Regulation of swarming behavior in Serratia marcescens-Roles of rfaD and manA
| Autor: | Yung-Lin Chang, 張永麟 |
|---|---|
| Rok vydání: | 2007 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 95 Serratia marcescens is a red-pigmented gram-negative enteric organism. In addition, it is an opportunistic human pathogen and causes many nosocomial infections. Swarming is a specialized form of bacterial surface translocation when bacteria were cultured on surface of solid media. S. marcescens CH-1 swarms on 0.8% LB agar at 30°C, but not at 37°C. In order to understand the underlying mechanism of temperature-dependent regulation of swarming behavior, transposon mutagenesis had been performed to screen for the mutants that swarm at 37°C. One precocious-swarming mutant was isolated and further experiments showed that insertion site of transposon lay in the predicted open reading frame ‘sspA’. The sspA encoded a lipoprotein which was uncharacterized. This gene was characterized by others in our lab. I undertake another open reading frame, rfaD, which convers ADP-D-Glycero-D-manno-heptose to ADP-L-Glycero-D-manno-heptose in LPS synthesis pathway. In order to investigate whether the rfaD was involved in swarming, I use homologues recombination to knock out rfaD in CH-1, and performed series assay to identify the gene function. Furthermore I found that this potential rfaD mutant was not involved in swarming and LPS synthesis. The underlying mechanism is unknown. Another part of this thesis is manA, due to a previously screened precocious swarming strain WW100 which was inserted in manA promoter by transposon. The manA was predicted to encode a protein named mannose-6-phosphate isomerase whose function is interconverting fructose-6-phosphate and mannose-6-phosphate, and link the glucose and mannose metabolic pathway. A manA knock-out strain was constructed. Also, manA overexperssion in S. marcescens CH-1 was performed to test the WW100 precocious swarming phenotype. I concluded that this phenotype was due to manA overexpression. Subsequently, ATP assay, NADH/NAD ratio and LPS pattern were determined. The precocious swarming phenotype was due to increase in TCA cycle activity. Whether the LPS plays a role in this manA mutant phenotype remained to be determined. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
| Externí odkaz: |
|