Abstract: In this study, whole genome sequencing of Bacillus velezensis L-39, an extracellular polysaccharide-producing strain isolated from Pixian Douban, was carried out through the combined use of second-generation Illumina HiSeq and third-generation PacBio platforms. The genomic analysis covered gene assembly, prediction, annotation, and the elucidation of secondary metabolite biosynthetic gene clusters and crucial gene functions, focusing on the gene clusters for carbohydrate metabolism, the nucleoside sugar synthesis pathways, and extracellular polysaccharide biosynthesis. The results showed that the whole genome size of B. velezensis L-39 was 3 970 591 bp in length, encoding a total of 3 770 genes. Through Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, the eps gene cluster and 32 functional genes were predicted from the genome, and a complete extracellular polysaccharide (EPS) synthesis pathway was mapped. Subsequently, polymerase chain reaction (PCR) was performed on the pivotal genes, with results expected. The aim of this study is to discover genes closely related to extracellular polysaccharide synthesis by B. velezensis L-39 in order to provide a scientific foundation for an in-depth analysis of the molecular basis for extracellular polysaccharide production by this strain and for its practical application and development.

Key words: Bacillus velezensis; whole-genome sequencing; extracellular polysaccharide synthesis; gene