Phylogenetic tree based on bacterial 16S rRNA gene sequences. The phylogenetic tree was constructed using the neighbor-joining method showing the bacterial organisms (numbers in brackets) used in this study. Bootstrap values (1,000 replicates) lower than 50% are not shown. ▲ Filled triangles indicate the phylogenetic position of human pathogens which have not been used in this study. The scale bar 0.02 indicates 2% of nucleotide sequence substitution. The strain numbers are indicated in brackets.