A Lactobacillus sp. has been isolated from infant feces and characterized according to its physiological properties and identified as Lactobacillus acidophilus KLA1012. A gene coding surface layer protein (SLP) has been cloned and the sequence has been determined. The nucleotide sequence of slpA was 1,338 bp in size and was identical to that of L. acidophilus ATCC 4356 (100%). Amino acid sequence of SLP-A was deduced from the nucleotide sequence and it had signal sequence at N-terminal, consisting of positively charged amino acid mainly lysine. slpA was cloned and heterologously expressed in E. coli M15 and the 45.2 kDa surface-layer protein band was examined by SDS-PAGE and confirmed by Western blotting using polyclonal antibody against L. acidophilus KLA 1012 SLP-A protein.