Lactic acid bacteria contribution to gut microbiota complexity: lights and shadows

Abstract

Lactic Acid Bacteria (LAB) are ancient organisms that cannot biosynthesize functional cytochromes, and cannot get ATP from respiration. Besides sugar fermentation, they evolved electrogenic decarboxylations and ATP-forming deiminations. The right balance between sugar fermentation and decarboxylation/deimination ensures buffered environments thus enabling LAB to survive in human gastric trait and colonize gut. A complex molecular cross-talk between LAB and host exists. LAB moonlight proteins are made in response to gut stimuli and promote bacterial adhesion to mucosa and stimulate immune cells. Similarly, when LAB are present, human enterocytes activate specific gene expression of specific genes only. Furthermore, LAB antagonistic relationships with other microorganisms constitute the basis for their anti-infective role. Histamine and tyramine are LAB bioactive catabolites that act on the CNS, causing hypertension and allergies. Nevertheless, some LAB biosynthesize both gamma-amino-butyrate (GABA), that has relaxing effect on gut smooth muscles, and beta-phenylethylamine, that controls satiety and mood. Since LAB have reduced amino acid biosynthetic abilities, they developed a sophisticated proteolytic system, that is also involved in antihypertensive and opiod peptide generation from milk proteins. Short-chain fatty acids are glycolytic and phosphoketolase end-products, regulating epithelial cell proliferation and differentiation. Nevertheless, they constitute a supplementary energy source for the host, causing weight gain. Human metabolism can also be affected by anabolic LAB products such as conjugated linoleic acids (CLA). Some CLA isomers reduce cancer cell viability and ameliorate insulin resistance, while others lower the HDL/LDL ratio and modify eicosanoid production, with detrimental health effects. A further appreciated LAB feature is the ability to fix selenium into seleno-cysteine. Thus, opening interesting perspectives for their utilization as antioxidant nutraceutical vectors.

The human gut microbiota: a dynamic interplay with the host from birth to senescence settled during childhood

“…This initial "bacterial imprinting" may later on differentially contribute to the onset of atopic diseases, allergies, and asthma, described as more frequent in CS-born children rather than in those naturally delivered (56). It might be interesting to consider that the vaginal Lactobacilli are bacteria occupying from the beginning (pioneers) specific sites in the niche of the newborn gut microbiota, establishing a defensive role against the pathogens but also creating maximum compatibility with the subsequent intake of Lactobacilli because of feeding (57). The presence of Lactobacilli in the vaginal microbiota may modulate the symbiotic mother-child interaction (2) and is indicative of maternal metabolic abnormalities, such as the high birth weight (e.g., excessive weight gain in pregnancy or altered glucose metabolism) (57).…”

“…It might be interesting to consider that the vaginal Lactobacilli are bacteria occupying from the beginning (pioneers) specific sites in the niche of the newborn gut microbiota, establishing a defensive role against the pathogens but also creating maximum compatibility with the subsequent intake of Lactobacilli because of feeding (57). The presence of Lactobacilli in the vaginal microbiota may modulate the symbiotic mother-child interaction (2) and is indicative of maternal metabolic abnormalities, such as the high birth weight (e.g., excessive weight gain in pregnancy or altered glucose metabolism) (57). In fact, many of the metabolic and immunological changes during pregnancy are the same as those describing the metabolic syndrome.…”

Effects of the Peptide Pheromone Plantaricin A and Cocultivation with Lactobacillus sanfranciscensis DPPMA174 on the Exoproteome and the Adhesion Capacity of Lactobacillus plantarum DC400

“…Some of these proteins were also identified in the exoproteome of other strains of L. plantarum (7,62,63). A number of CMG proteins express moonlighting activities (64). GAPDH from the cell surface of L. plantarum promotes adhesion to human colonic mucin (65).…”

Metabolism and physiology of Lactobacilli: a review

“…Homofermentative lactobacilli are classified exclusively as obligate because they always carry out glycolysis and produce only lactic acid (>85%) by the Embden-Meyerhof-Parnas (EMP) glycolytic pathway from the assimilation of hexoses, which are transported by membrane proteins called permeases, ABC (ATP Binding Cassette) transporters and phosphoenolpyruvate : carbohydrate phosphotransferase (PEP:PTS). This metabolism is characterized by the breakdown of 1,6-diphosphate fructose into two trioses phosphates, which are converted into lactate (Pessione, 2012;Salvetti et al, 2012;AbdelRahman et al, 2013).…”

“…In the first pathway, galactose is transported by the PEP: PTS system and enters the cell in the form of galactose-6-phosphate. In the second route, galactose is transported directly into the cell, without any change by a specific permease (Von Wright &Axelsson, 2012;Pessione, 2012).…”