Importance of Lactobacilli for Human Health

As an extraordinarily diverse group of bacteria, lactobacilli are now placed in several genera which names still contain “lactobacillus” in their core. Despite the names, this group of the lactic acid bacteria comprises microorganisms which are very important for our life especially in early development of the human microbiota and immune system. The interactions of the lactobacilli with elements of the mucosal immunity leads to its shaping and development, which is recognized as a potential driving force in the evolution of the human immune system. Although most of the evidence supporting the idea of the leading role of lactobacilli in housekeeping of the human health derives from articles on probiotics aiming to elucidate mechanisms of their functional activities and studies on mucosal immunity on germ-free mice, it is justifiable to extend observations on properties of the individual probiotic Lactobacillus related to health benefits onto other strains sharing common characteristic of the species. In this review, we will discuss acquisition, presence and functions of lactobacilli in different human microbiota throughout the whole life including those arising in amnion and their interactions with mucosal and immune cells. Examples of immune system modulation by probiotic lactobacilli due to competition for available nutrients in the colon, colonization site interference, and competition for binding sites on gut epithelial cells, production of bacteriocin, lowering of colonic pH, and nonspecific stimulation of the immune system will be shown.