Lactic Acid Bacteria and the Human Intestinal Microbiome

The great interest in the human microbiome has revived attention paid to LAB presence in the human intestine. This chapter first discusses the LAB associated with the human intestinal microbiota and their potential roles in health and diseases. It then addresses recent metagenomic studies that challenge the established belief that the human intestine is colonized by many lactobacilli and tries to offer insights into one highly relevant question: are LAB originally occurring (autochthonous) and/or just transiently passing (allochthonous) in the human intestinal tract? To further illustrate this, the chapter describes one particular case study: the well-characterized Lactobacillus rhamnosus species, which has been extensively studied at both genomic and phenotypic levels.