strain A), Vibrio sp. (strain B) and Aeromonadaceae sp. (strain C) by the 16S rRNA phylogeny. The rates of NP degradation were evaluated by the HPLC-UV. S. marcescens strain A manifested the best degradative. It could degrade almost 25 ppm of NP in 28 days. The degradative capability of Vibrio sp. (strain B), Aeromonadaceae sp. (strain C) and the enriched mix culture were 65%, 25% and 30%, respectively. Additionally, to know the limitation of degrading nonylphenol by strain A, we set the concentration to 100 ppm for the test. Strain A could degrade 72 ppm in this test. Bacterial composition of the enriched consortia was grouped by the DGGE method. The dominants were Ochrobactrum sp. and Alcaligenaceae sp. which may be to applied to environmental bioremediation.

Serratia marcescens is an opportunistic pathogen involved in predominantly nosocomial infections, however, it is also implicated as a common cause of microbial keratitis. Since many S. marcecens strains are also resistant to multiple antibiotics, this organism represents a growing public health problem. S. marcescens MG1 utilises a regulatory system for regulation of swarming motility and exo-enzyme secretion that relies on the production of a diffusible signal identified as N-butanoyl-L-homoserine lactone (C4-HSL). The aim of this study was to determine the role of C4-HSL in surface colonisation (adhesion and biofilm formation). In this thesis, the development of a novel biofilm in S. marcescens MG1 is described. The biofilm comprises of an intricate and complex structure consisting of long filamentous cells, cell aggregates and cell chains. Two C4-HSL controlled genes (bsmA and bsmB) are shown to be crucial for biofilm formation. It is proposed that C4-HSL regulated bsmA and bsmB gene products are engaged in fine tuning aggregation at a specific time point in late biofilm development. Since adhesion is the first stage of colonisation, the role of C4-HSL in adhesion to a hydrophilic abiotic surface (HAS) and a human corneal epithelial (HCE) cell line was assessed. While adhesion to the HAS was found to be C4-HSL controlled, this was not the case for adhesion to the HCE cells. In adhesion to the HAS, mutations in the following C4-HSL regulated genes resulted in reduced adhesion; a sensor kinase gene (rssA), a type I transporter gene (lipB), bsmA and bsmB. These four genes were found to effect the expression of type I fimbriae which is proposed to be the adhesin affecting C4-HSL regulated adhesion. While C4-HSL is not involved in adhesion to the HCE cell line, the genes bsmA and bsmB are important. It is proposed that bsmA and bsmB dependent HCE adhesion is due to the requirement of these genes for type I fimbriae production. Furthermore, C4-HSL was found to regulate capsule polysaccharide and OmpX production and repress cytotoxic activity against HCE cells and erythrocytes. It is proposed that cytotoxicity is mediated by ShlA haemolysin.

Serratia marcescens is an opportunistic pathogen involved in predominantly nosocomial infections, however, it is also implicated as a common cause of microbial keratitis. Since many S. marcecens strains are also resistant to multiple antibiotics, this organism represents a growing public health problem. S. marcescens MG1 utilises a regulatory system for regulation of swarming motility and exo-enzyme secretion that relies on the production of a diffusible signal identified as N-butanoyl-L-homoserine lactone (C4-HSL). The aim of this study was to determine the role of C4-HSL in surface colonisation (adhesion and biofilm formation). In this thesis, the development of a novel biofilm in S. marcescens MG1 is described. The biofilm comprises of an intricate and complex structure consisting of long filamentous cells, cell aggregates and cell chains. Two C4-HSL controlled genes (bsmA and bsmB) are shown to be crucial for biofilm formation. It is proposed that C4-HSL regulated bsmA and bsmB gene products are engaged in fine tuning aggregation at a specific time point in late biofilm development. Since adhesion is the first stage of colonisation, the role of C4-HSL in adhesion to a hydrophilic abiotic surface (HAS) and a human corneal epithelial (HCE) cell line was assessed. While adhesion to the HAS was found to be C4-HSL controlled, this was not the case for adhesion to the HCE cells. In adhesion to the HAS, mutations in the following C4-HSL regulated genes resulted in reduced adhesion; a sensor kinase gene (rssA), a type I transporter gene (lipB), bsmA and bsmB. These four genes were found to effect the expression of type I fimbriae which is proposed to be the adhesin affecting C4-HSL regulated adhesion. While C4-HSL is not involved in adhesion to the HCE cell line, the genes bsmA and bsmB are important. It is proposed that bsmA and bsmB dependent HCE adhesion is due to the requirement of these genes for type I fimbriae production. Furthermore, C4-HSL was found to regulate capsule polysaccharide and OmpX production and repress cytotoxic activity against HCE cells and erythrocytes. It is proposed that cytotoxicity is mediated by ShlA haemolysin.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1956. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 43-44).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1957. / Typescript. Abstracted in Dissertation abstracts, v. 17 (1957) no. 6, p. 1191. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 98-100).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1956. / Typescript. Abstracted in Dissertation abstracts, v. 16 (1956) no. 4, p. 635. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 96-98).