S. mutans is the bacteria that is found during the developmental stage of the caries process. Lactobacilli are usually found in the dentin during the process. Actinomyces are opportunistic and colonize after the initial infection. mutans is the bacteria that is found during the developmental stage of the caries process. Lactobacilli are usually found in the dentin during the process. Actinomyces are opportunistic and colonize after the initial infection.