| Acknowledgements | 第10-17页 |
| Abbreviations | 第17-19页 |
| Abstract | 第19-21页 |
| 摘要 | 第22-24页 |
| Chapter 1 Introduction | 第24-27页 |
| 1.1 Background | 第24-25页 |
| 1.2 Motivation | 第25页 |
| 1.3 Hypothesis and Objectives | 第25-27页 |
| Chapter 2. Literature Review | 第27-57页 |
| 2.1 Introduction | 第27页 |
| 2.2 Microbial quality of raw milk and its effect on dairy processing | 第27-29页 |
| 2.3 Sources of microbial contamination in milk powders | 第29页 |
| 2.4 Diversity of bacterial contaminants in milk powders | 第29-33页 |
| 2.4.1 Obligate and facultative anaerobic bacteria | 第30-31页 |
| 2.4.2 Pathogenic bacteria in milk powders | 第31页 |
| 2.4.3 Aerobic mesophilic and thermophilic spore forming bacteria | 第31-33页 |
| 2.5 Spoilage potential of mesophilic and thermophilic spore forming bacteria | 第33-37页 |
| 2.5.1 Factors affecting the production of proteases and lipases in bacteria | 第36-37页 |
| 2.6 Methods to quantify bacterial spoilage enzymes | 第37-39页 |
| 2.6.1 Proteases | 第37-38页 |
| 2.6.2 Lipases | 第38-39页 |
| 2.7 Heat resistance of aerobic spore forming bacteria | 第39-42页 |
| 2.7.1 Bacillus sporothermodurans, G. stearothermophilus and A. flavithermus | 第40-41页 |
| 2.7.2 Heat resistance of other aerobic spore formers | 第41-42页 |
| 2.8 Factors affecting the heat resistance of spores | 第42-46页 |
| 2.8.1 The role bacterial spore's structure in its heat resistance | 第42-45页 |
| 2.8.2 Molecular factors related to the thermal resistance of spores | 第45-46页 |
| 2.9 Introduction to biofilms | 第46-47页 |
| 2.10 Development of biofilms | 第47-51页 |
| 2.11 Importance of biofilms in the dairy industry | 第51-54页 |
| 2.11.1 Biofilm formation by mesophilic and thermophilic spore formers | 第51-52页 |
| 2.11.2 Factors affecting bacterial adhesions and biofilm formation | 第52-53页 |
| 2.11.3 Laboratory-based methods to detect and quantify biofilms | 第53-54页 |
| 2.12 Molecular determinants of biofilms | 第54-56页 |
| 2.13 Concluding remarks | 第56-57页 |
| Chapter 3. Prevalence and diversity of mesophilic and thermophilic spore forming bacteria inChinese milk powders | 第57-81页 |
| 3.1 Introduction | 第57-59页 |
| 3.2 Materials and methods | 第59-61页 |
| 3.2.1 Sample collection and selection of isolates | 第59-60页 |
| 3.2.2 DNA extraction and RAPD-PCR analysis | 第60-61页 |
| 3.2.3 Bacterial identification by 16S rRNA gene sequence analysis | 第61页 |
| 3.2.4 Statistical analysis | 第61页 |
| 3.3 Results | 第61-71页 |
| 3.3.1 Mesophilic and thermophilic aerobic plate count | 第61-63页 |
| 3.3.2 Distribution of RAPD profiles and identification of isolates | 第63-71页 |
| 3.4 Discussion | 第71-80页 |
| 3.4.1 B. licheniformis, B. sonorensis and B. subtilis group isolates | 第71-74页 |
| 3.4.2 G. stearothermophilus and A. flavithermus | 第74-75页 |
| 3.4.3 Actinomycetes | 第75页 |
| 3.4.4 B.cereus group | 第75-78页 |
| 3.4.5 Other spore forming isolates | 第78-80页 |
| 3.5 Conclusion | 第80-81页 |
| Chapter 4. Insights into heat survival and possible spoilage potential of the microbiota ofChinese milk powders | 第81-105页 |
| 4.1 Introduction | 第81-83页 |
| 4.2 Materials and Methods | 第83-87页 |
| 4.2.1 Materials | 第83页 |
| 4.2.2 Selection of the isolates | 第83-84页 |
| 4.2.3 Spoilage potential of sporeformers | 第84-86页 |
| 4.2.4 Heat resistance of spores | 第86-87页 |
| 4.2.5 Statistical analysis | 第87页 |
| 4.3 Results | 第87-97页 |
| 4.3.1 Spoilage potential | 第87-92页 |
| 4.3.2 Heat resistance studies | 第92-97页 |
| 4.4 Discussion | 第97-104页 |
| 4.4.1 Spoilage potential of mesophilic and thermophilic strains except B. licheniformis | 第97-98页 |
| 4.4.2 Spoilage potential and phenotypic variation of B. licheniformis strains | 第98-99页 |
| 4.4.3 Heat resistance of sporeformers | 第99-104页 |
| 4.5 Concluding remarks | 第104-105页 |
| Chapter 5. Biofilms: A survival strategy of spore forming bacteria prevalent in Chinese milkpowders | 第105-130页 |
| 5.1 Introduction | 第105-107页 |
| 5.2 Materials and Methods | 第107-111页 |
| 5.2.1 Selection of the isolates | 第107-108页 |
| 5.2.2 Biofilm screening assay using the CV staining method | 第108-109页 |
| 5.2.3 Quantification of viable biofilm cells in skimmed milk and TSB | 第109-110页 |
| 5.2.4 Scanning electron microscopy | 第110页 |
| 5.2.5 Statistical analysis | 第110-111页 |
| 5.3 Results | 第111-121页 |
| 5.3.1 Biofilm formation by mesophilic isolates except B. licheniformis | 第111-116页 |
| 5.3.2 Results of biofilm formation by B. licheniformis | 第116-118页 |
| 5.3.3 Results of Biofilm formation by thermophilic isolates | 第118-121页 |
| 5.3.4 Scanning electron microscopy images of cells | 第121页 |
| 5.4 Discussion | 第121-129页 |
| 5.4.1 Biofilm forming potential of all mesophiles including B. licheniformis | 第121-124页 |
| 5.4.2 Biofilm forming potential of thermophilic isolates | 第124-129页 |
| 5.5 Concluding remarks | 第129-130页 |
| Chapter 6. Molecular regulation of adhesion and biofilm production in Bacillus licheniformishigh and low biofilm producers using RNA-Seq | 第130-169页 |
| 6.1 Introduction | 第130-132页 |
| 6.2 Materials and Methods | 第132-138页 |
| 6.2.1 Selection of strains | 第132页 |
| 6.2.2 Growth conditions during the planktonic and biofilm state | 第132-133页 |
| 6.2.3 RNA extraction | 第133页 |
| 6.2.4 cDNA library preparation and sequencing | 第133-134页 |
| 6.2.5 Mapping and analysis of sequencing data | 第134页 |
| 6.2.6 Differential gene expression (DGE) analysis and expression patterns | 第134-135页 |
| 6.2.7 Gene Ontology (GO) and functional enrichment analysis of DEGs | 第135-136页 |
| 6.2.8 Comparison of RNA-Seq data with quantitative real-time PCR (qRT-PCR) assay | 第136-138页 |
| 6.3 Results | 第138-160页 |
| 6.3.1 Sequencing data and transcriptome overview of B. licheniformis | 第138-140页 |
| 6.3.2 Quantitative analysis of the B. licheniformis transcriptome | 第140-145页 |
| 6.3.3 Pathway enrichment analysis of DEGs in planktonic and biofilm states | 第145-151页 |
| 6.3.4 Genes involved in motility and matrix production | 第151-155页 |
| 6.3.5 Other genes related to biofilms | 第155页 |
| 6.3.6 Result of qRT-PCR analysis | 第155-160页 |
| 6.4 Discussion | 第160-167页 |
| 6.4.1 Transcriptional overview of B. licheniformis and correlation analysis | 第160-161页 |
| 6.4.2 KEGG pathway analysis | 第161-162页 |
| 6.4.3 Lack of transcriptional motility in biofilm cells | 第162-163页 |
| 6.4.4 Genes involved in biofilm | 第163-165页 |
| 6.4.5 Role of other genes in biofilm formation | 第165-167页 |
| 6.4.6 Coupling of sporulation and biofilms | 第167页 |
| 6.5 Conclusion | 第167-169页 |
| Chapter 7. Highlights and future perspectives | 第169-173页 |
| 7.1 Highlights | 第169页 |
| 7.2 Summary of discussion and major findings | 第169-170页 |
| 7.3 Recommendations and future work | 第170-173页 |
| References | 第173-207页 |
| Appendix | 第207-215页 |
| List of publications | 第215-216页 |
