Abstract
Lactic acid bacteria, groups of Gram positive bacteria, have thick peptidoglycan layers in their cell wall, which make the process of cell wall lysis in genomic DNA isolation difficult. A novel method, XS method to isolate genomic DNA from lactobacillus is introduced, which is different from conventional isolation protocol. This method is rapid, requires no enzymatic or mechanical cell disruption, nor multiple organic solvent extractions. Isolated DNA are proven can be used in various molecular biology analysis, such as PCR, restriction enzyme digestion, and cloning. Isolation of genomic DNA from Lactobacillus rhamnosus TCELL-1 using XS method faces the low yield problem, and hence, lysozyme treatment prior to XS treatment (XSL method) is introduced. DNA isolated from Lb. rhamnosus TCELL-1 via XSL method are used in cloning of alr gene. The partial length of this gene is 843 bp, which can be translated into ALR protein with 281 residues. Comparison of deduced amino acid sequence reveals 85.8 % identity with that of Lb. casei ATCC334. A highly conserved region in N-terminal, AVVKANGYGH, is found.