保加利亚乳杆菌是生产发酵乳最常用的发酵剂菌种之一，菌株的蛋白分解、乳糖代谢等生产特性将直接影响到发酵乳制品的品质。不同菌株有着不同的特性，但这些差异特性产生的起源目前还不得而知。本项目以实验室从不同地区分离的400余株保加利亚乳杆菌为研究对象，以前期MLST分析结果和表型特征为依据，选取典型的表型和基因型差异菌株，首次采用基因组重测序的方法，结合菌株表型特征，通过比较基因组分析具有不同生产特性菌株在基因组水平的差异，从编码区、非编码区、基因调控区以及DNA甲基化等多方面对不同分离株蛋白分解和乳糖代谢能力进行全面系统的研究，以期在基因组水平揭示其不同特性差异发生的机理机制，为我国乳酸菌发酵剂的进一步研究、开发和利用奠定理论基础，具有重要的实际生产意义。

Lactobacillus delbrueckii subsp. bulgaricus is one of the most common bacterial starter cultures in the production of fermented milks. Characteristics of the bacterial strains like protein degradation and lactose metabolism directly affect the quality of fermented dairy products. Different strains have different above mentioned characteristics. However, the genetic origin of these differences is still unknown. Thus, this project aims to reveal the mechanism giving rise to such phenotypic variation by analyzing more than 400 Lactobacillus delbrueckii subsp. bulgaricus target strains previously isolated by our laboratory from various geographical locations. Based on our preliminary MLST and phenotype analyses, typical strains differing from their phenotypic and genotypic characteristics were selected. A combined approach of whole genome re-sequencing together with strain phenotype analysis will be applied for the first time in this study. In order to comprehensively and systematically elucidate the different capacities in protein degradation and lactose metabolism between different strains, comparative genomic analysis of their coding, non-coding and gene regulatory regions in the genomes, as well as other features like DNA methylation pattern, will be performed. Such analysis will reveal the mechanism and regulation of these metabolic features at the genomic level. This project will advance the research, development and utilization of lactic acid bacterial starter cultures of China, as well as lay a solid theoretical basis in this research field. Therefore, it serves as a significant and practical reference for the development of future work.