Figure 4. Hypothetical model of GTF enzyme acquisition by oral Streptococci.

The genus Streptococcus acquired the gtf gene via horizontal gene transfer when it encountered lactic acid bacteria, such as Lactobacillus and Leuconostoc, in the human oral cavity. This event coincided with the introduction of fermented foods into the human diet, which was brought about by the development of agricultural practices and food preservation methods.